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ACA Mini "Almost Clone" Board

Finished tweaking the bias today after getting a sense of how much it drifted after some warmupand hooked it up in my second system.

Unfortunately, while it makes music, one channel is significantly louder than the other. I’ll be digging into that in the main thread, but wanted to present one more completed amp.

A78533AD-3FC2-4EA6-8F33-65700F08757D.jpeg
 
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KevinHeem

Member
Paid Member
2007-11-04 6:39 am
Hudsonville, MI
Finished tweaking the bias today after getting a sense of how much it drifted after some warmupand hooked it up in my second system.

Unfortunately, while it makes music, one channel is significantly louder than the other. I’ll be digging into that in the main thread, but wanted to present one more completed amp.
R2 and R3 should be 221K. I can't make out the values the way they are oriented on the board. Let that be a lesson to all builders. Can you verify the values?
 
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CoGT3

Member
Paid Member
2010-08-02 10:56 pm
Another board and Fets have safely arrived! If all goes well I will have started my journey to become a Fearless Amplifier Builder by next weekend. I checked all the parts against the BOM and tested values of all the resisters last night. It’s my daughter’s birthday so probably won’t be able to hit the solder station for another week.

Thanks again to Kevin for organizing this effort and our Papa for donating the Harris Fets!

477E139E-CCA9-41A7-83DA-5A0A79A7F2B8.jpeg
 
BOM listed in Nelson's article (Part 1) in 1st post of ACA mini thread:

https://www.diyaudio.com/community/threads/diy-aca-mini.379037/
There might be some mods that members recommend, but I haven't dug through all the posts to discover them. 6L6 and others suggest building our toys as stock, and then trying out variations. All part of the fun and the adventure. Cheers, - David
 
BOM listed in Nelson's article (Part 1) in 1st post of ACA mini thread:

https://www.diyaudio.com/community/threads/diy-aca-mini.379037/
There might be some mods that members recommend, but I haven't dug through all the posts to discover them. 6L6 and others suggest building our toys as stock, and then trying out variations. All part of the fun and the adventure. Cheers, - David
Not listed in the BOM, as pointed out earlier in this thread, are the jumper headers and jumpers/shunts themselves.
I had both on hand, so I can't suggest specific part numbers.
 

barryso

Member
2008-07-16 3:14 am
There were five separate orders needed for the aca mini build. Got it all right except for the 3/4 ohm resistors (missed it by that much). They have been ordered and should be here this week.

Anyway, it surprised me that this clone board isn't exactly like the board in Nelson's pdf or in 6L6's build guide. The LED resistor has moved to under the smaller caps and now resides with the bank of 4 other resistors. Not much of a change really but it made me take notice.

The direction of the FET's has also changed ... in the original artwork the two pairs face different directions but the clone board has both sides to be installed in the same direction. Is this also a matter of being tidy?

Is this just part of the evolution of the board as the project matures?
 

Mark Johnson

Member
Paid Member
2011-05-27 3:27 pm
Silicon Valley
Sounds like you are genuinely surprised that the "Almost Clone" PCB is not an exact duplicate of the one in Nelson Pass's pdf document. Almost Clone. Almost. Hmmm.

Have a look at a thread from December 2021, in the Swap Meet forum. Title was "Free PCB: Clone of ACA Mini -- to a good home"


_
 

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barryso

Member
2008-07-16 3:14 am
Sounds like you are genuinely surprised that the "Almost Clone" PCB is not an exact duplicate of the one in Nelson Pass's pdf document. Almost Clone. Almost. Hmmm.

Never really contemplated the word Almost, just the word clone. For the 50 boards offered in the group buy it seemed likely they would be made using the original artwork. That would have been the quickest and easiest path.

Obviously there's nothing wrong with the clone board and I'm tickled to have gotten one. Just surprised someone went to all the trouble.

:)
 
A Huge Thank you too Kevin and Nelson Pass for this incredible amp the Video was a big help with the Bias .
It bought back memories of my F5 bias !
Thanks again everyone! very nice sounding enjoying the Music! working well with a H2 generator as a pre-amp yet even more PaPa awesomeness!
 

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barryso

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2008-07-16 3:14 am

Mark Johnson

Member
Paid Member
2011-05-27 3:27 pm
Silicon Valley
I use two pair of needle-nose pliers to separate those "breakaway header" sticks, into pieces with exactly two pins. One pair of pliers on the left of the V-cut valley, the other pair on the right. Bend slowly and voila, the plastic breaks along the V-cut. You are holding the freshly cut two-pin piece in one pliers, and the remaining stick in the other pliers. Nothing flies away, nothing falls to the floor, nothing jams the vacuum cleaner.
 
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barryso

Member
2008-07-16 3:14 am
Parts received and the almost clone has gone from almost done to actually done. Put two of the mosfets in the wrong place and the LED just sat and blinked madly. Finding the issue and fixing it made it work. It biases and sounds OK. Any learned thoughts on if the out of place mosfets were damaged? They weren't on for very long.

It's got a few hours on it and it's already sounding good. It was kinda bassy at first but that seems to be tightening up and improving nicely. Time for tunes!

A great big thanks to papa (again) for such a nice project. Another thanks to Kevin for doing the almost group buy and to 6L6 for the great build guides. This is a wonderful place.

It is hooked to a pair of 4 pi speakers with a Whammy (with a 2107 opamp) as preamp. It sounds great.
 

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