valviac.com -> audio/diy ->
(click photo to download schematic pdf - ~150kB)
My first Preamp with DHT Tubes was a copy of
Doumas DDPRE (a 30 Tube in a mu-follower configuation) .
After doing some researches on the Web and having purchased two "Ba's"
at ebay that were laying around
several months, I decided to layout a
preamp around the "Ba".
The "Ba" is a german Post-Triode.
especially produced to the specs of german public authorities.
Triode Dick and Doede Douma it is the best sounding DHT in a
Dick uses this tube in his Cleo V-Preamp and to my knowledge
Doede uses this tube in a preamp, which he hasn't published
Nevertheless I decided not to use a mu-follower- but a
This decision was heavily influenced by the LC-coupled Phaeton Preamp from Jim
de Kort (VT52.com).
the normal power-amp the amp is connected via the "Direct" output.
works only if the power-amp has a relatively high input impedance and
is not too far away.
decided also to do "CF" output with "bad rept" CF-Stage
especially for my Computer "Audio-In" which is ~5m away from the amp.
It is a
C-coupled bootstrap CF-Stage like it's used in the famous Shindo-Claret-PreAmps.
Additionally it comes with a switchable negative feedback loop.
The subjective sound performance is excellent and in
comparision to the DDPRE
it has "bigger balls" but a
little lesser resolution in details.
Like in all my designs I used normal components.
All R's are standard
2W MO Types from Reichelt.
The C's are MKP Types and the Cathode R's
Bypass Electrolytics are bipolar types.
The power supply ckoke is from
Hammond, the plate-load-chokes are from Reinhöfer
The main trannie is from HB Ampdesign. Tubes are from ebay, "ask Jan
first" and Tubeworld.
You can find their
Web Sites at the audio/diy-linkz.
Addendum January, 28th. 2007
O.K. after not mentioning minor updates to the layout - this is version
2.0 and - yes -
I spent some money on voodoo-components (Elna silmic
eC's and Mundorf C's) and did a new layout to the CF stage.
moment I will not give any judgement of the sound - the whole stuff
needs to burn in.
So as always, STAY TUUUUUUUUUUUNED . . .
Feel free to contact
me, if you have any questions, suggestions, comments etc.