ST-70 & 6L6's

[larryderouin]

Big Bill has a ST-70. I've got a bunch of 6L6 types and a technical Question came up.

Would a 60's version 6l6WGB ( JAN Sylvania 6l6WGB, Brn Base Single Side Getter, Grey Plate.) work in the ST-70, or would he need the 6L6GC due to plate dissipations.

Thanks

Larry

 

[Audioexcels]

Hey Larry,

I was bored and decided to see if this can work. This person here made it work and it looks like they should be no problem granted I've seen other tubes in the ST70 that have higher or lower plate:

http://dynacotubeaudio.forumotion.com/t190-another-stereo-70-resto-mod-completed

 

[Kegger]

6l6WGB would be pushing them a bit, if wired the ST70 for cathode bias you'd be good.
(as far as stressing the tube goes)

---------------

I've ran them and the 6BG6G, they do work, but my observation was they were pushed.

 

[PakProtector]

hey-Hey!!!,
It is a workable, but far from ideal sol'n. The 6L6's are not capable of delivering the high current at low plate voltage the EL34's can. Power will suffer, and likely by enough to hear. Within this power output it may work for your particular tastes...can't say anything about that though...
cheers,
Douglas

 

[maxhifi]

I use my ST-70 series II daily with Sovtek 5881s, and works great. I forget what current I biased them to, probably around 40mA each. They've been in there a few years already, and it's not lacking for power. Originally stuck them in there due to lack of good EL-34s, and never felt a need to change them out.

See page 10 of the manual (page 14 of the pdf) <http://www.curcioaudio.com/st7_mnl.pdf>

"In emergencies, substitution of tubes can be made with other types,
the 5881 and KT-66 can be used in place of the EL-34s provided the
bias is readjusted to give 1.56V at the biaset check point. The
5U4G or 5U5GB can be used in place of the GZ-34. There is no
substitute for the 7199 tube"

Since the good quality (i.e. Sylvania, etc) 6L6GB is essentially the same as a 5881, I say you're good to go.

 

[Kegger]

hey-Hey!!!,
It is a workable, but far from ideal sol'n. The 6L6's are not capable of delivering the high current at low plate voltage the EL34's can. Power will suffer, and likely by enough to hear. Within this power output it may work for your particular tastes...can't say anything about that though...
cheers,
Douglas

I'm defiantly with you on how the 6L6 performs with the ST70 setup Doug, my
point was the lower 26 watt and under tubes of this family are stressed at the
voltages placed on them in the 70, mainly on the screens, but also "dissipation".
(the 6L6G and GB are just 19 watt plate tubes, same as the 807 and 6BG6G)

The 6L6GC is fine as far as "living" in the 70, still not best operating points here.

 

[larryderouin]

Thanks guys for the re-enforcement.

Larry

 

[drewbolce]

I've been running 6L6WGC's in my ST70 for a couple of months now. I found it necessary to change the bias to get into the range for these tubes. If I remember right I pulled the 10k resistor to ground. This removed the voltage divider in the bias and allowed me to adjust the tubes to 38ma per tube.

The unit sounds great, the bias is rock stable and runs cooler. Some of this difference may have been due to the poor condition of my EL34's vs the NOS condition of the 6L6's.