Which 12ax7 choice for cathode follower?

Frostbite Slim · Post by **Frostbite Slim** » Wed Dec 23, 2015 2:48 am

Are there certain brands (NOS or current production) of 12ax7 that perform well as CF? Long or short plates matter?

splgeo · Post by **splgeo** » Wed Dec 23, 2015 2:49 am

what application are you using it in? like what type of circuit?

Frostbite Slim · Post by **Frostbite Slim** » Wed Dec 23, 2015 2:51 am

Oh..sorry.

SSS

splgeo · Post by **splgeo** » Wed Dec 23, 2015 12:09 pm

most use a 12bz7 or 12bh7 or a 5751.
12az7 are great gain stage tubes. a 12at7 or any tube listed above are great current driving tubes. That whys Fender used the 12at7 as the PI tube a lot of times

Frostbite Slim · Post by **Frostbite Slim** » Thu Dec 24, 2015 3:56 am

splgeo..thanks for the info . Anyone else care to comment? Maybe some folks here who have built an SSS w/CF

martin manning · Post by **martin manning** » Thu Dec 24, 2015 10:12 am

SSS circuit values as shown in the schematic are for a 12AX7. There are no special requirements, so I recommend you try a few and find one that you like.

mhartman · Post by **mhartman** » Thu Dec 24, 2015 2:59 pm

12ax7 is fine, but you'll want to avoid certain designs. For instance, through experimentation, I've found that Tung Sols aren't a good choice.

mhartman · Post by **mhartman** » Thu Dec 24, 2015 3:00 pm

12ax7 is fine, but you'll want to avoid certain designs. For instance, through experimentation, I've found that Tung Sols aren't a good choice.

Frostbite Slim · Post by **Frostbite Slim** » Thu Dec 24, 2015 4:06 pm

Mhartman, thanks. Would that be the current production Tung Sol?

mhartman · Post by **mhartman** » Thu Dec 24, 2015 5:08 pm

Yes, current production. They tend to hum.

JD0x0 · Post by **JD0x0** » Thu Dec 24, 2015 6:53 pm

mhartman wrote:Yes, current production. They tend to hum.

Not IME. The one's I've used have been very quiet, and have had a nice detailed high end, IMO.

rp · Post by rp » Fri Dec 25, 2015 2:29 pm

I have a recollection of posts here or elsewhere regarding some modern 12AX7s not being up to CF duty, issues w/ the cathodes not handling the voltage well. Maybe others can follow up or the OP might want to google it.

and Merry Christmas.

mhartman · Post by **mhartman** » Fri Dec 25, 2015 10:34 pm

JD0x0 wrote:
mhartman wrote:Yes, current production. They tend to hum.
Not IME. The one's I've used have been very quiet, and have had a nice detailed high end, IMO.

Maybe it was just the batch that I had. They were fine everywhere except the Post-PI CF.

Frostbite Slim · Post by **Frostbite Slim** » Fri Dec 25, 2015 10:47 pm

I'm gonna try a few different brands...mostly NOS. Do they benefit if they have matched sections?

sergio · Post by **sergio** » Sun Dec 27, 2015 8:58 pm

I used an RFT 12AT7 NOS in CF stage , good choice!
S.

The Amp Garage

Which 12ax7 choice for cathode follower?

Which 12ax7 choice for cathode follower?

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Re: Which 12ax7 choice for cathode follower?

Re: Which 12ax7 choice for cathode follower?

Re: Which 12ax7 choice for cathode follower?

Re: Which 12ax7 choice for cathode follower?

Re: Which 12ax7 choice for cathode follower?

Re: Which 12ax7 choice for cathode follower?

Re: Which 12ax7 choice for cathode follower?

Re: Which 12ax7 choice for cathode follower?

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Re: Which 12ax7 choice for cathode follower?