Gold Lion 12at7 vs JJ 12ay7 ?

Discussion in 'Amp Central Station' started by Fullmoon07, Oct 9, 2018.

  1. Fullmoon07

    Fullmoon07 Tele-Meister

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    I want a lot more detailed clean, less gain, in my monoprice Champ one. Currently it has a Chinese 12ax7. I have already decided on a Genalex Gold Lion 6V6 and a Weber alnico 8S speaker upgrade. Now, I am trying to decide between the preamp Gold Lion 12AT7 or simply save a few bucks and use a JJ 12ay7. Advice would be appreciated.


    Gain Factors
    12AX7=100
    12AY7=70
    12AT7=60
     
    Last edited: Oct 9, 2018
  2. derekirving

    derekirving TDPRI Member

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    I don't know, I'd actually stick with what the circuit calls for which I believe is a 12AX7. Not sure you're going to get a ton of clean headroom anyway. You can try a diff more efficient speaker to get more clean headroom otherwise I'd try a high-quality new 12AX7 or good nos 12AX7. Trying a 12AT7 or 12AY7 may change the character of the amp. You "could" try a 5751 to see if that helps a bit but you're not going to get "a lot more clean headroom" out of the champ. Are you looking to gig with the amp or ?
     
  3. Nickfl

    Nickfl Tele-Afflicted

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    I assume you are talking about a new Gold Lion, which BTW are made in China just like what you have in there now. As for clean headroom, there is a lot more than gain factoring into that. If you want more volume without breakup, you are better off switching out speakers rather than tubes. If you just want a different sound without much volume change, go ahead and change out the preamp tube... I've never tried a 12AT7 in a champ, but I would expect it to sound crappy, in my experience 12AT7 sound dull and sterile in the first stage of any amp. A 12AY7 might sound good, but it won't make your amp louder while staying clean, though it will be cleaner further up the volume control, which some people mistake for more headroom, but not actually louder...
     
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  4. JD0x0

    JD0x0 Poster Extraordinaire

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    Common misconception here. Reducing gain on the input tube doesn't increase headroom, it decreases gain. This gives the perception of more 'clean headroom' because the player can, or has to, turn up the preamp volume more to compensate for the gain loss. In reality, in most cases, if you just haphazardly swap from a 12AX7 to another tube type, you're changing the load line, where the tube was biased... If the tube was originally bias for the center of the load line (max headroom) moving it off center in either direction is going to REDUCE headroom, as the tube will either be biased closer to saturation, or cutoff, depending on which direction it moved on the load line.. But again, because of the gain reduction, it may not be very noticeable, as the reduced signal will compensate somewhat, you still technically are reducing headroom, and could've just run the volume control lower for the same effect as the gain reduction of the tube.

    Preamp tubes are cheap though, so experimenting isn't a bad thing, you wont hurt anything by trying them, and sometimes a bit more asymmetrical load line, while having less headroom, may sound better to certain ears.. When the stage does clip, since it's more asymmetrical, you get more even order harmonic dominance compared to a center biased (max headroom) stage, which will clip later, and when it does clip, there will mainly be odd order harmonic dominance..

    If you want to increase clean headroom on a champ, I'd suggest replacing the tube rectifier with a solid state one, to increase the B+ voltage for more headroom. (note this will increase bias, since plate and screen voltage will be higher) I'd also reduce some dropping resistors for the same effect, and I'd increase the filtering in the power amp. If the amp doesn't have NFB, add it, or you can increase the NFB to suppress (more) distortion. You could also add LNFB on the first triode. Larger output transformer can help increase headroom, and while you're at it, you could get one spec'd with the primary so you could run 5881/6L6 at max efficiency, assuming your power transformer is up to the task. I've got a soup'd up champ like this, and I can basically turn the dial to the max and the amp will still stay fairly clean, unless I really dig into the strings. It's running 12X7 in the preamp slot.

    FWIW, the higher B+ voltage and NFB on stages seemed to help the clean headroom most. The OT swap almost seemed to act as turning a compressor limiter down, in that the louder peaks didn't sound quite as limited and compressed, and the amp on a whole seemed to stand out a bit more and seem less 'squashed' when playing loud.
     
    Last edited: Oct 9, 2018
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  5. Nickfl

    Nickfl Tele-Afflicted

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    All of which translates to "if you want clean headroom, you got the wrong amp"! :lol:
     
  6. VintageSG

    VintageSG Friend of Leo's Ad Free Member

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    The JJ 12AY7 was a disappointment in every amp I tried it in. The Electro-Harmonix has some life to it. The JJ?, a veil over the sound. Their 5751 seems quite good though.
    The 12AT7 sounds crappy, as does the 12AU7. They're not really for that application. JJ 12AX7 are dull in my Champ. A modern Tung-Sol, not bad, but the EH 12AY7 wins out.

    Run it through an efficient speaker, then the volume control is lower for a given volume. The joy of a Champ is its, well, Champ-ness. I've built a couple of them and they are a treat to the ear. Loud little spuds. Not much headroom, but who cares?

    As for output valves, I don't know about the Gold Lion. I do know that the 6p6s sounds superb in mine, as do 1940's NOS 6V6. The JJ is quite good, but the 6p6s is worth a try.
     
  7. Fullmoon07

    Fullmoon07 Tele-Meister

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    Fender Guru . com writes
    "12AY7 or 12AT7 as preamp tubes – Less preamp gain.

    "If you want cleaner and spankier preamp distortion charcteristics, you may replace the V1 or V2 12AX7 preamp tube with 12AT7 and 12AY7. These tubes have different frequency responses than 12AX7, particurlarly when distorting. People describe these tubes to have less harsh and buzzy distortion. This mod does not alter the tone significantly when amp is played clean or when only the power amp section distorts. You’ll have to increase the volume setting to achieve a similar volume as before. The reason is that 12AX7 tube has a voltage gain factor = 100, while 12AT7 = 60 and 12AY7 = 45."


    http://fenderguru.com/amps/bandmaster/
     
  8. Fullmoon07

    Fullmoon07 Tele-Meister

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    They claim they are made in Russia, not China...the Gold Lion audio tests I have just listened to surpassed all other current brands under $60.

    Please explain why you think a Genalex Gold Lion 12AYT sounds crappy but a Genalex Gold Lion 12AY7 sounds good. Are you sure?
     
  9. Fullmoon07

    Fullmoon07 Tele-Meister

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    George Benson Hot Rod Deluxe
    "Has one 12aT7 preamp tube for cleaner headroom, lush smooth sound at med to high volumes."

    Hve you all really done the side by test to really know the 12at7 is so horrible? Especially the Lion one from Genalex? $44
     
  10. Andy B

    Andy B Friend of Leo's Gold Supporter

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    Try a Tung Sol RI 12AX7. Everyone whos amps I've installed them in loves the sound.
     
  11. E5RSY

    E5RSY Poster Extraordinaire

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    The 12AT7 is the last tube I'd put in V1, and I have actually tried it in a Pro Junior. A quote from Aspen Pittman's book: "The 12AT7 is rarely used in a tone-generating stage, but rather in function stages..."

    For tone-generation stages I wouldn't use a 12AU7, either. Stick with a 12AX7 or, if you want less buzz saw, a 12AY7.

    The Champ is an old tweed circuit. I know it had a 12AX7, but most of the Fender tweeds had a 12AY7 in V1. Fender only went to 12AX7s in the mid '60s when 12AY7s became difficult to source.
     
  12. Jonnyb73

    Jonnyb73 TDPRI Member

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    This
     
  13. Dacious

    Dacious Poster Extraordinaire

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    The HRDx/Dv is an interesting amp. It's an early Fender preamp circuit, which originally used 12AY7s as the first preamp, with reverb to a generic 40/60 watt poweramp. Many people note, the stock amp can be harsh and unruly with early breakup and compression, signs of highish gain.

    We swapped firstt position tubes in my bandmates and it became much nicer, reverb, clean, dirty. But, amps ain't amps, and tubes ain't tubes. So you can't just say it worked here, it will have the same impact elsewhere.

    As JD0x0 said, changing preamp tubes is easy and swapping 12A*7 family tubes will do no physical harm. AT7 and AU7 tubes are usually used for driver stages, they're tough but sometimes a bit nonmusical.

    Most people stick with AX7, 5751, AY7 for that reason. A 12AU7 in the reverb/gain channel driver stage of my 80s Superchamp sounds much better than the AT7 that came stock. That is a circuit shared between the reverb drive on clean and Lead/gain channel for drive.

    If the amp is optimised around a 12AX7 in the first slot, the main thing you will notice swapping to lower gain is lower volume, and generally milder tone. Sometimes, if the amp breaks up early that can result in a little more clean volume. But changing amp/guitar settings can too.

    If there's early breakup, it can be caused by preamp gain, power amp sag due to rectifer or 'starved' power tube, an output transformer not quite able to translate the tube's transfer of power into articulate output or a speaker breaking up. Or, some combination.

    Champs and knockoffs are a great little device because they often have elements of all the above.

    If you're a dimed-volumeknob guy, learning to ride the volume on your guitar yields surprising headroom results, without volume loss.
     
  14. Fullmoon07

    Fullmoon07 Tele-Meister

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    From JJ WEbsite:

    " 12AT7
    R.F. DOUBLE TRIODE
    ECC81 is 12AT7 medium gain pre-amplifying double triode. Can be also used as replacement for 12AX7 in many applications. Very smooth and warm sound. Very low microphonic. Good for phase inverters or reverb drivers."
     
  15. Nickfl

    Nickfl Tele-Afflicted

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    You're right, looks like the gold lion 12ax7 is made in China but the 12at7 is from Russia... strange

    Just because it can be used as a substitute for a 12ax7 doesn't mean it should be... note that they say it is good for PI and reverb driver positions, but say nothing about preamp gain stages. Thats not to say it definitely won't sound good there, but you asked for opinions and the prevailing opinion is clearly not positive.

    Because one is the right kind of tube for the v1 position in that amp and one is not. The brand of tube makes a subtle difference, the tube type (AX vs AY vs AT) makes a much bigger difference. If you want lower gain a 12ay7 or 5751 is more likely to sound good than a 12at7. Neither will give you more headroom, just breakup at a different point on the volume knob, but at about the same actual volume.

    Also, IMO $45 is nuts for a current production 12AT7 (Russian, Chinese or Slovakian) when you can get NOS 12AT7 for $10-20, or less, all day long. Maybe try a cheaper 12AT7 first to see if it even does what you think it will? Then consider a more efficient speaker or a different amp if you actually want more headroom.

    And yes, I have put a 12AT7 in the first position of a couple of amps, with consistently bad results. Never tried it in a champ, but I would expect the same or worse there since that tube is the entirety of the preamp. Dull and anemic is how I would describe it (JJ calls it "warm" in the description you quoted). I once put one in V1 of a new amp build by accident and wondered why it sounded so crappy when I was testing it, when I looked at the tubes and realized I had a 12AT7 in v1 I immediately knew that was the problem.
     
    Last edited: Oct 10, 2018
  16. Fullmoon07

    Fullmoon07 Tele-Meister

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    Thanks everybody. I was able to cancell the 12AT7 order at tubedepot and instead I have ordered a Groove Tube 12AY7, a Tung Sol 5751, and a Russian made Genalex Gold Lion 12AX7 gold tip.

    I also ordered a a Russian made Genalex Gold Lion 6L6 gold tip.
    I should be all set now. Let the swapping begin.


    Thanks again!
     
  17. zombiwoof

    zombiwoof Tele-Afflicted

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    A 12AY7 has a gain of 40, or 45 (I've seen both on preamp tube gain charts). It definitely does not have a gain of 70, the 5751 does and is useful in gain positions. Don't use a 12AT7 in a gain position, as stated previously it is designed for driver positions.
    Al
     
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