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In Reply to: RE: What type tube is this? N/t posted by Sondek on July 11, 2015 at 07:17:23
Can I use this in my pre amp,
Follow Ups:
I dug up an old thread on the AA forums and modified my Foreplay III to use the 6CG7's with a grounded shield and I was blown away! The bass bloomed and there is more depth to the sound (front-to-back soundstage). Female vocals almost have an eerie 3-D sound to them now as well.
For those considering this upgrade, I give it 3 thumbs up (???)! It only took about 30 minutes with a soldering iron:
1. Unhook heater wires from the 12AU7 tubes.
2. Unhook heater ground reference from Pin 9 of the one 12AU7.
3. Re-wire the heaters to Pins 4&5 of the 12AU7's (observe polarity!).
4. Tie the heater ground reference to Pin 4 of the one 12AU7.
5. Tie Pin 9 of both 12AU7's to the closest ground terminal (one used for cathode LED ground).
6. Replace 12AU7's with 6CG7/6FQ7's.
7. Enjoy!
The Mind has No Firewall~ U.S. Army War College.
If the heater supply is 6.3 volts and can deliver the increased current (.6 amps vs. .3 amps) it's a drop in replacement that is MUCH more linear.Edit, As JJ Triode pointed out, the above is only true after you rewire the heater connections on the tube socket.
Thanks again JJ for catching my mistake.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 07/12/15
The heater connection for 6.3V operation is different. In the 6CG7/6FQ7 there is 6.3V across pin 4 to pin 5 and no connection or ground on pin 9. For 12AU7 operating on 6.3V, pins 4 and 5 are connected together, with 6.3V between them and pin 9.
For 12V operation of the 12AU7 a 12FQ7 may be a drop-in.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
My pre can use any type 12- type tube in this pre and any combination . But this tube I never heard of.
What preamp do you have?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
It's A custom made Ton cat Audio pre, uses any combination 12a- tubes.
Without a schematic I can't really help or guide you.
Is it like this one?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
It was design to take any 12au7 at or au and 5814a tubes, takes 4 tubes,
timīs stats are hard to believe!
in the 12AU7 gain position of my gear i checked nearly every estimated "better" replacement you can imagine like 6067, 5965, 12BH7, E80CC etc. but i always swapped back to 12AU7/ECC82 (Siemens E82CC long plates currently) as it always performed better than all the others!
N.
The times, they are changing...
You don't think that's true?
Some further points?
i)If you didn't change the circuit values for each of those potential substitute tubes they wouldn't be operating properly, anyway.
ii) Unless the tubes you are rolling are the same design, the circuit values around that tube position will almost certainly need to change. And that's only if there's sufficient reserve heater current
iii) The 12BH7 shouldn't need any circuit value changes but will draw more current, and if it can't the sound isn't likely to be any good. In a circuit that has enough current any 'to spec' 12BH7 will beat any such 12AU7.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
For me it's the RFT. The RFT is ruthlessly revealing and many would say cold, or hard sounding. And to some extent that criticism is true, but what we so often find when rolling tubes it's all about synergies. Nowadays, the only piece if gear I have left that uses a 12AU7 is my Primaluna CD player. The sound of the RFT when paired with the (I know, I'm starting to sound like the spokesman for them) JJ 5751 is just beautiful. That same RFT with just about any other AX7 type I own always ends up being just too much and gets rolled out.
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