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Old 22nd December 2008, 03:55 AM   #1
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Default 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.
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Old 22nd December 2008, 05:09 AM   #2
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It would help to know what RH84 is. The 6FQ7, as you probably know, is a miniaturized 6SN7.
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Old 22nd December 2008, 08:05 AM   #3
Stixx is offline Stixx  Germany
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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...
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Old 22nd December 2008, 10:10 AM   #4
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Thanks, Stixx. In that case, the 6FQ7 might not provide enough gain. Its mu is < 0.3 times the mu of the ECC81.
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Old 22nd December 2008, 06:25 PM   #5
ilimzn is offline ilimzn  Croatia
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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.
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Old 22nd December 2008, 08:48 PM   #6
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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.

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