ECC99 operating points?

[skyraider]

ecc99 operating points?

Hi all,

It seems there have been a lot of rave about ecc99, but I have not been able to get good results with it. So far, I found it very 'forceful' sounding with pronounced highs and SS qualities.

Ok, I havent tried that many operating points yet, but would appreciate if someone who has good results with it, point me a good direction to try. Thanks


p/s- Currently My B+ is 330v, plate resistor 23k and cathode resistor is 390R. Will measure my plate voltage/current and post it tomorrow.

Thanks

 

[Eli Duttman]

Look into Lynn Olsen's work. He uses the '99 as a driver in PP 300B amps.

 

[dmcgown]

You will get more body from the tube if you increase current. Try reducing the cathode resistor to around 270 ohms, and adjusting the plate resistor to drop half of the B+ as a start. This tube wants to see current.

Davie

 

[skyraider]

Hi all,

I checked the voltages, and found the current operating point around 135v/11mA. My B+ is about 330v, and my plate resistor is 23k.

Should I increase the current further? My problem is more related to over-emphasized (unnatural) highs. How much gridstop resistor is needed to tame oscillations?

I checked Lynn Olson amity amps, but he did not indicate specifically how he uses the ecc99.

Thanks

 

[Brett]

I checked Lynn Olson amity amps, but he did not indicate specifically how he uses the ecc99.

It's quite clear on the schematic here the op points he uses. Scale anode resistors to suit if not using Tx's.

 

[Gluca]

I liked it much more with a LED in the cahode...

 

[skyraider]

It's quite clear on the schematic here the op points he uses. Scale anode resistors to suit if not using Tx's.

Thanks!