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C3g Operating point question....

68.48.209.51
Posted on November 6, 2009 at 17:18:32
slownlo
Audiophile

Posts: 1067
Joined: October 11, 2003
 Looking at the load lines it appears like 205V Vp, -3.5V Vk, 13mA is the sweet spot for best linearity/swing in Triode... I'll be using it to drive a 2A3 (Interstage coupling)...I'll have a CCS on the plate...

anyone have any suggestions?

RE: C3g Operating point question...., posted on November 7, 2009 at 16:04:40
elektron
Audiophile

Posts: 761
Location: midwest
Joined: February 18, 2004
 slownlow, hi. Very very nice indeed. I am thinking you will have excellent results with what you have described. There is something amazing in the music produced with such an iron rich environment. More and more I am gravitating away from RC coupling. For those who have not tried it I would say you are missing out on something very good. Happy Building and Happy Listening.

RE: C3g Operating point question...., posted on November 7, 2009 at 02:05:13
reVintage
Audiophile

Posts: 120
Location: Eskilstuna
Joined: June 19, 2008
 Note, due to the fact that the 2A3 isnīt fully linear, a slightly unlinear working-point for the driver can compensate for this through distortion-cancellation.

This is valid for two-stage amps.

But I would anyway start with the most linear point. The unlinearity can then be implemented by changing the value of the presceding stages gridresistor.



Brgds
Lars
Thats an interesting point..., posted on November 7, 2009 at 07:02:35
slownlo
Audiophile

Posts: 1067
Joined: October 11, 2003
 But I am using a silk permalloy 4000H grid choke on the input driver...

RE: Thats an interesting point..., posted on November 7, 2009 at 09:01:33
reVintage
Audiophile

Posts: 120
Location: Eskilstuna
Joined: June 19, 2008
 Itīs not harder than parallelling the gridchoke with a resistor(if necessary). You still have the benefit of the low DCR of the premier.
Brgds
Lars
RE: C3g Operating point question...., posted on November 6, 2009 at 22:03:05
twystd
Audiophile

Posts: 1663
Location: Austin,Texas
Joined: December 9, 2000
 That looks pretty good, 170 on the plate @ 14ma with a -2.5V bias looks slightly more linear. You won't swing as much volts, but looks like it will still swing around 200V, more than enough to drive a 2A3. Only running the tube at about 70% max as to about 78% with your original points. Not a huge difference either way. Of course the real test is in the listening.

twystd

Yes, you're points are more linear..., posted on November 7, 2009 at 07:09:45
slownlo
Audiophile

Posts: 1067
Joined: October 11, 2003
 I think I'll go for that and report back...
I got some more cascode CCS's from K&K, so the adjustment will be simple to compare the two points..

I was thinking of doing the "Ultra-Path" arrangement for this one as well. I'll be using one of the Lundahl LL1692A's for the IT, and I'll be using a Silk Permalloy grid choke on the C3g...
LL1623s for the interstage???, posted on November 7, 2009 at 09:13:54
twystd
Audiophile

Posts: 1663
Location: Austin,Texas
Joined: December 9, 2000
 Think you may have made a typo on the transformer. I've always wanted to use a grid chokes, just never could afford them.

twystd

Correction....LL1692A Interstage. (nt), posted on November 7, 2009 at 09:49:19
slownlo
Audiophile

Posts: 1067
Joined: October 11, 2003


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