Some tube advice on 12AT7WC-EH vs 12AT7EH

Discussion in 'Amps and Cabs [BG]' started by therealbigsteve, Jan 25, 2015.


  1. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    The Raytheon plant did a lot of government work. Those were massive factories and they employed a lot of women who had a great attention to detail. It's amazing how much work went into their production when you consider what they sold for. There are a couple of PR videos on youtube that I've seen.
     
  2. B-string

    B-string Supporting Member

    Yes, they did not produce "consumer" tubes at that plant. He implemented air filtering, fuel filtering (glass torches), waste gas evacuation from the torches and nitrogen flushes before evacuation of the bottles in his time there. Decreased rejection rate by almost 40%. Sounds good but at that time barely paid for the added expenses.
     
  3. Thanks for the input everyone!
     
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  4. ThisBass

    ThisBass

    Aug 29, 2012
    Germany
    Some of the old production machines on which the good old NOS tubes where made somewhere in the past are still in use but nowadays owned by a different company to produce tubes.

    In the late 80's I bought a complete set of "quality" tubes made in usa for my svt. The 12dw7 set did not fit the specs at all and where completely impractical, the GE 6c4 tended to cause feedbacking, one of the two 12BH7 was faulty, the GE 6550 sextett did not last very long, after some hours of playing one of the powertubes failed. I did not bother to much all about that because I did not liked the sound of the GE 6550 ....

    That was my experience with (so called) qaulity tubes of the golden age where tubes where supposedly of better quality then nowadays.
     
    Last edited: Jan 29, 2015
  5. waltdogg

    waltdogg

    May 24, 2014
    That would be JJ who has the old Tesla equipment and makes their tubes on it. And I gotta say, the JJ E34L sound and looks a lot like a 60s Tesla EL34.

    Something about those weird tubes that Ampeg chose that aren't even very common or good tubes for audio amplification. 6550s I find to be quite stiff and sterile sounding, in any amp, any make, any era.
     
    Last edited: Jan 29, 2015
  6. B-string

    B-string Supporting Member

    IIRC New Sensor has the Mullard tooling.
     
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  7. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Lost arts today. So much of that technology retired with the workers that knew about it.
     
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  8. BurningSkies

    BurningSkies CRAZY BALDHEAD

    Feb 20, 2005
    Syracuse NY
    Endorsing artist: Dingwall Guitars
    I'm of the mind that 'having the tooling' of whatever golden tube laying baby of the old days isn't going to do it. It wasn't that it was magical gear, it was people with an esoteric knowledge of materials and construction. To the same extent that you can have an original Fender that Leo himself whittled by pocket knife, but it won't sound any better than a 100 starter pak guitar in the hands of someone who can't play.
     
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  9. Coolhandjjl

    Coolhandjjl Supporting Member

    Oct 13, 2010
    Appleton
    I wanted more clean headroom in my Orange TB1000 before it started to grind. I went with a NOS RCA 5751.

    Here's a gain chart I made for preamp tubes:

    100 Mu .12AX7 | ECC803 | E83CC | 7025 | 6681
    85 Mu . .CV4004
    70 Mu . .5751
    60 Mu . .12AT7 | 6679 | 6201
    45 Mu . .12AY7 | 6072
    41 Mu . .12AV7 | 5965

    NOS 5751 tubes like RCA and GE are a good value right now, $30~$50.
    Take a look at http://www.audiotubes.com/ Brent Jesse is very helpful, and offers a generous guarantee.

    NOS Mullard or Brimar CV4004 (which is a Mil Spec 12AX7) are really pricey. Recording studio guys love 'em though.

    I didn't bother to post the 12AU7 as it's only 19Mu
     
    Last edited: Jan 29, 2015
  10. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    For my money, it's by far the best sounding tube of that bunch though. Not necessarily as a sub though, more for designs that are optimized for it.


    Brent is cool, and his guarantee is great -- don't like how it looks, return it, no problem. I'm still only at about a 50% hit rate for keepers even with him though.
     
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  11. BurningSkies

    BurningSkies CRAZY BALDHEAD

    Feb 20, 2005
    Syracuse NY
    Endorsing artist: Dingwall Guitars
    Depends on your definition of 'good value'. A dude named Stevie Vaughan came along and told the world to charge more for 5751 tubes a couple decades ago. So a decent RCA blackplate will now run you 90ish bucks. Or if you want to cork sniff your way into some of the original european brands, you can expect to pay 150+.
     
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  12. Coolhandjjl

    Coolhandjjl Supporting Member

    Oct 13, 2010
    Appleton
    No Amperex Bugle Boys for this dude. I have a family to support.

    There are lots of good ideas out there. I posted on Demeter's Facebook page about tube rolling their VTBPM800D, and they suggested Tung Sol 12AX7, but only as NOS. There are simply too many solid recommendations for anyone to realistically try out.

    Or as I once said about something else: the permutations are unfathomable. :cigar:
     
  13. BurningSkies

    BurningSkies CRAZY BALDHEAD

    Feb 20, 2005
    Syracuse NY
    Endorsing artist: Dingwall Guitars
    The cool things about the 12AU7's is that they're plentiful and cheap. Don't let their 'gain factor' scare you away from tasting a few, given that you can buy singles for really little cash. I needed one for my Kern's output and DI stage and ended up buying a FEW DOZEN to try out. You know, the classic brands...Mullard, TeleFunken, Amperex, GE, Philips, KenRad, Tung Sol, RCA, Sylvania, Raytheon, etc. I tested them for tone in my lil' blackface Fender champ and found that they were totally useable with low gain and in some ways made the little guy sound closer to the 'big brother' higher wattage classic Fender amps.
     
  14. B-string

    B-string Supporting Member

    12AU7 are lower gain, but they are higher current capable. Gain is only one factor of many. To make all your decisions on only one parameter is to say the least, short sided.
     
  15. waltdogg

    waltdogg

    May 24, 2014
    Exactly. Typically the lower gain the tube, the high the current it passes through working later stages of the circuit harder. That's why people swap their 12AX7 phase inverter with a 12AT7 or something with even lower gain for more current to push the power tubes into distortion before the phase inverter distorts.
     
  16. ThisBass

    ThisBass

    Aug 29, 2012
    Germany
    Power tube distortion is mainly drawn by the number of VA of the line transformer, and yes also the OT must be capable to trnsform sufficiant power from power tubes to the load.

    Whenever a phase inverter distorts long before the line transformer reaches its rated VA I'd guess a very badly fault in schematic design! In conclusion it would mean lots of none useable output power in backround.

    By the other hand sometimes some folks believe they may tweak output power by rolling different power tubes and/or preamp and/or inverter/driver tubes .......
     
    Last edited: Jan 29, 2015
  17. B-string

    B-string Supporting Member

    It can also be a voicing choice. The only position/circuit I have liked a 12AT7 in was in reverb recovery. Other positions they generally sound course and brittle.
     
  18. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    Jun 21, 2021

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