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ECC99 Pin 9 confusion

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Posted on February 14, 2017 at 09:38:00
banpuku
Audiophile

Posts: 927
Joined: January 19, 2006
I am confused about the filament heater wiring for pins 4, 5 and 9. I have read various information on the audio blogs and no definitive answer.

I want to use only 1/2 of the ECC99 with a 6.3V for the heater. So, which pin(s) should get the heater voltage (pins 4 only, 4 and 5, 4 and 5 tied together)? Where should I connect pin 9?

Any help would be greatly appreciated. I will be doing a nice write-up on the ECC99 and 2A3 tubes for Audio Asylum in the near future. Thus, I want to ensure that the tubes are connected correctly and biased optimally.

Thanks, Pat.



 

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RE: ECC99 Pin 9 confusion, posted on February 14, 2017 at 09:43:26
Eli Duttman
Audiophile

Posts: 9409
Location: Monroe Township, NJ
Joined: March 31, 2000
The ECC99 pins out like the common 12A_7 types. Pin 9 is the CT of the 2 heater sections. System 1 uses pins 5, 6, 7, 8, & 9. System 2 uses pins 1, 2, 3, 4, & 9.

Eli D.

 

RE: ECC99 Pin 9 confusion, posted on February 14, 2017 at 09:43:35
maxhifi
Audiophile

Posts: 520
Location: Alberta, Canada
Joined: August 4, 2004
Connect one wire from your 6.3V source to pin 9. If you use the tube normally, pins 4 and 5 are tired together, and connected to the other wire from the 6.3V source. If you plan only to use either the left or right half of the tube, it's possible to apply 6.3V between pin 9 and pin 4 or 5, depending which half you intend to use. The unused half heater pin would be left floating.

 

RE: ECC99 Pin 9 confusion, posted on February 14, 2017 at 13:21:43
banpuku
Audiophile

Posts: 927
Joined: January 19, 2006
Thanks, very helpful.

 

RE: ECC99 Pin 9 confusion, posted on February 15, 2017 at 10:38:49
Michael Samra
Dealer

Posts: 35580
Location: saginaw michigan
Joined: January 30, 2005
Contributor
  Since:
June 24, 2005
Pat
Try a scheme to up the B+ on the 2A3-40 because your OPT trafo is a 20 watter so you can at least get to about 12 watts.

"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

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