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Amp Camp Amp - ACA
Amp Camp Amp - ACA
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Old 5th June 2019, 08:02 PM   #7541
Ericc1 is offline Ericc1
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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.
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Old 5th June 2019, 08:36 PM   #7542
mg16 is offline mg16
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Default 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/
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Old 5th June 2019, 08:41 PM   #7543
Mazeppa is offline Mazeppa  United States
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Amp Camp Amp - ACA
Quote:
Originally Posted by mg16 View Post
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/
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Old Yesterday, 05:45 AM   #7544
darkstargtk is offline darkstargtk
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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?
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Old Yesterday, 07:09 AM   #7545
mrdave45 is offline mrdave45  United Kingdom
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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.
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Old Yesterday, 07:21 AM   #7546
MEPER is offline MEPER  Denmark
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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.
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Old Yesterday, 10:10 AM   #7547
SuppersReady is offline SuppersReady  United Kingdom
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Amp Camp Amp - ACA
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.
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