Simple tube preamp?

[picklgreen]

I want to build a simple tube preamp to feed my Dynaco St-35. Could someone please lead me to a project for this? I want something similiar to the pramp stage of the SCA-35 or the PAS2/3 preamp minus all the tone/ blance/ phone stage stuff.

 

[FastEddy]

Yes ... a dual channel please ... Kit or just a good diagram would do it. The KISS principle would hopefully apply ... although I would like to keep the phono pe-amp stage, but no need for tone, balance, etc, Prefered: 3 stereo inputs, for CD/DVD-A, Balanced AUX., PHONO ... balanced output?

 

[Bas Horneman]

How about a Foreplay III? Heard one when I was in NY...with a Fi 2a3 and Big Horns....wonderful sound.

 

[Zen Mod]

just build 12B4 preamp with plain vanilla PSU.........xformer,SS rectifiers,CRC (as many times you want it) filter etc.

can't be simpler than that

 

[FastEddy]

Wow, that Foreplay III is a knock out! Very cool and almost exactly what I was looking for. Thx 2 U, Bas Horneman ... not a bad price either.

(Wondering why these tube guys don't use torrid transformers in the power supplies ?)

 

[Zen Mod]

.............
(Wondering why these tube guys don't use torrid transformers in the power supplies ?)

because they are not better in preamp PSUs than good ole EI

 

[Shoog]

Toroidals couple any high frequency power line hash from primary to secondary. This is difficult to filter out once in your power supply. This will lead to distortion of your signal as it is imposed on top of it.
EI's are poor at carrying high frequencies (this is why EI output transformers are so difficult to build and hence so expensive), and so the line hash never gets into your signal.

Shoog

 

[dejanm]

and passive pre-amp ? with trainnies ... S&B and if that is to expencive than similar trainnies from Sowter ... no active parts only input selector, wired with trannies and trannie secondaries are connected with the volume pot ... YOu can buy this thing under the name of Music First or Bent Audio or .... Promitheus is Far East option that costs no more than $350 (not very pretty though but it sounds very well).

Only an idea ...

Regards
Dejan

 

[FastEddy]

" ... Toroidals couple any high frequency power line hash from primary to secondary. ... EI's are poor at carrying high frequencies ... and so the line hash never gets into your signal. ..."

Informative and to the point. Thanks ...

Is there a way to distinguish EI's (defination please?) of lesser quality or usability for the purposes of power supplies?

 

[Shoog]

EI's are the standard block type transformers. Named after their laminations which look like "E"'s and "I"'s.

Shoog

 

[danny_66]

Take a look at the aikido preamp, it works with different kinds of tubes.
To get an idea how good the circuit is just do a search here on diyaudio.
http://www.tubecad.com/2005/January/blog0030.htm
You can also buy the PCBs from the author.