12YA7 vs 5751 in a Champ ?

[Fullmoon07]

I am an old school jazz player using P90s and an ES-330 clean tone. I’m curious how a EHX 12AY7 compared to a Tung-Sol 5751 tube would effect my guitar’s bass-mid response in my Monoprice 5 watt Champ clone. ( I gather they have gain factors of around 40 and 70%)
But which would sound fatter at equal dB levels ? I assume the lower gain 12AY7 would sound fatter. (I understand the 5751 is louder and the 12AX7 even louder).

I’ve already put Gold Lion Tubes in but the Gold Lion 12AX7 i installed has too much gain and overdrive paired with the Gold Lion 6V6 and the result is a harshness in the little Chinese Champ clone. I do like the Gold Lion 6V6. I also have a Weber S Alnico speaker installed.

 

[Wally]

Those two tubes will lower gain. The effect will be that the sweep on the volume pot in the amp will become more precise...and, yes, the amount of total gain with the amp maxed will decrease. I have never tried that or needed to, but why not give it a shot. 12AX7 has a gain factor of 100, 5751 is at 70, and the 12AY7 is at 40, iirc.

 

[SnidelyWhiplash]

It wouldn't hurt anything to try. Easy to change preamp tubes. You may be pleasantly surprised by the result.

Good luck.

 

[jimgchord]

I use 12ay7 in 5f2a builds to lower the gain and smooth things out. Its safe to substitute these two in most cases, wether it sounds good or not can vary, they are different tubes that have different operating points. A 5751 would bias closer to what an ax7 would and they almost always sound good. For 12ay7 tubes i like the ehx over the jj.

 

[cobaltu]

If you are looking for 'fatter' and 'rounder', I would go for the 12ay7. They typically sound a bit less 'raspy' or 'fizzy' than 12ax7s. To me, 12ay7s tend to sound sweeter and maybe a bit more hi-fi, but in a very good way. The lower gain of the 12ay7 would probably work a bit better for hotter Gibson guitar as well.

I don't know if you're any good with a soldering iron, but a smaller cathode resistor actually is technically 'better' for a 12ay7. Anything from 1.8K to 3K would work, with 2.7K being roughly center bias with a 100K plate resistor.

 

[jrblue]

As noted above, the gain factor is the one that counts. I use lower powered preamp tubes in several of my amps. You should try both and go with what your ears say, as it's hard to predict in advance. I usually end up using lower power than I would have thought. Many of the tubes out there, especially new production, are crappy (esp. noisy) so sometimes the tone you get is affected by the tube build. Monoprices are not Champ "clones," as they use cheaper parts. They are not identical to Fenders.

 

[telemnemonics]

I'm not sure what those brands of new production tubes will do to the eq, but for my dollar I find one brand and another brand or production era of 5751 changes the tone, vs a gain factor changing the tone.
I like a 5751 and almost never like a 12ay7 due to the extremely low gain.
But what I hear as muddy pickups into a muddy amp might benefit from the much reduced gain.

No judgement I just hear HBs and even most P-90s as more muddy and less clear than low wind SCs.
And for certain the Champ circuit is a muddy amp.
So boosting clarity might be more the goal than adding fatness to already fat toned guitars.

 

[Wally]

If you are looking for 'fatter' and 'rounder', I would go for the 12ay7. They typically sound a bit less 'raspy' or 'fizzy' than 12ax7s. To me, 12ay7s tend to sound sweeter and maybe a bit more hi-fi, but in a very good way. The lower gain of the 12ay7 would probably work a bit better for hotter Gibson guitar as well.

I don't know if you're any good with a soldering iron, but a smaller cathode resistor actually is technically 'better' for a 12ay7. Anything from 1.8K to 3K would work, with 2.7K being roughly center bias with a 100K plate resistor.

I am thinking that you are meaning to say one could use a larger resistor value there, correct? That is, a change from the 1.5k ohm value we usually find to a higher(larger number) resistance there. Fwiw, a Leo and Co. used that 1.5k effective value for the cathode resistor in the 5F6A, which used a 12AY7 in the input gain stage. The two channels’ cathodes are tied together with an 820 ohm resistor, which when shared that way yields about 1640 ohms on each cathode. Other tweed amps sow the same input gain structure with the 12AY7.

 

[ScottJPatrick]

5751 all the way for me, my favourite V1 position valve.

 

[schenkadere]

Just put a 5751 in the V1 of my 5w combo and it really did the trick.

 

[cobaltu]

I am thinking that you are meaning to say one could use a larger resistor value there, correct? That is, a change from the 1.5k ohm value we usually find to a higher(larger number) resistance there. Fwiw, a Leo and Co. used that 1.5k effective value for the cathode resistor in the 5F6A, which used a 12AY7 in the input gain stage. The two channels’ cathodes are tied together with an 820 ohm resistor, which when shared that way yields about 1640 ohms on each cathode. Other tweed amps sow the same input gain structure with the 12AY7.

Correct.

I always think about the effect (i.e. lower bias point) rather than the actual hardware value. That's the second time you caught that Wally.

With respect to the 12ay7 bias most Fender's used on their first gain stages: there is nothing really wrong with it. If it sounds good; and doesn't melt, that's all that really matters. But, the effective 1640 ohm bias is a bit hot for a 12ay7. Also, the bias on the first gain stage of an amp is not very important. That stage of any guitar amp is not likely to overdrive, even if very off-center bias. But a good center bias might be important the bear in mind for later gain stages. Seeing as how the second gain stage is the second triode in that same tube. this might be worth experimenting with.

 

[Fullmoon07]

Reporting back.
I found I like to run the 5 watt Monoprice Volume and Tone knobs at 10, and then dial up my guitar Volume and Tone from 0. It provides a very full and round tone. This is something I wish I had known about when I was younger. But I could not do it with the 12AX7 in the amp because it was frightfully noisy and broke up at 3-4. I heard B.B. King ran his amps at 10 and then simply dialed up his guitar from 0.

The 5751 was very close to the 12AX7. The Amp at idle was still very noisy at 10 and still started to break up quite early. In contrast, the 12AY7 was relatively quiet at idle at level 10. It also allowed me to dial my guitar much further up from zero before it began to overdrive. Thus I had far more control over gradual levels of overdrive. Excellent! The tone is also less harsh and fuller in my opinion. So am staying with the 12AY7. The 5751 was just too powerful for my application.

 

[Wally]

Full moon, the same thing would have happened if you had turned the volume down on the amp with those higher gain tubes. I take my set up cues from an old article in Guitar Player...an interview with B.B. King, iirc. Since the true nature of the pickup is to be found with volumes and tones on the guitar at max, that is how I set the amp up. Set the amp’s controls for the hottest sound that you find to your liking....then run things from the guitar.
If one sets the amp up really hot while the guitar controls are at less than max, then one cannot take advantage of maxing those guitar controls out without running the unavoidable situation of overdriving the amp past the point where one finds things useful. I like to be able t9 dual back from the maximum volume/overdrive but then to be able to go t9 that max point without going past it into mush land. OMMV......but why limit the output and therefore the true sound of the pickups by running the amp where it cannot handle what the max output of the guitar causes??

 

[jimgchord]

Thats interesting wally. I get the idea of running the pickups wide open, my strat set seems to sound best rolled off just a touch. Pretty easy to drive things a little too hard, a little too early on those amps, especially a 12ax7. Even with low output pickups. Tends toward unpleasant preamp distortion.

 

[Wally]

Thats interesting wally. I get the idea of running the pickups wide open, my strat set seems to sound best rolled off just a touch. Pretty easy to drive things a little too hard, a little too early on those amps, especially a 12ax7. Even with low output pickups. Tends toward unpleasant preamp distortion.

Setting the amp up with the guitar wide open prevents that “easy to drive things a little too hard” syndrome that leads to “unpleasant preamp distortion”. One has the full range of options for the guitar output.