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December 14, 2019, 11:10:44 AM

Author Topic: SII-45: Switching between 40H and 20H plate choke configurations?  (Read 187 times)

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Online Deke609

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Is it possible/ok to switch between the 40H/20H plate choke configs?  I have in mind a switch per choke under the chassis for swapping between the 40H and 20H taps.  Assuming it would be ok to run the SII-45 with the 20H PC winding, do I need to do anything more than just swap the PC wires?

Reason (besides the fun of it): overall, I still much prefer the SII-45 to the SII-2A3, but the 2A3 amp does something special with treble that I really like. There's a level of clarity and ease with the treble on the 2A3 that my 45 doesn't have - regardless of which 45 tubes I use.  So I am wondering whether this is attributable to either or both of (a) the 40H/20H config difference; or (b) something specific to the JJ 2A3-40 tubes. Adding the switches would help me test (a).

Many thanks,

Derek
Derek
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Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4

Offline Paul Birkeland

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Re: SII-45: Switching between 40H and 20H plate choke configurations?
« Reply #1 on: June 02, 2019, 02:25:05 PM »
That's a pretty high voltage spot to be switching.  Since you're just doing this as an experiment, I would just move the wires manually. 
Paul "PB" Birkeland

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Offline Paul Joppa

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Re: SII-45: Switching between 40H and 20H plate choke configurations?
« Reply #2 on: June 02, 2019, 02:35:13 PM »
The parafeed cap value would be in a different range, but that should not affect the treble. And changing the cap probably WOULD affect the treble.
Paul Joppa

Online Deke609

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Re: SII-45: Switching between 40H and 20H plate choke configurations?
« Reply #3 on: June 02, 2019, 02:47:15 PM »
Many thanks both.

That raises another possibility: switching between parafeed cap values! But I suppose PB's HV concerns still apply. Then again, I have impedance switches on the SII-2A3 and have managed not to fry myself ... so maybe

Interesting, in this regard, is that I recently changed the stock parafeed and coupling caps in my SII-2A3.   I used 0.22 uF instead of 0.1 uF for the coupling caps (b/c Parts Connexion was out of the 0.1 Vcaps, but had the 0.22's) -- and I noticed no loss of treble, nor any lag.  I kept the parafeed cap at 3.3 uF, but with the Audyn True Copper Max.  Do the parafeed caps have more of an impact than the coupling caps on freq response? (I may be misusing that term here - but i trust you know what I mean :) )

Many thanks,

Derek
Derek
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Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4