Updated on: 12 February 2004
After a few months of tweaking, modifying and listening to my 'gainclone' amp I decided that it was time to put some information about it on the web. Gainclone amplifiers use opamps instead of the tubes and transistors that can be found in most amplifiers.
Update: This project is superseded by the Chill-amp (II) project!
|Opamps ??? I thought they sounded bad ???|
Yes, I thought that too. My interest in trying something with opamps was born when I saw the raving reviews of the Gaincard of 47 Labs and the article "Op-amps are More Fun than Tubes". Soon, I found some pages describing various clones of the gaincard (gainclones). The most interesting was a forum dedicated to making amplifiers with opamps, the Amp Chip DIY Forum. I found an interesting circuit made by Thorsten Loesch there, an inverting gainclone. This amplifier is not really a direct clone of the gaincard amplifier of 47 Labs, but some concepts are shared between these. After enjoying listening to my freshly built amplifier based on Thorstens circuit, I decided to name my amplifier the Thor-amp. The idea of this page is to summarize some of the knowledge available on the amp chip forum and some things I have learnt by experimenting with the amp.
|The third version of the Thor-amp
A very important topic regarding gainclones is the choice of speakers. Thorsten recommends speakers with 90 dB/W or higher efficiency. Also, speakers with 8 ohm input impedance (or higher) are better. Currently, I use my gainclone with 82 dB/W 8 ohm speakers. The sound is good at low volumes, but the amp loses control if played louder. At very high volumes, the amp overheats or clips. The amp is quite neutral, so neutral speakers are recommended too.
The sound of the Thor-amp is in my humble opinion quite special. It's very warm and pleasant, though also detailed and fast. Maybe it's a mix between tube amps and solid state amps. It has something of the warmth of tube amps and the control of solid state amps without the grainy and lifeless character. The bass is quite tight. Also, the stereo placing is good. I am very happy with the sound, it is a quite musical amp. I have yet to compare it to very expensive amplifiers. When compared to amplifiers in the price class of 500-1200 euro, the Thor-amp wins in many aspects and sometimes in a large amount. A downside of the amplifier is the low power capability. So to be better than other amplifiers during playing loudly, the speakers have to be of a higher efficiency.
Thanks Niels for making these photos! Regrettably, the amp looks a bit messy after a lot of tweaks. Also, at the moment the photos were taken I was trying polycarbonate capacitors at the input instead of the MKT's under them. The stepped attenuator is mounted on the back. I stil have to find a long axis to be able to control the volume from the front side. Currently, no input selector is used because I use my DAC as the only source.
My gainclone in close-up
The right channel nearby
The schottky bridges
Nonoz I DAC page, here you find info about my first DAC project|
Nonoz II DAC page, the follow-up...
47 Labs, the company that makes very inspiring audio designs!
Amp Chip DIY forum, forum about Gainclones and non-oversampling DACs
Audio-cube, page about 47 Labs and other high-end products
Craig Frasers gainclone page
Maartens gainclone page
Richard Murdeys gainclone page
Thorstens inverted gainclone