Rohde und Schwarz Begrenzungsverstärker ABR / U23

[Falk]

Presumably one doesn't actually need the calibration voltage in the box. Does this unit need calibrating a lot ? Could one use a bench PSU ?

The calibration is a gimmick. Yes, it only needs some sine voltage to be fed to the input tx secondaries center tap to check for matching of the ef83s. This way one calibrates for maximum cancelation. One could also calibrate for maximum voltage before the first gain stage. I put A LOT of test points all over the board. No need to worry too much about the 12V for calibration.

 

[Falk]

Ich found this one:

https://www.don-audio.com/Audio-Toroidal-Transformer-Pri-2x115v-Sec-240V-50V-2-x-12V

This should work.

 

[echoplex]

Hey Folks,

is anyone here quick and good in designing frontpanels?
Maybe someone could design a panel for this particular built we all can use.
Maybe even a group buy of panels is possible.
Me personally I'd like a design which is reminiscent of the Vacouvox design or Thermionic Culture Phoenix and the likes.

 

[Murdock]

@Falk Do you have a Spice Model of the EF83 tube? I searched but couldn't find one... or how did you simulate the circuit?

EDIT: Just saw in one of your first posts that you used a EF89 model which I also found.

 

[Murdock]

Would you or somebody else be so kind to explain how to propperly simulate a compressor in Spice?
I've simulated a few vari mu circuits and frequency response, gain and voltages seem to be good but when trying to somehow plot the compression I get weird results. I tried it with stiff supplies e.g. batterie supplies but also with "normal" power supplies. What puzzles me is that the controlls somehow work but the gain is always way to high at the output... So when feeding something like 1Vpeak I get the amplification of the whole amp at the output and the waveform is severely distorted.
What exactly are you plotting? I would assume the transient response, right?