What are some low hum 12AX7 types?

[Pearly Gator]

My Hot Rod Deluxe had a clean channel hum problem related to V1. I like the sound of a 5751 in both the V1 and V2 slots but find the hum is too much. Trying a NOS RCA 7025 and an unlabeled 12AD7 in V1 got rid of the hum. Now, there is too much gain and the sonic sweetness I enjoyed with a 5751 is lessened. What other preamp tubes are designed specifically with low hum characteristics? Anything in the 5751 gain zone?

TIA

Gary

[pbradt]

I've never heard a tube that was designed to be low hum.

Try a NOS 12AY7 in V1. Less gain, sweeter. AX7s are (IMO) too high gain for V1 in any Fender.

[Pearly Gator]

Thanks for the reply. According to my RCA tube manual...

7025 HIGH-MU TWIN TRIODE

Miniature type used as a phase inverter or resistance coupled amplifier in high-quality, high-fidelity audio amplifiers. Outlines section 6B; requires miniature 9-contact socket. This type is identical with miniature type 12AX7A except that it has a controlled equivalent noise and hum characteristic.

I'm looking for others with the "controlled" hum characteristic.

PG

[Jon Silberman]

I had the same problem with one of my amps. What I found is you can't go by brand of tube. You have to find the lowest hum one by trial and error. Begin with no preconceptions as to tube brand quality, NOS versus new, etc. Just listen. If you have 10 or 12 12AX7s lying about to try it's virtually certain one will be exceptionally low hum, that's the one you stick with.

[jspax7]

Originally Posted by Jon Silberman

I had the same problem with one of my amps. What I found is you can't go by brand of tube. You have to find the lowest hum one by trial and error. Begin with no preconceptions as to tube brand quality, NOS versus new, etc. Just listen. If you have 10 or 12 12AX7s lying about to try it's virtually certain one will be exceptionally low hum, that's the one you stick with.

Agreed. If you like 5751's, get half a dozen and put the best in V1. Try several AT7's too. Mullard AT7's are available at little more than current production prices.

[Pearly Gator]

Aha! I didn't think to try other 5751's. The hummer was a Philips. I have an RCA and a GE in my stash. I'll try them next. Thank you!

:BEER

[Mike9]

For new production tubes the EH 12ax7s are pretty quiet in in terms of hum and microphonics. I'd like to try some EH 12ax7s that are cryo treated.

[Jon Silberman]

I have EHs in my Reverend Hellhound which is more succeptible to hum than most amps because the filaments are AC. I found EHs to be just as variable as any other tubes in terms of hum which is to say, try a dozen, keep the pick of the litter!

[go7]

Or try a E83CC,mliltary version of ECC83. These usually have thicker glass. My fav pre amp tube for quietness and tone is the Tesla Rosnov E83CC. Good Luck!

[jspax7]

Originally Posted by Pearly Gator

Aha! I didn't think to try other 5751's. The hummer was a Philips. I have an RCA and a GE in my stash. I'll try them next. Thank you!

:BEER

If your amp has plenty of overdrive, 5751's can be just the ticket to clean it up. Makes the OD more articulate, and sweeter IMHO.

Try a 5751 in V1, and a 12AX7 in V2, then switch them. Still too much? Try 2 5751's. You should find something to you liking.

[Pearly Gator]

Thanks to your suggestions, I found a pair of 5751 tubes that worked with minimal hum. Even between two identical tubes, there was a major difference. I was quite surprised!

I connected my oscilloscope across the speaker load and swapped tubes until the hum was lowest, settling on an RCA in V1 and a GE in V2. Yes, a 12AY7 had low hum in V1 but the gain was a tad low.

A big thank you to all!

PG

[teleamp]

7025's & 12AX7A's

Some times you've got to weed through some noisy ones.

Mike

[mockoman]

I went through the trial & error method with a Pro Jr. V1 is real sensitive,and it took some searching to quiet it down.
I found a short plate Mullard that worked.
For new production,every Sovtek WXT was quiet for me.
Short plates seem to be the answer in my amp.

[plexi67]

Originally Posted by pbradt

I've never heard a tube that was designed to be low hum.

Try a NOS 12AY7 in V1. Less gain, sweeter. AX7s are (IMO) too high gain for V1 in any Fender.

There are quite a few that were designed to be low hum low noise tubes.

[Pearly Gator]

Originally Posted by plexi67

There are quite a few that were designed to be low hum low noise tubes.

Two would be the 12AD7 and the 7025. Please list others.