Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: mls on January 24, 2012, 05:57:23 pm
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I came across some 2C51/396A tubes. Wondering if anyone has tried them in a guitar amp. Does anyone have any schematics worked up?
thx
(http://www.frontiernet.net/~stutler/Western%20Electric%20396a.jpg)
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OMG, the fetish for Western Electric stuff is so enormous, you could probably trade those two tubes (or sell them on ebay) for (enough $$ to buy) a Champ Amp. No, I'm not kidding.
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Yeah, I know they have a different pin out. I was hoping some one has allready done a load line and had values worked up.
thx
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OMG, the fetish for Western Electric stuff is so enormous, you could probably trade those two tubes (or sell them on ebay) for (enough $$ to buy) a Champ Amp. No, I'm not kidding.
+1
anything branded Western Electric will sell at a premium.
Besides what do expect them to do with a Mu of 35?
it would be great seed money for a great amp project!
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Mu of 35 = effects loop or tone stack cathode-follower. Can't think of anything else.
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12ax7 is just 30V higher and IMO not really an issue.
--DL
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OMG, the fetish for Western Electric stuff is so enormous, you could probably trade those two tubes (or sell them on ebay) for (enough $$ to buy) a Champ Amp. No, I'm not kidding.
Maybe in the right setting/to the right buyer.
I looked up recent ebay listings. It's my opinion that the low end of actual completed purchases likely represents the actual market. I saw a lot of completed listed selling a pair of these tubes (in WE branding) for $15-20. I did see occasional sales at 3-4x this price.
Regardless, as TD pointed out, the mu of 35 puts this tube gain-wise between a 12AU7 and a 12AY7. Plate resistance is as-low, and Gm higher, than a 12AU7 running at higher current than the 2C51; this makes sense, given mu is the ratio of Gm and plate resistance.
The data sheet touts this tube as being capable up to VHF. The combination of reasonably good gain, low plate resistance and high Gm seems like a good candidate tube for RF circuits working into plate chokes instead of plate load resistors and/or for a tube that needs to drive low input impedance circuits, like grounded-grid stages. What I'm saying is this seems like a specialist tube that makes more sense in an RF or video circuit, rather than an audio circuit. It might be a good tube in a line-stage, where only slight make-up gain is needed. The tube is a current hog if you want to take advantage of all its features.
It could however make a good low output impedance cathode follower; the problem is the impedance of such a circuit would be low, but there's not a lot of excess gain to reduce the impedance even more through the resulting feedback.
Take me as an example: I bought around 100 or so 12AU7's in a single batch, because they were offered at a very good price (don't remember, but it might've been well under $1 a tube) and were NOS early-60's. Forget NOS dealer prices, you just about can't give away 12AU7's to the guitar amp crowd, cause the amps just don't use too many of them. And you get maybe 18x the gain from a cascaded pair of 12AX7 triodes than you get with the same from a 12AU7. Luckily, I have a build in progress that should be utilizing my 12AU7 stash.
I'm thinking you're best off selling these to someone who really needs this specific tube for their vintage gear, where nothing else will do. Or someone that's really excited about using WE stuff to build an audiophool amp of some sort.