Home Tube DIY Asylum

Do It Yourself (DIY) paradise for tube and SET project builders.

Choke in the Tail

I have a small stock of 70H audio chokes, so that's what I use in SPICE for scenarios like this. The sims indicate that, while current balance is improved, distortion at each anode doesn't benefit much. Specifically, the improvement appears to be 3dB or so with the 6J6. That's not insignificant, but it may not be worth the cost of good chokes if the overall design includes NFB that pushes harmonics below audibility.

The issue of the contribution to distortion at the output of the amplifier is a different matter, because LTP balance plays a role. It's tempting to assume even-order harmonics will be improved with the choke (or a SS CCS) in the tail. However, best balance isn't necessarily achieved simply by equalizing current through the tubes. The exact value of the anode resistors also comes into play, as does the output loading on each section. All things considered, I believe any LTP should have a balance pot and should be tested and realigned periodically to compensate for aging of the various components. In my mind, this points to the most significant benefit of the CCS or choke in the tail, which is not that it balances the sections (that can be accomplished with a pot), but that it compensates for aging in the tube. That should minimize the need for periodic maintenance and significantly lengthen the alignment intervals.












This post is made possible by the generous support of people like you and our sponsors:
  Western Glow Tube Service  


Follow Ups Full Thread
Follow Ups
  • Choke in the Tail - Triode_Kingdom 23:35:44 05/05/21 (1)

FAQ

Post a Message!

Forgot Password?
Moniker (Username):
Password (Optional):
  Remember my Moniker & Password  (What's this?)    Eat Me
E-Mail (Optional):
Subject:
Message:   (Posts are subject to Content Rules)
Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:  Automagically notify you when someone responds.