Amp Camp Amp - ACA

Pleased to hear its working 🙂

If it happens again:
i do not know how to take the measurement at the 5W resistors or Between Q1D and Q2S.

You got most of the way there... taking one channel you measured Q1 Drain at 11.5 and Q2 Source at 12.5 volts. If you look at the circuit you will see that equates to 1 volt across the resistors. Measuring between the resistors can be a bit more accurate as it removes errors due to long term temperature drift.

All good 🙂
 
I see that now. Thanks for the explanation. One question: looking at the top surface of the PCB, I’m going to guess “between the 5W resistors“ starts at the right pin of R1 and ends at the left pin of R4. I’m just going by the traces and the schematic.

I'm going to experiment with turning off the amps at night to see if it’s an intermittent temperature related issue. I sure hope not. I generally leave them on.
 
One question:................

Well I've never built an ACA or seen the real PCB's but looking at a picture what you describe sounds correct.

You measure between any points on these traces. One lead on one trace and the other lead on the other. Depending which around you connect the leads one reading will be negative (ignore the - sign) So on this board you could measure between R15 and R8 and get the same result... just don't short anything 🙂

Screenshot 2024-09-05 180735.png
 
Can't recommend speakers, but just thought I'll make you aware that the preamp you use should have some gain otherwise you'll be disappointed in the ACA's - even if you use quite sensitive speakers. And while I'm mentioning speaker sensitivity, you want at least 94dB, preferably 100dB or thereabouts.
Hi Skylar88, please forgive my ignorance. My basic knowledge of electricity is from grade 9 Industrial Ed in the late 60s. My old Adcom GFP-750 is still operating. The specs from Stereophile mag shows the following. Just wonder if the Adcom pre can work with the ACA. Thanks in advance!

Adcom GFP-750 preamplifier Sidebar 1: Specifications

Description: Solid-state, remote-control preamplifier switchable to passive attenuator/switcher. Rated main output level: 1V. Frequency response: 5Hz-85kHz, ±0.5dB. S/N ratio: >102dB, A-weighted. Input sensitivity: 183mV balanced, 365mV unbalanced. Input impedance: 94k ohms balanced, 47k ohms unbalanced. Output impedance: 1200 ohms balanced, 600 ohms unbalanced.
 
I have a basic question. What are the advantages of the 1.8 wiring over the 1.6 wiring other than the mono block options? If I don't care about those additional choices, can I just use the 1.6 wiring and get all the sonic benefits of the ACA amp? Thanks.
 
And the great news is that the wiring changes shown in the build guides between batches 1 and 2 for V1.6 and V1.8 have absolutely nothing to do with the ability to drive lower impedance loads or the output power availability. 🙂

@smype - you are correct. Below is the list of all differences between V1.6 and V1.8:
  1. Rear switch is a 3 position DPDT instead of 2 position, necessitating a change in wiring
  2. Rear panel is printed with a connection diagram
  3. Chassis rails are improved using weld nuts and secured by bolts
  4. Blade terminals are included for the front power switch
  5. Longer wire
  6. LED resistors have been changed from 10k to 33.2k to reduce LED brightness
Edited to add - and you still do have all the same options. Forgot to include link below.

ACA V1.6 Operating Modes
 
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Hi all. Looking at maybe putting two ACA kits into one case. I have a power amp by Adcom, GFA-8520 that has one dead channel. The heat sink area is quite large (350 x 200 x 50 mm). The amp is A/B and IMO, ran hot when it was working. Just wondering if this is a wise idea if I were to gut the interior and put these little guys in it. The case is in excellent shape, and quite beautiful to my eyes. Love to not see it in the dumps.
 

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