I received another bin of unfinished projects and I am trying to decide if I can salvage an almost complete β22 kit.
I do not understand the 3rd board for an "active ground" in the recommended set-up.
So, I would not want to use that.
I would most likely use 2 β22 boards for the amp and 1 σ22 board for the power supply.
The AMB website covers this option as follows:
With this note:
"The wiring scheme for the 2-channel passive-ground configuration is shown in the illustration above. Of particular note is the ground-return wiring from the headphone jack. It should be connected directly to ground at the power supply (e.g., one of the σ22's "G" terminals). Do not connect the ground-return from the jack back to the β22 board. If the PSU is located in a separate chassis (as shown), then the ground return wire should be part of the inter-chassis umbilical cable."
I am a little confused because according to the schematic, signal ground and power ground are connected on the β22 board, so the ground return from the headphone jack is in fact connected to both signal and power ground. Why insist that headphone jack ground return be a direct line back to the power supply ground?
Can this be built in a more "normal" way without risking ground loops?
I do not understand the 3rd board for an "active ground" in the recommended set-up.
So, I would not want to use that.
I would most likely use 2 β22 boards for the amp and 1 σ22 board for the power supply.
The AMB website covers this option as follows:
With this note:
"The wiring scheme for the 2-channel passive-ground configuration is shown in the illustration above. Of particular note is the ground-return wiring from the headphone jack. It should be connected directly to ground at the power supply (e.g., one of the σ22's "G" terminals). Do not connect the ground-return from the jack back to the β22 board. If the PSU is located in a separate chassis (as shown), then the ground return wire should be part of the inter-chassis umbilical cable."
I am a little confused because according to the schematic, signal ground and power ground are connected on the β22 board, so the ground return from the headphone jack is in fact connected to both signal and power ground. Why insist that headphone jack ground return be a direct line back to the power supply ground?
Can this be built in a more "normal" way without risking ground loops?
The AMB forum at https://www.amb.org/forum/ is still active and you might get better responses there.
If you post the same thing about the two board configuration I'm sure AMB will chime in with answers. It's a perfectly valid configuration.
The reason for the ground channel is covered under the tech highlights:
I suspect the reason for a dedicated return wire is similar - it reduces the ground impedance and corresponding crosstalk.
The reason for the ground channel is covered under the tech highlights:
In short, the ground channel reduces the impedance and other non-ideal characteristics of the ground by buffering it with the same high performance amplifier as the L and R channels.
I suspect the reason for a dedicated return wire is similar - it reduces the ground impedance and corresponding crosstalk.
Thanks! I only get about an hour at a time to work on mine, so taking it slow isn't 100% by choice. That gives me lots of time to obsess over trivial details during work while making tiny bits of progress in the evenings.
I'll mostly use it with higher impedance phones, but I'll keep an eye out. I want to be able to use it with speakers and I think I'll want higher gain for that... maybe. I also have an M^3 and I adjusted the gain down from 8x to closer to 5x on that one, mostly just to have more usuable volume knob range.
You had plenty of measurements for yours, but how does it sound?
I'll mostly use it with higher impedance phones, but I'll keep an eye out. I want to be able to use it with speakers and I think I'll want higher gain for that... maybe. I also have an M^3 and I adjusted the gain down from 8x to closer to 5x on that one, mostly just to have more usuable volume knob range.
You had plenty of measurements for yours, but how does it sound?
Last edited:
It sounds very good. Good detail, clarity and power.
I do not typically use audiophile terms to describe amplifiers, so I can’t tell you more than that. 😆