Kevin Gilmore's Mini Diamond Buffers

[sweetleaf]

Can't seem to find any info or examples of these in use, but someone here must have tried them. I have found that buffers on the output of a Muses electronic volume control works very well and had good results with Sjöström Audio diamond buffers but Kevin's little PCB's might be even more compact.

Can anyone remember a thread or post where these were introduced?

They are a very simple circuit and could possibly do with some extra PSRR with caps right on the power pins, they are so compact I have found a neat way to stack them, in the pics below is a quad channel balanced stack, all the PBCs are connected through the power pins, leaving the i/o's separate.

Edit: Spritzer may have done the layout for these.

[jamesmking]

1 hour ago, sweetleaf said:

Can't seem to find any info or examples of these in use, but someone here must have tried them. I have found that buffers on the output of a Muses electronic volume control works very well and had good results with Sjöström Audio diamond buffers but Kevin's little PCB's might be even more compact.

Can anyone remember a thread or post where these were introduced?

They are a very simple circuit and could possibly do with some extra PSRR with caps right on the power pins, they are so compact I have found a neat way to stack them, in the pics below is a quad channel balanced stack, all the PBCs are connected through the power pins, leaving the i/o's separate.

Edit: Spritzer may have done the layout for these.

the smd version is at https://www.head-case.org/forums/topic/12733-balanced-to-unbalanced-board/page/2/ intermixed with the balanced to unbalanced board discussion. It looks like it is based on the 2017 through hole and does not have adjustment pots for dc offset.

The 2018 through hole version has extra circuitry for controlling the dc offset and adjustments pots.

I built the through hole version 2018 and found that with a 10K tkd pot on the input it had some high frequency instability with the volume control almost all the way up. I also got some dc offset with varied as the buffered heated up. The transistors gain seems to be very temperature sensitive and although I matched the pnp transistors and matched the npn transistors I could not get a good match between the npn and pnp - the slope of the curves were too different.

I don't know if a smd version of the 2018 was released.

 

Edited May 9, 2021 by jamesmking

[sweetleaf]

Thank you James, I see now they are designed to install onto the SMD balanced board next page. Very neat, I could try this for a soekris DAC output stage.