6FQ7 in RH84

[ThSpeakerDude88]

Has anyone tried this? It requires a simple heater rewire to be pin compatible, but would it sound okay/ be compatible with the circuit? I don't have very many good tubes to try in the 12AT7 category, but I did pick up 5 RCA 6FQ7/6CG7 cleartops that I would like to try.

 

[ray_moth]

It would help to know what RH84 is. The 6FQ7, as you probably know, is a miniaturized 6SN7.

 

[Stixx]

It would help to know what RH84 is.

The RH84 is an EL84 based amplifier originally designed by Alexandar Kitic... see thread here...

one of many...

 

[ray_moth]

Thanks, Stixx. In that case, the 6FQ7 might not provide enough gain. Its mu is < 0.3 times the mu of the ECC81.

 

[ilimzn]

And it's Rp is too low for the plate-to-plate feedback in the RH84 to work properly. In fact, i believe the requirements of a driver tube in that amp are pretty well laid out on the author's website and in numerous posts on this forum.

 

[Shoog]

ideally the driver should be a pentode and should have a reasonable current capablility. Alex did extensive computer modeling to get the right triode for the job and since its a reasonably cheap tube I wouldn't be inclined to change it.
However if it was me I would redesign for a decent pentode driver such as the 6AU6.

Shoog