Measuring Audio Interface Outputs with Multimeter - Need help please - Page 1
Forum section: electronics / beginners

author: Voltzs
author_rank: Contributor
timestamp: November 23, 2022, 04:19:07 pm
content: Hi everyone! I am new to the forum and so glad I found a place specialized in electronics!I am calibrating my monitoring chain in my music studio and before doing so I wanted to confirm that the outputs of my pro audio interface are +4dBu when a -20 dBFS sine wave tone is played in my audio software.I know that a +4dBu signal is equivalent to 1.23 Volts - what I am having trouble with is my multimeter (Voltcraft VC 130). I have attached a picture showing my settings and connections. I did read the manual but I only manage to get a reading showing '125' (no decimal point) when using the 'Diode' setting, not '1.23' Volts.As you can see from the attached pic, when I have the sine wave playing and am connected to the TRS cable from the Interface's output I get a reading of 125 - if I increase the level of the sine wave to 0 dBFS the multimeter's display reads 280 so there is a direct increase occurring at the output of my interface.I am just not sure if I am using the multimeter correctly? When I plugged the red cable into the 'V' input and set it to any of the Volt settings I didn't get any number/figures that made any sense or at all correlated to 1.23 Volts.I'd be grateful for any and all tips! Thank you!!

author: wasedadoc
author_rank: Super Contributor
timestamp: November 23, 2022, 05:06:05 pm
content: You donotuse the diode setting of any multimeter to measure a voltage source.You can try the AC volts setting but be aware that many digital multimeters do not give accurate measurements when the frequency is above a few hundred Hz.Update: I see that the most sensitive AC volts range of your meter is 200. That is not sensitive enough for the signal level you want to measure. You also need to understand the accuracy specifications. Look at page 38 of the manualhttps://asset.conrad.com/media10/add/160267/c1/-/gl/001090519ML04/manual-1090519-voltcraft-vc130-1-handheld-multimeter-digital-cat-iii-250-v-display-counts-2000.pdf. On AC, 1.5% + 8. On the 200 volt range that means the error can be 3 volts (1.5% of 200) plus 8 counts. Total error can be 3.8 Volts. Not much use when you are trying to measure less than 2 Volts. And yes, even that only applies to 40-400 Hz.

author: Voltzs
author_rank: Contributor
timestamp: November 23, 2022, 05:15:40 pm
content: Hi wasedadoc! Thanks for your reply - yeah, I was also trying to establish my Multimeter's freq response as in the manual it also showed the freq response for a more expensive modelsomething like 10Hz to 10mHz...Just so I understand clearly, are you saying my multimeter is not capable of reading the voltage output of my converter or not capable of reading the 1kHz tone? Should I try sending out a 200Hz tone? And if so could you please advise me of the settings?I thank you for your patience!!

author: golden_labels
author_rank: Super Contributor
timestamp: November 23, 2022, 05:16:45 pm
content: The diode test is used to measure at what voltage aPN junctionstarts conducting. Using that feature makes no sense in your case.You want to measure AC voltage. According tothe VC-130 datasheetit has only two AC voltage ranges: 200V and 250V, to which you must feed 40Hz–400Hz sine wave. Unfortunately it seems that accuracy is not high enough to measure 1.23V. Even with the better 200V range it’s ±0.82V error, so 2/3 of your expected value.I suppose you could build a circuit to record envelope of the signal (search for terms “envelope” and “circuit” for examples, preferrably with “op-amp”) and then use the more accurate 2V DC range. But then you still need some way to calibrate it, which creates a chicken and egg situation.Perhaps it will be simpler to buy a $5 DT-830?(edit: see posts below)

author: wasedadoc
author_rank: Super Contributor
timestamp: November 23, 2022, 05:20:08 pm
content: Quote from: golden_labels on November 23, 2022, 05:16:45 pmA DT-830 is no better. Lowest AC volt range is 200. Accuracy may be even worse than the Voltcraft.

author: Voltzs
author_rank: Contributor
timestamp: November 23, 2022, 05:23:47 pm
content: Quote from: wasedadoc on November 23, 2022, 05:20:08 pmMy multimeter is not the cream of the crop but I paid 50 Euros for it - is what I am trying to test so advanced?Can you recommend the cheapest multimeter capable of carrying out this test?I only need it for this. Thanks for your help!

author: golden_labels
author_rank: Super Contributor
timestamp: November 23, 2022, 05:50:14 pm
content: wasedadoc:Why in my mind DT-830 had a 2V range? I am silly. Thanks for pointing that out, corrected my post.Voltzs:No, it’s by no means anything that advanced. I am surprised that a multimeter in 50€ price range has no lower ranges.As for suggestions, wait for opinions of others.Used Uni-T UT70A is the same price. Goes down to 200mV, and in the range you need (2V) has 0.8%+3mV accuracy. Uni-T UT890D+(note the letter!), though I did not use it myself, claims to have 6V range with 1%+3mV accuracy at half that price. While ordering, pay attention to the exact model number and — if possible — ask if they have the specified range.

author: Voltzs
author_rank: Contributor
timestamp: November 23, 2022, 06:09:08 pm
content: Thanks - are you sure the models you have suggested have a frequency range up to 2kHz?

author: ledtester
author_rank: Super Contributor
timestamp: November 23, 2022, 06:11:36 pm
content: What frequencies do you want to perform the level test at?If testing at < 1 kHz is ok then meters such as the Aneng 8008 or Aneng 870 will do the job. They are both inexpensive, have a lot of features and you can find a lot of posts about them on this forum. Note that they will measure in RMS so you will have to convert to peak voltage if that's what you want.Another approach is to build a rectifier circuit like this one that appears on page 10 in the LM3915 datasheet:https://www.electroschematics.com/wp-content/uploads/2010/02/LM3915.pdfIt has good linearity but it has an offset of about 300-400 mV. It would still give you a pretty good idea of your output level, especially relative output levels. A more sophisticated circuit could give you a more precise level measurement. With a rectifier circuit you wouldn't have to get a new multimeter.A third option is to get a cheap hand-held oscilloscope like the DSO138. You should be able to find one for around $20 USD. They suck at being a general purpose oscilloscope, but they should be fine for just looking at audio signals. Note that if you have more money to spend on a hand-held scope there are much better options.

author: Voltzs
author_rank: Contributor
timestamp: November 23, 2022, 06:30:11 pm
content: Thanks for the info - I would want to check a 1kHz tone.I am not that handy and have no experience with electronics so a rectifier circuit seems (while interesting) not for me.

author: wasedadoc
author_rank: Super Contributor
timestamp: November 23, 2022, 06:40:48 pm
content: I can second the Aneng 8008 or 8009. I have one of each among my collection of approaching 20 multimeters!

author: Voltzs
author_rank: Contributor
timestamp: November 23, 2022, 06:55:26 pm
content: I see in the manual it says 40 - 1kHz for AC Voltage? I am hoping this means it would be acceptable for my needs? I am a total beginner here.Would I not also need to read DC voltage? For DC there is no info about freq range?

author: agehall
author_rank: Frequent Contributor
timestamp: November 23, 2022, 07:06:12 pm
content: There is no frequency in DC, that is why there is no info on it…

author: Voltzs
author_rank: Contributor
timestamp: November 23, 2022, 07:16:46 pm
content: Ah ha! Ok - always learning something new here! Ok, so for my purposes of measuring the voltage of a 1kHz Sine wave coming out of my interface's Outputs, the ANENG AN8008 would be able to accomplish this, correct?Thanks for your patience!

author: bdunham7
author_rank: Super Contributor
timestamp: November 23, 2022, 10:02:08 pm
content: Quote from: Voltzs on November 23, 2022, 07:16:46 pmMaybe, but inexpensive on-chip TRMS systems typically perform worse than basic average-responding system and you don't need really need TRMS for your purpose. My cheap-POS Harbor Freight meter (non-TRMS, not the free one) doesn't reach 10% error (~1 dB) until >6kHz.I don't know how accurate a $10 TRMS meter will be at 1kHz. Since your pro audio equipment is likely pretty flat, you can try it at 100, 400 and 1000Hz to see how it responds. Or, you could buy just a little bit better meter that will work over the entire audio range--perhaps it will come in handy in the future.

author: TimFox
author_rank: Super Contributor
timestamp: November 23, 2022, 10:40:05 pm
content: OP: are you looking for small differences between the voltage of different signals, or evaluating over a wide range of voltage?This is a quantitative question.

author: Voltzs
author_rank: Contributor
timestamp: November 23, 2022, 10:47:14 pm
content: Hi Tim! I am trying to establish if a -20 dBFS 1kHz sine wave is equal to +4dBu at my interface's outputs. The reason this is important to me is so I have gain stage my other analog gear down the line through to my speakers. I hope this answers your question?

author: ledtester
author_rank: Super Contributor
timestamp: November 23, 2022, 11:17:19 pm
content: FWIW, here is a table of AC readings from my Aneng 8008. The input in each case is a sine wave of amplitude 1 V generated by an Analog Discovery.Code:Freq V RMS2000.7214000.7216000.7218000.72110000.72112000.72014000.71816000.71418000.70720000.69822000.68424000.66526000.64228000.61230000.576It is evident there is a drop-off in the meter reading around 1 kHz.

author: TimFox
author_rank: Super Contributor
timestamp: November 23, 2022, 11:59:14 pm
content: Quote from: Voltzs on November 23, 2022, 10:47:14 pmYes, that means you want a reasonably accurate absolute measurement of a voltage (that should be +4 dBu = 1.23 V rms), when you set a control to -20 dB.A decent voltmeter will have the required specifications to determine the accuracy at your frequency.

author: wasedadoc
author_rank: Super Contributor
timestamp: November 24, 2022, 12:11:04 am
content: Quote from: ledtester on November 23, 2022, 11:17:19 pmRelative to 1 kHz:1600 Hz -0.08 dB2000 Hz -0.3 dB2400 Hz -0.7 dB3000 Hz -1.95 dB

author: SmallCog
author_rank: Frequent Contributor
timestamp: November 24, 2022, 02:07:56 am
content: Know anyone with one of these?https://www.gwinstek.com/en-global/products/detail/GVT-427B_GVT-417B(Type of instrument, not specific model although I'm sure it'd do what you need)Mine is a HP I pulled out of an e-waste bin as some people assume anything with a needle on it is useless...

author: EPAIII
author_rank: Super Contributor
timestamp: November 24, 2022, 10:08:40 am
content: A multimeter is a general purpose instrument and not necessarily well suited for audio measurements. While it is true that the better multimeters will have scales/settings that can do this kind of work, there is no guarantee even for those models. The meter you have is a brand X and from the photo and other comments it is plain that it is not one that is up to this use. It appears to be OK for testing things like automotive, door bell, or perhaps home wiring.I am not familiar with what is available in your country, but I would look for places that sell professional electronic test equipment, not just electrical equipment. Find one you can trust and tell them what you wish to do. There are good quality meters in a wide range of prices that will do what you want.One final thought: I have spent many decades working as a professional radio/TV engineer. Much of the work I did was with analog meters with accuracy levels in the 2% to 5% range. There is nothing magic about one given audio level. Many systems can work almost equally well with levels that differ by 2 and even 4 or more times from the ideal level. Often it is MATCHING levels that are really important instead of a precise level. And even an inaccurate meter can be used to match levels.

author: BeBuLamar
author_rank: Super Contributor
timestamp: November 24, 2022, 12:53:36 pm
content: For 50 euros I think you can buy a meter that can do what you want adequately. Not very high accuracy but at least one with a 2V AC range..I have a Fluke 8050a DMM which I paid $25 for over 20 years ago would make reasonable accurate measurement for at 0.5% and 10 counts. It's a 4 1/2 digit meter.

author: Voltzs
author_rank: Contributor
timestamp: November 24, 2022, 01:49:35 pm
content: I just ordered the Aneng 8008 - but as it only displays RMS voltage how would I calculate the Peak voltage which is what I need?There are calculations online but math never being my strong suit, are a bit over my head - if someone would be so kind as to present me with a calculation in layman's terms I'd be grateful!RMS Voltage (simple equation) = Peak VoltageI thank you all for your help and patience!

author: DavidAlfa
author_rank: Super Contributor
timestamp: November 24, 2022, 02:33:58 pm
content: Generate a 50/60Hz signal, any multimeter will work perfectly as it's designed for it (AC mains).Then as you say, adjust for 1.23V, multimeters read RMS voltage.

author: themadhippy
author_rank: Super Contributor
timestamp: November 24, 2022, 02:46:18 pm
content: And if your going for totally accuracy don't forget to load the meter down so its the correct input impedance for your audio output interfaceQuoteVRMS= Vpk x 0.7071Vpk = VRMSx1.414

author: ledtester
author_rank: Super Contributor
timestamp: November 24, 2022, 03:07:09 pm
content: Quote from: Voltzs on November 24, 2022, 01:49:35 pmRMS * sqrt(2) = peak voltage

author: Voltzs
author_rank: Contributor
timestamp: November 24, 2022, 03:23:33 pm
content: Quote from: themadhippy on November 24, 2022, 02:46:18 pmThanks for your reply - how do I load the meter down to match the impedance to my audio output interface? I guess there is an option on the Aneng 8008 for this?I attached a screen shot of my interface's specs - though the monitor outs (which is what I am testing) may differ from the line outputs.

author: bdunham7
author_rank: Super Contributor
timestamp: November 24, 2022, 03:26:07 pm
content: Quote from: Voltzs on November 24, 2022, 01:49:35 pmWhy do you need peak voltage? 4dBu is 1.228Vrmsacross 600 ohms.

author: wasedadoc
author_rank: Super Contributor
timestamp: November 24, 2022, 04:00:56 pm
content: Quote from: Voltzs on November 24, 2022, 03:23:33 pmNo, there is no such option on any general purpose multimeter. Such a multimeter is usually desired to place only the lightest load on whatever voltage source it is measuring. Typically the multimeter puts a 10 MOhm (=10,000,000 Ohm) load. The Aneng 8008 is no exception. You need to provide your own 600 Ohm resistor.If you get an "audio millivoltmeter" it will likely have an option to switch in a 600 Ohm termination. But expect to pay many times the price of the Aneng.

author: TimFox
author_rank: Super Contributor
timestamp: November 24, 2022, 05:39:15 pm
content: "dBu" is actually a voltage measurement, and does not imply the impedance at the node being measured."dB" is technically a power ratio, but can be used to express a voltage ratio (with the silent assumption that the impedances at each voltage measurement are equal).A suffix after "dB" (e.g., dBm, dBu, dBV) indicates the denominator of the ratio (mW, etc.).0 dBu is the voltage equal to the voltage that produces 1 mW (0 dBm) in a 600 ohm load, but may well be measured into an undefined high impedance.In practice, if the load impedance seen by your source in use is not a very high resistance, you should add a suitable resistor and measure the voltage across it for an accurate value.If your source has an output impedance of, say, 600 ohms and your normal load is 10,000 ohms (a "bridging" value), the difference between 10 k and infinite load is 0.5 dB.

author: ledtester
author_rank: Super Contributor
timestamp: November 24, 2022, 10:13:57 pm
content: Here is a dBu / dBV / V / Vpp converter:https://reference-audio-analyzer.pro/en/v-dbv-dbu.php#gsc.tab=0

author: DavidAlfa
author_rank: Super Contributor
timestamp: November 24, 2022, 10:34:26 pm
content: You need to connect a 600ohm resistor to the multimeter tips.Or measure with a receiver connected, starting at min. level and rising the level slowly to avoid overloading the input.

author: David Hess
author_rank: Super Contributor
timestamp: November 25, 2022, 05:34:17 am
content: Some modern multimeters, and many older ones, have the frequency response and even readout in dBu or dBm to support audio applications.

author: wasedadoc
author_rank: Super Contributor
timestamp: November 25, 2022, 09:49:40 am
content: Quote from: David Hess on November 25, 2022, 05:34:17 amAny sub US$50 examples?

author: Kleinstein
author_rank: Super Contributor
timestamp: November 25, 2022, 09:59:14 am
content: Moden audio gear does not use impedance matching. So the output are low output resistance, like 10-100 ohm, audio input are more like 10-100 kOhm input impedance.The 600 Ohm are mainly used to convert the power scale to a voltage scale. AFAIK the u in dBu is there to show it is about measuring the voltage and not actual power.Some audio range gear still sometimes has 600 Ohm impedance, but this is more like a problem.Many of the new DMM chip sets include RMS reading, not by an analog RMS -> DC converter, but by using a moderately fast SD ADC and than do digital RMS calculation. These DMMs (e.g. likely the mentioned Aneng 8008) are not that bad for AC readings, but a bit different from the old style analog RMS converters with difference weak points:The digital ones are usually relatively limited bandwidth (e.g. 1-5 kHz) with a usually relatively sharp drop and the maximum crest factor near full scale may be limited.The analog ones are somewhat sluggish to react, have problems with small signals (e.g. < 1-5% of FS) and often a bandwidth that depends on the amplitude. The response at low frequencies (e.g. < 30 Hz) is often not good (no longer true RMS) - they have to compromise with response speed.So it depends which version is preferred. Just because it is cheap the build in RMS option is not bad - in some aspects it even beats much more expensive old style meters with analog RMS converters.

author: RJSV
author_rank: Super Contributor
timestamp: November 25, 2022, 10:12:28 am
content: There needs to be A WORD for this...STAMPEDE !!!Dear lord God...And sorry to you, after posting a decent question, for enduring this mess of unhinged responses...1.) First of all, looking at picture, I see a stereo jack, with the voltmeter across,...Left channel hot, measuring whatever voltage is, related to...right channel, HOTThat's going to beNot even sure, as that relates to what program you've got playing (music), or likely it's 2 separate sine waves, left and right channel. But you probably need to measure one channel, relative to the that stereo jack ground...that would be one or the other if the two 'tip' signals, on the stereo jack.Now, please note; my response isn't gonna go off into the weeds, with A CIRCUIT YOU NEED TO BUILD FIRST.Yeah, sure, folks, that's like telling (this poor OP);Before you type in your response ...you NEED to build a...A Table, for your laptop, (get some wood...).OK 2.) My Velleman DVM890F has 2VAC range, but likely not accurate for audio at 1 khz, as some responses have indicated here. Between the Spec. and, assuming proper connected probe(s), there might be an acceptable de-rating, like "reading at 1 khz is low and multiply by 1.5 or whatever".3.). After all this 'stampede' of things that OP needs to build, or 'resolve'...by the time it gets to "YOU NEED 600 ohms, in series...NO, YOU NEED one 600 ohms on EACH probe tip...so that's 2 resistors, (and it's virtually an infinite impedance meter. OK, 1 million ohms, whatever. By this time, though, I'm done...even if the 600 ohm thing is valid.Folks responding: I am very disappointed, as this poor fellow / gal is getting a stampede of stupid, instead of help. Is it too much EGGNOG, out there tonight ?Hopefully, my sarcasm doesn't scare off a beginner with good questions, it's these 'responses' that are a ludicrous STAMPEDE.Maybe, it would help to ask some folks at recording studio: "What meter is good for reading db levels, at standard 1 khz, along with maybe a corrective factor for frequency response, at 1 khz ?".SOME replies here have that, if you can sort out this mess.

author: RJSV
author_rank: Super Contributor
timestamp: November 25, 2022, 10:17:36 am
content: ...oh and I believe there might also be some confusion about 'line' or 'speaker' outputs from or to your 'monitor'. A speaker output probably reads lowish voltage, vs line out, when measuring open circuit.

author: The Soulman
author_rank: Super Contributor
timestamp: November 25, 2022, 10:33:34 am
content: RJ,I haven't replied to this thread because op's question isn't clear to me and the thread gained enough attention already.But as a response to your post:1) that's likely a balanced signal on that jack.3) 600 Ohms resistor could be parallel to simulate the minimum load impedance, as the output impedance is not zero this will have some effect.edit: it all depends on the entire setup/signal chain, in the good old (analog) days a 1KHz sine wave signal and a calibrated meter was used to line all different stages up.Everything recording/playback device (where absolute values matter) is digital these days, if you want fancy:https://www.orban.com/freeorbanloudnessmeterPersonally I'd use what is in on my digital consoles together with a blackmagic smartscope duo 4k to show signal levels and x-y plot.

author: Voltzs
author_rank: Contributor
timestamp: November 25, 2022, 11:00:14 am
content: Quote from: The Soulman on November 25, 2022, 10:33:34 amHi there Soulman, I thought my question was worded clearly - and in your above reply you actually touched on a key part of what I have been trying to establish: matching the inputs and outputs of analog gear that is connected!Most professional audio companies will include what calibration signal was used to establish 0VU (+4dBu) at the product's analog outputs, most typically either -20 or -18 dBFS will equal 0VU.Let's say I do not know if my interface's outputs where calibrated for 0VU to mean -20 or -18 dBFS - what happens down the line when I calibrate my speakers to a specific dBSPL is I do not know if this dBSPL refers to one particular level or another.Besides speaker calibration, there are countless other reasons to want to level match gear which, assuming from your reply, you understand.This brings me to my search for a multimeter capable of reading the voltage level at my interface's outputs when playing either a -20 or -18 dBFS 1kHz signal.

author: David Hess
author_rank: Super Contributor
timestamp: November 25, 2022, 04:53:35 pm
content: Quote from: wasedadoc on November 25, 2022, 09:49:40 amI did a search and the lowest cost option I found was the UNI-T UT61E which has a bandwidth of 10kHz and costs$72 on Amazon. It does not read out in dB but that is not really necessary. I assume that you want a new meter and not an older used one.

author: BeBuLamar
author_rank: Super Contributor
timestamp: November 25, 2022, 07:02:26 pm
content: dBu doesn't need the 600 ohms resistor. Only dBm needs it because it's specified in term of power. dBu is in term of voltage only. And yes it's RMS voltage not peak.

author: radiolistener
author_rank: Super Contributor
timestamp: November 25, 2022, 09:34:47 pm
content: you're needs to add proper termination load on your source before measurement.Usually audio equipment uses 600 Ω impedeance, but you're needs to check it for your audio equipment.This is needed because unloaded source will have about twice higher Voltage.When you place proper termination load, you're needs to switch your DMM to measure AC RMS Voltage.Just FYI, on your screenshot DMM is switched to measure diode drop down, this is the reason why you see random value.+4 dBu = 1.228 VrmsQuote from: BeBuLamar on November 25, 2022, 07:02:26 pmBut since any signal transmitter has some internal impedance, it's Voltage output depends on receiver equipment impedance. This is because transmitter and receiver impedance is a kind of Voltage divider. If you try to measure unloaded source, you can get up to 2 times higher Voltage. So, if you want to measure real Voltage, proper termination load is required.In some cases receiver equipment can use Hi-Z input, in such case termination load is not required for Voltage measurement. But if receiver has 600 Ω input and measurement is performed with disconnected receiver, then you're needs to put 600 Ω termination load on transmitter for proper Voltage measurement.

author: BeBuLamar
author_rank: Super Contributor
timestamp: November 26, 2022, 12:43:02 pm
content: I feel 1.28V at -20dB is too high because at 0dB it's 12.8V.

author: donlisms
author_rank: Frequent Contributor
timestamp: November 26, 2022, 08:18:20 pm
content: Wow.The goal you have expressed is called "gain structure." The idea is that within in an audio system (used for making live or recorded sound), there are many places along the way to adjust the signal level, and having it high "here" and low "there" will produce the same output level as having it low "here" and "high" there, so... which one is right?The answer is "it depends," but generally speaking, the goal is to get the input signal into a range that's good for processing and mixing, and keep that approximate signal level all the way through the processing, and then get it into a proper range for listening. Listening is usually either headphones or a power amplifier feeding a speaker, sometimes with the power amplifier inside the speaker's box so you don't have to think about it very much.Measuring the output level from one of your boxes should be a simple matter of using an AC voltmeter that can measure the appropriate range, which is typically (but not always) 2 volts down to a small number of millivolts.Do not worry about 600 ohms; that came from a book, based on how audio was done a long time ago -- not how it's done today. Measure the voltage with your meter, and that is that. If you really need to know input and output impedances, first assume 100 ohms for an output impedance, and then assume 1000 ohms for a balanced mike input, and 10k ohms for a line input. But to make use of those, now you have to learn about voltage dividers, and I don't think you're ready for that yet. The bottom line here is that the output level will depend, to a small degree, on what you plug it into. And my best advice is "ignore that." Measure the voltage with the output unloaded, and assume that if the level drops, you will turn a knob or slide a fader to make it go up again.So, yes, you want a meter that measure AC voltage below 2 volts, and hopefully, ideally, to 20kHz (or beyond). While you can get by with this one particular task if it's limited to 1kHz, it will not be as good in the long run. This has mostly to do with the fact that any audio signal other than a sine wave is going to have harmonics at 2kHz, 3kHz, 4kHz, and so on, all the way up, and the things that make the sound "what it is" are going to be above 1kHz. If the meter cannot see them, any interesting signal (something beside a flute or a super-clean synth patch) will not be accurately represented. For you, that low-level AC spec, with the voltage and frequency, is obviously the most important, but understanding the rest will help you. (For example, understanding current might help you understand why you can't just keep adding more and more (unpowered) speakers to the same amplifier channel; why the amplifier maker says you can use it down to 4 ohms, or 2 ohms if it's a really good one.)A balanced signal, which is what I think you're dealing with, has a positive version and a negative version. On an XLR connector, these appear on pins 2 and 3; on a tip-ring-sleeve connector, they appear on the tip and the ring. The signal level is the difference between those two points; that's what you want to measure. Pin 1, or the sleeve, is ground, and it is not relevant to a balanced audio signal. It's used for the shield, to help reduce noise.I'm not sure why you introduced the word "peak." There are two distinctly different kinds of "peak" in audio. One of them is shared with electronics in general, i.e., that the peak level is sqrt(2) times the RMS level. This kind of peak is extremely rare, one might even say "never!", to use such a level in audio. It's always an RMS level, but... that level is changing all the time, because that what sound does: it gets louder and softer. So that's the other kind of "peak": when it's loud loud loud.(There is a third kind of "peak", used by companies that make cheap amplifiers and try to convince you they are powerful enough to blow up a house... When they say "1000 watts peak power", they are saying "we are lying to you to get you to buy this thing.")In other words, the idea of "peak" depends on the context. If we were sitting together, I would ask you where that word came from; what did you see that made you start thinking about it?As to the specific meter, I think the most helpful thing for you would be to learn to read the specs. Look at each one, and try to learn what you need to learn to understand what they are saying. First would be the ranges; look at the voltage ranges for both DC (which might be interesting, but not for your current problem), and for AC (which is very important). So for AC, you might see "200mV", which is millivolts, the three digits after the decimal point. Let nothing go unlearned! Look for an answer for every specification, every measurement. This sort of thing will serve you in the future as well.As to your overall project, I think it's an interesting one and will give you lots of things to learn. But at the same time, levels in audio are pretty much always subjective, especially because music and voice (and other) levels are changing all the time. It's not "one level", it's an approximate "range of levels." So getting it close is the best you can do. You want it in a reasonable range so that your equipment can work properly, so you're not overloading the inputs (too high!) and you're not getting too much noise mixed in (too low!). Then, you just see how you like it, and push it up or down as appropriate.And it's always a matter of thinking about how to deal with it. Suppose, for example, I'm mixing a recording of a band, and sometimes I listen to it on "these" speakers, which take 0dBu for full volume, and sometimes "those" speakers, which take -20dBu for full volume. When I switch the speakers, I set the master (output) volume of the mixer higher or lower by 20dB, and everything is fine. More likely what I would do is just slide the slider until it sounds like the level I want. Generally speaking, that is NOT going to be the maximum volume the speakers are capable of producing, because my music has interesting peaks (there's that word! This is the "loud loud loud" version) of at least 10dB over the normal, average level. So now I need to make sure the average level is at least 10dB lower than the peaks, in order to keep the peaks from exceeding the speaker's maximum. And that will still sound nice and loud, because acoustic levels don't usually have to be anywhere near as extreme as most marketing departments would like you to believe.About your audio interface, I would bet that it's pretty darn close to what they say it is. I have never measured any of mine; they just work. And they work fine. "More is more," and you turn the knob up, "less is less" and you turn the knob down. Much more interesting is how much hissy noise comes out when you turn the knob up.If you're not doing music or other "real" sounds, and instead you're actually doing something technical, then you've got a whole lot of considerations to think and learn about! Much of the discussion changes.

author: EPAIII
author_rank: Super Contributor
timestamp: November 28, 2022, 11:45:44 am
content: Audiophiles are a real big PITA! They don't know what they are doing and they never let that stop them.There are two ways of setting up an audio system. The first is for a professional system where audio must constantly be sent in different directions for different purposes. It can go to from item A to item B for one reason and then from item A to item C a few minutes later. In such a system ALL the equipment should be capable of sending and receiving a common audio level so that you are not constantly adjusting the levels as the work day progresses. This is where the system designer must establish a single level and implement it across the entire system. That single levelis going to be a compromisebecause there is always going to be some items of equipment that are different. Pads and amplifiers can help a lot. Professional equipment, like mixers, will have ways to cut down or boost up each of the inputs. And in equipment with multiple outputs, each one is often individually adjustable.A second type of system is mostly connected ONE way and left that way: no switching, no patching. In such a system the best level for connecting A to B can be determined by not only the standard levels that each of those items work with, but also by looking at the NOISE FLOOR and PEAK WHERE DISTORTION WILL OCCUR. The difference between those two levels is your operating range and, depending on the type of audio you are processing, an operating point (zero level) somewhere between them can be established. You want head room for the peak levels while not hearing the noise which should be at least 40 db down from the chosen operating point. Those operating levels may and probably WILL be different for every combination of two pieces of equipment. That is how such a system is optimized. And all this discussion about what meter to use and "true RMS", and other nit-picking specs is just a lot of hot air. Get a working, USED,NAME BRAND, ANALOG meter with a 0 to 1 Volt AC scale and take all your measurements with the circuits connected as they will be while operating: A output to B input. Forget the termination resistors too: they are for the other type of system I described above. Most such meters will respond well to a 400 or 1000 Hz test signal and give you a good indication of actual audio's relative levels. That is how such a system will operate (with permanent connections) and that is the only way that signal measurements in it make any sense. And the very last thing you need to spend money on is "true RMS".As to how to determine the noise floor and distortion limit, the human ear is a great test instrument. Well, if it has not been exposed to too much extremely loud audio. And if your ears have been damaged by loud sounds, well you probably don't care anyway. So save your money for better beer or wine to sip while listening. Boosting the level further down the line, at the speakers, will help to hear the noise when no audio is present.PS: Some NAME BRAND, analog meters include Simpson, Triplett, Hickok, Honeywell, RCA, Sencore, Siemons, Western Electric, and Weston. There are probably more but avoid anything made in the orient.

author: Brianf
author_rank: Regular Contributor
timestamp: November 29, 2022, 09:42:13 am
content: Quote from: BeBuLamar on November 25, 2022, 07:02:26 pm^^^ That.Audio equipment, except in a very few niche applications, hasn't needed 600R terminations since the last century. And even then it was only for a few special applications. Anything built in the last 40 years has been low impedance out, high impedance in, which renders the whole concept of termination meaningless.Termination was all about the transfer of maximum POWER, today we are interested in the transfer of maximum VOLTAGE.

author: Voltzs
author_rank: Contributor
timestamp: November 29, 2022, 11:34:13 am
content: Quote from: donlisms on November 26, 2022, 08:18:20 pmThanks for your brilliant reply - so informative and helpful! These days a musician/music producer has to have a solid understanding of their recording equipment if they want to get the best results. I will never be an electrical engineer and I am ok with that -- but I have been a student of audio engineering since buying my first microphone 20 years ago and while I am always learning something new, I want to also understand what some of these more technical terms actually mean in the real world - like input sensitivity, or dBu, etc and so on. I got the Aneng 8008 today and plan on testing my Interface's Outputs a bit later and will reply with my results!

author: Voltzs
author_rank: Contributor
timestamp: November 30, 2022, 04:37:18 pm
content: Hi all! so I just did my first tests with the Aneng 8008 and with a 1kHz sine wave played at -20dBFS my interface's outputs read: 0.754I know that 1dBu = 0.775 voltsNow I want to convert the 0.754 RMS signal to Peak.I am absolutely terrible at math (at least I never paid attention in class) - so with a calculator how would I convert this? Someone did already post an equation but I do not know how to input that into a calculator?And one other small side note - the Aneng 8008 has a +/- 1-3% accuracy.I thank you for your patience!

author: bdunham7
author_rank: Super Contributor
timestamp: November 30, 2022, 04:40:24 pm
content: Quote from: Voltzs on November 30, 2022, 04:37:18 pmPress the following keys on your calculator:0.754 x 1.414 =Butwhydo you want the peak value? I don't think it has any meaning in your context.

author: David Hess
author_rank: Super Contributor
timestamp: November 30, 2022, 04:54:57 pm
content: Quote from: bdunham7 on November 30, 2022, 04:40:24 pmThe peak value is needed to prevent clipping.

author: wasedadoc
author_rank: Super Contributor
timestamp: November 30, 2022, 05:09:52 pm
content: Quote from: David Hess on November 30, 2022, 04:54:57 pmBut as already explained in an earlier post in this topic, "peak" in the context of audio level frequently does not mean 1.414 times RMS. For example when recording on an audio cassette deck, one would be adjusting the input level control to have the VU meters peak at, say, 0dB. Yes, to avoid distortion but the VU meters already took the RMS versus maximum voltage excursion into account.

author: David Hess
author_rank: Super Contributor
timestamp: November 30, 2022, 06:05:51 pm
content: Quote from: wasedadoc on November 30, 2022, 05:09:52 pmI agree, but if testing with sine waves, it is still useful to know the peak value after making an RMS measurement.

author: Voltzs
author_rank: Contributor
timestamp: November 30, 2022, 06:26:00 pm
content: Many thanks for the replies!As my initial goal was to establish what dBFS value in my DAW produced +4dBu at my interface's Outputs, I measured 1.915 VRMS with a -20dBFS 1kHz sine wave.I know that my meter has, according to its manual, a+/- 1.0%+3- so I am wondering if this is why my meter does not read 1.228 VRMS?As I have no previous experience with these measurements, is a reading of 1.915 VRMS (when the signal is technically 1.228 VRMS) close enough to be considered accurate - again, taking into account the meters +/- discrepancy?

author: bdunham7
author_rank: Super Contributor
timestamp: November 30, 2022, 06:46:49 pm
content: Quote from: Voltzs on November 30, 2022, 06:26:00 pmNo, your specification means that the reading should be off by no more that 1% of the reading (0.019V) plus 3 counts of your meter, which should mean 0.003V if it is in the 10.000V range. So +/- 0.022V would be the maximum expected error. So something is way off.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 30, 2022, 06:49:28 pm
content: 1.23 V and 1.92 V are quite different - more than 30% or some 3 dB off. So the meter should not be that inaccurate. A common problem is that frequency generators usually specify there output amplitude when loaded (e.g. 50 Ohm or sometimes 600 ohm). There could also be some confusion the full scale range, this may be in volts peak and not RMS.

author: Voltzs
author_rank: Contributor
timestamp: November 30, 2022, 07:29:18 pm
content: Hi Klenstein - thanks for your reply - I think the confusion might be because of how I read my multimeter:There are 3 'range' options when reading a signal:When I used the first range option the meter read 1.915 - the 2nd range option read 0.1.19 - and the 3rd read 001.9I think the accurate reading is 0.1.19 VRMS, right? I am not skilled with these types of things - learning by doing. Haha0.1.19 VRMS would of course be much closer to 1.23 VRMS which is equivalent to +4dBu.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 30, 2022, 08:05:50 pm
content: One may have to check if the meter reads the AC part only or also reacts to an DC offset. Some meter react also to DC, especially in the mV range. The higher voltage ranges could be different.

author: bdunham7
author_rank: Super Contributor
timestamp: November 30, 2022, 08:40:34 pm
content: Quote from: Voltzs on November 30, 2022, 07:29:18 pmI can't see what I need to in your picture, but I'm afraid the most likely reason for your results is that your new meter is either a complete POS or is somehow unsuited for this job. There shouldn't be a DC offset on an audio output--something is broken if there is--but the symbols on the Aneng 8008 may indicate that it does not have AC coupling at all. Does anyone have one that can check for the OP? In any case, one way to quickly test a meter is to compare its ranges against each other. Reading 1.915 V on the 10.000V range and then 1.19 on the 100V range is not good. I don't know what is going on there.

author: Voltzs
author_rank: Contributor
timestamp: November 30, 2022, 09:03:14 pm
content: With regards to the 'Range' function, the manual says:'RANGE: press this button to enter the manual range; each push increases the range; when the highest range is reached, next push will go back to the lowest range.On the middle range setting I had the reading of 0.1.19 VRMSAs far as the display goes - all that is seen on the lefthand side is 'AC' because that is what I set the meter to.Considering I am trying to establish if -20dBFS = +4dBu at my Interfaces's Outputs, couldn't one 'reasonably' assume that -20dBFS giving a reading of 0.1.19 VRMS is close enough to 1.23 to say, 'yeah, -20 dBFS = +4dBu?Thanks for your patience!

author: bdunham7
author_rank: Super Contributor
timestamp: November 30, 2022, 09:39:43 pm
content: Quote from: Voltzs on November 30, 2022, 09:03:14 pmAccording to what I can find (excerpt attached) your VAC function has three ranges, apparently only indicated by the decimal point. You are listing two decimal points in 0.1.19, so that isn't helpful and shouldn't be what you are seeing--is it? Anyhow, the meter has 10,000 'counts', from 0 to 9999. The ranges are 9.999V, 99.99V and 750.0 (limited by things other than the ADC). You typically want to take your measurement with the lowest range possible for best accuracy, so in this case it would be the lowest of the VAC ranges--9.999V. However, this reading should be pretty consistent with higher ranges, so if you have 1.915V on the 9.999V range, you really ought to have 01.9x in the 99.99V range, the 'x' being the only digit that would vary much. If you don't something is wrong.b/t/w--does it really not suppress the leading zero? Can you post good photos taking those two measurements?

author: BeBuLamar
author_rank: Super Contributor
timestamp: November 30, 2022, 09:43:12 pm
content: Quote from: Voltzs on November 30, 2022, 04:37:18 pm0.775 Volts is 0dBu not 1dBu.

author: Brianf
author_rank: Regular Contributor
timestamp: December 01, 2022, 07:16:56 am
content: Quote from: Voltzs on November 30, 2022, 06:26:00 pm-20dBFS giving a reading of 1.915 FOR YOUR EQUIPMENT is correct. A different piece of equipment might generate 0.775VRMS, another might generate 100VRMS. It depends on the equipment.dBFS is simply a measure of how far away from digital clipping you are.It has no equivalent voltage level.If you really want your setup, when outputting at -20dBFS, to make an analogue signal of +4dBu then you will need to attenuate the 1.915VRMS down to 1.228VRMS.

author: wasedadoc
author_rank: Super Contributor
timestamp: December 01, 2022, 09:57:43 am
content: You will get best accuracy from the meter by letting it autorange. And I doubt it ever shows 2 decimal points on any range in any mode.

author: Voltzs
author_rank: Contributor
timestamp: December 01, 2022, 10:12:10 am
content: Thanks for your reply.I hope the attached image is more clear for you. When I power the multimeter on I switch it to V, then press the orange select button to toggle into AC mode, and the first reading can be seen on the image to the L - the Middle image is the second 'range' option, and the third is the one that shows 00.13 (although to be specific, the '3' is not solid, it toggles constantly between 1,2&3.I hope this sheds light on the Multimeters behavior.As mentioned already, can one take a 01.19 VRMS reading and deduce it is a measurement of 1.23 VRMS being that it is so close and taking into account the cable used or the meter not being 100% accurate? Because I do not need 100% accurate - I just wanted to establish whether a -20dBFS 1kHz sine wave is equal to +4dBu.As an experiment I changed the -20dBFS to -19.77 dBFS and got a 1.277 VMRS reading.

author: Brianf
author_rank: Regular Contributor
timestamp: December 01, 2022, 10:21:14 am
content: Quote from: Voltzs on December 01, 2022, 10:12:10 amWhy do you think that it ought to be?

author: Voltzs
author_rank: Contributor
timestamp: December 01, 2022, 10:29:59 am
content: Hi Brian - asking questions rather than answering them is really frustrating - have you read this thread from the very beginning? If you did then you would know I am gain staging my analog recording equipment and want to properly match all my output to input levels, in particular my monitoring setup. I will not repeat that all again. You are not helping me gain clarity here.

author: JohanH
author_rank: Frequent Contributor
timestamp: December 01, 2022, 11:25:50 am
content: I think there is some confusion here (or you aren't reading the meter correctly). When and where did you get the 1.915 V reading? The three pictures shown:1.195 V01.19 V001.3 VThese readings are the same, they just vary in resolution of the meter. The first reading is correct and most accurate. Use the Auto setting.1.195 V could be rounded to 1.20 V (with two digits) and that's not far from your expected 1.23 V.

author: Brianf
author_rank: Regular Contributor
timestamp: December 01, 2022, 11:32:37 am
content: Quote from: Voltzs on December 01, 2022, 10:29:59 amYes I have, and I have many many years experience in professional audio engineering BUT I still see nowhere above that explains why you believe that a signal originated at -20dBFS will give you an analogue signal of +4dBu for your interface.If you read my reply here...https://www.eevblog.com/forum/beginners/measuring-audio-interface-outputs-with-multimeter-need-some-guidance/msg4555184/#msg4555184...you will see that I point out that there is no correlation between dBFS and dBu and that it depends on the equipment under test.All you can do is generate a signal at -20dBFS and measure the analogue signal generated. The voltage generated is the correct answer. If that happens to be +4dBu then happy days. If it isn't, and if it is important that it is, then you will need to either attenuate it or amplify it before passing it down the chain.

author: BeBuLamar
author_rank: Super Contributor
timestamp: December 01, 2022, 12:45:32 pm
content: I think you expect too much. 1.19V with 3% accuracy can be 1.23V. Also the audio interface if it actually put out 1.19V is close enough.

author: wasedadoc
author_rank: Super Contributor
timestamp: December 01, 2022, 01:02:23 pm
content: The spec for the Aneng 8008 on AC voltage is +/-(1.0%+3) 40Hz-1kHz. With an input between 1 volt and 10 volts RMS it will auto select the 9.999 Volt (ie 10) range. The % applies to the FSD. Full Scale Deflection is a hangover from analogue days and translates to the maximum of the selected range for a digital meter. The '3' is the error in the final digit. So the bound on the total error is 1% of 10 volts plus 0.003. That is 0.103. Means if the input is exactly 1.230 the meter could show any number between 1.127 and 1.333.In dB terms that uncertainty is less than 0.8dB.

author: radiolistener
author_rank: Super Contributor
timestamp: December 01, 2022, 02:44:47 pm
content: you're needs to measure Voltage when signal output is connected to your equipment audio input. Otherwise you're needs to measure it's impedance and use the same dummy load. Usually audio impedance is about 600 Ω, but not always. Some equipment may have different impedance.Note, that there is different Voltage when output is open and when output is connected to some audio input. And that Voltage drop depends on the load impedance.Regarding to your DMM, you can check it's RMS or Peak Voltage measurement with signal generator. Just setup some known Voltage on the signal generator and test your DMM. And again don't forgot to put proper termination load, because open output will have twice higher Voltage than output with proper load.

author: Brianf
author_rank: Regular Contributor
timestamp: December 01, 2022, 04:11:41 pm
content: Quote from: radiolistener on December 01, 2022, 02:44:47 pmNo, it's not and hasn't been since some time in the last century.Modern equipment (anything designed since the early '80s) is designed to have a low output impedance and a high input impedance. The screenshot the OP posted shows that their equipment has an output impedance of 56R and an input impedance of 11k2.

author: TimFox
author_rank: Super Contributor
timestamp: December 01, 2022, 04:40:56 pm
content: "Regarding to your DMM, you can check it's RMS or Peak Voltage measurement with signal generator. Just setup some known Voltage on the signal generator and test your DMM."I have not seen a modern AC voltmeter that measured peak voltage, or was not calibrated in V RMS.Some are "average responding" and the calibration converts the mean absolute value measured by the circuit to RMS voltage, assuming a sine wave.Others are "true RMS" and measure the RMS voltage directly, within limits for crest factor, etc.The old vacuum-tube analog voltmeters ("VTVM") often used a 6AL5 voltage doubler that actually measured peak-to-peak voltage.The moving-pointer meter would then have two scales: peak-to-peak voltage, and RMS voltage (where the calibration again assumed a sine wave).

author: BeBuLamar
author_rank: Super Contributor
timestamp: December 01, 2022, 05:11:38 pm
content: Quote from: TimFox on December 01, 2022, 04:40:56 pmWhile it can't measure the peak voltage of a 1000Hz sine wave something like the Fluke 289 can measure the peak voltage of a 60Hz AC voltage with decent accuracy.

author: bdunham7
author_rank: Super Contributor
timestamp: December 01, 2022, 06:19:12 pm
content: Quote from: Brianf on December 01, 2022, 11:32:37 amAnd I inferred that his particular setup is specified to produce the +4dBu signal from a -20dBFS test input, or in any case that is his goal. So he's calibrating his DAC/DAW/whatever to that level.

author: bdunham7
author_rank: Super Contributor
timestamp: December 01, 2022, 06:22:09 pm
content: Quote from: Voltzs on December 01, 2022, 10:12:10 amYes, that helps--typos can be a problem! Your readings are all OK and consistent enough to conclude that your setup meets your goal as accurately as you could hope for, better than 0.5dB.

author: radiolistener
author_rank: Super Contributor
timestamp: December 01, 2022, 07:09:27 pm
content: Quote from: TimFox on December 01, 2022, 04:40:56 pmSince generator produce clean sine, it doesn't matter which units it uses for Voltage tune. You can easy convert RMS to Peak or Peak to RMS, because you know that the waveform is clean sineFor RMS to Peak Voltage conversion just multiply RMS value by sqrt(2)For Peak to RMS Voltage conversion just divide Peak value by sqrt(2)

author: TimFox
author_rank: Super Contributor
timestamp: December 01, 2022, 07:12:01 pm
content: Yes.

author: Voltzs
author_rank: Contributor
timestamp: December 01, 2022, 09:35:10 pm
content: I want to thank you all for your input, patience and help. I know everyone was trying to assist - some with different perspectives.For me this is resolved - there was a slight discrepancy with the readings but I round that off to my TRS cable and the Multimeter itself.I was able to get the values I wanted, namely, spot on 1.228 and 0.775 - but rather than use -20dBFS I adjusted the sine wave level to -19.77 and the meter read 1.228 - and for 0.775 I again had to change -16dBFS to -15.8dBFS. Not optimal - but the world isn't perfect and the point of the tests was to establish whether my Outputs were calibrated to -20 or -18...and I can safely say they were calibrated for -20dBFS.