Alchemist Forseti APD21A Pre Amplifier PSU - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 25th November 2010, 01:27 AM   #1
Phil50 is offline Phil50  United Kingdom
diyAudio Member
Join Date: Jun 2008
Default Alchemist Forseti APD21A Pre Amplifier PSU

does anyone know the output voltages of the transformer in the
Alchemist Forseti APD21A Pre Amplifier's Power supply unit?

Its a small torroid with two secondary outputs each with a 0v centre tap so its six wires in all. The output on the DC plug end is two +v and two -v with one 0v.

The manufacturer no longer has data on this transformer and its dead short so no volts out!

I think its about 25v 0v 25 each winding but need to be sure. The colour codes on the PSU are
2 reds 1 black winding one

2 whites 1 green winding two

I await your replies

  Reply With Quote
Old 30th November 2010, 12:46 AM   #2
Phil50 is offline Phil50  United Kingdom
diyAudio Member
Join Date: Jun 2008
Well as there is no help whatsover available on this lamentable product its now in the skip and is being replaced with a cheaper imported alternative.

I wont post again.
  Reply With Quote
Old 23rd January 2013, 05:07 PM   #3
yairf is offline yairf  Israel
diyAudio Member
Join Date: Nov 2003
Location: Israel
Just found this thread after searching on Google for info on that preamp.
The design is weird, with dual-mono external power supply providing +/-32V, which is then regulated internally to +/- 18V, which is then regulated again to +/-12V by an adjustable regulator.
The actual circuit has 2 op-amps for the adjustable regulator, 1 op-amp for signal path, and another op-amp acting as DC-Servo. Output stage is using TIP-31C/32C biased into Class-A by the adjustable regulator.
Sounds confusing? it is !
Don't bother with balanced inputs/outputs, as they are converted into unbalanced by a crappy op-amp.
  Reply With Quote


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Alchemist Forseti ADP20 schematics Basill Solid State 10 1st September 2016 05:45 PM
Alchemist Forseti Adp 15mkii kzeprf22 Solid State 1 16th August 2013 01:31 PM
External PSU for Quad 22 pre-amplifier johnm Tubes / Valves 15 12th October 2008 03:42 PM
Tube pre-amplifier PSU senderj Tubes / Valves 10 28th July 2006 02:22 PM
Pre-pre; phono; pre line ;device discrete (bjt/fet) o op. amplifier GIPIONE Solid State 8 18th December 2005 09:09 PM

New To Site? Need Help?

All times are GMT. The time now is 01:50 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2