News: Trouble logging in? Log in from the login page.
January 25, 2020, 10:45:22 PM

Author Topic: Further upgrades to an already fully upgraded SII-45?  (Read 439 times)

0 Members and 1 Guest are viewing this topic.

Offline Paul Birkeland

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 12004
Re: Further upgrades to an already fully upgraded SII-45?
« Reply #15 on: November 11, 2019, 02:57:11 PM »
The TL431 biasing on the 12AT7 will bump up the gain a bit, which you'll want if you're running more bias voltage on the output tube.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Deke609

  • Sr. Member
  • ****
  • Posts: 855
Re: Further upgrades to an already fully upgraded SII-45?
« Reply #16 on: November 11, 2019, 03:03:55 PM »
Awesome. thx PB.
Derek
______

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 Deke609

  • Sr. Member
  • ****
  • Posts: 855
Re: Further upgrades to an already fully upgraded SII-45?
« Reply #17 on: November 11, 2019, 03:37:55 PM »
... 3.6W with 2nd @ -29dB should be easily doable with a 5K output transformer and a 300B at a very light duty operating point.  This is often referred to as a "Japanese" operating point, as it seems to pop up more over there in the DIY community.  You could run a 300B with 500V of B+ and a 5K transformer and get about 7W at similar THD.  I would not be surprised if the MonAmour with the JJ2A3-40 running on the 60mA position would do about 5W at those conditions; perhaps I'll have time to check on that this week.

This is a really interesting point. One of the questions it raises for me is: leaving aside linearity differences, to what extent is the different sound character of different tubes a function of different ratios of harmonic distortion? E.g., 2nd : 3rd?  My JJ 2A3-40s sound very different from my EML 2A3 mesh - the former sound a lot like 300Bs (and in particular, a lot like the JJ 300B upon which it is reportedly based -- but also a lot like my EML 300Bs in the Kaiju); whereas the EML 2A3 mesh has to my ears a sound signature much closer to a 45.  To what extent does the character of a tube change as you change it operating conditions - operating point, OT primary impedance? I have no idea at present b/c I've only ever listened to my 45s, 2A3s and 300Bs at the stock operating points of my BH amps. It will be interesting to hear the differences, if any, between the 45B at 4K5 and 9.7K. 

Should be interesting.

@PB - it would be great if you could experiment with the new monoblocks with different tubes/OTs and report what you hear.  The new amps look be very versatile: you can go "up" to 300B, stick with 2A3, or go "down" to 45.  That's a pretty attractive selling point (at least to me - but I suspect  to many others on this forum too).

cheers, Derek
Derek
______

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