807 E-Linear - Page 3

arnoldc · 9th January 2007, 11:09 PM

hi douglas, thanks mucho for the explanation. this is a good read although i've seen pete's site and have a schematic on my hard disk for a long time. maybe this be be a good weekend project as i have 807s and UL transformers too..

Bandersnatch · 10th January 2007, 12:14 AM

Quote:

Originally posted by Fuling

But perhaps more so than a resistor loaded triode with an unbypassed cathode resistor? I guess the cathode resistor decreases gm quite a bit?

I will try this out with IRF820 in the upper position, that´s what I have around at home.

Cheers,

Daniel

The unbypassed resistor does drop the gm a bit. It increases Rp, which is probably the reason the bass performance got better. In the very high Rp that you'd find with a pentode or a cascode it gets even better. Do bypass the cathode R in that case...

The IRF820 is a nice one too in that position. If you want to try un-bypassed cathode R, ref the gate to the cathode, not ground...or at least try both( I suspect you'll like the cathode ref better ).
cheers,
Douglas

Fuling · 10th January 2007, 12:38 PM

Thanks, I think I´m getting a bit enlightened about this kind of feedback now!

Edit: Would E280F be a good pentode driver for this amp?
I happen to have a few.

JoshK · 19th February 2008, 08:08 PM

Did you ever get to try the triode/mosfet cascode? How did it fair?

I was reading Pete's article yesterday and came upon this thread today.

Fuling · 19th February 2008, 08:37 PM

JoshK: No, I went for the E280F in pentode mode (with E-Linear feedback) and it was very successful.
The overall gain is a bit low so I´m going to build a 12B4A preamp for my brother.

JoshK · 19th February 2008, 08:51 PM

thanks for the response.

Gain...the other thing that has me scratching my head. How do you calculate the gain from this amp? Or do you just observe the result when done?

Fuling · 19th February 2008, 09:23 PM

I didn´t calculate the gain, but according to my brother the gain is too low when he plays vinyl. OTOH, as he doesn´t have any kind of preamp (not even a passive volume control) at the moment the sound is a bit too loud when he plays CDs...

Bandersnatch · 19th February 2008, 11:03 PM

hey-Hey!!!,
I am glad to hear of your good results with the E-Linear amp circuit. Have you the ability to try different taps? I ask because a friend who I helped with his PP 807 amp finds it best with g2 on 40% and the front end on 20%. This with 10k a-a in the form of a Heyboer-wound S-265-Q
cheers,
Douglas

pedroskova · 19th February 2008, 11:44 PM

so...how about using Alan Wright's 6dj8 cascode input, complete with CCS on the tail, in this topology?

Bandersnatch · 20th February 2008, 01:18 AM

Quote:

Originally posted by pedroskova
so...how about using Alan Wright's 6dj8 cascode input, complete with CCS on the tail, in this topology?

IIRC, Allen references the upper grid to ground, and wastes a lot of B+ in the 'here be Monsters' part of the cascode's plate curves. Not good for circuits with Class A-capable B+.

Tune it up a little bit, and it'll be quite OK I think.
cheers,
Douglas

19th February 2008, 11:03 PM	#28
Bandersnatch diyAudio Member Join Date: Jul 2003 Location: Ann Arbor, MI	hey-Hey!!!, I am glad to hear of your good results with the E-Linear amp circuit. Have you the ability to try different taps? I ask because a friend who I helped with his PP 807 amp finds it best with g2 on 40% and the front end on 20%. This with 10k a-a in the form of a Heyboer-wound S-265-Q cheers, Douglas __________________ the Tnuctipun will return

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9th January 2007, 11:09 PM	#21
arnoldc diyAudio Member Join Date: Apr 2003 Location: Makati	hi douglas, thanks mucho for the explanation. this is a good read although i've seen pete's site and have a schematic on my hard disk for a long time. maybe this be be a good weekend project as i have 807s and UL transformers too..

10th January 2007, 12:38 PM	#23
Fuling diyAudio Member Join Date: Aug 2001 Location: Sweden (Mora)	Thanks, I think I´m getting a bit enlightened about this kind of feedback now! Edit: Would E280F be a good pentode driver for this amp? I happen to have a few.

19th February 2008, 08:08 PM	#24
JoshK diyAudio Member Join Date: May 2004 Location: Toronto, ON	Did you ever get to try the triode/mosfet cascode? How did it fair? I was reading Pete's article yesterday and came upon this thread today.

19th February 2008, 08:37 PM	#25
Fuling diyAudio Member Join Date: Aug 2001 Location: Sweden (Mora)	JoshK: No, I went for the E280F in pentode mode (with E-Linear feedback) and it was very successful. The overall gain is a bit low so I´m going to build a 12B4A preamp for my brother.

19th February 2008, 08:51 PM	#26
JoshK diyAudio Member Join Date: May 2004 Location: Toronto, ON	thanks for the response. Gain...the other thing that has me scratching my head. How do you calculate the gain from this amp? Or do you just observe the result when done?

19th February 2008, 09:23 PM	#27
Fuling diyAudio Member Join Date: Aug 2001 Location: Sweden (Mora)	I didn´t calculate the gain, but according to my brother the gain is too low when he plays vinyl. OTOH, as he doesn´t have any kind of preamp (not even a passive volume control) at the moment the sound is a bit too loud when he plays CDs...

19th February 2008, 11:44 PM	#29
pedroskova RIP Join Date: Dec 2002 Location: C'ville VA, USA	so...how about using Alan Wright's 6dj8 cascode input, complete with CCS on the tail, in this topology?

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