These 30V 3/5/10A bench PSUs on ebay / amazon etc - Page 1
Forum section: electronics / beginners

author: jaffamuffin
author_rank: Newbie
timestamp: August 07, 2020, 10:49:38 pm
content: Hi allNew user here. Interested in audio and amplifiers, speakers, etc.Background:I'm looking to do a bit of work with these little D audio amplifier boards, having played around with some a few years ago and built an AMP6 project I think it was. There looks like some interesting things in this area I'd like to experiment with.I have been watching quite a few of johnaudiotech on youtube (https://www.youtube.com/user/JohnAudioTech) and I want to perform some similar tests of my own, i.e. power draw, clipping, some freq response measurement etc, before moving on to mods or building etc. I have a couple of tektronix oscopes that I picked up so looking forward to learning about them and using them.QUESTIONI'm looking for a decent-ish PSU to use with these small boards, having previously used old laptop PSU and universal things that lacked power required.I need the ability to go to at least 24V, ideally more and deliver about 5 AMPS but I think I need the capability for more, as some of these little audio amps can pull upwards of 4-5AMP as far as I can see.I notice johnaudiotech uses a siglent PSU that can be paralleled and seems to be a pretty decent unit . I've read it's very clean and good for audio . But it's about £300 or more.I was looking for something a little cheaper. (budget up to £100 ? )Are these amazon PSU's any good for my use case?Should I Get a 10AMP unit ? or stick with a 5AMP (thinking that he 5AMP Will be better quality?)Is there a brand/model that's respected enough to be recommended ? I've read a number of forum threads about dodgy insides, and poor quality control etcIn this case, what should I look to pay for a 'decent' unit ?Does anyone have any experience in this area? what do you use ?Are there any features I should look out for in any unit I buy ?One other question that might seem a little obvious -- some units have an earth socket, and some have only a -ve and +ve Is this literally just an easy way to earth stuff ? I think I don't need this, is there times when this might be of use for audio stuff?many thanks

author: ledtester
author_rank: Super Contributor
timestamp: August 08, 2020, 12:26:29 am
content: I am by no means an audio expert. Indeed, most of what I know comes from youtube channels like jontechaudio. But, anyhoo, where are some observations:1. The cheapo ebay power supplies are going to be switching power supplies which produce a fair amount of noise.2. A highly recommended switching power supply is the Gophhert NPS1601 (also very reasonably priced):https://www.voltlog.com/voltlog-255-gophert-nps-1601-review-possibly-the-best-power-supply-in-this-price-range/3. My understanding (and it may be incorrect) is that the power supplies for the speakers in a stereo amplifier are generally unregulated.4. You might be able to reuse the backend of a old stereo amplifier for your experiments. Then you only need a power supply for the Class D circuitry, and that might be a lot easier/cheaper to source.

author: wizard69
author_rank: Super Contributor
timestamp: August 08, 2020, 03:50:06 am
content: Quote from: jaffamuffin on August 07, 2020, 10:49:38 pmThat might imply high power demands depending upon what you want to achieve. I would put a number on the top end power you want to deliver to better fit a power supply to your needs.QuoteI've done nothng with such amps so forgive the question but wouldn't you need multiple power supplies?QuoteNever heard of this guy. The type of supply you might need will likely vary a bit based on your end product. Which brings up the question, will these always be experiments or do you intend to build some sort of audio amp for use? Here is the thing if you want to build an amp to use you probably should build the proper power supply too to go with it.QuoteThis is the problem we all have trying to get the right tools for our interests without breaking the bank. So you will need to ask how good is your research to be, ultimately you may need a linear power supply. That could be a pretty penny. In any event a few sugggestions:Buy a decent switch mode power supply and suffer from any noise that it might produce.This should be #1 but determine if you need a separate supply for "logic" circuits. That is any part fo the circuit not delivering power to the speakers. Because it can make sense to have a power supply suitable for this and simply make your own high voltage/current supply for the power stage.Just go DIY right from the start. Audio amps are a sort of power supply anyways, effectively delivering AC voltage to the load. So just bake in the power supply design right from the start. For an audio amplifier I really can't imagine why you wouldn't just build the proper supply for the output stage.Find and old HiFi amp and pilfer the power supply from that.Stack up a bunch of batteries to get the voltage you need. If all you are doing is testing this should actually work good enough for testing.On a limited budget it always makes sense to go used. With careful shopping you can often find supplies for pennies on the dollar.While it might be hard to find one at the moment, attend a HAM convention. Usually there are all sorts of used and new bits of electronics on salesQuoteMost likely since you can find anything on Amazon. Even there though your budget is tight.QuoteKinda impossible for us to answer isn't it? There are two questions for you to consider, one is how much output power do you want. The other is what sort of operating voltage are you comfortable with.QuoteIf money is no object you can go with Keysight. You can also consider:https://www.acopian.com/,B&K, SRA, Thurlby Thandar Instruments and a whole bunch of others. The problem is even a good import will end up busting your budget if you are not careful more so if you go linear.QuoteMy best bit of advice I can give is to do more research into your amplifiers and the recommended power supplies for them. I say this because it doesn't even sound like you know what you are about to build. Further you need to understand that once your DC voltage goes up the power supplies can be deadly. Now given that if you are going to experiment around an existing design, that design should have a specification for the operating voltage and current. Lastly with a limited budget you will not find one power supply that will do every thing you need in the future, most benches have more than one supply, so choose carefully but realize that at a $100 that supply likely will need to be supplemented in the future.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: August 08, 2020, 07:19:55 am
content: I really like this PSUhttps://www.amazon.com/Tekpower-TP3005P-Programmable-Variable-Regulated/dp/B06XCQN82X

author: jaffamuffin
author_rank: Newbie
timestamp: August 09, 2020, 01:43:27 pm
content: Quote from: ledtester on August 08, 2020, 12:26:29 amYes. I think a linear PSU Will be bestQuoteWell these class D chip amps are the the power amplifier section so i'm likely to need a psu for the pre amp and the actual chip it self.

author: jaffamuffin
author_rank: Newbie
timestamp: August 09, 2020, 01:47:23 pm
content: Quote from: wizard69 on August 08, 2020, 03:50:06 amThanks for your message.I looked at it more closely and a typical amp will be up to about 50W maybe x 2 at anything up to about 24V so that's 4AMP or so maximum draw so actually that helps to identify my needs. reading around a lot more i'm kind turned of by these lower end amazon type supplies. Probably OK maybe as a second unit but I do want something somewhat decent as a starter.I'm not looking to build any amplifiers just yet. More measuring and testing these £10-20 units on ebay/amazon and the likes. Do some mods, change components etc. Test results etc. down the line I may then look at a preamp / power amp from scratch. A gain clone or something similar. These are all fairly low cost things to experiment with.Then some arduino/embedded stuff as well (i'm more IT than electrical). Additionally some elctronic repair having repaired some things in the past a PSU for testing etc would have been very handy for these things in the past. So I've probably settled on the siglent 3303C all said and done, it's decent enough and a step aboe these cheap amzon things, but good value as a multiple outputs, good power and only about £215 here in the UK.

author: pcolbeck
author_rank: Contributor
timestamp: August 09, 2020, 08:03:32 pm
content: I'm by no means an expert but I have just purchased one of these:https://www.ebay.co.uk/itm/EA-ELEKTRO-AUTOMATIK-PS-3016-20B-Bench-Power-Supply-0-16V-0-20A-Ex-Cond-LAST-ONE/143669773796?hash=item217362c5e4:g:YA0AAOSwxjxdm6SXLooks like new and will do 16v and 20A. Its a big beast of a linear PSU and weighs a ton. May be a bit more than you wanted to pay but a good German linear PSU. If you can get by with 16v it will give you plenty of amps and power.

author: ledtester
author_rank: Super Contributor
timestamp: August 09, 2020, 08:46:43 pm
content: You might be interested in this video:https://youtu.be/aIOTOGJ9Djg

author: cdev
author_rank: Super Contributor
timestamp: August 09, 2020, 09:14:49 pm
content: If you get a "for parts or not working" power supply from certain reputable manufacturers you should be able to fix it. Make sure you can find the service manual and check it that the device does not have proprietary parts.Certain power supplies are so common repair parts are also common. I found a triple Sorensen XT power supply that already was 2/3 working units so I just fixed the part that wasnt and now I have a really solid triple supply. Apart from a hum (a physical hum, the DC output is incredibly quiet, as quiet as a battery) its perfect.But it weighs maybe 30 or 40 lbs. Its a real boat anchor. If it was bought 100% working it would have cost me at least $250 even used and >35 yrs old.

author: mariush
author_rank: Super Contributor
timestamp: August 09, 2020, 09:48:30 pm
content: Farnell rebrands a few of those adjustable power supply models under their own Tenma brand and sells them with decent warranty and all that.The ones that use switching regulators are cheaper, from around 35 pounds... linear power supplies (which give you smoother, nicer output but debatable if that matters with class D amplifiers) are a bit more expensive because they're heavy because of transformer insideThey have a "retail" uk only version of their website where they have some power supplies listed :https://cpc.farnell.com/w/c/test-equipment/bench-power-supplies-sources-loads/prl/results?brand=tenma&sort=P_PRICEFor example, single output 30v 5A for around 73 pounds :https://cpc.farnell.com/tenma/72-2690/power-supply-0-30v-5a-1ch/dp/IN07634There's a dual 30v 3A + third output (fixed three choices 2.5v/3.3v/5) :https://cpc.farnell.com/tenma/72-13300/dc-power-supply-3ch-adj-fixed/dp/IN07980You can connect the two 30A outputs in series to get 60v 3A .. it may work to do 30v 6A by paralleling the two outputs but I wouldn't risk it. 3A should be plenty for testing amps though, you're giving 30v x 3A = 90 watts to a an amplifier or double that if you go with up to 60vThere's also the main farnell website which may have more models in stock compared to the CPC version :very long farnell url with some filters appliedI'd also suggest contacting user toploser here on the forum, he gets Tenma units from Farnell that are returned for various reasons, he tests them and sells them at good prices.Here's an example, one of his power supply listings from last year:https://www.eevblog.com/forum/buysellwanted/fs-(uk)-tenma-72-10495-psus-2-channel-0-30v-0-5a/msg2642280/#msg2642280

author: jaffamuffin
author_rank: Newbie
timestamp: August 10, 2020, 11:34:55 am
content: great responses thanks ! Checking these out, some good options here certainly cheaper and will likely do for a first unit. I will watch that video when I have time this evening. Many thanks!