ACA V1.5 Illustrated Build Guide

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6L6

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Also, I believe that right speaker output wire should be in the left (red) post.

Nope.

In order to be bridged the speaker has to be attached to both channel’s outputs, one of them running backwards... the red posts are not the outputs, but ground, so if you did that, you’d be using only one channel, and get standard power to the speaker, not the additional power from bridging.
 
ACA 2U mini dissipante layout

6L6 Thanks for this awesome build thread! Hopefully this is not off topic. But my daughter and I are building a non ACA undrilled standard chassis for this project. We would like to drill and tap prior to the parts kit arrival. We want to complete the amp before she goes back to school. Does anyone have a back panel layout with dimensions or the 2U UMS pattern for the heat sinks?
Thanks
Kevin
 
Has anyone received their ACA Chassis?

I am hoping someone who has received the ACA chassis would verify some dimensions. Here are our rear panel hole diameter estimations. And have enclosed rough sketches of the distance measurements needed. Thanks for your help.

Hole Diameter
Neutrik 15/16”
Speaker post 7/16
RCA post 3/8
On/off switch ¼
Power plug 7/16
LED ?
 

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I found this on page 3. Also you can use the schematic.
It appears that everyone is using the original ACA thread for the 1.6 build.

awesome, thanks! i also made this table, maybe it will also be helpful:

R1 .47 3W
R2 .47 3W
R3 .68 3W
R4 .68 3W
R5 100
R6 100
R7 10k
R8 1K
R9 1K
R10 332K
R11 10K
R12 39.2K
R13 10k
R14 1K
R15 2.21k
C1 3300
C2 1000
C3 10
C4 10
Q1 IRFP240
Q2 IRFP240
Q3 ZTX450
Q4 2SK170
P1 5K
 
Just wondering if it's possible to go higher than 24V? If so, how high can we safely go?

As ZenMod has said above. And don’t forget to account for the increased dissipation, so capacitors and resistors will have to be changed.

And remember a few things:

You generally don’t want to exceed 1/2 the max dissipation of said device. Max dissipation of the IRFP 240 MOSFET is 150 watts. So 75 watts max.

Dissipation at +48V supply at a current of 1.45A is ~ 70 watts.

And of course your heatsink will have to be much larger.

Yes, it’s a new design, but not impossible;)

Best,
Anand.
 
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changes for 48Vdc are trivial ....... even if absolutely necessary

as general remark : one IRFP240 with more than 35W of heat is thingie demanding care and brains

that means - Keratherm pad (as best and easiest solution) , proper torque , proper chunk of heatsink

more than 50W , while not showed in bucket of oil , is recipe for trouble
 
Hi all, complete newbie here. I've had my 1.5 kit for ages and managed to find some time to start having a look. The start of the build guide says measure everything. Most of the resistors check out ok, but the low resistance ones R1-R4 measure differently. The 0.68 ohms reads 1.1 on my meter. The .47 reads 0.9. My meter is not very special so it could be that or even user error.

Should I ignore it and carry on anyway?

Cheers all
Graham
 
Hi Gridgway,

Yes, usually inexpensive multimeters don't measure well below 1 Ohm. There are a couple of explanations here, or on the 1.6 thread or on the ACA 'base' thread as to how to build a circuit that will allow measuring volts (which multimeters are very good at reading) and calculate the low Ohms on the resistors.

Still, there are others that have tested multiple low Ohm resistors and found that they are not very error prone, and they tend to be very accurate.

I would be happier if you would have said 0.8 Ohms rather than above one, but I think you are safe here.

If there is need, some of us could find the links to those circuits. What brand are your resistors? Where they part of a kit bought through the DIY audio store or did you source them yourself?

If they come from the store,I think they are very reliable!

Best regards,
Rafa.
 
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Joined 2002
Paid Member
Hi Graham,

The resistors should be fine. Try measuring the resistance of your test leads
(by just shorting them together) and you should see it's not zero. Subtracting
the values of the leads will get you much closer.

As Rafa mentioned, measuring low resistance values accurately takes a
bit more effort.

Cheers,
Dennis
 
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