Restoration: Dirk

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Sansui Tube Amps Restoration Project Done by Mr. Dirk Neudenberger  in Germany 


Before Restoration Photos:


Dirk Wrote  on 04/09/2005:

The transformers are much more huge like on the picture of the side view that is why the scanner puts its focus on the tubes in the fronts.
I put in a 6SN7GT, two KT66 and a GZ34 rectifier, this configuration should also work fine...
I don't like El34 sound very much, it has a kind of British tonality, I would always prefer a 6L6GC or KT66.


Dirk Wrote on 04/10/2005:

I just took off the output transformers of my mysterious Sansui Mono-blocks.
Each transformer is stamped "B705" on the underside.
It has the serial number:45671
the other one has the serial number 45644 and is also "B705".
So what he have are mono-block, equipped with:

P-70-B Power Transformer; B705 output transformer; Choke "C-901"; 2x EL34; 1x 6sn7Gt; 1xGz34


After Restoration Photos:


Dirk Wrote on 06/17/2005:

Sansui B705 Main Transformers are used on this amp.  The Power Transformers are "P70B".  The required tubes per mono-block are 1x 6sn7GT, 2xKT66/EL34, 1xGZ34.
This is a simple but good layout. An Eizo HF87 or Dynaco 70 does nothing better...
 I will have to replace the old Spraque/GE electrolytic due to some hum of both amps.
(The amps work good now, sound nice, but the caps have to be reformed or better replaced....)


If anybody has additional information about the purpose or data of these unique amps, I would be very thrilled to
getting these news...
Dirk Neudenberger
Amazing Concepts GmbH

Dirk Wrote on 06/28/2005:

Maybe these are the oldest still existing and working Sansui mono-tube amps.

Now I have replaced all electrolytic caps with similar looking German "F&T-brand" 2x50uf and 2x15uf caps.
, so the hum almost disappeared, but to get it dead-quiet, I will have to modify the heater circuit with one or two anti hum regulators.
I would love to get more info about my amps, for what kind of purpose where they made ?
Does anybody have a schematic?
What was the Sansui product number?
Does anybody have the data of the Sansui B705 output transformers?
Maybe these amps came from a kind of Japanese Jukebox or church-organ? (These amps where intended for use in a kind of console, because they did not have a bottom plate, I had to manufacture an aluminum bottom plate by myself..)
The internal foil capacitors where made by NTK, sadly I had to replace these Japanese caps, because they caused a crackling noise due to micro shorts at 400 Volts
plate current... Maybe they are not so durable as the old American ITT or Vitamin Q by Spraque foil caps...
But its better to have these amps running with American (vintage) caps, than keep them on a shelf totally original just for view.

I had to invest around 300 hours to get these amps to "like new" condition, I removed all parts and sanded them before repaint with German

metallic quality car paint made for VW cars and black Piano-paint on the transformers.
The oxidzed brass Sansui labels on the top of the Transformers just needed a special treatment with a light acid tincture for bathtubs cleaning and a soft re-polishing
with "never dull" chrome polish.



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Last changed: 02/01/15

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Last updated: 02/01/15.