Stereo integrated 845 SE amp
This amp was build on special demand, Werner allready comes long time to my shop and he really focused on an 845 ultimate high end amp but he wanted small size and stereo chassis. Also he asked for tube rectification and off course it should be top when comparing with other tube amps. He allready owned 845 Se monoblocs and so he expected these to be better.
From the mario magnificient i learned that a small PP stage was very beneficial to the sound quality and also from the 6DN7 i know that this tube sounds great, absolutely advisable. Lundahl started making new output transformers the LL1688 and so finally we can use a Lundahl tranny in the output stage of an 845 Se amp. Technically this is a very challenging amp as you need high voltages , extremely powerfull low impedance drive just for the output tubes and u need at least in my opinion negative bias to reach the last potential magic out of any tube design, but with the 845 tube everything is just 1 magnitude bigger . As coupling caps i used Mundorf silver in oil caps, its debatable if Jensen copperfoils or silverfoils would be better but the result is exttremely pleasing. I also used a softstart power up delay that delays the high voltage for about 50 sec, and 3 power toroids in the power supply. However the new kit or build version uses a smaller but taller chassis, and is actual dual mono constructed as we have a new power transformer specially wound for this amp.
6DN7 is also replacable with 6EA7 and 6GL7 , just bought 200 of them :-).
The Schematic described :
Long tail phase splitter with current source in the cathode, this arrabges the fase splitting to drive the mini push pull used to drive the 845
All signal cabling is point to point, Mundorf silverfoil capacitor and a combination of elctrolytic and mkp mpp in the powersupply.
No feedback and top quality resistors where necessary and a few high quality chokes strategically placed which are by the way made here in Antwerp
A further non negligble problem of such a tube amp is the filament supply DC ,10V 7A , well filtered but not regulated , thats a lot of current !
For all tubes negative bias , this with voltage and current sources so its absolutely stable.
Many printed circuit boards are used for all these accesoiries.
Its amazing how much the quality of the powersupply determines the sound and especially the tightness of the bass, and this amp is amazing and this of obviously pleases me as i put so much effort in this domain and in this design nothing has been cost reduced so its rewarding to have it work flawlessly.
this amp has such a tight bass that it outperforms many more massive and expensive transsitor amplifiers :-)
Kit or build , new version will be smaller but taller and all transformers will be inside, new version omits tube rectifiers too.
The insides :-)
Glowing in the dark
Schematics 6DN7 LL1660 PP and LL1688 80mA
no feedback and state of the art design
A few pictures of the prototypes that preceded
If you plan on building this , remember all safety procedures as this is your own risk. we are not liable in any case.
My special thanks go to Stephane Kempeneers whose continous help makes things happen.
Copyright 2006 Bg webdesign & Stephan kempeneers mail for info : firstname.lastname@example.org