Power supply for audio (beginner) - Page 1
Forum section: electronics / beginners

author: rena
author_rank: Contributor
timestamp: February 09, 2021, 12:59:11 pm
content: Hello everyone, I'm new here, I just discovered this community a few days ago thanks to youtube.I would like to learn electronic for "audio recording related gear" purpose.I mean building/ creating preamps, EQ, comp...If I could I would also like to try to build a mixer too someday.I'm currently looking at indispensable equipment to start my journey.I bought a Rigol DG4062 signal generator few days ago, second hand, dead cheap.I plan to buy a DS1054Z oscilloscope as soon as possible.My question is about the power supply.I plan to work mainly with opamps, so I need + and - voltages, and a third source for digital would be great too.So I m thinking about the Rigol DP832 and the DP831.My concern is about the grounding path.DP832 when configured for +/- voltages share the same ground for all the three channels while the DP831 has two separate grounds, one for the +/- and one for the third "digital" one, from my understanding.I rode a lot of things about noise coming from the digital ground path... but I m still a total beginner so I sure miss a lot of things yet.What would be the best for audio in your opinion please ?

author: blackdog
author_rank: Frequent Contributor
timestamp: February 09, 2021, 04:39:02 pm
content: Hi Rena,The DG4062 is a nice function generator.But not specifically for audio and then I am referring to the distortion in sine signals.This should not be a major problem, since most measurements on audio equipment involve frequency characteristics for which sine and square waves are used.The distortion of the DG4062 will be tipical below 0.02% which is not to bad for audio.Furthermore, one of my power supplies is a Rigol DP832 and I have upgraded for 1mV and 1mA resolution.It was cheaper than the DP832A when I purchased it.All the other extra features and color display I don't need.I use too green color for the display because it is not disturbing.In the case of the DP832, the middle and right outputs are paired with respect to the "-"This is not a big problem as far as I am concerned, then I use the left output for the negative power supply when I am going to feed opamps.The "+" output of the left power supply will then be jumpered with the "-" of the middle and left outputs.Another thing that is important to know!Most LAB Power Supply'syou can buy now all have comparatively large capacitors across the output.The value is often 470uF for a 3-Ampere power supply.If something goes wrong in your circuit under test, then all the energy contained in this capacitor can be absorbed by your circuit, and not always does your circuit like this....It doesn't matter if you then have the current limitation set to say 20mA, the current limitation cannot limit those discharge currents!Usually 1 LAB Power Supply is not enough, and it is useful if you take into account in your budget to buy another single or two channel linear power supply with it.This may well be one of the older HP Power Supplies, I have used several in the past.These are the types with the analog meters that can often be purchased 2nd hand for a reasonable amount of money.Buy good banana cables and clamps.My preference is Hirschmann brand material which is widely available i nin Europe.I have no idea in which country you live if this material is also for sale there.Pomona is usually good too, but a lot more expensive.Buy at least this: 50cm, Red, Black, Blue, 1-Meter: Red, Black, Blue and Yellow for ground connections.I have about 20 of these cables in use as I work on several projects at once.Also buy good bnc cables and at least one in line BNC 50 Ohm terminator.This terminator is needed for measurements that have a pulse behavior like square waves.If you use the Rigol DG4062 with wideband audio circuits, you will get overshoot on the flanks of the pulse signal if you don't terminate the cable properly.I hope this helps.Kind regards,Bram

author: pqass
author_rank: Super Contributor
timestamp: February 09, 2021, 05:17:17 pm
content: FYI:https://sound-au.com/is the ultimate audio DIY site. Many articles and projects are fully explained. [not a sponsor]I'm not familiar with the Rigol power supplies but given that there are separate plus (red), minus (black), for each channel, and a chassis/earth (green), you shouldn't have any problem with ground-loops/noise if you simply not connect the green terminal to anything.I would expect all three supplies are completely floating independently of each other leaving it up to the user to tie the terminals together however he may wish. eg. to form a bipolar supply using two channels, plus a third for the "digital" parts of your circuit.So "...+/- voltages share the same ground for all the three channels..." doesn't make sense to me. I suppose "share" the green terminal in the sense there is only one chasis and it's connected to the third prong on the power plug and is available for you to attach to shields or cases (for safety). But it's your call. "Ground" is such a loaded word. See:Fun Fact: I built an amp that had a metal case which I dutifully attached to the earth prong on its power plug. I used a small center-tapped transformer as its power supply so the circuit was galvanically isolated from earth. However, the shield of the RCA connector was bare metal and was screwed to the case. A hum was heard through the amp because the audio source had its shield earth grounded through its case. Solution: insulate the amp's RCA connectors from its chassis so the circuit's common (0V) is only attached to the earth potential of the source. Technically, your suppose to attach the circuit common (0V) to the chassis, but I should see if the hum returns if I attach it via parallel resistor/cap as seen here:https://sound-au.com/project04.htm

author: penfold
author_rank: Frequent Contributor
timestamp: February 09, 2021, 06:14:40 pm
content: Power supplies are something worth collecting a few of as time goes on but definitely start of with a good dual channel 0-30V 3A (the 5V is just a bonus) and later on add to your collection maybe with second hand ones (by which time your skills will be up to repairing them)(disclaimer I've not used the Rigol PSUs so if I say something which disagrees with the data sheet, the data sheet is probably right)To me, the DP832 look like a much more useful power supply, the independent output channels don't constrain you to always having one positive and one negative output, you could have two positive channels if you wished, and they needn't share the same 0V.The 5V output can be useful... maybe for some control circuit or something, but its not worth sacrificing output 0-30V power over... which is what it looks like the DP831 does.From my impressions, the DP381 is more of a "digital-guy's" PSU, with the higher current 8V/5A output being the biggest feature and they've clearly compromised the output current of the 0-30V channels to allow for it.Just for pre-amps, you'd probably never need the full 3A output, but you may want to play around with some power amps, which when you're testing with a 8 ohm resistive load, "fits" neatly in the 30V 3V envelope (3A * 8 ohms = 24V and with some headroom is almost 30V), and I'd suggest that's much more useful than the 0-8V 5A channel.

author: David Hess
author_rank: Super Contributor
timestamp: February 11, 2021, 01:23:09 pm
content: For work with operational amplifiers, you are probably better off building a couple of dedicated +/-15 or +/-12 volt linear power supplies using fixed voltage regulators.

author: blackdog
author_rank: Frequent Contributor
timestamp: February 11, 2021, 01:36:21 pm
content: Hi,I use rigol's DP832 at least once a week for testing opamp circuits.It doesn't matter that the power supply can deliver 3-Ampere for those tests.What does matter is what I pointed out earlier, the current limitation cannot limit peak currents due to the output capacitor of the Power Supply, but that is true of almost every Power Supply.If you have a power supply like the Rigol DP832, then you can also test your power amplifiers with it.You can also link the channels in terms of voltage and current, so that if you vary the voltage, the other channel runs with it.As for a power supply that has e.g. 5V 10V 12V and 15V for opamps, I have found that to be a major limitation in my testing.Regards,Bram

author: MikeK
author_rank: Super Contributor
timestamp: February 11, 2021, 07:33:35 pm
content: This is a decent simple +/- power supply. It doesn't track, so you'd have to adjust both outputs. And take note of the caps; mine came with underrated ones that I'm replacing with better ones. (Complain if this happens and get a discount to pay for better caps.) But you can't beat the price. I paid under $7. You could put it in a box and add some suitable adjustment pots. You could even add display(s) so that you don't have to check it with your multimeter.https://www.aliexpress.com/item/32877603452.html

author: rstofer
author_rank: Super Contributor
timestamp: February 12, 2021, 01:12:23 am
content: Quote from: pqass on February 09, 2021, 05:17:17 pmThe ground (black) terminals are not completely independent on the DP832 so it is worth reading the manual on proper connections.https://www.eevblog.com/forum/testgear/rigol-dp832-negative-voltages/

author: rstofer
author_rank: Super Contributor
timestamp: February 12, 2021, 01:20:51 am
content: Quote from: David Hess on February 11, 2021, 01:23:09 pmI have one of these dual output supplies for op amp projects:https://www.jameco.com/z/PD-2515-MEAN-WELL-Power-Supply-Dual-Output-Open-Frame-15V-1A-Negative-15V-1A-24W_2100857.htmlI haven't spent much time with it but it should work fine.

author: rena
author_rank: Contributor
timestamp: February 12, 2021, 01:24:48 am
content: Hi everybody, first thank you so much for all your comments !It seems that the DP832 will better fit my needs it the future so I ordered one.I took the A model since it was cheaper than the DP832 for whatever reason.I receive it tomorrow.Blackdog --> Thank you, I wouldn't have know about those capacitors !I realize that there is something I'm not sure to understand about the current setting. If for example I set it at 1A (and say current limitation at 1.2A) it will deliver 1A in my circuit all the time ? Even if the circuit needs only say 0.5A ? And if for example I turn on a part of the circuit that needs more current it will be able to draw 1.2A max right ?-About the "HP Power Supplies", any recommendation about the features ? I often spot some "kikusui" ones but some of them don't have a fine "tuning" knob for the voltage for example.-I found those Hirschmann cable (btw I'm in Japan)https://www.monotaro.com/g/04610149/Is it the ones you are talking about ?-About the "in line BNC 50 Ohm terminator", it is to be plugged on the oscilloscope side right ?qpass --> Thank you very much for this video, extremely informative !Great you talk about sound-au.com because I was wondering for a few weeks now what to think about this site. This is really a basic beginner question but in your opinion are those circuits legits ? I'm willing to learn a lot and I spent the past few weeks gathering many schematics of famous gears from API, Trident and so on... and studying them. And of course I stumbled upon this site that is extremely interesting but I almost couldn't find any reference about it on groupdiy.com for example so I didn't know what to think about it.David Hess --> Thank you for your idea. Actually I thought about it and at some point I might try to build one for training !MikeK --> Thank you for the link ! I will take a look at it !rstofer --> That was one of my concern. Thank you for the links !

author: pqass
author_rank: Super Contributor
timestamp: February 12, 2021, 02:20:17 am
content: Quote from: rstofer on February 12, 2021, 01:12:23 amI see that now. I suppose the "COM" label between the two black terminals was a clue.I know these fancy supplies can be software configurable but, in my opinion, if there is a hard design constraint that channels aren't independent then there should be only one black terminal between them like I've seen elsewhere.And the mention of "noise" and "grounds" took me off on a tangent about multiple earth connections on audio equipment.

author: pqass
author_rank: Super Contributor
timestamp: February 12, 2021, 02:56:20 am
content: Quote from: rena on February 12, 2021, 01:24:48 amhttps://sound-au.com/is beginner friendly because many projects are low-complexity AND all are fully explained. Most of the time when you find an interesting project on the internet there is no explanation. You could build it but you don't really learn anything. Even if you don't build any of his projects, there is much wisdom between the projects and articles that would take a life-time to figure-out yourself. And much of it is applicable to just general electronics DIY. For example:https://sound-au.com/articles/bench-supply.htmDave Jones thinks highly of the site and even interviewed Rod Elliott.

author: rstofer
author_rank: Super Contributor
timestamp: February 12, 2021, 04:47:24 pm
content: Quote from: rena on February 12, 2021, 01:24:48 amNo, and that's why I object to the term 'constant current' in this context. A better term would be 'current limit'. You set the current limit for 1A and the voltage to whatever and the PS will deliver the set voltage until the current reaches the limit and then the voltage backs off to keep the current at no more than the limit. At this point the current is constant but if the load only draws half as much as the current limit, the PS doesn't increase the voltage above the setpoint to drive at the selected current.There is also a second current limit on the DP832 known as OCP (Over Current Protect) and, should the load current exceed that number, the output is shut down (tripped).

author: NOON Design
author_rank: Contributor
timestamp: February 14, 2021, 10:06:54 am
content: As a few people mentioned sound-au is a great resource. For an active forum where you can read a range of opinions from very experienced audio design professionals and diyers and ask questions you can't beat GroupDIY. Avoid Gearslutz except for entertainment value. I'd also recommend building a fixed +/-15v supply for prototyping use. A good quality usb audio interface and software capable of signal generator, oscilloscope and fft functions (several good free options) is all you need for most audio design and testing to get started.

author: NOON Design
author_rank: Contributor
timestamp: February 14, 2021, 10:08:38 am
content: Forgot to mention, buy yourself a copy of Douglas Self Small Signal Audio Design and a copy of The Art of Electronics and you have almost everything you need.

author: rena
author_rank: Contributor
timestamp: February 16, 2021, 01:37:56 am
content: Thank you everyone for your comments and explanations !

author: Bassman59
author_rank: Super Contributor
timestamp: February 16, 2021, 05:12:24 am
content: Quote from: NOON Design on February 14, 2021, 10:06:54 amTRUTH.You will not find a more wretched hive of scum and villainy. You must be cautious.

author: rena
author_rank: Contributor
timestamp: February 16, 2021, 09:29:57 am
content: Understood !Gearslutz is more about using gear than building them I guess.I have one more question.I stumble upon a second hand LeCroy 9362, ~365$, without probe.Is it an interesting oscilloscope in your opinion and in regard of my project that is building audio recording gear ? (I’m absolutely not interested un Hi-fi consumer gear).