High gain tubes?

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George60
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High gain tubes?

Postby George60 » Sat 02/25/12 5:59 pm

I built a Ceriatone 36W EF86 and used all JJ tubes. The amp has, at the most, 200 hours on it and one of the JJ 12AX7's has bought the farm. All of the voltages are OK. I would like to try NOS pre-amp tubes in the TMB channel but I don't have a lot of money.

I found two different tubes that may be all right that I can afford. One is pre-war Ei 12AX7's. All that the dealer has are listed as testing as high gain. Is the high gain thing good, bad, or indifferent?

I also found RCA 12AX7's. The dealer has short and long plate tubes. I would imagine that short plate would be the choice but I'm not sure. Any opinions on this?

Thanks in advance to anyone who replies.

Solder on,
George
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Daviedawg
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Postby Daviedawg » Mon 02/27/12 2:52 am

Some makes from UK, USA are very expensive. But you don't have to pay a fortune for good valves. I have been buying less well known makes for £2 to £10 for ECC83/12AX7 preamps on eBay. At that price you can buy and try a large number for the cost of one good NOS Mullard.
For example in my 18 watt at the the moment I have three NOS Trigon ECC83 which are just great with a modern feel to them. In total they cost £12. I have tried Brimars which were nice but quite soft. They were also very cheap. Both those makes are described as "Made in England". The Brimars certainly were and are a good make.
I have run Marconi EL84s. They were used stock, pretty worn out but gave hope that a good set would be excellent. I am not sure of the provenence of the make.
Having said all that I like JJs and they have been totally reliable for me.

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nyazzip
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Postby nyazzip » Fri 04/13/12 11:36 pm

One is pre-war Ei 12AX7
what war? 12ax7 wasn't developed till the late 1940s
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sub
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Postby sub » Sat 04/14/12 12:54 am

nyazzip wrote:
One is pre-war Ei 12AX7
what war? 12ax7 wasn't developed till the late 1940s
http://en.wikipedia.org/wiki/Yugoslav_Wars
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Re: High gain tubes?

Postby dotfret » Tue 05/01/12 11:02 pm

George60 wrote:I built a Ceriatone 36W EF86 and used all JJ tubes. The amp has, at the most, 200 hours on it and one of the JJ 12AX7's has bought the farm. All of the voltages are OK. I would like to try NOS pre-amp tubes in the TMB channel but I don't have a lot of money.

I found two different tubes that may be all right that I can afford. One is pre-war Ei 12AX7's.
Usually a smooth long plate design, nice in V1 position.
George60 wrote:All that the dealer has are listed as testing as high gain. Is the high gain thing good, bad, or indifferent?
Generally speaking, 12AX7 with high gain have a poorer S/N ratio than lower gain valves that are in-specification. The gain of a 12AX7 is nominally 100, but in NOS production they routinely exceeded that - most production Mullards came off the line with a gain around 114-118. They would select out valves with a lower gain, say 100-105, because these would have a better S/N ratio, and label those as 12AX7WA. 95-100 gain and they would be labelled as 12AX7WB - even better S/N ratio.

You probably wouldn't feel the benefit of the low noise types in an 18watt, but you might want to impress some hifi buff ...

George60 wrote:I also found RCA 12AX7's. The dealer has short and long plate tubes. I would imagine that short plate would be the choice but I'm not sure. Any opinions on this?
RCA made good valves - and they did invent the 12AX7, yknow.
Long plate types are generally older designs. Whereas they have a smoother and sweeter sound than the short plates, they tend to become microphonic more easily than the short plates.
Short plates are a more reliable design and live longer than long plates, but lots of people prefer the sound of a long plate in V1, the first input position. In V2 it doesn't make much difference, and V3, the phase splitter, hardly contributes to the sound.
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Postby blaren » Sat 05/12/12 12:16 pm

Maybe try an RFT? They can be pretty cheap.
It may have been an oddball but my favorite 12AX7 I've ever used was an old blue labelled JAN Philips.
It had more gain than any I've tried (and I've tried them ALL). Unfortunately it went microphonic and I've (for some reason) never bought another :(.

The eI can be a REALLY nice tube. They have quite a bit of gain and I found that they have a lot of bite or crunch. I actually LOVE me some Ei 12AX7s....BUT....they are VERY bad for microphonics. Not sure why..they have smooth plates but so do the nice teles.

I probably had like a half dozen Ei tubes and probably 3 of them were microphonic out of the box. I sold one to a buddy and it went micro shortly after. I still have one and would like to keep it but..I would never trust it enough to gig with it.
as decent as they sound and as cheap as they can be had...to me they aren't worth the unreliability. If I can't play my bag off without constantly listening for and expecting a tube to go...skip it!

The Dutch Philips can have some hair.

all in all though...(and I dont have any high gain machines)..to me, vintage glass isn't what you want for high gain. I'm sure that if there is a MESA forum (no doubt there is), people there would have some suggestions for high gain 12AX7s.
Again...I have no experience with shred but if I was gonna recommend a preamp tube to a shredder I'd probably say to get a new production JJ or something...or maybe a telefunken. High gain likes TIGHT bottom end and not a whole lot of mid heavy overtones.
They probably like tubes that we would call "sterile" sounding...kinda like the hi-fi geeks.

Old tubes that sound "sterile" to me are the telefunkens, brimars, and to some extent, the nice old Tesla ECC83 or Ecc803s or whatever it's called. Sterile isnt the word for those but tight might be.??
YMMV
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Re: High gain tubes?

Postby CAlbertson » Thu 05/17/12 6:29 pm

George60 wrote:I built a Ceriatone 36W EF86 and used all JJ tubes. The amp has, at the most, 200 hours on it and one of the JJ 12AX7's has bought the farm. All of the voltages are OK. I would like to try NOS pre-amp tubes in the TMB channel but I don't have a lot of money.

I found two different tubes that may be all right that I can afford. One is pre-war Ei 12AX7's. All that the dealer has are listed as testing as high gain. Is the high gain thing good, bad, or indifferent?

I also found RCA 12AX7's. The dealer has short and long plate tubes. I would imagine that short plate would be the choice but I'm not sure. Any opinions on this?

Thanks in advance to anyone who replies.

Solder on,
George
If a brand new JJ failed after 200 hours you may want to try and figure out WHY it failed before to plug an expensive NOS tube into the same socket. You said "voltages checked out" What about current? How were they bipeds. Also what was the heater voltage? I like to run heaters at 6.0 volts. tubes last "forever". What about cooling and vibration? Was this a combo amp? The JJ is a robust tube. OK
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Postby kleuck » Tue 11/06/12 4:41 pm

Gain is not µ : no real tube can exhibit a voltage gain of 100 in our amps, more like 55-65.I know two tubes with very high gain : the old smoothplates either TFK, EI or Siemens, they look and sound the same ; and the old Tung-Sol long plates (some Motorola are the same)
RFT do not have a lot of gain, they just crunch early.
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Postby zaphod_phil » Tue 11/06/12 5:07 pm

You're talking about stage gain here, which is a slightly different topic. Preamp tubes, even of the same kind, do have different levels of µ, which translate into different amounts of stage gain. However, I don't think the resulting differences in stage gain are really all that great, once you you've factored everything in. One way to get a significant increase in stage gain is to put a high-impedance follower stage after a gain stage.
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Postby kleuck » Tue 11/06/12 5:19 pm

zaphod_phil wrote:I don't think the resulting differences in stage gain are really all that great, once you you've factored everything in.
They are -depends on the circuit too, that's obvious with large plate resistors, like 220K on simple amps with a single triode in the pre, less with the more common 100K, but still...
And that's not a matter of individual µ, i have a bunch of TS and EI/TFK Siemens, some old, some NOS, along with other tubes (****, RCA, RFT, GE, modern JJs and EH) and the results are consistently the same : the TS has the highest gain, slightly more than the smoothplates, all other tubes are lower in gain.
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Postby zaphod_phil » Tue 11/06/12 7:49 pm

...depends on the circuit too, that's obvious with large plate resistors, like 220K on simple amps with a single triode in the pre, less with the more common 100K, but still...
And it's affected a lot by the impedance of what comes after it.
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kleuck
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Postby kleuck » Tue 11/06/12 8:56 pm

Of course :)
BTW, i wanted to write "a single 12AX7", so two triodes -i made my comparisons in a VHT Special 6 (heavily modified) and it's important, as i did not like before the TS in more common circuits -too bright- nor the TFK -too clean- but with such a load/circuit, on the contrary, i love them.
Same for an Mazda "air" silver, way better with a big load, though it's still not a tube for a guitar amp imho (really too clean, bright, linear).
Circuit design comes first, i'm cautious now with general advices about tubes.
Anyway, TS and TFK smoothplates are the tubes with the more voltage gain (by ear) that i'm aware of (i have some old long plates with the ladder design on hand, but not mine, i did not found time to compare yet) whatever circuit i tested them in.
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Postby zaphod_phil » Tue 11/06/12 11:49 pm

I have a couple of NOS Sovtek's that have high µ. I think they're 12AX7WXTs, if I remember correctly, and I'm too lazy to walk into my lab and check.... :)
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Daviedawg
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Postby Daviedawg » Wed 11/07/12 3:08 am

"Same for an Mazda "air" silver, way better with a big load, though it's still not a tube for a guitar amp imho (really too clean, bright, linear). "

Interesting. I have a Mazda ECC83 which I thought at first I liked because it was crisp and bright. But after a week it was back in the box where it has stayed for a year. I never really analysed why. But probably too bright as you say or maybe not enough "character" in the tone.

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Postby kleuck » Wed 11/07/12 5:31 am

Yes, have a friend who loves them (he gave me the only one i own), but they are Hi-Fi tubes imho, the best Hi-Fi 12AX7, but not for us.
He sold one to the local studio, for a tube microphone, we tried Mullards, Phillips, TFK, but the Mazda silver was the best by far, noise floor only is way lower.
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