SS power amp

[xtian]

Up to no good, and not a tube in sight.

I got a Sure Electronics AA-AB31194 1x300W Class D Audio Amplifier Board - T-Amp

and Qualtek QPDF-320-36 Switching Power Supply 36 VDC 8.8A 320W Single Output

to make a power amp for my Line 6 Helix.

Setting up to test.

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[M Fowler]

Looks to familiar, should make a good amp.

Mark

[pompeiisneaks]

I've been debating doing something with class d power amps and tube preamps for a while, just because they get so small and have no OT required, so cost is significantly less, but could still be a high quality hand wired amp that will last forever. Just need to find time to design a small board for just the class d part, instead of buying those prebuilt ones. (or maybe just buy the prebuilt ones? not sure)

~Phil

[ChopSauce]

I think I read in Merlin's book that he tested some pre-amp designs with an SS power section.

I have a solid state power (bass) amp, which I intend for a similar purpose, as soon as I'll have finished repairing it
(these MT 200 mica insulator are a pain to find - unless you want to buy a few tenths of these - )

Nice (and also clean) project (as usual), by the way

[roberto]

I've done several amps like that one, for friends and me, and they work perfectly: one 12ax7, a IRF820, a class D power amp.
I'm sure I've posted something here too, both with baxandhall (with mid pot), both with standard passive cathode loaded eq.
I've used one also for one of my two guitar racks.

[xtian]

All assembled and working nicely. The sound is as I expected: low noise floor, good clarity and punch, plenty of power to spare.

I am less happy about the fan in the power supply, which will never be noticed on stage, but is audible in my quiet room, and therefore a bit annoying. I may wire a fan on/off switch. I played loud for an hour, and there is no appreciable heat felt in the chassis.

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[norburybrook]

Have you built a FRFR speaker cab too? I thought about this for my Kemper too. Why are the power supplies so big?

does it need a 4 ohm speaker to perform at it it's best? that put me off as I never use single 4 ohm speakers.


And finally ....a helix! you heretic.... ..............I hide my Kemper.....



Marcus

[martin manning]

Ahem...

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[ChopSauce]

Maybe we could add "(pre-)" before the "amp" ?

[R.G.]

FWIW, several folks with one of my UL700 preamp clone boards have told me that they're going to couple it with a class d power amp to make a UL700 clone that ROARS.

I even slipped slipped into the Dark Side on my last surplus electronics order and got a $20 100W Class D amp.

[xtian]

I know! Solid state. *shame shame shame*

‘Evs. My mission is “tone, wherever it can be found.” Getting a grip on modern solid state is just another tool in the box I can offer myself and my clients.

I did add a switch for the fan last night, and am very pleased. Now it’s very quiet at idle, and sounds great. I’ll turn the fan on when I play gigs. I put Dymo labels on the backplate, and if they turn black, I’ll have a visual indication of a thermal issue!

The spec sheet indicates its max power is with 3ohm load, and scales lower as the impedance increases, obviously. I tried a bit with at 16-ohm load, just to check it out; seems like it drops 3-6dB versus 4-ohm. I think, though I haven’t tested, that I’m getting 80-100 watts with the 4-ohm load and the 36v power supply.

I did play with full range (Mackie SRM 450) for a bit, to check out that option, using cab and mic sims on the Helix, but didn’t like the sound nearly as much. Though, the Helix sounds exactly as I’d wish playing thru my studio monitors and headphones.

Using only the amp preamp sims (no cab or mic) on the Helix, and sending that signal to the solid state amp and to my 2x12 cab really sounds great. And dialing in different amp sims (the amps I know and recognize like Deluxe, Twin, JTM45, JCM800, Ingrid) really sound like the real amps. And NOT just at high gain settings—and this is where the Helix really blows me away—with very low gain and high volume settings it is VERY pleasing.

I’ve been on this ride a few times. I’m sure I’ll be back to guitar-straight-into-amp land again soon, but I’m certainly enjoying the view from here.

[xtian]

Forgot to mention, total weight of amp, power supply, and aluminum backplate is 4 pounds 5 ounces. Very light!

[drew]

For the benefit of anyone wanting to play around with something like this, you can get a Texas Instruments evaluation module instead of the questionable build quality Chinese boards for not a whole lot more money. Pictured is one of these ($75 with a promo code) with a Meanwell power supply that was about $30 from Arrow Electronics. The PS has a fan but it has either never come on or I’ve never heard it.

[xtian]

Nice enclosure!

[xtian]

with a Meanwell power supply that was about $30 from Arrow Electronics

Which Meanwell PSU? The amp I got requires 8.5A at full output.