hybridfree/eevblog-posts huggingface dataset:
AMP connector from the eighties - Page 1
Forum section: electronics / beginners

author: fabiodl
author_rank: Frequent Contributor
timestamp: August 12, 2022, 11:41:33 am
content: I am searching for the name of this connector. Pitch is 2 mm. It was used by Nintendo in the eighties. It reports AMP, but the only 2mm pitch connector now available from TE AMP seems the CT series, which does not look like this. Does anyone know how this (probably discontinued) connector was called?

author: Terry Bites
author_rank: Super Contributor
timestamp: August 12, 2022, 02:02:25 pm
content: Start here...https://www.te.com/usa-en/plp/amp-connectors/Zn60Y30Dq.html?q=&n=753283&type=products&samples=N&inStoreWithoutPL=false&instock=N

author: tooki
author_rank: Super Contributor
timestamp: August 12, 2022, 06:08:26 pm
content: How is a basically unfiltered list of 500 random connectors helpful?!?

author: fabiodl
author_rank: Frequent Contributor
timestamp: August 14, 2022, 08:56:22 am
content: Quote from: Terry Bites on August 12, 2022, 02:02:25 pmIf you filter by pitch, being generous and choosing close values (1.9, 1.91, 2.2) there are exactly 0 connectors for 5 and 6 positions.I guess it is really a matter of finding out someone who was born and already into electronics in that time period, and happens to have used that connector / saw it in paper catalogues

author: Terry Bites
author_rank: Super Contributor
timestamp: August 15, 2022, 02:04:24 pm
content: Nothing random about it. Use the filters to narrow it down. It may or may not be in there bu tis a start. Go to all the main catalog vendors sites and drill down. Or email AMP?

author: tooki
author_rank: Super Contributor
timestamp: August 15, 2022, 05:22:36 pm
content: Quote from: Terry Bites on August 15, 2022, 02:04:24 pmHow is it NOT random? It’s a mix of all sorts of connectors. It doesn’t help the OPat all.Was it just intended as “look at the TE website”? Because that’s really all you managed to do, but the OP clearly had already done that.I’ll be the first to say that TE’s website is an abysmal parody of a real website, to the point of being essentially useless, so the OP’s efforts may have been for nought, but the same basically applies to your link.Anyhow, my point is this: the OP here clearlydoesknow how to search for connectors, so explaining “try searching the manufacturer and distributor websites” is just insulting them.
Amp Power supply Wiring  - Page 1
Forum section: electronics / beginners

author: Jbliss
author_rank: Regular Contributor
timestamp: July 07, 2015, 09:13:05 am
content: Hey GuysIm building a amplifier power supply kit and need some reasurence about the wiring. i have attached a picture of the transformer windings and a picture of the circuit diagram. could some please explain how i connect the transformer up to the rectifier power supply circuit. And explain how I can put the two 40v winding in series as i believe that is required

author: Jbliss
author_rank: Regular Contributor
timestamp: July 07, 2015, 09:17:02 am
content: Heres the Circut

author: Jbliss
author_rank: Regular Contributor
timestamp: July 07, 2015, 09:17:34 am
content: and transformer

author: Simon
author_rank: Unknown
timestamp: July 07, 2015, 09:27:57 am
content: Your two 40V secondaries go in series, you need a 0V and a 40V connected in the middle. To make sure you have them right and if they are not labelled then connect any two together, them measure the voltage on the other 2 if it's 0V they are wrong, if it's 80V they are right.WARNING 80VAC can kill you, do not touch the probes while measuring.

author: Jbliss
author_rank: Regular Contributor
timestamp: July 07, 2015, 09:34:40 am
content: can i use any of the 0 winding

author: dom0
author_rank: Super Contributor
timestamp: July 07, 2015, 09:35:25 am
content: Those are probably intended as pre-amplifier supplies.A 400 VA toroidal transformer will need some kind of inrush current limiting (e.g. NTC, resistors and timed relays, transformer switching relay). A bigger fuse won't help (much), since a 400 VA toroidal can already trigger your circuit breakers .

author: Simon
author_rank: Unknown
timestamp: July 07, 2015, 09:42:45 am
content: Quote from: Jbliss on July 07, 2015, 09:34:40 amWell any of the two that are the 40V ones, each secondary is a seperate coil with a wire each end

author: Jbliss
author_rank: Regular Contributor
timestamp: July 07, 2015, 09:49:16 am
content: there is o 0v for the 40v secondaries

author: Simon
author_rank: Unknown
timestamp: July 07, 2015, 09:55:05 am
content: You have 2 wires for 1 40V secondary and 2 for the other. Take one from one secondary and one from the other and see what happens, if you get 0V across the two in series then swap one of the secondary wires.

author: LukeW
author_rank: Frequent Contributor
timestamp: July 07, 2015, 09:31:42 pm
content: I'm surprised Silicon Chip is only using 63V caps on those 57V rails. That's not much margin on the capacitor voltage rating - only 10% more, and even less than that if the 240V grid voltage is running a bit high. If you can get caps with a bit of a higher voltage rating that fit the same space and aren't too expensive it would seem prudent to use them.

author: Simon
author_rank: Unknown
timestamp: July 08, 2015, 05:46:42 am
content: Quad amplifiers had this problem and all the smoothing caps failed like clockwork.

author: Jbliss
author_rank: Regular Contributor
timestamp: July 08, 2015, 02:18:00 pm
content: Thanks guys !
Amp protection circuit modification & output flyback diodes - Page 1
Forum section: electronics / beginners

author: ExtraThiccBoi
author_rank: Contributor
timestamp: May 11, 2019, 07:02:15 pm
content: Hi,i have rebuilt this sweet little amp and it sounds great, managed to fix all factory issues caused by bad construction and wiring. I am still a beginner and i learn as i go.I am looking for a modification to bring the amplifier up more slower than stock (8s). This is done by this circuit (schematic).The circuit senses the amplifier output through Q5 and Q6. Diodes D3 and D2 are connected to the AC lines (AC-GND-AC), creating a negative power supply i suppose.It can short the inputs to ground with JFETs Q401 and Q402. Next, it controls something in the power amp through Q417 (and equivalent in the other channel), i think disables the output section.The circuit brings the amplifier up slowly, unshorting the inputs and turning on the power section after the 8 or so seconds after the supply voltage is turned on. It also senses the power amp output,overcurrent and short circuit (load of 2 ohms or less i think) protects the output section. I have been trying to have a crack myself on this, first i thought C11 along R5 and R6 might be creating a time constant. Using rc calculators, 33uF with 222Kohm (680K and 330K in par.), it's around 8s. Then i realized this might not be true and it might have an effect on the protection times and values. What would be the correct component change to increase the time to approx. 10-13 seconds?My second idea is to add a flyback diodes in the output, like higher-priced amplifiers from HK (more or less the same thing with slightly different components) had. I would like to ask if it's necessary to have them and if they have any negative effect on sound quality. I know from relays that inductors like to push back current and i don't know if this happens with speakers or not, as they're highly reactive load.Thanks for any help or info!
amperage circuit breaker 110v 60Hz - Page 1
Forum section: electronics / beginners

author: AlexisSIG
author_rank: Newbie
timestamp: May 05, 2015, 10:41:05 am
content: Hey guys,I am a mechanical technician intern in a french society (I am French too). I must export an installation with UL standards in US but I know nothing in standards in this country. In france, we choose the circuit breaker with the diameter of the cable. Could someone tell me which one can I buy if the diameter is 2,5mm² ?Thanks.

author: Zero999
author_rank: Super Contributor
timestamp: May 05, 2015, 07:32:27 pm
content: Don't you mean you normally choose the breaker to match the cable's current rating?The cross-sectional area is only one property which determines the cable's current rating: the ambient temperature, maximum temperature rating of the insulation and whether it's in a bundle of other wires or wrapped in thermal insulation also play a part.The circuit breaker's trip current needs to be less than the current rating of the cable. There are also other things which need to be considered such as the temperature rating, surge capability and maximum prospective short circuit current, which needs to be below the breaking capacity. The impedance of the cable also needs to be low enough to ensure the circuit breaker reliably trips.
Amperage Control - Page 1
Forum section: electronics / beginners

author: PsychoMaster
author_rank: Regular Contributor
timestamp: January 25, 2015, 10:01:37 am
content: Hello AllJust starting out and making my own PSU I am now at the stage of amperage control and really don,t like the look of a LM317/338 and a resistor to control current. It,s down to the inflexibility of finding a suitable bank of resistors to change the current value. After seeing Dave's current load device I was thinking could the resistor be replaced with a mosfet as in Dave's circuit.Would this not handle the current and also the resistance values?I wanted to use analog devices to reduce noise in the output as I am not sure about switch mode signals.Cheers

author: Paul Price
author_rank: Super Contributor
timestamp: January 25, 2015, 10:40:32 am
content: Instead of trying to waste heat using a large-valued sense resistor, use a tiny resistor to sense current and amplify the result to feedback to the voltage control so that current can be limited by reducing the voltage to the set current you desire.Take a look at the schematic below. It uses easy to find, off-the-shelf components.

author: PsychoMaster
author_rank: Regular Contributor
timestamp: January 26, 2015, 11:37:12 am
content: Cheers mate I will have a go at this one ,I am now using six lm388 in parallel that I was going to drive with a op amp and I,ll adapt this into the circuit.I am only going for 5 amps so the six lm388s should have a easy time of it.
Ampere meter using Shunt register  - Page 1
Forum section: electronics / beginners

author: RoadRunner
author_rank: Frequent Contributor
timestamp: January 01, 2012, 01:44:43 pm
content: Hi guysi want to build a Ampere meter using a PIC mircocontroller ,with range from (1mA to 1A) i m using a shunt register in the series with the load.but my problem is where to get a very low value resistor for shunt,so i extracted the shunt register from a cheap multimeter, but the problem is i don't know the value of shunt register which i have extracted from the cheap Chinese multimeter.did any body know the value or how to measure thisi have one more questiondoes the current sensing amplifier have the a shunt register built in

author: Unknown
author_rank: Unknown
timestamp: January 01, 2012, 04:00:40 pm
content: Quote from: Gaurav on January 01, 2012, 01:44:43 pmYou want a low value shunt resistor for 1A, but a higher value for 1mA. Multimeters often switch between multiple shunts when you switch current ranges. Any large distributor should sell current sense resistors, Digikey returns almost 500 through-hole in stock resistors when searching for current sense resistor.Quote from: Gaurav on January 01, 2012, 01:44:43 pmJust run a known current (eg. 1A) through it and measure the voltage. You can measure the current with a DMM and measure the voltage with another meter, and calculate the resistance from Ohm's law. If it's a 10A shunt, the voltage drop for 1 mA may < 1 mV, and could be hard to measure.Quote from: Gaurav on January 01, 2012, 01:44:43 pmWhat does the datasheet for your current sense amplifier say? The typical applications schematic usually shows an external shunt that is required.
Amplifier - Page 1
Forum section: electronics / beginners

author: abdullahseba
author_rank: Frequent Contributor
timestamp: July 08, 2014, 12:00:23 pm
content: can you connect lots of speakers to one amplifier board such as this?http://www.dx.com/p/2-x-50w-dual-channel-stereo-d-t-class-hi-fi-amplifier-board-module-blue-216854?tc=GBP&gclid=CjwKEAjwre6dBRC94d-Gma7g3wcSJACNatZe_4tLc3TAkMa2Aeq3OywNhkg7J5ovHch1UUyCCslAGRoCDoTw_wcB#.U7vc6VLQfcsor do you need a multi output board

author: TNb
author_rank: Regular Contributor
timestamp: July 08, 2014, 12:17:37 pm
content: Of course you can, just connect the speakers(serial or parallel) and plug it in one channel of the board(and then do the same for second channel).The only problem is you need to choose appropriate speakers in order to have a good volume and not overload the amp(look for specks to calculate what speakers you need).And of course you will have just L and R channels of stereo with this board, if you want to do some kind of 5.1 sound with different sound going to different speaker you will need different board.

author: sacherjj
author_rank: Frequent Contributor
timestamp: July 08, 2014, 12:17:55 pm
content: The output is specified as 6-8 ohm. So any combinations of speakers whose impedance works out to 6-8 ohms will work. However, you will divide the power between the speakers used.For example, you could use 2 of the same 4 ohm speakers in series. But then each would be driven with half the power.

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 08, 2014, 12:18:07 pm
content: Sure you can connect any number of speakers.As long as you maintain the load impedance within the range that the amplifier can handle.And you understand how much sound to expect based on the output power available and the efficiency of your speakers.

author: abdullahseba
author_rank: Frequent Contributor
timestamp: July 08, 2014, 12:54:51 pm
content: Quote from: abdullahseba on July 08, 2014, 12:00:23 pmthank you

author: abdullahseba
author_rank: Frequent Contributor
timestamp: July 08, 2014, 12:55:19 pm
content: thank you
Amplifier   - Page 1
Forum section: electronics / beginners

author: abdullahseba
author_rank: Frequent Contributor
timestamp: July 20, 2014, 03:36:37 pm
content: can you use a 5w speaker on a 50w amplifier

author: SeanB
author_rank: Super Contributor
timestamp: July 20, 2014, 03:46:17 pm
content: Yes, providing you do not turn up the volume too high, which will result in sound followed by distortion followed by smoke from the speaker.

author: abdullahseba
author_rank: Frequent Contributor
timestamp: July 21, 2014, 10:17:48 am
content: Quote from: SeanB on July 20, 2014, 03:46:17 pmthank you
Amplifier bias question help - Page 1
Forum section: electronics / beginners

author: reddish75
author_rank: Regular Contributor
timestamp: November 07, 2017, 09:47:50 am
content: Hi,I've just replaced the output transistors and emitter resistor which was cracked on my Jungson amplifier and now the bias on the repaired channel is around 10mv compared to the 'good channel' which is ~90mv, it does have the same value (560r) resistors in both channels adjustable position.My question is how would I change fixed resistor R269 to an adjustment trimmer, would I just put the trimmer where the resistor was and connect the wiper to one of the legs?Many ThanksChris

author: w2aew
author_rank: Super Contributor
timestamp: November 07, 2017, 03:57:09 pm
content: Quote from: reddish75 on November 07, 2017, 09:47:50 amI wouldn't replace it with a trimmer because you'd never adjust it near 0 - much of the range of the trimmer won't be use which will make adjustment tricky. If you want to temporarily replace it with a trimmer to determine an appropriate value to get the bias you want, then that's OK. If you want the trimmer to be permanently installed, I'd put a trimmer in series with a fixed resistor. The best solution is to determine an appropriate value for R269 and install a fixed resistor.

author: Damianos
author_rank: Frequent Contributor
timestamp: November 07, 2017, 04:03:07 pm
content: I think that the bias is adjusted via the RW3. The R269 is to adjust the temperature coefficient of the Q89/D29 to match that of the other transistors.To be sure, it is better to wait also for the advise of someone else.
Amplifier circuit making clicking and screeching noises  - Page 1
Forum section: electronics / beginners

author: abdullahseba
author_rank: Frequent Contributor
timestamp: September 07, 2017, 10:03:32 pm
content: HiI made a complex multi amplifier circuit which had a very decent sound output when I first made it.A few weeks later (in which it was not used) I was installing it and all I got was clicking sounds and random loud screeching almost like an old analog radio that not tuned in properly.The speaker still produces sound and sometimes stops the screeching but the clicking is still there.Its not the usual 50Hz hum afaik but more spaced out probably about 250ms (I dont have oscilloscope to measure it) and the TDA7266D (U3) also makes a similer noise since it was made but much lower that I wasn't bothered about it.The main amplifier is the TPA3124D2 (U5 & U8).Dont think this has anything to do with it but when no speaker is connected you can hear the audio coming from the PCB, probably through the inductors .I thought that the TPA3124D2 may have got damaged by static so I replaced it with the the same result.The circuit is powered by a 12V and 24V switch mode supply.I made a sort of main unit that plugs in to the amplifier (see third schematic) which has the audio on it and uses the pcm2901 USB to audio chip.This works fine except that it generates the same clicking noise that the amp does and other low weird noises.Just to be clear all these amplifier problems occur with or without the unit plugged in, and with a mic or audio input.I'm wandering if I made the same mistake in both circuits even though the amplifier worked fine at first.And I dont think its the PSU's otherwise the amp would have done this from the start.Anyone have any idea?Is it something obvious?Thanks in advance.(Edit woops double upload, first two is the amp, last is the contoller)

author: Audioguru
author_rank: Super Contributor
timestamp: September 08, 2017, 02:59:54 am
content: Your schematics have very tiny symbols and text. The images are backwards negatives (yellow lines on a black background instead of normal black lines on a white background so I cannot see anything.

author: abdullahseba
author_rank: Frequent Contributor
timestamp: September 08, 2017, 11:23:37 am
content: Quote from: Audioguru on September 08, 2017, 02:59:54 amNot sure why, they high res but here ya go.

author: abdullahseba
author_rank: Frequent Contributor
timestamp: September 11, 2017, 11:17:50 pm
content: Hmm I figured it out - for anyone who might come across this thread...Looks like I had serious ground loop issues with the test wiring, and I might have to use 24v to 12v dc-dc converter instead of two supplies.http://www.rane.com/note151.html
amplifier circuit - Page 1
Forum section: electronics / beginners

author: yalect
author_rank: Regular Contributor
timestamp: October 29, 2015, 10:54:43 am
content: Hello,I would like to ask you, how can I calculate the input impedance of the simple following amplifier and its bandwidth?Thank you

author: tron9000
author_rank: Frequent Contributor
timestamp: October 29, 2015, 11:16:47 am
content: http://www.electronics-tutorials.ws/amplifier/input-impedance-of-an-amplifier.htmlThat is a Common Emitter AMp - I googled: input impedance of CE amp

author: tron9000
author_rank: Frequent Contributor
timestamp: October 29, 2015, 11:40:28 am
content: Quote from: blueskull on October 29, 2015, 11:26:42 amStand corrected, hmm, must have seen 100 and assumed 100K. Principle is still same for Rin.Quote+1. I would recommend SIMETRIX or LTSPICE

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 29, 2015, 04:27:23 pm
content: It'll do both collector and emitter output, having little gain through either (about -0.09 out the collector and 0.99 out the emitter). It's also "suicide biased" (hFE dependent).Tim

author: LvW
author_rank: Frequent Contributor
timestamp: October 29, 2015, 05:37:46 pm
content: Quote from: T3sl4co1l on October 29, 2015, 04:27:23 pmYes - it is a bad biasing scheme. Horowitz/Hill: Don`t use such a circuit.The reason is as follows: The BJT is a voltage controlled device (VBE controls Ic according to Shockley`s famous formula.).Now - the resistor RE introduces current-controlled voltage feedback, which only works if the base voltage is asstiffas possible.That means: This feedback scheme is used in conjunction with a suitable voltage divider at the base (instead of a simple resistor as shown).Nevertheless, one can compute the input resistance simply based on the feedback rules:The input resistance (without feedback) ishie=VT/IBwith VT:Temperature voltage, IB:DC base current.This resistance is increased due to feedback by the factor (1+RE*gm) with transconductancegm=hfe/hieTherefore:r,in=[hie*(1+RE*gm)]||RB = (hie+hfe*RE)||RB
Amplifier PCB design, remove ground loop keeping short bypass return current? - Page 1
Forum section: electronics / beginners

author: hitech95
author_rank: Regular Contributor
timestamp: December 19, 2020, 06:31:36 pm
content: Hi, I'm designing a simple stereo AMPlifier board based around the TAS5731M chip.I've started to design the PCB, I've mostly used as a reference the EVM board from TI.Unfotunatly due to space constaints I had to compact a section of the board.Doing so I have the following situation:As you can see the pink color section is an analog ground, that section should be connected to the main GND via a single 0 ohm resistor.As you can see the copper fill is creating a loop around the IC pin.The rounded silkscreen parts are caps, and the top most component of the stack is the bypass for the analog supply of that IC.The vias are not connected to anythig; they was there due to my original plan of having a small AGND plane on the bottom layer.How can I prevent such type of loops?The board isat least a 2 Layer4 layer due to impedance matching for the 50ohm single endfed I2S signals, Bottom and inner layer are a ground fill and big power poligons.On bottom layer there are some power traces.On the same board I also have a 24.576Mhz (MCLK) clock signal track coming from another board, it is the master clock for the MUX IC (PCM9211).Such track is quite long, it is about 10cm in my board but it is coming from another chip on the other board, that one is quite far.So I presume that the total length of such track is around 30cm.AFIK that signal is feeded into different chips. Is there a way to tap it without adding delay and destroying the signal?Have a nice day,Nicolas

author: hitech95
author_rank: Regular Contributor
timestamp: December 21, 2020, 12:28:43 pm
content: Small update, about the clock I will be going with a complete different solution, I will find a way to use a clock driver to provide clocks to all the ICs, and use buffers to split the i2s signals.AFIK I2S is a 50ohm single ended signal so it looks like that I have to impedance match thoose lines. Especially the 25MHZ for the MCLK.I'm wondering if I also have to length match them.

author: hitech95
author_rank: Regular Contributor
timestamp: December 23, 2020, 11:34:56 pm
content: No one?My idea was to add another ground plane adn add some more vias to prevent as possible ground loops making a more equal possible analog ground plain.Is this a good way?

author: Hugo Balls
author_rank: Newbie
timestamp: December 24, 2020, 04:50:22 am
content: I mean edit that polygon so it wouldn't go over those pins? That tiny loop shouldn't affect anything anywaysAlso i dont't think there is a need for such ground splitting especially considerign it's all digitalOne solid ground plane should be plenty

author: hitech95
author_rank: Regular Contributor
timestamp: December 24, 2020, 12:37:27 pm
content: Quote from: Hugo Balls on December 24, 2020, 04:50:22 amThe fact is that the poligon part above the pin provide a short path for the analog supply bypass cap.While the bottom part is there to provide a path for the filters.
Amplifier from headphones jack to line in ... - Page 1
Forum section: electronics / beginners

author: PinheadBE
author_rank: Regular Contributor
timestamp: February 05, 2019, 06:00:13 pm
content: Hi,Yes. No mistake in the subject line....I will use a low-cost low-quality android tablet with "Samba MP3 Network player" free app to stream music from my network into my Hi-Fi.The only output available on the tablet is a headphone jack.I connect it to a line-in of my amplifier, and.... even whith the tablet volume at max, the sound level is pretty low.So, clearly, I need a bit of amplification.I found two modules on AliExpress. Could they do the trick ?-https://www.aliexpress.com/item/Aiyima-MAX4410-Headphone-Amplifier-Board-Headset-Amplifier-Mini-Amp-For-Pre-amplifier-Single-Battery-Power/32856061211.html?spm=a2g0s.13010208.99999999.260.49283c00vMYtva(based on MAX4410)-https://www.aliexpress.com/item/1pcs-New-47-classic-headphone-amp-amplifier-DIY-kit-with-case/32566790934.html?spm=a2g0s.13010208.99999999.263.49283c00vMYtva(based on NE5532P)Should you have a (relatively) simple schematics, I am also able to build one myself, but my knowledge in analogic electronics is insufficient to design one by myself.Thanks

author: richard.cs
author_rank: Super Contributor
timestamp: February 05, 2019, 07:37:37 pm
content: Those you linked might work but are not really the right kind of thing. They are designed to take a line in signal and buffer it to drive low-impedance headphones. They don't necessarily increase the signal voltage, but they provide power gain by increasing the available current.What you need is voltage gain, you don't really need power gain at all. A simple op-amp circuit could do that with around 6 components for stereo, or you could use an audio transformer which has the advantage of not needing any external power.

author: ArthurDent
author_rank: Super Contributor
timestamp: February 05, 2019, 07:54:15 pm
content: Have you considered using a bluetooth stereo receiver? There are quite a few and here is a video describing one.

author: PinheadBE
author_rank: Regular Contributor
timestamp: February 06, 2019, 05:31:09 pm
content: This is pure GENIOUSI didn't even know it existed for home use (other than the usual BT speakers), and for a mere 20 EUR, my problem's solved !Thanks for the tip, Arthur !
Amplifier gain measured with nanoVNA: fundamental issue - Page 1
Forum section: electronics / beginners

author: kronos
author_rank: Contributor
timestamp: November 02, 2021, 06:48:11 pm
content: Hello,I have an RF amplifier, and want to measure its gain and plot it using a nanoVNA. But I am stuck with a problem I found.First step is to perform a calibration; when calibrating the through step, the connection looks like this (I am ignoring an attenuator at the amplifier input to avoid overload, for simplicity):The through-cable has 0 dB gain (or loss); the voltage at its input is Vi=Vs/2, that is, 6 dB lower than Vs: like a 6 dB loss. The nanoVNA measures the voltage at its input (S21) and calibrates knowing that the cable is 0 dB, so that although the total gain Vl/Vs is -6 dB, it shows 0 dB: it adds 6 dB to the measurement.So I now connect the amplifier. Assuming its input impedance Zin is 50 ohm, flat, the connection is now this:The amplifier has a flat gain of G db (G=Vl/Vi). Vi has a loss of 6 dB with respect to Vs, as before, so when the nanoVNA measures Vl/Vs it sees a total gain of G-6; it adds 6 dB, and shows a gain of G. All is OK.But now I connect an amplifier with a high input impedance; in the extreme case, Zin = \$\infty\$, so that Vi=Vs. There is now no loss w.r.t. Vs, the nanoVNA sees a signal that is 6 dB higher than the previous case, and it then shows a gain of G+6, which is wrong. This is actually what I see, the nanoVNA shows an excess gain of 6 dB (compared to the gain I measure with the scope).Does this mean that I can only measure amplifier gain when Zin=50 ohm? Or am I missing something?But even if that is the case, that input impedance is not flat, it decays with frequency, distorting the Bode plot. So I can never measure amplifier gain with the nanoVNA! is this correct? It cannot be!
Amplifier kit - Page 1
Forum section: electronics / beginners

author: Dms1967
author_rank: Newbie
timestamp: August 18, 2025, 12:32:11 am
content: Total noob here, and looking for some info on a pre assembled Canakit amplifier.On the board the locations where all external sources are to be soldered in have pins with black gaskets around them. Should the pins be removed with wires soldered directly to the hole in the board or should wire be soldered to the pre existing pin? I’ve attached a photo showing what I’m talking about.

author: TimFox
author_rank: Super Contributor
timestamp: August 18, 2025, 12:51:58 am
content: Such black plastic pieces are typical for multiple pins, on 0.1 inch centers, in either one or two rows, that can be broken into single pins. Female sockets are made to mate with those pins, but they can be soldered. No need to remove the plastic bits.

author: themadhippy
author_rank: Super Contributor
timestamp: August 18, 2025, 12:58:26 am
content: looking at the layout the inputs are in front of the pot,thats gonna be fun if you decide to put it in a case

author: Dms1967
author_rank: Newbie
timestamp: August 18, 2025, 01:19:31 am
content: Thanks!

author: Analog Kid
author_rank: Super Contributor
timestamp: August 18, 2025, 01:22:05 am
content: Since those things with the black plastic bases are standard header pins, you could use mating header sockets if you want the connections to be detachable.Otherwise just solder wires to them. I do that all the time.
Amplifier low gain - Page 1
Forum section: electronics / beginners

author: jheatac
author_rank: Regular Contributor
timestamp: September 28, 2024, 12:57:09 pm
content: I have an car audio amplifier that has low gain.At about 1v 1khz in, max output is 4v at 2/3 gain. Any higher doesn't clip but looks like a phase shift on the scope. Amplitude and frequency don't change but it looks like a double trace.Rail voltage is + and - 53vIf I run the input up to 2v, output won't go any higher than 4vCan anyone give me a direction?

author: CaptDon
author_rank: Super Contributor
timestamp: September 28, 2024, 01:15:53 pm
content: What is the load on the amp? Be careful because more than likely the amplifier is a full H bridge amplifier and you must not ground the outputs!! In other words the speaker is floating and not ground or chassis referenced. It sounds like the amplifier is blown up with the output devices ruined. You are still seeing a bit of the drive voltage or current leaking through. Did you blow it up or was it given to you in AS-IS previously blown up condition? Your test setup may be placing an unintended ground on one side of the output and the amp is folding back for self protection.

author: jheatac
author_rank: Regular Contributor
timestamp: September 28, 2024, 10:02:53 pm
content: Thank you for taking the time to respond. I know no history. In trying to learn, I bought a stack of 6 broken amplifiers from facebook marketplace for 50 bucks. So if it goes up in smoke, it isn't the end of the world.Power supply load was 2.5 to 2.8 amps at 14v when the 4v output was into a 4 ohm resistor, if I recall correctly.I believe this is a class AB amp. SMPS ran by a TL494C producing + & - about 53vdc. Output transistors are ST TIP35C and TIP36CI'm going to go look at it a little closer in a few minutes but nothing jumped out at me earlier.

author: TimFox
author_rank: Super Contributor
timestamp: September 28, 2024, 10:16:33 pm
content: How are you measuring the output?As stated above, with a (very common) H-bridge output, you must not connect one side of the output terminals to the grounded input of an oscilloscope.If you use a DVM (floating), you will not ground the output (be careful for personal safety), but you still need a load resistor to simulate the loudspeaker.
amplifier module question - Page 1
Forum section: electronics / beginners

author: daniel444
author_rank: Regular Contributor
timestamp: March 30, 2025, 07:09:59 am
content: im looking at buying one of these MA12070 amplifier modulesit has multiple modes of operationthe pictures on the advertisement seem to suggest it needs to connect additional capacitors in series with the speakers on some modesis this correct ?any idea on the type of capacitors ?any suggestions on other high quality amp modules i can purchase instead ?thanks

author: benj38
author_rank: Frequent Contributor
timestamp: March 30, 2025, 08:24:25 am
content: Aluminum electrolytic capacitors. The values you need are shown at the bottom left. I suggest to get capacitors with a voltage rating of double the supply voltage you plan to use.The more low frequency response you want (i.e., bass), the bigger the capacitor you need. Note, however, that for good bass reproduction you will need a physically big speaker in a good enclosure, etc. (this is a Pandora's box I am not going to open further).That said, I will only comment that the four big electrolytic capacitors clearly visible on the left side of the board make me think that they have a mistake in the wiring diagram, and that the needed capacitors are already on the board.

author: MrAl
author_rank: Super Contributor
timestamp: March 30, 2025, 11:10:15 am
content: Hello,The capacitors already on the board could be for the power supply filtering, but it's not possible to say for sure without seeing the schematic of the power amplifier itself.Regardless, to get good bass response the power supply also has to be well filtered or else the power supply voltage could dip during low frequency peaks.

author: dietert1
author_rank: Super Contributor
timestamp: March 30, 2025, 06:11:43 pm
content: Other application circuits suggested for this amplifier module show that a capacitor is needed whenever one of the four channels is used separate from the others. There is DC on each amplifier output. The combination of two channels as one full bridge output can work without the capacitor, as the DC will be similar on the two channels.Regards, Dieter
Amplifier static - Page 1
Forum section: electronics / beginners

author: digitalnomadjc
author_rank: Contributor
timestamp: October 04, 2016, 12:53:53 pm
content: Hi I have an amplifier question.The details are going to be a bit light because someone else asked me.The amplifier design is a known working solution. The PCB is a old fashioned home etched single sided board.When the amplifier is powered with no input cable plugged in there is no staticwhen the input cable is plugged in and there is no signal there is staticwhen there is signal (such as bass/loud sounds) the sound is crackly.I'm thinking dry solder joints or some sort of grounding issue. I haven't seen the board yet.any ideas?

author: danadak
author_rank: Super Contributor
timestamp: October 04, 2016, 04:16:27 pm
content: Grounding in cable shields, grounding in general.Old caps, especially electrolytics, possibility.Use a scope and start on output stage and work backwards.Regards, Dana.

author: digitalnomadjc
author_rank: Contributor
timestamp: October 05, 2016, 02:33:36 am
content: Thanks

author: digitalnomadjc
author_rank: Contributor
timestamp: October 10, 2016, 11:57:55 am
content: Hey I worked out what it was.working backwards from the output we replaced the 2200uF Cap and discovered the trace had lifted. Then the LM1875T looks pretty sick and after confirming that the output was not producing anything and the input was ok we replaced that too.After that it came to life. Also worked out the power supply was under rated for the power amp and replaced it with a supply with 3 times the wattage.
Amplifier testing/repair and dummy loads - Page 1
Forum section: electronics / beginners

author: Mick Duprez
author_rank: Contributor
timestamp: September 11, 2023, 07:24:05 am
content: Hi All,I have watched some videos where the presenter didn't use a dummy load for signal through the circuit. I can't remember correctly but I think it was a valve amp and the volume and gain was set 'just on', he did mention dummy loads but noted it was ok how it was setup for that purpose.Is this setup only suitable for valve amp's or can this be used for solid state/mixed technology amp's?As a safe alternative, if I build say just a 100 watt dummy load (for each channel) would that be ok to use with low gain/volume just for signal tracing? I'm thinking it would be ok as I'm not pushing too much 'power' around with low settings or will I need more power to test the signal path correctly?The amp's I'm working on are usually around 450 rms watts per channel and some much greater but I'd like a simple setup just for signal tracing/testing for a complete audio path, not testing for clipping etc. I do intend on building a large dummy load at some point using something like water heaters in a drum but that's a bit cumbersome at the work bench for preliminary testing etc.Are there any other alternative for this type of testing to narrow down to the problem area?Thanks,Mick

author: donlisms
author_rank: Frequent Contributor
timestamp: September 11, 2023, 03:12:01 pm
content: Solid state amps are perfectly happy to run with no load. Fire 'em up and take all the measurements you like. It's tube amps that have trouble.

author: Mick Duprez
author_rank: Contributor
timestamp: September 11, 2023, 08:49:32 pm
content: Quote from: donlisms on September 11, 2023, 03:12:01 pmThanks for confirming that, it will make things a lot easiercheers,Mick

author: TimFox
author_rank: Super Contributor
timestamp: September 11, 2023, 08:54:37 pm
content: The hazard with unloaded tube amps is not from the tubes themselves, but from the output transformer coupling the tubes to the load.Without secondary load, the load presented to the tube plates is the magnetizing inductance of that transformer, which is a very high impedance.Very few solid-state audio amplifiers use output transformers.

author: Mick Duprez
author_rank: Contributor
timestamp: September 12, 2023, 02:55:33 am
content: Quote from: TimFox on September 11, 2023, 08:54:37 pmThanks for that extra information TimFox, that makes sense if I understand correctly:If I have speakers then the load is removed from the output transformer reducing the impedance, that is, it gives the constant build up of current somewhere to go whereas with solid state, the current is simply reduced (due to things like feedback etc) as it has no where to go?cheers.

author: Mick Duprez
author_rank: Contributor
timestamp: September 13, 2023, 12:41:11 am
content: I found this whitepaper from Peavey which helps explain this in much more detail:https://peavey.com/PDFs/Chapter7.pdfThanks All for your help!
Amplifier - Page 1
Forum section: electronics / beginners

author: Simon123
author_rank: Regular Contributor
timestamp: December 28, 2013, 12:03:14 pm
content: Hello!I built thishttps://lh3.googleusercontent.com/-zE1Eh1U18MU/UTyhJzfwVEI/AAAAAAAAAGU/Qrq0BWrF6YA/s1600/2013-03-08+17.12.50.jpgamp a year ago, but it seems, that something is missing here.When i look at the other schematics i see emiter capacitor and resistor, but i dont have any.That can make my amp unstable, so i dont know if i should improve anything?Thanks.

author: mrkev
author_rank: Regular Contributor
timestamp: December 28, 2013, 04:11:45 pm
content: Quote from: Simon123 on December 28, 2013, 12:03:14 pmIs it working? If yes, don't bother.In your solution, you want to have like 6V at the output 270R resistor with 0V~ input. (So when the input voltage is negative, your transistor have some space to close.) This means that bias current trough AC176 should be 6V/270R = 22,2mA.By a datasheet, h21e(=gain) of AC176 should be in range 50 - 250. And your adjustment of bias point (by the 100k trimmer) is amplified by this number too.Since the voltage drop over BE of transistor and h21ecan slightlychangeover time and with temperature, this amp can move from it's bias point quite quickly (it won't be unstable, but it will disort one half of the signal).The resistor in emiter actively reduce the h21e. So even with temperature change, bias point will stay at right place. This would ofc. reduce gain of whole amp. That is why you also add an capacitor, which acts like "short" for AC signal. Anything with a higher frequency will have the full h21e, but DC bias will have reduced h21e.

author: filip_cro
author_rank: Regular Contributor
timestamp: December 28, 2013, 05:25:22 pm
content: Like mrkev said you could use REand CEfor negative feedback.

author: Simon123
author_rank: Regular Contributor
timestamp: December 28, 2013, 08:09:04 pm
content: Thanks!Only thing is, i dont know what you mean by is bias current, when you are talking about current threw 270R resistor?And the amp is working.

author: mrkev
author_rank: Regular Contributor
timestamp: December 28, 2013, 09:09:39 pm
content: Quote from: Simon123 on December 28, 2013, 08:09:04 pmSorry if that wasn't clear. I started with C-E bias current, which is supposed to be about 22,2mA (since with 0 input, you should get 1/2vcc at output). For that, you need cca 50 - 250 (gain of transistor) lower B-E bias current. Since that gain can change (with time&temperature), your bias point (which means the state of transistor with 0V input) can shift somwhere else.It's just a basic circuit and it will work for a wide range of bias points, so it's not that hot problem... If you wanna know more, just google up: 'class A amplifier'.

author: Simon123
author_rank: Regular Contributor
timestamp: December 28, 2013, 09:29:40 pm
content: Thanks
Amplifying a 0-2.5v DAC output to -x to +xv? - Page 1
Forum section: electronics / beginners

author: MarkS
author_rank: Unknown
timestamp: February 13, 2023, 01:33:34 am
content: I want to build a frequency generator out of a MCU and a 16-bit DAC. I know there are special purpose ICs for this, but I like learning the hard way. I've never messed with op amps and I'm not sure what to google. I want to take the 0.0-2.5 (or 3.3; still planning...) DAC output and amplify it to -x to +x, where x is user selectable from (3-12v). What type of circuit is this? Differential? How do I do this?

author: dobsonr741
author_rank: Frequent Contributor
timestamp: February 13, 2023, 01:48:19 am
content: Single opamp will do the translation - here is the TI design guidance:https://www.ti.com/lit/an/slaa869/slaa869.pdf

author: MarkS
author_rank: Unknown
timestamp: February 13, 2023, 01:52:51 am
content: Quote from: dobsonr741 onTodayat 19:48:19https://www.ti.com/lit/an/slaa869/slaa869.pdfWow! Thank you! I was making this far harder than it needed to be! I cannot believe I've stayed away from op amps for all this time. I've been an electronics hobbyist since I was around 8 years old!

author: Zero999
author_rank: Super Contributor
timestamp: February 13, 2023, 01:22:54 pm
content: A single op-amp can be used to amplifiy 0V to 3.3V to +-12V.Switching from 3V to 12V out is tricky, so why bother? Just reduce the output of the DAC.

author: MarkS
author_rank: Unknown
timestamp: February 13, 2023, 05:37:18 pm
content: Quote from: Zero999 on February 13, 2023, 01:22:54 pmI'm not quite sure what you mean?

author: Zero999
author_rank: Super Contributor
timestamp: February 13, 2023, 06:34:42 pm
content: Quote from: MarkS on February 13, 2023, 05:37:18 pmYou said:Quote from: MarkS on February 13, 2023, 01:33:34 amChanging the gain to give +-3V or +-12V out without affecting the bias is the tricky part, because several resistor values would need to change, so why bother? Just design the circuit for +-12V out and change the output of the DAC to compensate. You'll lose a couple of bits, but 16-bits is more than enough anyway.

author: MarkS
author_rank: Unknown
timestamp: February 14, 2023, 02:15:01 am
content: Quote from: Zero999 on February 13, 2023, 06:34:42 pmI get what you're saying, but I'm actually looking for the challenge. This is less about building a frequency generator and more about the process and project.
Amplifying a function generator output - Page 1
Forum section: electronics / beginners

author: beanbr173
author_rank: Newbie
timestamp: April 04, 2024, 05:33:23 am
content: I have a Siglent SDG2082X - Function/Arbitrary Waveform Generator (2 Channels/80MHz/1.2 GSa/s).I am trying to create a wave train characterized by a pulse repetition frequency of approximately 30 to 40 cycles per second, a pulse width of approximately 1.8 to 2.0 milliseconds, and a pulse amplitude of 18 to 24 volts.Specifically I am trying to replicate a 1966 patent through the use of this function generator:https://patents.google.com/patent/US3255753I have done googled searches but am not making sense of any of the results provided, seems like it's not possible?Thanks in advance for any support!

author: Andree Henkel
author_rank: Regular Contributor
timestamp: April 04, 2024, 08:20:39 am
content: well, more info needed:*load impedance / load current / load resistance*cable length*desired rise/fall time of pulses at load.if rise/fall time can be long compared to round trip delay depending on cable length and type, and load current is small (impedance or resistance large), then it is a quite easy task.edit:well, I read the patent short: it is pretty much self explatory what is needed to implement the deviceThere is a principal schematic drawing showing a implementation.Today you would not implement it using discrete Transistors and Transformers.But if you can´t make sense of it (sorry if I´m impolite) you are probably wrong person for the task at HandAnd it is a "medical device" so while I could design an implementation I´m not firm with the special compliance rules for medical equipment.

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 04, 2024, 02:14:10 pm
content: Quote from: beanbr173 on April 04, 2024, 05:33:23 amsounds super easy with just one or a few transistors and passive elements. you dont even need a AWG i think.. in fact it looks like transistor multivibrator in the patent sheet to generate the pulses.. ymmv.https://technologystudent.com/elec1/dual1.htmhttps://www.electronics-tutorials.ws/waveforms/astable.html

author: Andree Henkel
author_rank: Regular Contributor
timestamp: April 04, 2024, 02:27:25 pm
content: me just trolling:as it is a "medical device" use of the AWG is actually forbidden - because no complete galvanic isolation to the power grid

author: abeyer
author_rank: Frequent Contributor
timestamp: April 04, 2024, 07:52:10 pm
content: Quote from: Andree Henkel on April 04, 2024, 02:27:25 pmI am quite curious, though, why there seems to be a sudden influx of new users all doing diy medical devices recently.it'll be 'aight, just remember to mount yourscratch monkeys, though.

author: DiodeDipShit
author_rank: Regular Contributor
timestamp: April 05, 2024, 04:39:25 pm
content: Abeyer, Thank You for leading the way to : The Jargon File .....http://www.catb.org/jargon/html/