I read that converting the 12AU7 sockets to 6FQ7/6CG7 is a great sound modification. I see that Ebay sells several of these adapters and all of them specify 6.3v heater voltage. Does this mean one must drop the heater voltage when using these adapters or does the adapter do this for you? They all come from China so I am loath to try to get an Engli9sh answer from them.
Here is an example:
https://www.ebay.com/itm/1920854637...hcTrqRbdrCphJ1/f17eH1LWKQj|tkp:Bk9SR8bl18aXYw
Thoughts?
f1jim
Here is an example:
https://www.ebay.com/itm/1920854637...hcTrqRbdrCphJ1/f17eH1LWKQj|tkp:Bk9SR8bl18aXYw
Thoughts?
f1jim
That first 6 in 6FQ7 means that tube needs 6.3VAC for its filament.
The ebay listing does not say what the adapter actually does.
You would be better off simply rewiring the original socket for 6.3VAC,
as measured between pins 4 and 5.
The ebay listing does not say what the adapter actually does.
You would be better off simply rewiring the original socket for 6.3VAC,
as measured between pins 4 and 5.
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If the original amplifier has 6,3V heater voltage you can use the adaptor , usually it is like that , but if it uses 12,6V you can't
I'll look for a jumper between pins 4 & 5. It's a Prima Luna Prologue Premier integrated. Uses 4 12AU7's. They tell me to tube roll the very front 2 12AU7's. They are the ones I want to try 6CG7/6FQ7's in. I have a boatload of brands of them.
Is this for a preamp/line stage? Make sure the 6.3v heater supply has enough extra current for 6CG7, as it's significantly more than a 12AU7.
jeff
Does this mean if the tube is marked 6CG7/6FQ7 that jumper between the pins is already there so it's usable?
Boy, am I getting an education!
f1jim
Boy, am I getting an education!
f1jim
No the jumper is at the tube socket in the amp.
Ok I found a pic of the underside here: https://www.primaluna-usa.com/prologue-premium-integrated There's no mention of tube rolling options for the 12AU7's in the writeup.
Pins 4 & 5 have individual wires, and there doesn't appear to be a connection at pin 9, so looks like 12.6v wired. The image isn't hi-rez, so best to check your amp.
jeff
Ok I found a pic of the underside here: https://www.primaluna-usa.com/prologue-premium-integrated There's no mention of tube rolling options for the 12AU7's in the writeup.
Pins 4 & 5 have individual wires, and there doesn't appear to be a connection at pin 9, so looks like 12.6v wired. The image isn't hi-rez, so best to check your amp.
jeff
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Thanks Jeff. For now I'll not pop 6CG7's in. Tubes are too expensive to be frying them needlessly.
f1jim
f1jim
I would contact Upscale in Cali., as they are the US distributors for PrimaLuna, and ask them what the deal is.
jeff
jeff
I have a headphone amp that uses a 12BH7 for the line out driver. I attempted to use one of the ebay adapters for a 6CG7 and it burned out the filaments. Looking closer, the filaments are wired for 12.6V to pins 4 and 5. The adapter I have can't reduce the voltage. I didn't want to modify it and try grounding pin 9, and possibly pop another RCA 6CG7. I found some 12FQ7 tubes and I am using those with success.
@f1jim,
Based on the questions you ask I think you may not be aware the published base diagrams for these tubes that will show where what is connected. 12au7 tubes are often heated by 6.3V connected between 4&5 jumped, and pin 9. Sounds like your PrimaLuna amp may heat the 12au7s with 12.6v between pin 4 and 5, with pin 9 unconnected.
6CG7 and 12FQ7 tubes heat via pins 4 and 5 only with 6.3 and 12.6 V respectively.
Check the tube data here: https://frank.pocnet.net/