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RE: Mystery chokes

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In Reply to: RE: Mystery chokes posted by caffeinator on April 15, 2009 at 20:36:31

The 18122 is a power supply filter choke suitable for choke input duty.
Nominal specs are 2 henries at 450 madc.
It was designed by Peerless in April of 1970 for a famous guitar maker.
We made a few of these some years ago. I think I might even have some coils left from that run. And I can vaguely recall selling you a pair a long time ago.

MSL

Builder of MagneQuest™ & Peerless™ transformers since 1989

Edits: 04/15/09 04/15/09

Follow Ups:

RE: Mystery chokes - Paul Joppa 22:38:27 04/17/09 (4)
2 henries at 450 madc??!!

This thing must have been running dozens of 6550s!
- a technical question... - mqracing 10:14:00 04/18/09 (2)
  Paul or others...
  
  you guys have seen the "compact" circuit, right? It's the one where the phase inversion is done in the PP power output stage. So that the driver circuit is a straightforward single ended voltage amplifier which must simply swing the grid volts of the output tubes. Most commonly this voltage amp stage is capacitively coupled to the output stage though Keto posted a novel direct coupled "compact" circuit on this forum a long time ago.
  
  Here is my question--- is there any reason that the compact would not also work if the output stage was a parallel push-pull (four tubes instead of two per channel)???
  
  MSL
  
  Builder of MagneQuest™ & Peerless™ transformers since 1989
  - an example of the compact amp circuit (Open in New Window)
  - compact - keto 12:05:55 04/26/09 (0)
    Hey all,
    
    since I just strapped a pair of Bottlehead 15K SW's to my Cobalt 15K B7's, and so am finally listening to tunes via MQ goodies (a la "sex kitten" or "pseudo ingot"), and figure I can only NOW chime in ...:-)
    
    To my ear the direct-coupled compact circuit always sounded single ended, or "unconfused" when compared to other PP circuits I tried.
    
    I viewed the strong force at work being the AC balance in the OPT primaries, which worked well with an old Stancor 5KPP OPT and really well with MQ S240A's.
    
    The AC balance "strong force" seemed to trump the 2K (?) shared output cathode resistance, that is, there was no forced DC balance.
    
    A forced DC balance would seem to support AC balance with a small signal and distort it with a large signal.
    
    I tried to measure AC signal at the shared output cathode and the "2nd half" output 2A3 grid with a DVM and came up with nothing, leading me to conclude that the "2nd half" plate was passively going along for the ride, according to the strong-force AC balance of the OPT primary.
    
    I also didn't seem to run out of driver headroom the way I'd expected, given the logic of the first, active driver having to do double the voltage swing.
    
    Note all the fuzzy, non-tech terminology.
    
    The problem with my version is that I can barely lift each monoblock, and so eventually dismantled one. I definitely need to do a 2.0 version. I've also thought it would be interesting to do a PP300B version with DC blocking caps and a negative supply for the input.
    
    If MQ ever does another SETH batch of PT's and chokes, I think that would be the ticket, for me.
    
    viva MQ!
    
    --keto
  - RE: a technical question... - Paul Joppa 20:04:05 04/19/09 (0)
    No problem if the tubes are perfectly matched.
    
    Gordon has some opinions about the probability of tubes being - or staying - matched, and the consequences of mismatching. I can't disagree with him on that.
    
    Just a note - the driver of a "Compact" must provide twice the drive voltage, and the driven tube suffers a larger variation in operating conditions than the other tube. So it would work best (IMHO) when the output tubes have a small bias voltage, i.e. high mu for triodes.
    
    Anybody up for a 211 "Compact"? Mike, what do you have for 20KCT primary, 1200WV, 50 watt output transformers?
    
    :^) OK just pulling your chain. You couldn't lift one even if you had the drawings until the Doc says OK. Take care!
- RE: Mystery chokes - mqracing 09:36:58 04/18/09 (0)
  Your right Paul--- but not dozens per side I don't think.
  
  You should see the output transformer design that Peerless did for this customer--- 2200 ohms CT primary (no screen taps) rated at 150 watts at 40 hz.
  
  Built with all kraft paper (wax impregnated) for tone... huge pads btwn pri and sec windings. Capacity must have been rocket low...
  
  tri-filar secondary windings.
  
  I just painted six of these outputs yesterday--- all are sold.
  
  makes me almost want to build a big 120 watt quad KT-88 PP amp---
  years ago I had a pair of the Dyna Mk VI amps (120 wpc quad 8417 per channel)--- they sure did have that macro dynamic slam thing way down pat--- and went down to the basement frequency wise with authority.
  
  I have some small bookshelf specialty Japanese made speakers--- the Pioneer malt speakers and I also have the JVC wooden cone (from saki barrels) speakers--- 120 wpc ought to wake them up a bit :=)
  
  MSL
  
  Builder of MagneQuest™ & Peerless™ transformers since 1989
Thanks! (nt) - caffeinator 06:02:21 04/16/09 (0)
nt

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