Jonte Knif
Well-known member
Here is a project which started as a thought piece for a colored pre for a friend and eventually developed into a therapy project. I just wanted to build something completely different from my product line and have fun. Let me say first that I'm not particularly experienced in p2p wiring and this project is probably not going to be commercial and does not reflect my general building practices. That said, look at the (bad) pictures.
http://picasaweb.google.fi/jonte.knif/TherapyPre#5443655352963125618
The topology is very simple. First there is an amp based on ECC88 and pretty common adjustable feedback arrangement. Basic gain is set here.
Output stage is based on easy to get and high quality E81L pentode. Mode can be switched between pentode, UL and triode.
Grid feedback can be applied and different loads switched to the trannie secondary. So, there are plenty of different distortion characteristics available to be applied _in a controlled fashion_ . With feedback and triode mode it has pretty low distortion.
All power supplies are passive. Many part choices are based on what I happened to have in stock. Caps are Rifa and Mundorf elkos, and the rest are Soviet PIO.
The pre has EIN of -134dBu A-weighted and maximum gain is 93dB with 1:10 input trannies, in pentode mode without feedback.
Max output is high enough and can be padded to play with extreme distorions without clipping gear next in chain.
This is somewhat preliminary post to ask if folks are interested in the schematics (which I have not finished yet.) I will not be providing exhaustive help, so this project would not be for everyone but I'm very open to discussion and suggestions how to modify and/or improve any aspects of the topology.
There is nothing particularly revolutionary in the pre, but many knobs and levers Sound is good and distortions pleasing, ranging from easy and fat to soft clipping.
It has started a studio tour, so I'll have more info about the sound later.
-Jonte
http://picasaweb.google.fi/jonte.knif/TherapyPre#5443655352963125618
The topology is very simple. First there is an amp based on ECC88 and pretty common adjustable feedback arrangement. Basic gain is set here.
Output stage is based on easy to get and high quality E81L pentode. Mode can be switched between pentode, UL and triode.
Grid feedback can be applied and different loads switched to the trannie secondary. So, there are plenty of different distortion characteristics available to be applied _in a controlled fashion_ . With feedback and triode mode it has pretty low distortion.
All power supplies are passive. Many part choices are based on what I happened to have in stock. Caps are Rifa and Mundorf elkos, and the rest are Soviet PIO.
The pre has EIN of -134dBu A-weighted and maximum gain is 93dB with 1:10 input trannies, in pentode mode without feedback.
Max output is high enough and can be padded to play with extreme distorions without clipping gear next in chain.
This is somewhat preliminary post to ask if folks are interested in the schematics (which I have not finished yet.) I will not be providing exhaustive help, so this project would not be for everyone but I'm very open to discussion and suggestions how to modify and/or improve any aspects of the topology.
There is nothing particularly revolutionary in the pre, but many knobs and levers Sound is good and distortions pleasing, ranging from easy and fat to soft clipping.
It has started a studio tour, so I'll have more info about the sound later.
-Jonte