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Amp Camp Amp - ACA
Amp Camp Amp - ACA
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Old 13th May 2019, 02:18 PM   #7451
TungstenAudio is offline TungstenAudio  United States
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Join Date: Jan 2014
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@tborzic: That is a beautiful ACA!
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Old 13th May 2019, 02:24 PM   #7452
mraudioguru is offline mraudioguru  United States
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Quote:
Originally Posted by TungstenAudio View Post
@tborzic: That is a beautiful ACA!
+1 Very nice dude!

I wish I had 1/100th of the talent that most of you guys have. I can barely follow the directions...
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Old 13th May 2019, 03:19 PM   #7453
oc11 is offline oc11  United States
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@tborzic. I have never seen an ACA with this much heat sinking. What temperature does your ACA operates at? I assume it is not hot at all.
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Old 13th May 2019, 05:07 PM   #7454
tborzic is offline tborzic  Croatia
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@TungstenAudio: thanks. It was my first diyaudio build, and I was not limited in time or dimensions (often a problem when buying premade enclosure). There are still a thing or to to make/improve, but as it sits - I am satisfied. Thank you very much!

@mraudioguru: that is exactly what I was thinking before start. ACA is just THE RIGHT THING to make, having optimal number of parts to make it a beginner's project, exactly as was Mr. Pass idea.

@oc11: well, to my surprise, it is not that cool as I was thinking it will be. I can not find photos at this moment from when I was measuring finished amp, but I did find some from testing phase. Anyway, temperature of complete amp inside rack was cca 50 deg C (so 122 deg F), and I decided it is not best idea to keep it in rack, so it is on top now. Also, I have made some kind of wooden stand for it (like wooden brick, oak wood, I couldn't find teak wood that big), but I removed it for safety reasons (my kid's birthday). I guess that temperature now is 42-43 deg C (cca 110 deg F), so really nice.
Here are two photos few minutes ago. It was really difficult to cut that one peace of aluminum heatsink into four pcs, than grind them (by hand) to make them same thickness, and drill all holes, and thread most of them. 90% of that was done on kitchen table . Not to mention holes on top cover, or frame made of aluminum L and U profiles.
Well worth the effort .
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Old 13th May 2019, 10:02 PM   #7455
oc11 is offline oc11  United States
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Wow!, thank you for describing what you did with the heatsinks, lots of work involved. I am surprised the temperature is as high as you describe, but it certainly is entirely fine. Great work and thanks for sharing.
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Old 15th May 2019, 10:05 PM   #7456
elb is offline elb  Australia
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Quote:
Originally Posted by TungstenAudio View Post
Indeed, it's fun to see old gear get turned into a Q ship by the addition of some really nice class A amplifier modules hidden inside.


The ACA responds well to a 24V supply, along with some tweaks to the input and feedback resistors. I like using 20k for R11 and 90.9k for R12. The trim pot should be adjusted to get about 12.2V for the "bias voltage" to take advantage of the higher rail voltage. Those changes will get your power output closer to 9 Watts, which will be a noticeable improvement.
Is this in reference to the ACA v1.6?
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Old 16th May 2019, 01:02 AM   #7457
oc11 is offline oc11  United States
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@elb. If you read this thread (and I know it is extremely large) you will find out any number of changes and alterations that have been used by people in their ACA units, 1.6 and prior versions. Some things are agreed upon: 1. The increase in voltage to 24 volts is beneficial for the performance of the ACA. 2. Lots of people have had issues with low output from the ACA when used without a preamp, it is therefore generally accepted that a preamp is a very good addition to the system particularly when used with certain types of speakers. I think you should feel free to try the mods suggested by TungstenAudio and see if you like them and feel they improve the sound. Let your ears decide. Remember one of the reasons Mr. Pass started the ACA kits was to foster experimentation and to propagate knowledge about amplifiers.
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Old 16th May 2019, 03:45 AM   #7458
rnjorge is offline rnjorge  Brazil
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I have just finished building the B1 with the Korg NuTube to use with my second version of ACA (1.5?). Both were very happy with the match!
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Old 16th May 2019, 04:13 AM   #7459
elb is offline elb  Australia
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Quote:
Originally Posted by oc11 View Post
@elb. If you read this thread (and I know it is extremely large) you will find out any number of changes and alterations that have been used by people in their ACA units, 1.6 and prior versions. Some things are agreed upon: 1. The increase in voltage to 24 volts is beneficial for the performance of the ACA. 2. Lots of people have had issues with low output from the ACA when used without a preamp, it is therefore generally accepted that a preamp is a very good addition to the system particularly when used with certain types of speakers. I think you should feel free to try the mods suggested by TungstenAudio and see if you like them and feel they improve the sound. Let your ears decide. Remember one of the reasons Mr. Pass started the ACA kits was to foster experimentation and to propagate knowledge about amplifiers.
@oc11.
Thank you for the explanation.
I have just recently built the ACA as per the excellent build guide.
Fired it up and it works.
I have no problem with the output.
The sound quality of this little amp is wonderful and I will leave the modifications to the experts.
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Old 16th May 2019, 05:47 AM   #7460
oc11 is offline oc11  United States
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@elb.
Glad to hear you are enjoying your ACA with no modifications. If it is not broken don't fix it. All the best.
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