Parallel triodes - CONS?

XZur · 24th January 2006, 06:17 AM

Thinking of using ecc99, parallel triodes, to drive 2A3 or 45.

Saw from previous posts about pros of parallel.

No change in gain (Of course loudness is not an issue in my case)
GM=2x
Internal resistance/2.

Any weak points to consider in this approach?

i_should_coco · 24th January 2006, 11:15 AM

Hi there, some people say it doesn't sound as good as a single triode half. I reckon it depends on the application, e.g. the lower driving impedance may do better job of driving the grid.

My suggestion it to try it both ways and decide for yourself.

Cheers,
Pete

ilimzn · 24th January 2006, 12:18 PM

Depends on triode matching inside the bottle - not overly problematic for completely separate triodes, since you can still use separate cathode resistors and bypass. With common cathode double triodes, you get a new triode which may be significantly off from Gm*2, Rp/2... but that does not mean it will sound worse. Just think of it as a different triode and optimize for that.

SY · 24th January 2006, 12:57 PM

Do remember the doubling of input and Miler capacitance. That might be important in your design.

XZur · 24th January 2006, 02:07 PM

with the already impressive specs of ecc99, it may be wiser to use single triode per channel than having to contend with Miller capacitance and possible imbalance of the two triodes?

24th January 2006, 06:17 AM	#1
XZur diyAudio Member Join Date: Oct 2005	Parallel triodes - CONS? Thinking of using ecc99, parallel triodes, to drive 2A3 or 45. Saw from previous posts about pros of parallel. No change in gain (Of course loudness is not an issue in my case) GM=2x Internal resistance/2. Any weak points to consider in this approach?

24th January 2006, 12:57 PM	#4
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Do remember the doubling of input and Miler capacitance. That might be important in your design. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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24th January 2006, 11:15 AM	#2
i_should_coco diyAudio Member Join Date: Dec 2003 Location: Surrey, UK	Hi there, some people say it doesn't sound as good as a single triode half. I reckon it depends on the application, e.g. the lower driving impedance may do better job of driving the grid. My suggestion it to try it both ways and decide for yourself. Cheers, Pete

24th January 2006, 12:18 PM	#3
ilimzn diyAudio Member Join Date: Feb 2005 Location: Zagreb	Depends on triode matching inside the bottle - not overly problematic for completely separate triodes, since you can still use separate cathode resistors and bypass. With common cathode double triodes, you get a new triode which may be significantly off from Gm*2, Rp/2... but that does not mean it will sound worse. Just think of it as a different triode and optimize for that.

24th January 2006, 02:07 PM	#5
XZur diyAudio Member Join Date: Oct 2005	with the already impressive specs of ecc99, it may be wiser to use single triode per channel than having to contend with Miller capacitance and possible imbalance of the two triodes?

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