6FQ7 in RH84

ThSpeakerDude88 · 22nd December 2008, 03:55 AM

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 · 22nd December 2008, 05:09 AM

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

Stixx · 22nd December 2008, 08:05 AM

Quote:

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 · 22nd December 2008, 10:10 AM

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

ilimzn · 22nd December 2008, 06:25 PM

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 · 22nd December 2008, 08:48 PM

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

22nd December 2008, 03:55 AM	#1
ThSpeakerDude88 diyAudio Member Join Date: Jun 2005 Location: USA	6FQ7 in RH84 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. __________________ always preach the gospel- and when necessary use words.

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22nd December 2008, 05:09 AM	#2
ray_moth diyAudio Moderator Emeritus Join Date: Jan 2004 Location: Jakarta	It would help to know what RH84 is. The 6FQ7, as you probably know, is a miniaturized 6SN7.

22nd December 2008, 10:10 AM	#4
ray_moth diyAudio Moderator Emeritus Join Date: Jan 2004 Location: Jakarta	Thanks, Stixx. In that case, the 6FQ7 might not provide enough gain. Its mu is < 0.3 times the mu of the ECC81.

22nd December 2008, 06:25 PM	#5
ilimzn diyAudio Member Join Date: Feb 2005 Location: Zagreb	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.

22nd December 2008, 08:48 PM	#6
Shoog diyAudio Member Join Date: Aug 2002 Location: Eire	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