[rif]

Class A amps are not suited to hot areas residents, after some years the PCBs and components are fully roasted and may not live much longer, but they are nice to have in Canada or Northern Europe.

play music loud!     

class A has a constant power draw so it equals power to the soeakers + amp heat.  am I wrong. 

[JMW73]

Let’s refocus, shall we?

I had a long talk with poseidonsvoice last night. Very helpful guy and plugged into the DIY amp building community. While I haven’t ordered anything yet, I have basically decided to build the ACA monos, and use that experience as a jumping off point to maybe build something more advanced in the future.

Thanks you for all of the help. I wish I could own them all!

I’ll update here as things progress.

[Stercom]

Let’s refocus, shall we?

I had a long talk with poseidonsvoice last night. Very helpful guy and plugged into the DIY amp building community. While I haven’t ordered anything yet, I have basically decided to build the ACA monos, and use that experience as a jumping off point to maybe build something more advanced in the future.

Thanks you for all of the help. I wish I could own them all!

I’ll update here as things progress.

Sounds like a plan. Good luck with the build!

[FullRangeMan]

I said the post #34 why since the 1990s already various used Class A amp I was interested to buy the main board and components mainly resistors and SMDs were visibly toasted by the heat inside the chassis, this is a hot city, so I didnot buy any of them because these amps were compromised and thats why they were for sale.

Today if here the Customs Duties were not 100% to 110% of product cost, more shipping and insurance I would buy a Class D or the Aegir with a nice tube pre-amp IMO, and I always would use it with the top cover removed for constant cooling.

[opnly bafld]

I said the post #34 why since the 1990s already various used Class A amp I was interested to buy the main board and components mainly resistors and SMDs were visibly toasted by the heat inside the chassis, this is a hot city, so I didnot buy any of them because these amps were compromised and thats why they were for sale.

Won't be a problem if they are properly designed and made.

[FullRangeMan]

Won't be a problem if they are properly designed and made.

It would be good to know when it was well designed and built
Small heatsinks are a obvious fault, along with small transformers.
Always prefered laminated EI power transformers in regards to Toroidals, hence my preference to the Aegir.

In the 1980s when I had this 30Kg, 350W Class AB power below it got hot when driving my Amazings, so I had to remove the cover.

[JMW73]

Update:

Part way through the build of my ACA amps.  The boards are done and just mounted to the heat sinks last night.  So, I'm ready to start the case build/internal wiring.  This is a fun project; I'm taking my time and enjoying the process.

[FullRangeMan]

Looks great, very interested in these ACÀ.

[JMW73]

***Update***

I've had this system together now for a bit.  My daughter has been the one to use it mostly and has definitely run it in.  Here are the components:

WiiM Pro as music source (also a TV connected digitally)
Emotiva XDA-3 DAC/Pre
Monoblock Pass ACA
Klipsch RP-600M on Stands
REL 8" sub

This little system rocks!  My kids tend to use it the most.  I wish I had something like this when I was their age!  But I do sit and enjoy it from time to time.  The amps need a TON of gain to come alive, but when they do they sound really nice.  And the XDA-3 does a good job with them.

It doesn't look like I put this in this thread, but I ordered some upgraded parts for the amps.  Output caps and mosfets, but also some different sized resistors that came recommended.  They came together very nicely and I highly recommend this as a project to anyone interested.  I am curious as to what a tube pre-amp would do in a system like this.

[CWelsh]

I know it has been a few months since this topic has been active, but I'm curious how you feel about the ACAs after having them for a while?

I have a single ACA powering my Klipsch Forte IIIs and love it! I'm currently using a Marantz 1060 as my preamp and have been thinking about building either a tube pre, or a Pass designed SS pre to replace it. Also considering trying a Pass designed bi-amp active crossover. If I get crazy, I might build another ACA, use two as monoblocks for the mid/high side and throw in a Class D amp for the bottom end. At least that is one avenue I'm considering...LOL

[JMW73]

I know it has been a few months since this topic has been active, but I'm curious how you feel about the ACAs after having them for a while?

I have a single ACA powering my Klipsch Forte IIIs and love it! I'm currently using a Marantz 1060 as my preamp and have been thinking about building either a tube pre, or a Pass designed SS pre to replace it. Also considering trying a Pass designed bi-amp active crossover. If I get crazy, I might build another ACA, use two as monoblocks for the mid/high side and throw in a Class D amp for the bottom end. At least that is one avenue I'm considering...LOL

Having lived with it for awhile, it's still amazing how good it sounds!  I think a tube pre would sound great! 

[RDavidson]

Having lived with it for awhile, it's still amazing how good it sounds!  I think a tube pre would sound great!

The ACA is a wonderful little amp. It has been described as a baby F5, which I can understand the comparison. It isn’t necessarily the most “refined” amplifier, but is pretty mind boggling for what it does at its price. I agree a tube preamp, like the NuTube kit or something like the Schiit Saga would be good places to start. The tube preamp would be great way to knock a little of the ACA’s edge off and flesh out the sound a bit and provide nice synergy. Couple them to a pair of Omega CAMs or maybe Klipsch RP600MII’s and one would have a very cool, over-achieving, and relatively inexpensive setup.

[FullRangeMan]

If one needs only 125Wrms 8ohms ($725) I would suggest an Stereo GanFet amp,
There is more power versions.
https://classdaudio.com/product/gan-fet-amplifiers-3/

[poseidonsvoice]

The ACA is a wonderful little amp. It has been described as a baby F5, which I can understand the comparison. It isn’t necessarily the most “refined” amplifier, but is pretty mind boggling for what it does at its price. I agree a tube preamp, like the NuTube kit or something like the Schiit Saga would be good placeshttp:// to start. The tube preamp would be great way to knock a little of the ACA’s edge off and flesh out the sound a bit and provide nice synergy. Couple them to a pair of Omega CAMs or maybe Klipsch RP600MII’s and one would have a very cool, over-achieving, and relatively inexpensive setup.

Just a small correction.The ACA Mini is the baby F5 (both in sound and design topology), the original ACA which is still selling is not. The original ACA has more 2nd harmonic content which may or may not suit folks, being a bit more forward in the midrange and a less taut robust midbass unless you run them balanced as monoblocks with a balanced source. This cancels a lot of the 2nd harmonic making it more 3rd harmonic specific. The ACA is single ended Class A. The ACA Mini however is push pull and is Class A except at the power extremes or into lower loads. This has to do with how bias current affects push pull topologies vs single ended ones. The original ACA being single ended, is always Class A and will never be Class B, it will just clip.

That being said, it’s all subjective and they can both sound good in the right mix.

Here is a link: https://www.firstwatt.com/wp-content/uploads/2023/12/art_aca_mini.pdf

If you want to move beyond the ACA mini, I suggest the F5m. Then the F5. Then the F5 turbo. From there there are several branches including the The F5p-M2OPS combination, the USSA 5 and USSA 3, and so on. Basically, if you are prolific at diy building, the acquisition of that elusive amplifier you yearn for becomes dramatically easier and cheaper.

Enjoy the journey,

Best,
Anand.

[FullRangeMan]

Thankyou Anand, this was a good post, if one live in a cold area the regular SET ACA seems perfect for a hi sensitivity speaker.

[planet10]

ACA is SE, ACA mini is PP.Bridged ACA sound much like the ACA mini.

One of my ACAs is happily driving a set of FA22eN downstairs. Sounds really decent.

dave