Hi Everyone
I changed the electrolytics in my friend's Pass Volksamp Aleph 30 based on the recos I received in this thread:
Best choice for Aleph 30 re-cap
I'm now testing the amp to confirm everything is operating within spec. Can someone kindly confirm if following measurements are OK?
1) Both + & - power supply measurements show 25.6V DC with 64 mV ripple.
2) DC offset is 73 mV on one channel and 10 mV on the other; I believe these are fine, but is it unusual for the channels to vary that much?
3) I'd like to check the bias, but I'm not sure where the test points are. The amp is physically a little warmer than I'd expect at 56C.
Thanks in advance
I changed the electrolytics in my friend's Pass Volksamp Aleph 30 based on the recos I received in this thread:
Best choice for Aleph 30 re-cap
I'm now testing the amp to confirm everything is operating within spec. Can someone kindly confirm if following measurements are OK?
1) Both + & - power supply measurements show 25.6V DC with 64 mV ripple.
2) DC offset is 73 mV on one channel and 10 mV on the other; I believe these are fine, but is it unusual for the channels to vary that much?
3) I'd like to check the bias, but I'm not sure where the test points are. The amp is physically a little warmer than I'd expect at 56C.
Thanks in advance
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Here is some interesting reading:
https://www.passlabs.com/wp-content/uploads/2020/05/a30manr0.pdf
From the owner's manual:
"The Aleph 30 is unique in that there are no adjustments of any kind in the circuitry. There are
no potentiometers to adjust. The operating parameters of bias currents and DC offset and so
on are defined by physical constants, and will not go out of adjustment."
Schematic found on the internet - R37 to R39 source resistors will give you the bias.
https://www.passlabs.com/wp-content/uploads/2020/05/a30manr0.pdf
From the owner's manual:
"The Aleph 30 is unique in that there are no adjustments of any kind in the circuitry. There are
no potentiometers to adjust. The operating parameters of bias currents and DC offset and so
on are defined by physical constants, and will not go out of adjustment."
Schematic found on the internet - R37 to R39 source resistors will give you the bias.
Attachments
The offset is quote low and not worth worrying about.
Check the bias, make sure it’s in the ballpark and if so, button it all up and enjoy, as there’s no adjustments on this amp. They were put together pretty nicely at the factory. (Which was Nelson’s table. Literally.) 😀
Check the bias, make sure it’s in the ballpark and if so, button it all up and enjoy, as there’s no adjustments on this amp. They were put together pretty nicely at the factory. (Which was Nelson’s table. Literally.) 😀
Power supply voltage is spot on and you now have the info to physically measure the bias (standing operating current through the output devices)
56 deg C on the heatsink is about Pass normal for class A amps.
56 deg C on the heatsink is about Pass normal for class A amps.
Many thanks for the replies. I realize there's no adjustments in amp, but I thought I should check the bias for due diligence and also to satisfy my OCD.
I do have the schematic however I don't have drawings of the board to easily locate R37 to R39 (the labels are under the resistors). Can someone explain this to me like I'm 5, or would it be helpful if post a picture of one of the outboard boards?
I do have the schematic however I don't have drawings of the board to easily locate R37 to R39 (the labels are under the resistors). Can someone explain this to me like I'm 5, or would it be helpful if post a picture of one of the outboard boards?
The link to the manual in Ben's post is missing a few pages, the one I'm attaching has details on the board layouts.
