Gainclone sound & review

I run the Gainclone using a pair of Jensen SPX-7 speakers bought second-hand from eBay which are (surprisingly) very well built. Temporary source currently either my IBM Thinkpad X31 (WinXP) or my IBM T23 (Ubuntu) but a proper tubed-DAC is on the way.

The Gainclone is a very nice, musical-sounding amps. I needed to run it in for about 48 hours and then it is simply is very hard to fault. Very detailed and fast -- from high to lowest frequencies, it reveals many sounds I did not notice before. It is a very musical amp and makes listening very relaxed and enjoyable.

I enjoy a wide range of music using this amp, from the clarity of piano and tenor voice of Christian Willisohn in Hold on I'm waiting for you ... to Metallica's Lars Ulrich snare drums in Holier than thou.

The Gainclone delivers big time!

Gainclone built progress

I decided I won't spend $300 for casing but if you search the term 'Gainclone' in Google images there are heaps of excellent design samples. Mine uses Jaycar $15 casing which looks nice and tidy for its price.

The toroid and amps circuit fit perfectly.

30/12/07 - Managed to cram 4 channels of 3875 amps into this little box. It's a two-tier setup. The whole system now sounds really great but I'm having problems with hum on the second pair of amp (pulling hair...). Also I don't know why the new pair runs hotter even though they are exact same design.

7/1/08 - Upgraded the pots using two 100k ohms linear ALPS blue velvets. Result is not much difference.

Gainclone assembly & testing

I decided to put both 2 channels and their power supply circuits into one board. This will shorten all signal length.

The wiring is point-to-point. I forgot to take the picture underneath but it is quite tidy due to very simple design. The feedback resistors were directly soldered onto the chip's pins for the shortest distance possible.

The assembly took me the whole night but it was straightforward. I plugged in the power and after looking cautiously for smoke I plugged in the speakers and it made a nice sound. There was a problem though.

The Gainclone would make beautiful sound but after 30-40 seconds it would get into some kind of oscillation problem. The sound was like bbrbbbbrbb ... after some thoughts and investigation I pointed out grounding as the culprit. It was using one transformer with two 0-30 outputs. I changed the wiring as shown here and the problem was fixed.

Gainclone design

Simplest and best-sounding DIY amp, based on LM3875 amp. This part list is based on Australian pricing.

The topology is drawn by Mark Houston ( Many great sample builds there.

A simple, unregulated power supply.