Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups

Your Tube Stash - was: any old AX7 will do?

Discussion in 'Glowing Bottle Tube Amp Forum' started by ndcaster, Aug 18, 2016.

  1. ndcaster

    ndcaster Poster Extraordinaire

    Nov 14, 2013
    I've got some gigs in the fall and want to have some extra tubes on hand in case my SFBMR goes down. Currently I've got a couple EHX AX7's for the preamp stages and Groove Tube 6L6GC's for the power.

    Fender's circuit specifies "7025" for the preamp stage. I've read that 7025 is just what Fender called the 12AX7 tubes it sold. Does that mean I could use an AX7 like this in its place?

    As for the 6L6GC power tubes, how much advantage is there in having RCA NOS's in there instead of the Groove Tubes I've had in there since the 80's?

  2. screamin eagle

    screamin eagle Friend of Leo's

    Oct 9, 2008
    S. CA
    Yes those 12AX7's will work. If you wanna spend the money on RCA's go for it, but you could buy a few sets of others and bet money ahead. I like the GE 6L6GC's and they're cheaper than the RCA's. Cheaper still are the 6l6wgb's. They don't quite dissipate 30 watts, but there are reports of folks using them in twins.

    This is a reputable source for NOS tubes: I can afford the RCA, but they're still too rich for me.

    I don't have a problem with current product Tung Sol 6l6GC's, or TAD's.
    ndcaster likes this.

  3. DaveKS

    DaveKS Friend of Leo's

    Oct 21, 2013
    Yep those 6L6wgb at KCA are a steal, slightly less wattage and they crunch up a bit earlier on vol knob, superb sounding, long lasting tubes.

    But most effect on your overall tone will be v1-2 input preamp tubes, spend your money there and get some TAD 6L6WGC fat bottles for power tubes. Most people I know don't even come close to pushing a BM into power tube od in reg use, thats where you really start to hear difference in power tube selection, when their pushed. But maybe in your usage you actually get to wind that amp up into power tube drive, only you can answer that question.

    I'd rather spend $$$ on a good old RCA 7025/12ax7a for v1-2, or even cheaper GE 12ax7 and a Mullard cv4024 for v3 reverb send cause overall that's where you'll get biggest improvement in your sound.
    Darkness and ndcaster like this.

  4. ndcaster

    ndcaster Poster Extraordinaire

    Nov 14, 2013
    Two posts send it out of the park. I love this place. Thanks gents.

    As long as I'm picking up tubes, I also wonder whether there are any for my circuit that would get me closer to an EH-150 type of sound. There's this comment over

    "The tone your chasing predates the "E" series amps (5e3 Deluxe , 5e5 Pro, 5e8 Twin etc.). Those had noval preamp tubes and cathodyne phase inverters and fixed biased power tubes (except for the Deluxe which had cathode biased power tubes). You want an octal front end and a paraphase phase inverter and cathode biased power tubes. Look at the 5b/c5 TV-front Pro."

    Er... hmm.

  5. dan40

    dan40 Tele-Holic

    Aug 19, 2015
    Richmond Va
    Octal preamp tubes do impart their own signature sound but your amp would require new sockets and rewiring to be able to use them. I have been itching to build one of those circuits myself sometime soon!

  6. telemnemonics

    telemnemonics Doctor of Teleocity

    Mar 2, 2010
    Wow, those new electro harmonix Russian made Gold Lions in the link are expensive! The name is the same but the tube is not.
    For that money you can get lots of better NOS tubes.

    I agree with suggestions that great 12ax7s will be more noticeable than great 6l6s, so using those "Gold Lion" EHX 12ax7s and NOS RCA power tubes is not the way I'd go.
    If you're wanting spare tubes on hand you can buy a quad of 6l6, or buy a new pair of the same number GT 6l6 as you have now and keep the old ones as spares that the amp is biased for.
    I like less expensive vintage tubes like Baldwin branded GE 6l6, or other great but not holy grail types. Sometimes you'll find three matched power tubes where the 4th in a quad failed, great for a pair and a spare.
    You can pay $400 for a matched pair of NOS RCA blackplates at tube depot, or $50 for a "tested matched" pair of great used '60s GE/ Sylvania/ Philips/ RCA gray plate etc 6l6 on ebay.

    The only current production tubes I use in my amps are driver tubes, for the rest the prices on NOS/ ANOS vintage tubes is just too low to even bother with new stuff. A bit of a risk but excellent 12ax7 types are under $25 all the time on ebay.
    I just bought a fairly hard to find CBS Hytron 12ax7 in good shape for $10 delivered. Never heard one but read they are very nice, so I added it to the stash.

  7. uriah1

    uriah1 Doctor of Teleocity Silver Supporter

    Feb 12, 2011
    Do not get 6l6gb. Lot lower transcon closer to a 5881.

  8. Ringo

    Ringo Poster Extraordinaire

    Mar 16, 2003
    Memphis TN
    What's wrong with some newer production 6L6s? Ruby, EH,TAD, Tungsol all get some good reviews and are much cheaper than finding some old probably NOT NOS 6l6s.
    It won't hurt to have some spare 12AX7s ( you could always use the one in the normal channel for the reverb channel in a pinch) but in my experience, preamp tubes rarely go bad, it's usually the power tubes that go out, doesn't hurt to have a spare rectifier tube too.
    ndcaster likes this.

  9. ndcaster

    ndcaster Poster Extraordinaire

    Nov 14, 2013
    What happens if I use a Mullard 12AU7 as preamp for channel 1?

    I normally don't use this channel, but will use it for amplifying an upright bass in September.

    Doing this would allow me to put a 12AU7 for reverb send (which I've read would give finer granular control of the reverb effect) and use the two tubes as a matched pair -- if the latter is even important in this situation.

    I don't know the demands of the circuit, so maybe this is a bad idea.

  10. Sea Devil

    Sea Devil Tele-Afflicted

    Sep 23, 2006
    Brooklyn, NY
    AU7's are very low gain. I wouldn't recommend it. You'll just turn the volume knob higher, and the power tubes will have to work harder to compensate. A 5751 is a good option for slightly more controllable volume.

    I don't recommend a lower-gain tube for the reverb send, either, as it it introduces the potential for more noise from the reverb uptake/mixer tube when the reverb is set at the same level. Just turn the reverb knob down, or once again try a 5751, which will have a slightly less abrasive high end.

    12AT7's are not a good sub for 12AX7s, btw, although I used them for years. The voltages are not them same and they should be avoided; AU7s and AY7s are OK, but in most cases will just change your settings and increase the possibility of unwanted noise as you make up the difference later in the signal chain, as noted above.

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