Working on two new SissySITs , first one is finished, soon to make happy my Webhamster Mikorist (short Miko).
Last and final iteration of already known AVC based preamplifier , with JFet buffers and all bells and whistles
This one is balanced ( so no SE in name) , made for Robert from Poland
Plenty of pics , hopefully will add full set of schematics later
It started not by plan , but by chance ….. several (or even more than several) months ago , I tried to help one of our Greedy Boyz at Diyaudio.com/Pass Labs subforum , to improve things with his Aleph X monoblocks.
Problem was simple but not so simple ……. in first incarnation , amp was sounding divine , but it was unreliable and eventually it gave up in flames ……. or at least with some gray smoke puffing out .
As usually ……. ZM at work :
Result of first tests , hardly optimal ( using two halves of 6SN7 in parallel and loaded with ancient xformer from vertical section amplifier of ancient B-W tube TV set) , I was blown with ‘till then unknown dimension of sound – everything was so alive ….
Later I made several iterations of line stage with same approach , being so proud for reinventing boiled water , until I got some xerox copies of Sound Practices , where I found that even in boiled water reinventing I wasn’t first ….. boyz from Italia already made Euridice preamp ; anyway , intermediate iteration was with two halves of 6DJ8 in parallel , latest one being with ubiquitous EC8010 and custom made xformer . That being even published on my old site – WOT preamp and battery charger
Well ,it started as solution for two customers; both having my Babelfish amps, both driving Dynaudio Contour 1.3 with them.
Whatever solution they had for preamplifier in that time, they weren’t on par with amp quality ….. so logical development of situation is to mate amps with line stage simple enough but not simpler than necessary …… simply put -preamp made in same manner.
After some chat , consensus was that “plain” buffer (so , no gain ) is adequate,so I decided to make a quick mockup with buffer pcb I had from yore,as part of Poor Serbian Man Lightspeed project.
Frankly – not “plain” buffer anymore , but I simply couldn’t go with less .
Basically-4 separate buffer cells , and simple but witty bipolar (+/-12V) shunt reg on board.Cells are made of scarce and expensive Toshiba JFets (2SJ74BL , 2SK170BL) as source follower. In this case , just two buffer cells are populated, as not needed more for unbalanced operation. For more details, it’s easy to check my signature on diyaudio.com .
Schematic sketch and first proto , conveniently put in dreky casset deck case :