Hi U-man, great to hear from you. I built a ACA from the first kit series offered, which just had a HeatsinkUSA 8.46 heatsink, which is 8.46" x 1.3" by 3' tall. It was fine for the earlier 1 amp bias current, but I would not want to put much more heat through it. Your heatsink should take the higher bias and 24 VDC. I took that ACA to a friend, and we rigged up a temporary output from one of his guitar amp preamp sections (I do not remember which one). He tried it on several different guitars and even a bass guitar. We were very impressed. It was more smooth, clear and detailed than his other solid state amps. It let through what was sent to it (more undistorted distortion, or is that an oxymoron?) We decided a necessary component would be a good tube preamp that would allow you to overdrive it to get the desired distortion and not try to overdrive the ACA. Zen Mod knows a lot about that and might chime in here with ideas.The best sounding guitar speaker we tried it on was the one that came with the Orange Tiny Terror.
Give me a PM or call me some time and we will talk more about it.
Give me a PM or call me some time and we will talk more about it.
If the ACA is the target amplifier, then the IRFP240 (pbf) is the default choice, and the best place to start. Since that transistor is also the default for the Aleph J and other FW clones, it is convenient as well. The ACA does not require matched power transistors, so it may use 'leftovers' from matching devices for other builds.
I am presently experimenting with IRFP140 devices in one of my ACA builds. This transistor shows a lot of promise, but needs a higher voltage to distinguish itself from the IRFP240. Something to do with the forward transconductance vs Vds properties.
I am presently experimenting with IRFP140 devices in one of my ACA builds. This transistor shows a lot of promise, but needs a higher voltage to distinguish itself from the IRFP240. Something to do with the forward transconductance vs Vds properties.
Thank you very much for the advice
I also read that 240 is good. Now many people praise 250, many variations.
Everyone praises his concept. It distorts the truth.
Hey 6L6 and proitious
Thanks for your replies
I'll contact you Propitious. Glad you liked it with the guitar.
Uriah
Thanks for your replies
I'll contact you Propitious. Glad you liked it with the guitar.
Uriah
Head to store and if you find yourself at the chassis page for the ACA, you'll see it mentions a 2U chassis.
Go to the chassis page and check out a Mini Dissipante 2U. As I understand it, that's the bare bones equivalent of the ACA. Dimensions can be found there. Don't forget to divide by 10 to convey from mm.
Hi, my ACA 1.6 sounds great.
Unfortunately, with the volume on reasonable sound, (not loud), it is crackling the tweeters on our Rogers speakers.
If I add an extra Pass ACA, would it make enough power for a variety of speakers that would stop the crackling in the speakers or should I swap to something else with higher power to build? Would want something that sounds as good as the Pass ACA.
Unfortunately, with the volume on reasonable sound, (not loud), it is crackling the tweeters on our Rogers speakers.
If I add an extra Pass ACA, would it make enough power for a variety of speakers that would stop the crackling in the speakers or should I swap to something else with higher power to build? Would want something that sounds as good as the Pass ACA.
Rogers Speakers Question
Maybe the caps in your crossovers need to be changed?
Also, with what are you driving the ACA? Make sure your source audio is not being clipped.
Maybe the caps in your crossovers need to be changed?
Also, with what are you driving the ACA? Make sure your source audio is not being clipped.
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Good idea about the caps on the Roger. It is the Roger LS7 and bought it in around 1994.
Will test the system with our old amp, it never had the crackles though.
Driving the ACA is the AKSA Lender, with the system sorted for the ACA #957:
https://www.diyaudio.com/forums/ana...ender-preamp-40vpp-output-96.html#post5641366
Question. I'm planning on building a set of CSS Criton 1TDs this year. My plan to drive them was to start with a Hypex or Ice Power class D amp, then at some point biamp them. I had hoped to build a pair of ACA's to drive the tweeters, but the tweeter in the Critons is 4 ohm, and doesnt come in an 8 ohm variant.
The question is, the ACA is not designed to drive a 4 ohm load in balanced monoblock form, but would it make a difference if it were only fed crossed over signal over 1.8Khz?
The question is, the ACA is not designed to drive a 4 ohm load in balanced monoblock form, but would it make a difference if it were only fed crossed over signal over 1.8Khz?
Your mileage may vary - however:
I drive a 4 ohm loads with my ACA.
If your drivers are reasonably efficient to outstandingly efficient you won't need but a half a watt or so. Having used both active and passive crossovers. Crossed around 800 hz - ACA does an outstanding job driving my Heil AMT's and in the room I listen it is plenty of sound. With the stock crossovers, driving the woofers and tweeters and the crossover point around 1 kHz. It sounded pretty good.
Current setup uses an active crossover. Driving the AMT drivers with two ACAs configured as monoblocks: and use an Emotiva XPA-200 to drive the way less efficient ESS woofers. It is class A/B. But is a better choice for the back emf of the woofer.
All rooms are not the same as this one so cant vouch for how your setup will work. But can say the ACAs have run non stop hours and hours for about 8 months now working into the AMTs which are more like a 4 to 5 ohm resistor electrically. And they keep on sounding incredible.
I drive a 4 ohm loads with my ACA.
If your drivers are reasonably efficient to outstandingly efficient you won't need but a half a watt or so. Having used both active and passive crossovers. Crossed around 800 hz - ACA does an outstanding job driving my Heil AMT's and in the room I listen it is plenty of sound. With the stock crossovers, driving the woofers and tweeters and the crossover point around 1 kHz. It sounded pretty good.
Current setup uses an active crossover. Driving the AMT drivers with two ACAs configured as monoblocks: and use an Emotiva XPA-200 to drive the way less efficient ESS woofers. It is class A/B. But is a better choice for the back emf of the woofer.
All rooms are not the same as this one so cant vouch for how your setup will work. But can say the ACAs have run non stop hours and hours for about 8 months now working into the AMTs which are more like a 4 to 5 ohm resistor electrically. And they keep on sounding incredible.
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Thanks so much for the reply. Looks like I'm back in business. It seemed to me that driving a tweeter at 4 ohms would be much less demanding than driving a full range, multi driver speaker or woofer. That helps me narrow my options for the class D amp. I'm thinking a Hypex amp that will do around 125W @ 8 ohms would be fine for both full range use, and be good to go with 18 or 20W from a pair of ACAs. I thought it was strange to think of using a class D amp, and a pure class A amp on the same speaker, but I think it may sound awesome.
