Studer 169 269 : de-magnetizing input transformers
« on: April 02, 2009, 09:22:59 PM »
I'm writing this for future reference,  because I've not seen this issue mentioned somewhere, except in the service manual
[and deeply hidden, as hypotesis, in a rec-audio-pro long thread, but I've found it only after having the prob solved.. thats happens often to me]

The Studer 169-269 consoles have transformers on all the line & mic inputs.

On the 269 I'm calibrating/modding, I've noticed a huge bass roll-off on 2 line inputs.

Luckily, I remembered [from the service manual] that if high DC is connected to transformers, they can become magnetized.
And this is not so unlikely, IMO  ;).

So, I've quickly done the de-magnetizing procedure suggested: sine wave at 30 Hz, 30 secs sweep 0V-3V [point of saturation], 30 secs sweep 3V-0V.

After that, I was not believing to my ears/eyes:
the frequency response became perfect  :o

I was prepared to do the usual checking, desoldering, checking, replacing..
great one, this time  ;D

PS: I'm more and more amazed about how this console is customizable, and its built quality.
These things can last centuries.


Re: Studer 169 269 : de-magnetizing input transformers
« Reply #1 on: April 03, 2009, 04:03:10 AM »
very interesting. Will try the same on mine

thanks 1954U1 !


Re: Studer 169 269 : de-magnetizing input transformers
« Reply #2 on: April 03, 2009, 07:56:22 AM »
It's good info, pops up in various Studer-publications, also in the 900-service doc IIRC.

In case http is added to the link below is may not work; copy link directly:



See the tutorial by Peter Frigo of Studer on page 5 of:


Demagnetization of microphone transformers: "Optimum recording."

This article was also to be read in Studio Sound May 1987 Page 50.

What do the people here think of that proposed method ?
Sounds decent & practical to me, but haven't any experience with it yet.



« Last Edit: April 03, 2009, 08:02:19 AM by clintrubber »


Re: Studer 169 269 : de-magnetizing input transformers
« Reply #3 on: April 03, 2009, 04:37:18 PM »
I thought that it was common knowledge ?!?

I've got a cd that came along with a book about audiotestprocedures (mainly for analog tape and vintage audiostuff). The CD also contains a track with sines for demagnetizing audiotransformers.


Re: Studer 169 269 : de-magnetizing input transformers
« Reply #4 on: April 03, 2009, 05:48:40 PM »
I've only wrote about my real experience, for reference, because
I've not found similar reports, and because the improvement has been enormous, and super-easy to obtain, with a simple sine-wave generator.
Also, in Studer docs, the transformers are mainly referred as mic input transf.
To me, the thing happened with line input trafos.

Assuming that this forum will be alive for many years, people with Studers or other transformers filled consoles will be able to google for de-magnetizing transformers and find not only theory..
If, instead, all of that is so obvious, no prob, I've only done a bit of spam redundancy on an useful issue  ;D


Related Topics

  Subject / Started by Replies Last post
47 Replies
Last post August 29, 2010, 06:26:58 AM
by jejor
0 Replies
Last post August 04, 2010, 07:20:19 AM
by Gert
2 Replies
Last post March 04, 2018, 07:06:22 AM
by radwoc
16 Replies
Last post February 03, 2020, 06:46:21 AM
by nhaudio