Just thought I'd mention that for whatever reason I have 8ohm 98db/m efficiency speakers and oddly enough, while the aca does provide a more balanced lower end, my 8 watt class A tube amp can drive my speakers to a point where the neighbors get to listen to my music and the higher end and instrument decay is better....the ACA gets to normal listening levels with those speakers but being both single ended class A with 8 watts per channel amplifiers I figured the ACA would drive my speakers a bit more....or be on par with the tube amp, but I was wrong.
Do you have a PRE with some gain in front of your setup? For me, that was the difference between 'ok sound' (not only volume, but body as well) and: YES! This is what everyone talks about when talking about the ACA.
Ps. I mean, is te gain of both the ACA and your TubeAmp more or less the same? If not,match that to 'compare' the volume at X gain.
Ps. I mean, is te gain of both the ACA and your TubeAmp more or less the same? If not,match that to 'compare' the volume at X gain.
yeah, currently I'm using an NAD 1020B preamp....the normal pre outputs. It does have high level pre out....like with an output of 15volts, but theres a cold solder joint on one channel that I need to repair. But I have others as well...I've also used an aikido preamp, and the preamp in my Sansui AU-517.....as always, it's all about synergy.....I think my higher rated efficiency speakers most likely have some bigger impedance swings, etc. because even though my boston acoustic A-150 are only like 91 DB/watt efficient it's an 8Ohm speaker which across the frequency spectrum never dips below 6Ohm and that seems to obviously be making a difference......but yeah, long story short , I've been able to drive the ACA to the point where ya hear distortion in terms of throwing gain at it.
RIght now I'm just torn and will probably buy another ACA and have two monoblocks....yeah, the consensus is that the Aleph J and others are better amps with 25 watts class A etc.....but since I've already got one ACA, I would think having two ACA 15 watt monoblocks would be hopefully be close in overall equality or enjoyment and I'd only have to spend another 329 dollars....I'm not familiar with the other amps but I'm sure they cost a lot more to build than another ACA.
For who it can serve, I have built a "normal" ACA, I mean the site kit proposal just plain and simple and it drives a pair of Klipsch KG3 with ease . I have no pre-amp, to the contrary it is a passive limiter , the Schiit SYS.
I listen at low level because I live in a flat and every listening is a pleasure.
- Just as a reminder, one of the most important link is the recording quality, most do not pay enough attention to this parameter and blame their system.
I listen at low level because I live in a flat and every listening is a pleasure.
- Just as a reminder, one of the most important link is the recording quality, most do not pay enough attention to this parameter and blame their system.
Will a pair of ACA amps configured as monoblocs have sufficient power to run transmission line design IPL S-5TL speakers with 10 inch woofer, 5 inch midranges and ribbon tweeters? Can the XLR output monoblocs be bi-wired to the speakers using the pair of speaker terminals? the manual shows only one pair of speakers being connected with the balanced output.
My speakers are rated 94db and I also noticed a well done improvement overall, but particularly in the mid bass over my 125W/ch AB Mosfet amp.
That's using the same unity gain, tube buffer pre amp with both amps.
A pre with some gain is in the works for me and I look forward to trying it with the ACA's after all I've heard about how well the ACA's respond to some gain ahead of them.
That's using the same unity gain, tube buffer pre amp with both amps.
A pre with some gain is in the works for me and I look forward to trying it with the ACA's after all I've heard about how well the ACA's respond to some gain ahead of them.
I also have a Sys and ran it for a while. Nice piece of gear.
May I suggest you consider a Saga? That tube buffer adds some jump and more life overall to the music is my finding. It also has a passive mode should you find you prefer things that way after all.
EDIT: Low volume performance is greatly enhanced by the tube buffer. Somehow it seems to improve dynamics & separation without increasing volume.
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Thanks for the suggestion, I don't know if I would try it but I would certainly keep it somewhere in my head. I am just not fond of tube stuff and that was why I eliminated it right away when I was looking for a preamp but also because tube seems to me to be at the opposite of Pass amp's ideas.
ACA + Klipsch RP 600M
This is a great match for the ACA. I use a 2134 dual op-amp preamp running on +/- 9V batteries.
Very rich mids. This speaker surprised me, especially at $380 pair at
Video Only, Mountain View, CA (NO RELATION)
Very good bass, no sibilance. - Reviews are correct to my experience.
My ACA is Version 1.6 with a 24V supply that came with the kit.
This is a great match for the ACA. I use a 2134 dual op-amp preamp running on +/- 9V batteries.
Very rich mids. This speaker surprised me, especially at $380 pair at
Video Only, Mountain View, CA (NO RELATION)
Very good bass, no sibilance. - Reviews are correct to my experience.
My ACA is Version 1.6 with a 24V supply that came with the kit.
I whole heartedly agree with the statement about recording quality. In the end it's what makes single ended class A, whether it be single ended triode tube type or ACA type amplifier. I'm blessed to have an old high school friend who because of the hobby 20 years ago has turned into one of the biggest vinyl collectors and dealers in Louisiana. So, I have access and get to thumb through the best pressings of records. It's amazing to hear the difference in a great recording or great pressing in sometimes even the same exact record...and that's what makes amps like the ACA, etc. even more precious. Sometimes one minute you are sitting there like musicians are literally playing in the room and unfortunately ya might throw on something next and it makes your ears bleed.
Higher power ACA
Just wondering if anyone explored a slightly higher version of the original ACA, by increasing power supply voltage to 24 VDC, and subsequently reducing R1//R2 + R3//R4 to a lower value. To get 1.5 Amps bias, you could parallel 1 ohm resistors across each of R3 and R4. Equivalent resistance drops from .578 ohms to .43 ohms, requiring 1.5 amps of current to trigger Q3 on at .65 volts.
This should up power out to 9 watts per channel. Dissipation of each heatsink would require 36 watts .
I am already using a 24 vdc power supply, with enough available current to try it.
I am enthralled by how good this little amp sounds, but so far, can only listen to acoustic Jazz etc., at moderate volume, gives acceptable distortion levels. It sounds great, but a tad more volume would be ideal. Anyone try this? How far do you think we could push the original design as far as increased Voltage and Bias current/
Just wondering if anyone explored a slightly higher version of the original ACA, by increasing power supply voltage to 24 VDC, and subsequently reducing R1//R2 + R3//R4 to a lower value. To get 1.5 Amps bias, you could parallel 1 ohm resistors across each of R3 and R4. Equivalent resistance drops from .578 ohms to .43 ohms, requiring 1.5 amps of current to trigger Q3 on at .65 volts.
This should up power out to 9 watts per channel. Dissipation of each heatsink would require 36 watts .
I am already using a 24 vdc power supply, with enough available current to try it.
I am enthralled by how good this little amp sounds, but so far, can only listen to acoustic Jazz etc., at moderate volume, gives acceptable distortion levels. It sounds great, but a tad more volume would be ideal. Anyone try this? How far do you think we could push the original design as far as increased Voltage and Bias current/
I've been kicking around the idea of building an ACA and am wondering if it'll have enough oomph for my setup.
I've got a pair of Golden Ear AON3's (Bookshelf Speakers: Aon Series | GoldenEar Technology) Specs from the mfg say they're 90db efficient and '8 ohm compatible'.
I'm passing the speaker output from my receiver though the speaker level inputs of a powered Golden Ear Forcefield 3 sub (Subwoofer: Forcefield Series | GoldenEar Technology) which has a high-pass filter somewhere around 150Hz.
So I guess my question is does having the high-pass filter pulling out some of the lower frequencies free up a little more power for the speakers? Anyone have any experiences with something close to 90db efficient speakers and non-monoblock ACAs?
I've got a pair of Golden Ear AON3's (Bookshelf Speakers: Aon Series | GoldenEar Technology) Specs from the mfg say they're 90db efficient and '8 ohm compatible'.
I'm passing the speaker output from my receiver though the speaker level inputs of a powered Golden Ear Forcefield 3 sub (Subwoofer: Forcefield Series | GoldenEar Technology) which has a high-pass filter somewhere around 150Hz.
So I guess my question is does having the high-pass filter pulling out some of the lower frequencies free up a little more power for the speakers? Anyone have any experiences with something close to 90db efficient speakers and non-monoblock ACAs?
Hi darkstargtk,
I'm using my aca with these
Bookshelf-3WC
90db large bookshelf and I find this amp is fine. Although it's not quite party loud on full volume, it fills the a largish kitchen dinner with a full sound.
The high pass should block the low frequency so yes, that should help reduce the current demand on the amp.
It maybe worth experimeting running the tops full range and using a mono sub line out if your receiver does that. You may be able to do away with quite a lot of speaker cable.
Im using a yamaha wxa50 (I think that's the one, it's an unpowered, streaming dac preamp) that sits very nicely under the amp camp.
I'm using my aca with these
Bookshelf-3WC
90db large bookshelf and I find this amp is fine. Although it's not quite party loud on full volume, it fills the a largish kitchen dinner with a full sound.
The high pass should block the low frequency so yes, that should help reduce the current demand on the amp.
It maybe worth experimeting running the tops full range and using a mono sub line out if your receiver does that. You may be able to do away with quite a lot of speaker cable.
Im using a yamaha wxa50 (I think that's the one, it's an unpowered, streaming dac preamp) that sits very nicely under the amp camp.
Before you think you need more power (higher volumen) it is important to find out if it is because you need more amplification at the input stage/preamp or because you drive ACA to clipping. Maybe measure with a DMM (at ACA output) that has a peak hold function and see you ever pass 10V in peaks. If you don't do that at full volumen you may need a pre-amp with more voltage swing.
Hi darkstargtk,
I'm using an ACA with a Naim 32.5 preamp and Linn Keilidhs (claimed sensitivity of 92dB, which I feel is optimistic). The combination works well due, l believe, to the bandwidth limiting of the Naim preamp. It gets plenty loud enough for day to day use and it sounds very detailed and engaging with a good variety of music.
I have tried this with an Aksa Lender preamp which is not bandwidth limited. The bass become muddy, poorly controlled and the ACA quickly runs out of steam. I can't listen to that arrangement for any length of time.
The Aksa Lender sounds perfectly good in other set-ups.
As a result of building my ACA, I have enjoyed it so much that built a second one, then the Aksa Lender preamp. I now have a Gainclone, Aleph P and an F5 in the pipeline.
I would thoroughly recommend building an ACA anyway. It is a great educational exercise and it is a joy to listen to.
I'm using an ACA with a Naim 32.5 preamp and Linn Keilidhs (claimed sensitivity of 92dB, which I feel is optimistic). The combination works well due, l believe, to the bandwidth limiting of the Naim preamp. It gets plenty loud enough for day to day use and it sounds very detailed and engaging with a good variety of music.
I have tried this with an Aksa Lender preamp which is not bandwidth limited. The bass become muddy, poorly controlled and the ACA quickly runs out of steam. I can't listen to that arrangement for any length of time.
The Aksa Lender sounds perfectly good in other set-ups.
As a result of building my ACA, I have enjoyed it so much that built a second one, then the Aksa Lender preamp. I now have a Gainclone, Aleph P and an F5 in the pipeline.
I would thoroughly recommend building an ACA anyway. It is a great educational exercise and it is a joy to listen to.
I thought I'd add my experience. I got two v1.6 kits end of last year to drive my Quad ESL57s. I run a pair of quads per channel - each pair connected in parallel, I use an ACA monobloc per pair driven differentially by Audiolab MDAC+ DAC/digital preamp. The sound is very good indeed, I also have a Quad 22/II setup which I use as reference. Sadly the 22/IIs are a bit old and temperamental hence the ACA experiment. So comparing ACA to 22/IIs the ACA sound is every bit as nice, and have the added bonus that I don't need to worry if I forget to turn things off. Thank you Mr Pass for making this design available. I'm just about to embark on building another pair of mono blocs so that I can use one ACA mono bloc per ESL57? WHY? Curiosity.....btw can anyone suggest the size (V) led that should be used since I am sourcing the components directly, rather then use the kits which attract a nasty surprise from HMRC/Customs. I have however bought PCBs from the store.