Power supply for a plate amp 2.1

Hi folks,
I’ve just started experimenting with my plate amp 2.1 and I’m using a 12v 0.5 A power supply and everything is working fine. I also have a 24 V 0.5 A supply that I can use, or a 19 V 6.7 A supply that came with a backup disc drive or I could also change the plug on a computer power supply 19.5 V 3.3 A.
I’m making a guess that the higher the voltage and current the better, as far as driving a 10" woofer and a mid range and tweeter 3 way speaker. Is that correct, or is it wise to not have quite such a high current rating? All I can find is a reference to using a power supply between 12 and 24 V, with no real further guidance.

Hi Kirky,
My choice would be one of the 19v supplies with the higher current rating, you will get greater performance from the amplifier at the higher voltage input into the unit.

2x50W@4Ω + 100W@2Ω BTL load at 24V
2x30W@8Ω + 75W@4Ω BTL load at 24V
2x22W@8Ω + 48W@4Ω BTL load at 19V

Great, thanks for the advice Steve, much appreciated!

Hi the specifications of the amp chip used on the amp 2.1 (TI TPA3116) state you would have with a PS voltage of 20V, approx 50W per stereo channel with 4 ohms speakers, 25 approx if 8 ohms, and 100W for the sub under 2 ohms. Doing the math, you would need a max current capability for the PS of the total added power / voltage, i.e in the worst case (2x50 W +1x 100w) =10Amps… in the ‘best’ case, (2x25W +1x50W) = 5 amps…
This depends on the impedance of the speakers…
Besides, if you are picky, computer power supplies are not the best option as they are not designed to cope with rapid variations of the supplied current as needed for powerfull bass music… the best solution would be to use the old solution… linear power supply with good well sized capacitors …
(old 20’s century amps do have these… you may fin d one when opening the box…)

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Hi Nobu, thank you, that makes sense! I hadn’t thought about the need for for high transient performance - I don’t know why I hadn’t made the connection that the performance of the power supply for the plate amp is as important as the PS performance for my conventional stereo amp!

For many years I was a staunch advocate for linear supplies but having read so many posts on DIYaudio and other audio websites about the use of switching supplies I have come around to using them.
It seems like the major issue with them is HF switching noise which is apparent more on cheaper units, but this can be greatly overcome by using a LC filter on the output of the supply.

Thanks for the feedback Steve. I was going to try my laptop PS first, as I already have it, and make a linear supply if necessary. At what frequency does the switching noise become evident? Is it high enough for an ACP low pass to block it rather than filtering the power supply, or is it well and truly in the audible range?

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In a audio circuit switching noise can introduce some harmonic distortion to the input signal, but it typically generates minimal to no high-frequency interference.
But I’m lead to believe that a poor quality SMPS with an unfiltered output can lead to glitches in digital circuits.

Hi Steve, I’ve been travelling and only recently picked up this thread again.
I’ve had a look for a power supply output filter and was wondering whether this might suffice:

I was going to pick the 10A variant to cater for a 6.7A supply, and I guess its 50V limit is more than enough for a 19V supply. Most of the products I looked at on-line (including this one) refer to EMF filters, which to me sound like suppression of mains hum and/or RF interference. Is something like this suitable?

You might be interested in some tests that I did earlier which included trialing a filter.

Same here, using 19V Laptop PSU.
I bought 2 other 24V ones and testing those.
But i measire my hissing noise and it seems to be at 3khz in the Horn Compression Tweeter. So thats nothing to block out with with a filter.
Even tested it with Workbench, but problem is, the noise is there even if i play nothing.

Hi Bense, your email arrived on the very day that I fired up my boombox build in its ‘breadboard’ form (well, actually the box is fully constructed, so a bit more than a breadboard. I tested with 2 PSUs, one from a walkie talkie charger (12 V 3 A) and a 19 V Dell laptop PSU. The Dell charger has a small ferrite slug, which I left in place but the charger has no isolation at all. Neither of these PSUs caused any problems with hissing, in fact they both sounded pretty darn clean. I have a cheap RFI filter unit coming thru Ebay, but I haven’t installed it yet, and as you say that wouldn’t eliminate a 3 KHz hiss.