For Sale or Trade: IC: Diamond buffer daughterboard for Millet Hybrid amp

Back in the day, i built two diamond buffers for my millet hybrid. One with the default MJE series transistors, one with Toshiba transistors. Both of them sound, to me, much better than the buf634, but i liked the Toshiba version better and ultimately soldered it right to the board.

So I've had this spare buffer knocking around for years.

It fits RevMH millet boards - the ones with DIP buffers, not the ones with to220 buffers. You could probably make it work with the to220 based boards, but it would be tricky.

It is NOT PRETTY. I initially used the wrong small-signal transistors in it, which had to be desoldered in order to install the correct transistors, and in the process i lifted some pads on the bottom. Also, i ordered the wrong physical size trimpots, so close inspection will reveal that the trimpots are mounted a little funny.

Electrically, it works just fine, or did 3 years ago when i last used it. From above, it does not look terrible - under close inspection, though, i have to admit that it looks a bit rough. I will post pictures when i get a chance.

I've hung onto it this long because i keep dreaming of using it to beef up some other amp board, but i never really go there.

If you have some other amp which uses DIP-8 buf634 buffers which are within the feedback loop of an opamp, or has a capacitor-coupled output, or which has a DC servo of some sort, this board can be cut into two individual buffers which can be used in place of a buf634 in those applications. Since the transistors are not closely matched and it has no DC-zeroing mechanism built in, you cannot use these buffers in an amp which does not have a method of removing DC offset from the output.

Since the toshiba buffer is soldered into my RevMH, i have no way of testing that this still works before sending it out, but i have no reason to believe that it wouldn't work, and there is no chance that it will damage your amp if for some reason it has failed. If i do sell it to someone, I will give a full refund (for return of buffer) if it doesn't work.

These do sit a bit higher than most components that could end up on a RevMH millet board, and substantially increase the heat output. If your enclosure is especially small, you might need to add ventilation, or it might not even fit.

They increase the required power for the amp. If your power supply is marginal, you may need to upgrade it to use a diamond buffer. 500mA should do it, though.

If you look at your amp board, you will notice a white rectangle outline around your buffer chips in the middle of the board. If any capacitors have a radius that overlaps that line, you cannot use this buffer board without installing skinnier capacitors. It is a close fit.

More info about these boards here: http://www.diamondstar.de/dDB_overview.html