I think the above stuff is correct. The DIY Carfrae little big horns I use are full range speakers with no crossover between the ACA and main driver but the speaker cable is split at the terminals of a170watt plate amplifier in each speaker that’s manually adjusted for gain and crossover cutoff. The ACA never sees the load from the subwoofers. It was pretty easy to play lots of music and dial back the upper frequencies of the sub whenever it was a bit boomy. I don’t know how true it is but I was told that since your hearing is less sensitive in the low base area going all out Audiophile there won’t get you huge gains. It’s worth pointing out the sound from my subs is very well integrated. Seas 10 inch sub as same size passive radiator. It’s working well for me.
I'm running a pair of ACA's (stock 1.6 build for now) in a bi-amped configuration. Each uses one channel to drive a tweeter and one channel to drive a woofer in my B&W CM5's. It's a whole different ballpark from a single ACA. As much as I love my ACA's, it's not an end-game amp. That wasn't the goal of the design. I'm sure 4 would do more than 2, but I can't commit to an amp that only meant to be the beginning like that. I'm building an F5 and an F6. When I'm done experimenting with how they each sound (and how many more?), I'll come back to how many amps I want to drive each speaker.
Question for Mr Nelson and anyone else - If your speakers are suitably sensitive ie a big set of horns and a you can couple direct to the driver with no cross over from a single ended transistor amp how do you improve on that? Can you build a much better single ended amp than an ACA with minimal components in the signal path?
I've considered single ended tube amps in the past but I'm not in a position to test one of those alongside the ACA.
I'm just a massive believer in a minimalist approach where possible.
I had made 1 a month ago, my virgin journey into class a. Full takman carbon matched.
Feedback bypassed with 10pf silver mica.
Running crc with 5400uf 35v paralleled x8 resistor then 5400uf x8 paralleled. +0.1uf mylar
Elna output capacitor
Yamaha ns 10 speaker.
I thought sansui au505a/au777/au555a is unbeatable in value and musicality. Well aca camp is just one step above. Even like this even more than cayin with kt88 pushpull.. I'm floored. It's magic. I'm listening to it in the morning when I can. I don't think any one can believe it's a 8w class a
Feedback bypassed with 10pf silver mica.
Running crc with 5400uf 35v paralleled x8 resistor then 5400uf x8 paralleled. +0.1uf mylar
Elna output capacitor
Yamaha ns 10 speaker.
I thought sansui au505a/au777/au555a is unbeatable in value and musicality. Well aca camp is just one step above. Even like this even more than cayin with kt88 pushpull.. I'm floored. It's magic. I'm listening to it in the morning when I can. I don't think any one can believe it's a 8w class a
I'm with you. But I have to share this:
“Everything should be made as simple as possible, but no simpler.” - Einstein
I think Papa did an amazing job designing an amp that virtually anyone can build, get amazing results from, and not have to mess with mains voltage to boot! I doubt he'd describe it as the best listening experience, bar none. It might be a touch to simple for that.
I've had lots of fun studying the First Watt designs. I picked an F5 as my second build because it's also pretty simple, but very different than the ACA. I picked an F6 for my third build, again, because it's different.
The ACA is fantastic, though, I love my pair!
Makes sense: Fidget!
In the words of the wise professor (or, at least someone like him) -
"There is no such thing as a perfect amplifier. All audiophiles and their associated equipment have specific needs, but in each case there is such a thing as a best amplifier - the one that makes you happy."
For me: The ACAs do a really good job of that. But they are not for everyone.
Have fun!
In the words of the wise professor (or, at least someone like him) -
"There is no such thing as a perfect amplifier. All audiophiles and their associated equipment have specific needs, but in each case there is such a thing as a best amplifier - the one that makes you happy."
For me: The ACAs do a really good job of that. But they are not for everyone.
Have fun!
I just finished my ACA and couldn't be happier with the result. It is driving my desktop speakers (full-range DIY Aplair 6P). The ACA easily outperforms the modified Dynaco SCA-35 el84 tube amp I had been using. There is some real magic with the ACA & Alpair combination!
I am using a choke input linear power supply. PSU designer predicted 22v and I ended up with 26v so even with the big heatsinks it runs hot!
I tweaked the circuit a little. For my setup I found that reducing the feedback sounded considerably better (R12=68k, R11=6.5k). I replaced the cheap input electrolytic with a 4.7uf Solen film cap and while it did sound better the benefit was marginal. I am working on a kludge to substitute the output cap with 4x 1000uf standard Blackgates since I have a box of them.
Given the great results for the lowly ACA I am planning to build an Aleph J next.
I am using a choke input linear power supply. PSU designer predicted 22v and I ended up with 26v so even with the big heatsinks it runs hot!
I tweaked the circuit a little. For my setup I found that reducing the feedback sounded considerably better (R12=68k, R11=6.5k). I replaced the cheap input electrolytic with a 4.7uf Solen film cap and while it did sound better the benefit was marginal. I am working on a kludge to substitute the output cap with 4x 1000uf standard Blackgates since I have a box of them.
Given the great results for the lowly ACA I am planning to build an Aleph J next.
Attachments
I found that's adding a buffer pre amp really made a big difference more detail and better dynamics
Salas hotrodded blue DCB1 build
I've got a the Korg Nutube on order with Khozomo selector and attenuation all on one $200 board plus bigger Galaxy U2 to fit it all in.
Only worry is a couple of comments from folk that say the B1 Buffer sounds better and that the Korg is a bit too much of a good thing. Wait and see, I'm used to a valve sound and whilst the ACA is super clean sounding with a massive sound stage (Almost everything better than my push pull triode amp) it hasn't got my feet taping in quite the same way just yet.
Khozmo stuff will sound very revealing, analytical and... authentic. With Nutube, you may get a match made in Heaven. Fine-tuning can be done with internal wiring and choice of those 3 coupling capacitors. To add, you can play with the power supply rail voltage and/or plate voltage to further tune the sound and make it suitable to the rest of your system, and your listening preferences.
Oh yes ill catch up one day Korg is the route id choose today but dcb1 will have to do me for a while yet.
FWIW, I’m using an ACA 1.1 with an Aikido LV in my office system (driving Linaeum LFX monitors and a Dayton Titanic 10” sub) and an active preamplifier stage works extremely well with the ACA.
My previous boss now retired has spent a considerable amount over a long period on a huge NAIM System that I think i’ll match or exceed with DIY speakers and amplification. I swapped out the ACA hook up wire on all the signal and speaker connections with solid copper core gold plated 0.9mm stuff. Nearly 3 metres in total on a pair of ACA. My feet are tapping more this morning ��