[ProAudio] Western Electric 111C transformers

[Bill Whitlock]

Yes, increasing series R on the drive side will exaggerate magnetic non-linearities of the core material (i.e., THD).  If you want to shift the mix of odd to even order harmonics, add a few mA of DC on the primary side (say 0 to 30 VDC through a 10 k-ohm resistor directly to the primary side.
The R and C (in parallel) across the secondary will control the frequency and Q of the self-resonance.
You can read my "Audio Transformers" chapter in the Ballou "Handbook for Sound Engineers" for more details.
Bill


-----Original Message-----
From: Bob Katz via ProAudio <proaudio at bach.pgm.com>
To: proaudio at bach.pgm.com
Sent: Sun, Jan 30, 2022 8:39 am
Subject: Re: [ProAudio] Western Electric 111C transformers

 Now we're cooking! Dear Bill: Thanks. 
  Yes, I am looking for color. I understand the series resistor. I'll probably use a dialpot so I can log the setting for recall. On the secondary side, are you suggesting a variable load R with the C across it? 
  If I am looking for color and want to do some measurements to see the effect of various source and load devices, clearly a square wave investigation will tell me something. Frequency response will tell me something. What about harmonic distortion... probably look at THD at low frequencies??? 
  Best, 
  
  Bob 
  
  
  
  On 1/29/22 5:15 PM, Bill Whitlock via ProAudio wrote:
  
 
If you're after coloration, the strongest influencer of distortion is source impedance, so I'd put something like a 1 or 2 k-ohm pot (connected as a rheostat or variable resistor) in series with the primary high side terminal.  At high-resistance settings, you'll' get some level loss - and possible high-frequency loss if there's much capacitive load (or cable) on the secondary side.  Putting a variable load resistance on the secondary, along with some intentional capacitive load to bring resonance down toward 20 kHz) will allow control of the resonance's Q.  I don't recall off-hand where the natural self-resonance of the secondary is, but I'd start with 1 nF or so and use a 50 k-ohm pot (with a series 1 or 2 k resistor to keep resistance from going to zero) variable load resistor.  Results  will, of course, guide you from there! 
  Bill Whitlock AES Life Fellow Whitlock Consulting Ventura, CA
 
 
 -----Original Message-----
 From: Bob Katz via ProAudio <proaudio at bach.pgm.com>
 To: proaudio at bach.pgm.com
 Sent: Sat, Jan 29, 2022 1:16 pm
 Subject: [ProAudio] Western Electric 111C transformers
 
   Hola, Guys. I’ve got a pair of these sitting around doing nothing. I’m sure their effect will be subtle but it might be nice to package them into a passive box for their color in a mastering session. 

To vary their color would you have any suggestions on switchable buildout or termination resistors or zoebel networks I might want to add to the box, in addition to hard wire bypass?

Appreciate any suggestions. Thanks 


Bob -- 
 

If you want good sound on your album, come to
Bob Katz 407-831-0233 DIGITAL DOMAIN MASTERING STUDIO
Author: Mastering Audio
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 -- 
 

If you want good sound on your album, come to
Bob Katz 407-831-0233 DIGITAL DOMAIN MASTERING STUDIO
Author: Mastering Audio
Digital Domain Website

No trees were killed in the sending of this message. However a large number
of electrons were terribly inconvenienced.
  _______________________________________________
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