6CG7-6FQ7 Vacuum Tube Replacements

[mediumjim]

Merry Christmas!

I love tube rolling and have a FP2 that is nicely modified and is set up for 6CG7/6FQ7's.  What if any other preamp tubes are there that can be plugged in without any circuit modifications? 

There is no problem with the presentation provided by 6FQ7's, I do love to try different tubes and was hoping to find a couple of possibilities. 

Thanks,
Jim

[Kingrat]

6gu7 might be worth a try, slightly lower mu/lower plate resistance, I was pleased by their performance in another project that was a little low on voltage for ideal operation with 6cg7/6fq7/etc

[Grainger49]

I searched ebay and there are no cross references in the auctions.  My RCA Tube Manual lists none either.

[mediumjim]

Hi Grainger:

That what I thought as well.  Kingrat is right that you can try a 6GU7, but I believe it draws more current and narrows the soundstage from what I can gather about them.  I guess that I will have to be content with different 6CG7's and 6FQ7's.   I have a duet of RCA Clear Tops coming that are said to be the schnizzle.   I next hunt down some others if the price is right. 

Jim

[2wo]

I think the 6FQ7 is a most excellent tube.

 If you have the itch, it would not be hard to convert back to the 12AU7 family and roll to your hearts content.

Search the forum, I think it's just a few changes to convert from one to the other. You're not locked in to one tube...John   

[mediumjim]

2wo:

I agree that there's nothing wrong with 6FQ7/6CG7's and really like the spacious soundstage it produces.  I will have to be content with rolling different makes.  If I was going to go the 12AU7 route, I would go with 6922's or Cca's. 

There's a duet of RCA Clear Tops coming my way and am trying to put together a matched duet of Realistic Gold Pin 6FQ7's, to my knowledge they're the only gold pin in the 6CG7/6FQ7 family other than the newer Ei's and EH's made in Russia.

Jim

[Grainger49]

I think I posted in your first thread that one of the best sounding preamps I ever heard used 6FQ7s for the line stage.  The tube can sound expansive!  But for tube rolling you seem to be stuck with the 6FQ7/6CG7.

There are a number of variants of the 12AU7:

http://www.bottlehead.com/smf/index.php/topic,1027.0.html

[mediumjim]

Grainger:

I wholeheartedly agree that the 6FQ7 is a wonderful tube in the line stage and am more than content with what they give me.  I suppose this thread was a lesson in futility on my part, but you never know and I was hoping that there was something that may not be a direct replacement that was close enough to try.   There are still so many tubes out there that haven't yet been experimented with. 

Jim

[mediumjim]

At some point 6922 Pinched Waist tubes were out there, so were Cca's 803's, in just the 12AU7 category of vacuum tubes.  These tubes now command so much money.   Sure, they were always premium tubes and did cost more, today they're in the hundreds of dollars per tube. 

I feel that there is still a lot of good industrial, foreign, or obsolete tubes out there that have merit that can be tapped into by those who are industrious and willing to experiment.  This forum from what little exposure I have seems to be populated by some amazing thinkers and tinkerers. 

One of the best things that happened to me in a long time was when a good friend and business associate got me back into Tube Stereo Gear as I had forgotten how wonderful it was and had become.  Another one was when I discovered Bottlehead!  I was looking for a 2nd Tube Preamp to complete a system I was building and was trying to buy a restored and ungraded Dynaco PAS-3 and the seller drew a line in the sand.   I then looked for alternatives and the Bottlehead FP2 that I now possess intrigued me and I figured for the money I couldn't go wrong even if it fell off of the truck on the way to me.  I really do believe in what goes around...and this was a payback for something good I did. 


Sorry for my bird-walking!

Jim

[Doc B.]

6922s and CCas are not in the 12AU7 family except in the broad sense that they are both 9 pin mini dual triodes. They are in the 6DJ8 family and typically require some adjustments to the circuit design to employ them in a circuit that uses 12AU7 tubes or those of similar operating characteristics like 6SN7, 6FQ7 etc.

[mediumjim]

Doc B.

You're right.

Jim

[Doc B.]

One other tube you might want to look into trying is the 12BH7, which will require the same heater pin rewire as a 12AU7 - pin 9 for one heater winding connection, pin 4 and 5 together for the other connection.

[mediumjim]

Doc B.

I could devise a jumper that could be easily applied and removed to do something like that.  From what I can gather the 12BH7 has nice space and is airy.   

When I get the RCA Clear Tops I will have to do some critical listening.   Right now my FP has a pair of mutts, albeit they're matched but are different construction and feel I'm not fully experiencing what the FP can really give me.   I do have the original 6CG7's from my Marantz 9's, but I want to leave them alone for prosperity sake. 

Jim

[mediumjim]

The RCA Clear Tops arrived today and I must say WOW!  The highs have a bit more attack, clarity and more spacial.  I lost a little bit of bass yet it is now faster and more defined.  The soundstage got wider and deeper with more micro detail and is dead quiet. 

I'm in such a good place right now, this is after a real bad day yesterday when I pulled my Parasound HCA-1200II out of storage and discovered it has a bad left channel.  I will test the DC Offset on it soon...I will most likely get an Adcom to replace it or even a nice Dynaco I've been eyeing. 

Needless to say, I'm fine with the RCA's and have no desire to fix what isn't broken!

Jim

[Grainger49]

Could the lighter bass, "I lost a little bass" be the result of a looser bass being tightened up? 

I prefer tight to loose in bass....