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Here is something for you guys to try.

97.95.43.235
Posted on April 15, 2017 at 02:39:17
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 The Grommes 260a amps use a 12AU7 in the first gain stage.What I did was use a 12AU7 to 6CG7 adapter and install the 6CG7 in place of the 12AU7 and got some nominal improvement. I then stuck a 6DJ8/6922 in that same adapter and it performs exceptionally well to.Now keep in mind this is for a gain stage so it's not going to give the same result putting it in the McIntosh for the 12AU7 phase inverter. There you need to use the 6CG7 as that is better than the 12AU7 and I measured the distortion numbers to verify it.The voltage would be too high there for a 6DJ8 anyway but I like the sound in the Grommes.I'm not saying the 6DJ8 is better in that position but it is different but both tubes performed better than the 12AU7 in that first position.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

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RE: Here is something for you guys to try., posted on April 15, 2017 at 07:12:16
sony6060
Audiophile

Posts: 1465
Location: USA
Joined: August 8, 2014
 Try a USA built Raytheon 6CG7. It is a great brand.

 

RE: Here is something for you guys to try., posted on August 25, 2017 at 12:57:35
Audio Pete
Manufacturer

Posts: 152
Location: Long Island,NY
Joined: May 22, 2015
 Michael - Just a reminder that the 6CG7 draws twice as much heater current as a 6DJ8. Be sure you still have 6.3v +/- 10%.

 

RE: Here is something for you guys to try., posted on August 27, 2017 at 18:09:49
Lee of Omaha
Dealer

Posts: 1800
Location: Omaha NE
Joined: September 8, 2006
 We did exactly that to a pair of MC30s, one amp at a time with single blind testing. The difference was readily apparent. I don't know why the 6CG7/6FQ7 is better than the 12AU7, but it certainly is. And don't worry about the extra heater current in the MC30, as the MC30 was designed to also power an unpowered preamp, so heater drive current is no problem.

And it's a 15 minute mod--you just rewire the heater pins.

 

RE: Here is something for you guys to try., posted on August 28, 2017 at 02:05:19
awesterner
Audiophile

Posts: 23
Location: Seattle
Joined: May 7, 2017
 The 6CG7 is a 9-pin version of the 6SN7. The 6SN7 is a great tube. Read a LONG article wherein many dual triodes were tested and the octal tubes consistently bested the 9-pin tubes with the exception of the 6CG7 and 12FQ7 because, again, they are a 6SN7 in a 9-pin bottle.

 

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