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Old 17th August 2006, 10:00 PM   #11
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Quote:
The 6CG7/6fQ7 do sound like a 6SN7.
Which is no wonder

Reportedly, RCA and GE did even re-transplant 6CG7 systems back into octal envelopes at the end of their active 6SN7 production

Tom
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Old 17th August 2006, 10:34 PM   #12
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Depends on the circuit configuration.

12BH7 will sound a little weak in the mids, with solid bass and clear treble in grounded cathode. However, make it the top tube in any totem pole and you have a clear winner

12AU7 has a sound people love or hate. It has a sweet spot in grounded cathode where it has great HiFi qualities, but you have to burn it hot. Used as a mu follower, it makes a nice sounding bass guitar linedriver that I dare anyone to show me better (for tone, Z is kinda ick .

6CG7/FQ7, I have yet to hear a bad configuration for it. It's just a darn great tube

(all this is my HO of course)
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Old 17th August 2006, 10:40 PM   #13
kegger is offline kegger  United States
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Curious when you say "BURN IT HOT" do you mean high voltage, high current or just plain disipation?

Not being confrintational just curious as to your thoughts.
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Old 17th August 2006, 11:36 PM   #14
lndm is offline lndm  Australia
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Running a 12AU7 at low current (around a couple of mA), I have found some to be a little bass heavy, possibly tending between a little syrupy rich in the mids (RCA) to a little muddy (Mullard). There are too many variables here to draw a conclusion, but I prefer not to run them lean.
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Old 18th August 2006, 12:44 AM   #15
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Bad thing about praising a tube is you can guarantee the ebay price will double as a result.
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Old 18th August 2006, 02:45 AM   #16
AJT is offline AJT  Philippines
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Quote:
"BURN IT HOT"
it means operate it at its plate dissipation ratings or very close to it..
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Old 18th August 2006, 03:27 AM   #17
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Quote:
Originally posted by kegger
Curious when you say "BURN IT HOT" do you mean high voltage, high current or just plain disipation?
Yes, as Tony said, run near it's dissipation rating, but in the 'AU7's case, run with max current rather than max voltage.
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Old 18th August 2006, 05:42 AM   #18
AJT is offline AJT  Philippines
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in the case of the foreplay, they run it at 50volts plate and about 1mA wonder what will happen if it were run at 5mA say, or even 10mA....running it at 10mA, plate dissipation is still low at 500mW still way bellow the tubes max plate diss of 2.5W if i am corrrect...
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Old 18th August 2006, 06:58 AM   #19
kegger is offline kegger  United States
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Yes it would still be way below it's plate rating but you'd loose all your voltage in
that application. Running it with that much current in the foreplay you would want
a bigger power trannie with more voltage and more current capabilities.
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Old 18th August 2006, 08:19 AM   #20
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I looks wrong to me to see 6CG7/6FQ7 lumped together, as though they were the same. I know both are supposed to have the same electronic characteristics as the 6SN7 but the 6CG7 is considered to be inferior. It's reputed to be variable in performance from one example to another, while the 6FQ7 is much more consistent.
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