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12AX7 variant as quiet as 12AD7?

GuyNoir

GuyNoir

Hallowed State
Hi there:

I've rolled a fair share of 12AX7s through my amp in the last six months , and I've found that the only tube in V1 that gives me a dead silent background at fifteen paces is a 12AD7. Sylvania long grey greenies are fairly close, as are RCA LBP, and Chinese 3 mica 12AX7A. Yet, I can hear a faint hum with the latter selections.

I just purchased a trio of "matched" Tungsol RI 12ax7's. which I really enjoy. However, due to hum, these are practically unusable in V1, though are quiet in the tone control sections. Admittedly, I did not have them screened for noise.

To the point - mighth someone recommend a 12AX7-ish candidate for V1; vintage or otherwise? I like the 12AD7, but it's a bit fizzy on top with some program material.

TIA,

Cary
 
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The 12AD7 is the most 12AX7-ish I have seen to date. Probably best to collect 12AX7A, or perhaps live with the lower mu of the 12AY7( which is a favourite of mic amp circuits ). There is of course the 12BZ7 which has double the 12AX7 gm, and thus has the potential to be quiet.
cheers,
Douglas
 
Hi vintage Euro ecc83 low noise types like the e83cc or ecc803s. But those are Uber expensivo. There is also Mullard box plate ecc83 the CV designation of M8024???? I can't remember the number off hand. 8024 might be a 12at7 type.
 
GuyNoir said:
Hi there:

I've rolled a fair share of 12AX7s through my amp in the last six months , and I've found that the only tube in V1 that gives me a dead silent background at fifteen paces is a 12AD7. Sylvania long grey greenies are fairly close, as are RCA LBP, and Chinese 3 mica 12AX7A. Yet, I can hear a faint hum with the latter selections.

I just purchased a trio of "matched" Tungsol RI 12ax7's. which I really enjoy. However, due to hum, these are practically unusable in V1, though are quiet in the tone control sections. Admittedly, I did not have them screened for noise.

To the point - mighth someone recommend a 12AX7-ish candidate for V1; vintage or otherwise? I like the 12AD7, but it's a bit fizzy on top with some program material.

TIA,

Cary
Click to expand...
I would recommend JJ ECC83S, a new production, made the same way as the famous tesla. Try it, it won't cost a fortune and you might be surpriced.
Do come back here and report !
 
peterh said:
I would recommend JJ ECC83S, a new production, made the same way as the famous tesla. Try it, it won't cost a fortune and you might be surpriced.
Do come back here and report !
Click to expand...
I don't think these are real frame grid types. The closest the advertisers go is 'similar'...which in tube audio-speak means it might have shared air freight with a piece of paper that had 'frame grid' written on it.
cheers,
Douglas
 
PakProtector said:
I don't think these are real frame grid types. The closest the advertisers go is 'similar'...which in tube audio-speak means it might have shared air freight with a piece of paper that had 'frame grid' written on it.
cheers,
Douglas
Click to expand...
Noone said anything about frame grid.
I mentioned JJ ECC83S for their documented silence and fidelity. Just like the tesla E83CC but at a fraction of the cost of near unobtanium tubes from the bay.
 
mashaffer said:
Is your amp susceptible to microphonics? If not have you tried these?

https://www.thetubestore.com/sovtek-12ax7-lps
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Well, it doesn't seem to be. Perhaps just a bit more prone to hum than others. I did in fact pick up a quintet of both 12AX7LPS and Sovtek 12AX7WA. I can hear a bit of hum from my listening position with the LPS. I found the LPS to be a good overall tube, though I prefer a more forward midrange. The WA were slightly worse for hum; which is curious, because purportedly they should be the quieter of the two.

Tubologic said:
I assume you meant 7025 (not 7027), which was a "controlled" noise and hum version of the 12AX7 (whatever that means). They were only made by RCA (the designer of this tube) , all the other 7025's I've seen were rebranded 12X7WA's (at best) or any garden-variety 12AX7's.
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Sounds like a possibility, and true 7025 don't seem to be particularly expensive. :thumbsup:

primosounds said:
Hi vintage Euro ecc83 low noise types like the e83cc or ecc803s. But those are Uber expensivo.
Click to expand...

A medical grade Tele, maybe? In my dreams! :king: I'll keep an eye out for bargains.

peterh said:
I would recommend JJ ECC83S, a new production, made the same way as the famous tesla. Try it, it won't cost a fortune and you might be surpriced.
Do come back here and report !
Click to expand...

The much maligned JJ ECC83S, huh? I will! I know they are affordable. I have a single JJ ECC803s (longest plates in history?) which seems fairly quiet, more bass than any other tube I've tried, sweet top end, though sound stage seems narrow.

I have to say, I have three Baldwin greenie long grey plates in right now and they are quite good, and only fractionally more hum that the 12AD7. When I first auditioned the trio many months ago, I judged them as "wooly". Probably because I had read all too often (granted, guitar forums) that mentioned that they can be "wooly". The power of suggestion. o_O

Thank you ALL!
 
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oh, worth a mention, but the 12AD7 does run higher heater current than a 12AX7 or 7025. May or may not be important depending on the configuration of things, but it cannot be mixed with a 12ax7 in a series heater string. In a more conventional parallel wired setup this probably won't matter unless the heater supply is just barely enough to get the job done.
 
It seems I had read about that caveat before I put her in. I'm sure they're parallel. On a side note, I had been running the amp with just the three essential 12AX7, minus the two for the phono section, which I will never use. Someone suggested the reduced load could be an issue for the power supply. Forgive me my ignorance; at least I think that was the implication. I reasoned that the 12AD7 would help offset that.
 
mashaffer said:
Does your amp have elevated heaters? If not just doing that might eliminate the hum. It is 60Hz not 120Hz right?
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That's above my ken, though per your suggestion, I am researching it now. I've assumed it's 60hz, though I might have to cue up my Alan Parsons 'Sound Check' cd to be sure. Edit: Yep, 60hz.
 
Running things with missing tubes can cause trouble. If this is in that Sherwood in your avatar, the phono heaters also provide some load on the bias supply. Without them present it will mess with the bias voltage on the output tubes which could cause some issues. I'd toss some cheap ones in there just so its "whole" even if you don't use the phono stage. The phono heaters are in series too, so they need to be 12ax7's.
 
gadget73 said:
Running things with missing tubes can cause trouble. If this is in that Sherwood in your avatar, the phono heaters also provide some load on the bias supply. Without them present it will mess with the bias voltage on the output tubes which could cause some issues. I'd toss some cheap ones in there just so its "whole" even if you don't use the phono stage. The phono heaters are in series too, so they need to be 12ax7's.
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Done! Thanks for clarification.
 
The biggest issue seems to have been a noisy 7199 upstream. For giggles, I swapped a myriad of 6GH8s, 6U8s and a pair of GE branded Euro E80CFs through the phase splitter sockets, the latter being the best of all. Ultimately, a pair of Raytheon 7199s were their equal. So now the new Tung-Sols are singing beautifully w/o audible hum.

gadget73 said:
Running things with missing tubes can cause trouble.
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And it did. I've noticed the preamp tubes are now quite hot to the touch, whereas before I could turn off the amp, grab them and pull them out immediately without scalding skin. The amp sounds so much more
"right" now., FWIW.
 
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Per your recommendations, I did get a trio of JJ ECC83s. I can tell you that they are quieter than the 12AD7. While they lack the euphonic qualities of some of the other new production tubes, their tonal balance is hard to fault, and they really seem to get out of the way of the music.
 
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