Of those three, the Aleph J and F5 are conventional amps with gain, and can be driven by a typical preamp. The F4 has no voltage gain, so it requires a separate gain stage (which can be built inside the same chassis), or a special preamp with about 21dB of gain and sufficient voltage swing to drive the F4 to full power. Special preamps like that are somewhat rare.I don't think the three amps you've mentioned (AJ, F4 and F5) are particularly
tricky to build.
...
And yes, all three are great.
The M2x also sounds wonderful, but requires care in construction to prevent PSU transformer hum from being coupled into its transformer gain stage.
After going through just about every single ended class a power amp design I could find, I've settled on building the ACA for its accessibility and simplicity.
I've got the 40x120x200 mm 0.5C/W heatsinks, now I need to make a chassis out of them. I was thinking aluminum plate front and back, with perforated sheet on top.
Does anyone have ideas for a really easy chassis to build for the ACA? I've looked through the thread to get some inspiration. My only concern is wood panels may not be the way to go with all the discussion about how hot the amp runs.
I've got the 40x120x200 mm 0.5C/W heatsinks, now I need to make a chassis out of them. I was thinking aluminum plate front and back, with perforated sheet on top.
Does anyone have ideas for a really easy chassis to build for the ACA? I've looked through the thread to get some inspiration. My only concern is wood panels may not be the way to go with all the discussion about how hot the amp runs.
Fancy! How did you attach the heat sinks to the top and front? Mine came with threaded holes in each corner on the inside face, so I'm trying to think of how to use those.
I used those same threaded holes. Front panel sides and top are folded back and drilled to mount using those holes as well as provide for mounting the top. I also made an additional top support using the hole drilled for the center mount on the PCB. I bought the same heat sinks as you from the store so had to drill and tap the holes to mount the PCB. Photo of the rear of the amp and you can see how the sides are folded.
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Very nice! Thanks for the explanation, I've definitely got some better ideas now.
No Problem. You'll find with those heat sinks it does not run too hot. At least I don't think so, they are definitely warm but not what I would consider hot. Now the heads on an old two stroke air cooled motorcycle, those are what I consider hot! Also remembered I have a better photo of the front and rear panel mounting but this is on the matching preamp. Same method just no heat sinks. Wish I had cleaned my bench before the photo though. Oh and you are going to love it!
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I've made lots of amps with wooden panels, some have been running for 15+ years now with no problems. Here is one of my ACAs: Pictures of your diy Pass amplifier
Others are in my signature links.
Others are in my signature links.
I've got a question as I was perusing through a Parts Express catalogue...I saw some switching or DC power supplies much like the one that came with ACA...I figure the ones we get with the kit are carefully selected, especially in terms of being quiet....but I keep seeing some that put out 36volts instead of 24volts....I was curious if anyone has tried to up the power and consequently the bias higher than the current specs of 24 volts DC/12 volts per channel ?
You rang?
Yes, since I finished my original ACA monoblocks, which used the kit SMPS, my builds since then have all run the amp boards at higher voltages. I am pleased to report that they work very well that way. So far I've been building with linear power supplies, starting with 22V, then going to 24V secondary windings on 300VA transformers. I've also tried a few different types of diode bridge rectifiers to eek the most out of the transformer output voltage. Here is a summary of where I ended up: ACA amp with premium parts
I also bought a couple sets of enclosed chassis-mount SMPS, including 27V and 36V outputs, but haven't built any amps with those yet. I'm being thoroughly distracted by M2x for the time being. However, amp board doesn't know or care whether it's getting its voltage from an SMPS or a toroidal transformer. While the K170 JFet used in the Q4 position can handle somewhat higher voltages (30V +), it is a good idea to add a resistor between the main power rail and the Drain of the JFet. This is R16 in my modified ACA schematics. I've also added a 100uF cap on the output of that resistor to provide a better filtered supply to the input stage of the amp.
Besides running at higher voltages, I also bias at higher currents, by changing the values of R3 and R4. All of my ACA builds have been using 1.6 Amps as the bias current. This seems to be a good spot for a smaller amp with smaller heatsinks. The last ACA that I built used IRFP140s for the power Mosfets, and I plan to continue using those for higher voltage builds.
Please note that the Hafler chassis and the Mini Dissipante 3U chassis have larger heatsinks than the standard ACA kit. My highest voltage Hafler chassis build runs pretty warm, but not quite hot. I intend to push that envelope a little further when I finally build with the 36V SMPS.
Yes, since I finished my original ACA monoblocks, which used the kit SMPS, my builds since then have all run the amp boards at higher voltages. I am pleased to report that they work very well that way. So far I've been building with linear power supplies, starting with 22V, then going to 24V secondary windings on 300VA transformers. I've also tried a few different types of diode bridge rectifiers to eek the most out of the transformer output voltage. Here is a summary of where I ended up: ACA amp with premium parts
I also bought a couple sets of enclosed chassis-mount SMPS, including 27V and 36V outputs, but haven't built any amps with those yet. I'm being thoroughly distracted by M2x for the time being. However, amp board doesn't know or care whether it's getting its voltage from an SMPS or a toroidal transformer. While the K170 JFet used in the Q4 position can handle somewhat higher voltages (30V +), it is a good idea to add a resistor between the main power rail and the Drain of the JFet. This is R16 in my modified ACA schematics. I've also added a 100uF cap on the output of that resistor to provide a better filtered supply to the input stage of the amp.
Besides running at higher voltages, I also bias at higher currents, by changing the values of R3 and R4. All of my ACA builds have been using 1.6 Amps as the bias current. This seems to be a good spot for a smaller amp with smaller heatsinks. The last ACA that I built used IRFP140s for the power Mosfets, and I plan to continue using those for higher voltage builds.
Please note that the Hafler chassis and the Mini Dissipante 3U chassis have larger heatsinks than the standard ACA kit. My highest voltage Hafler chassis build runs pretty warm, but not quite hot. I intend to push that envelope a little further when I finally build with the 36V SMPS.
Hello! I ordered my ACA a couple of days ago - my first electronics project. Has anyone tried running the Klipsch RP 600m with a single ACA? It seems to be a very popular speaker with the online reviewers. Would anyone strongly recommend going with dual mono for these? This is going to be a second system for me so I'd prefer to not go financially too deep into this if I can help it. Thanks.
36volts would probably blow up the JFETs in the amp from what I’ve heard. We’ve already upped the standard voltage from 19 to 24v. And now include brand name Meanwell power bricks.
I think Parts Express sometimes sells some Meanwell 24v PSU bricks and the diyAudio store sells the 24v Meanwell PSUs bricks separately. The kit supplies aren’t specially selected but are also from Meanwell and that brand is quieter and more powerful than cheapo PSU’s. Various online sources sell Meanwell 24v open frame PSUs (the kind with the perforated covers) which are great if you feel confident that you can attach a power cable with line voltage to the terminal screws without shocking yourself and that said terminals won’t be exposed to friends, family or pets. The 6.5amp ones are more than enough for 2ch.
The 2 channels of the amps are already 24v each because they are wired in parallel to the PSU.
If you have an ACAs with the inexpensive 19v generic supplies, an upgrade to the 24v Meanwells is well worth it.
I think Parts Express sometimes sells some Meanwell 24v PSU bricks and the diyAudio store sells the 24v Meanwell PSUs bricks separately. The kit supplies aren’t specially selected but are also from Meanwell and that brand is quieter and more powerful than cheapo PSU’s. Various online sources sell Meanwell 24v open frame PSUs (the kind with the perforated covers) which are great if you feel confident that you can attach a power cable with line voltage to the terminal screws without shocking yourself and that said terminals won’t be exposed to friends, family or pets. The 6.5amp ones are more than enough for 2ch.
The 2 channels of the amps are already 24v each because they are wired in parallel to the PSU.
If you have an ACAs with the inexpensive 19v generic supplies, an upgrade to the 24v Meanwells is well worth it.
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I have a few Mean Well SMPS units on hand to try in future ACA builds. One pair of RSP-150-27, and another pair of RSP-200-36. I have also considered the HRP-200 series. These all have active power factor correction and built-in constant current limiting under overload conditions. I will be using higher power units for the higher voltages in order to maintain at least 5.5 Amp output capacity for the two channels.
Supply filtering will be CRC or CLC, with the intent of removing 60 to 80 kHz power switching frequencies instead of 60/120 Hz line / rectifier frequencies. It is also necessary to be mindful of the maximum recommended capacitive load, so the values will look very different from what we are used to seeing in a FirstWatt style PSU.
The input JFets on my boards are protected against excessive voltage by an RC dropping network. As I push the supply rail toward 30V, I will be using 1.0 kOhm and 100 uF. I will adjust other resistances on the board as necessary.
Supply filtering will be CRC or CLC, with the intent of removing 60 to 80 kHz power switching frequencies instead of 60/120 Hz line / rectifier frequencies. It is also necessary to be mindful of the maximum recommended capacitive load, so the values will look very different from what we are used to seeing in a FirstWatt style PSU.
The input JFets on my boards are protected against excessive voltage by an RC dropping network. As I push the supply rail toward 30V, I will be using 1.0 kOhm and 100 uF. I will adjust other resistances on the board as necessary.
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If the specs are true and these are 96dB 8 ohm speakers, go single and try it first. I think it would be more than enough and you will surely enjoy it!
They do rate them as 100W/400W, which is a bit of a stretch in terms of power (more on this later!). My 86dB 4 ohm speakers were happy with a single ACA at 19V PSU, so I am not talking about actual test with those speakers. Still, I think you will mostly be OK. Have you done the test of actual volts required to reach your desired levels? It's an interesting eye opener: A Test. How much Voltage (power) do your speakers need?.
For what it's worth, Herb Richert said that they are REALLY LOUD with even 8W of tubes, so you are good to go! (Klipsch Reference Premiere RP-600M loudspeaker Page 2 | Stereophile.com)
Rafa.
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Thanks, Rafa. I appreciate your input! I don't own the speakers yet but I think it will be easy to pull the trigger once the amp gets near completion. Charles