Pete S. and other EE types...

[johnnyrichards]

I just scored a power supply very similar to this (http://www.ebay.com/itm/NEW-POWER-ONE-POWER-SUPPLY-24VDC-7-2AMP-HE24-7-2A-/400080489502) one. I paid considerably less for it than the $88 eBay price. Like around $73 less. "Obsolete" parts on the shelf at work are going for pennies as they are trying to clean up inventory. Anyways...

Would it be worth pairing with one of these (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=320-300) for a beginners attempt at a DIY amp?

[Sydney]

Should work

[PWR RYD]

It should work very well.

[Pete Schumacher ®]

Concurrence has been established. ;)

[johnnyrichards]

Thanks guys, looks like I'll be getting another pair of raised eyebrows when the Visa statement comes :)

Sometimes, working in an industrial environment decidedly does not suck.

[fbov]

I've done a little research into the 2-ch Sure amps. I have an old integrated amp that's gone bad in the amp stage. It already has pre-amp outs, so I was thinking I could just tap the power supply. Turns out the chips have a very severe overvoltage sensititivity, consistent with inclusion of over voltage protection, and I had 40+ volts. I expect any protection to be a cut-out, so it's a non-starter for me.

You'll be fine...

HAve fun,
Frank

[scottq]

I am familiar with these power supplies.... we had a couple of them in our lab at work in my last job. They get hot if you run them anywhere near their rated current capacity. The "heatsink" cases are nowhere near sufficient for their rated capacity. It's more of a "peak" level than a steady state operating level rating. They are basically just zener/BJT linear regulators, and there's lots of heat to dissipate. The transformers aren't robust enough for their max rating either. That said, you won't have a problem at "normal" listening volumes in room for that amp. But, if you're planning to put it in the garage to blare some speakers for hours on end during a party, you'll want to consider adding some additional heatsinks. ;)

Can you get any more that cheap? I'm interested... basically the same application :)

[johnnyrichards]

I am familiar with these power supplies.... we had a couple of them in our lab at work in my last job. They get hot if you run them anywhere near their rated current capacity. The "heatsink" cases are nowhere near sufficient for their rated capacity. It's more of a "peak" level than a steady state operating level rating. They are basically just zener/BJT linear regulators, and there's lots of heat to dissipate. The transformers aren't robust enough for their max rating either. That said, you won't have a problem at "normal" listening volumes in room for that amp. But, if you're planning to put it in the garage to blare some speakers for hours on end during a party, you'll want to consider adding some additional heatsinks. ;)

Can you get any more that cheap? I'm interested... basically the same application :)

Well, the manual states that fan cooling is required for maximum operation. We have a lot of these in operation in an environment harsher than most people have ever been exposed to (or electronics for that matter) and so far, one failure in ten years :) I fixed that one by soldering in new caps.

I can get a few more, but one I will be using and the other is already kind of promised to someone else.

[weinstro]

I just scored a power supply very similar to this (http://www.ebay.com/itm/NEW-POWER-ONE-POWER-SUPPLY-24VDC-7-2AMP-HE24-7-2A-/400080489502) one. I paid considerably less for it than the $88 eBay price. Like around $73 less. "Obsolete" parts on the shelf at work are going for pennies as they are trying to clean up inventory. Anyways...

Would it be worth pairing with one of these (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=320-300) for a beginners attempt at a DIY amp?

It should work. However, you won't get rated power out of the Class D amp with this supply. Also, this is a regulated supply. It may work better with the regulation disconnected as the load is a switcher.

Regards,

Rob

[cpcarter]

Johnny,
We used similar Power One open frame units in Frequency Synthesizers back in the 80's. Power disappation wasn't an issue but noise was. I would look at that voltage carefully with a scope under full load. The Synthesizer had noise and spurious spec of -70dBc. The line Freq harmonic content plus the switching "hash" made it nearly impossible to use those supplies in a low noise application. Power One worked with us to create a custom supply. Never tried them at Audio frequencies so might be ok. Just a heads up.
CC

[scottq]

Well, the manual states that fan cooling is required for maximum operation. We have a lot of these in operation in an environment harsher than most people have ever been exposed to (or electronics for that matter) and so far, one failure in ten years :) I fixed that one by soldering in new caps.

I can get a few more, but one I will be using and the other is already kind of promised to someone else.

Yeah, we ran them in temp/humid test chambers too; didn't mean to give the impression that they aren't "robust." Abusing them and overheating them in a lab is different than I would treat it in my home though.

If you can get hold of an extra one, please PM me.


Johnny,
We used similar Power One open frame units in Frequency Synthesizers back in the 80's. Power disappation wasn't an issue but noise was. I would look at that voltage carefully with a scope under full load. The Synthesizer had noise and spurious spec of -70dBc. The line Freq harmonic content plus the switching "hash" made it nearly impossible to use those supplies in a low noise application. Power One worked with us to create a custom supply. Never tried them at Audio frequencies so might be ok. Just a heads up.
CC

Harmonic and HF garbage out to 1MHz+ is present in any rectified output power supply. Those darn diodes are noisy buggers in when they turn off and on. Enter pi and common mode filters. I don't think it's any worse than any other "standard" rectified output though. Perhaps, upgrading the caps on the rectified output would be a good idea, depending on how old the units are. The output does indeed start to sag at higher currents with these, but for a small Class-D home amp, I believe these are sufficient.

Agreed - the voltage output isn't high enough to get "max" out of the amps themselves.

[weinstro]

.....
Harmonic and HF garbage out to 1MHz+ is present in any rectified output power supply. Those darn diodes are noisy buggers in when they turn off and on. Enter pi and common mode filters. I don't think it's any worse than any other "standard" rectified output though. Perhaps, upgrading the caps on the rectified output would be a good idea, depending on how old the units are. The output does indeed start to sag at higher currents with these, but for a small Class-D home amp, I believe these are sufficient.

Agreed - the voltage output isn't high enough to get "max" out of the amps themselves.

In the link Johnny posted, there are lots of TO-3 transistor cases in the photo, which is an indicator of a linear power supply. I googled the model number in the eBay auction, and downloaded the datasheet from Allied -- sure enough, it's a linear supply.

Noise should be lower in magnitude, but will occur at 120Hz, rather than some out of band frequency. Step-load response should be better, though. Efficiency is also lower, and this thing will run warm.

I would try it out of the box. If the voltage sags during higher output times, maybe consider increasing the filter capacitance.

Regards,

Rob

[arlis_1957@yahoo.com]

That's a ps one might to show off.

[johnnyrichards]

I was worried about the amp not delivering full power, but then I realized it will need a 4 ohm load running at <10% THD before I hit the 100 watts per channel. I am fairly certain I will be running it closer to the 30W x 2 @ 6 ohms with less than 1% THD. So, no worries there.

Plus, the price was right and I am willing to give it a whirl.

What else do I need? Assuming I will be using a PC for as much of my preamp duties as possible, that is.

[weinstro]

What else do I need? Assuming I will be using a PC for as much of my preamp duties as possible, that is.

8" of 4/c #16 cable (+,-, and remote sensing) between amp and supply
6' 2/c #16 power cable and AC plug (3/c w/ ground will increase your chances of hum)
panel mount fuseholder and 1.5 amp slo-blow fuse, before power supply
possibly a connector for power supply connection to amp
Chassis to mount the power supply and amplifier, unless you want to go "open frame" on the whole thing

Regards,

Rob

[moron#99]

you say the P/S you got is similar but not same.

When you look at the screw posts for connection do you see one labeled -24V?
Having +-24 might make other amps slightly more appealing.

[johnnyrichards]

Amp and the Sure volume control board on the way.