|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
74.96.73.210
In Reply to: RE: Implementing a " Super Linear Cathode Follower" posted by Bartas on March 31, 2011 at 08:40:56
FYI, Shortly before he died, AW posted here about his preference for the sound of an all-tube SLCF. I asked him which side (CCS or voltage strap) would be least damaging to the sound if done in SS devices instead of using a tube. He responded that the CCS would be his choice to do in SS, that the sound was best using a tube as voltage strap. Accordingly, I am doing my SLCF with an ECC99 as voltage strap on top of a 12SX7 (~6SN7) as CF. Using a K&K cascoded ss CCS kit for CCS. (I have no room on my chassis to build the SLCF using all tubes.)
Follow Ups:
Allen said the same thing to me a year or so ago: I showed him the schematic for my active crossover, which has the differential input stage of the RTP3 and the SLCF buffer stages of the hybrid RTP5 with a 6922 as cathode follower and IRF710 MOSFETS for the bootstrap and CCS.He said that a MOSFET ought to be near-inaudible as a current sink, but that the nonlinear gate capacitance of the IRF710, in his experience, was audibly objectionable when used as the bootstrap device, and a valve was preferable by a long way .
Allen did suggest, however, that a bipolar transistor like an MJ350 should work much better than a MOSFET in the bootstrap position, although its biasing requirements will be rather different.
Alex
Edits: 04/05/11
Yep, I`ve been reading several posts about SLCF. Allen really stated that all tube SLCF has the best sonics. I also found several statements of his about Mosfet being poor thing any there near signal.
This really got me thinking about all tube SLCF and my phono has no limiting chassis so far :)
Could anyone here enlighten me in voltage strap design principles.
For "design principles", check AW's book, The Tube Preamp Cookbook (aka TPCB), John Broskie's treatise on CFs on his site (he finally arrives at a version of the SLCF), and I guess you could do a search here and on DIYaudio.
...
Here's a couple of choices for you.
Naz
Before someone picks me up on this, you don't need the same ref voltage for the SS CCS as for tube. When I drew the circuit I swapped the tube with SS CCS without thinking. Here's the way it should have been ... not that it will work any different, it's just simpler.
Naz
Hey, thanks, Naz,
I was just studying all tube SLCF. This is a nice way of biasing the sink.
What is the better way of organizing this all tube circuit:
1. Tube 1 - VS L/R, tube 2 - CF L/R, tube 3 - CCS L/R
2. Tube 1 - VS L/CF L, tube 2 - VS R/CF R, tube 3 - CCS L/R
Ore other combination...
Hmmm, I'd go for option 2 but if you are going all tube and don't want to share triodes sections for L & R channels then consider using a different tube type for the CCS. Something like a 6C45P would work really well, a single high performance triode that is better on paper than a 6SN7 for the application and is as cheap as chips on EBay.
Naz
I have some 7193 on hand.
Could strap a 6SN7 with 5687 and current sink with a couple of 7193.
I'm not familiar with a 7193 but it looks interesting. I like the 5687. Technically, higher gain tubes should be better but I find that a good quality tube is more important for better sound in most applications ... unless of course it's a critical circuit.
Cheers
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: