Clear and Smooth tone V1 Tube

[Arya44]

Hi there,
I like to find out if you are using tube amp for a smooth and tame jazz tone and if you have changed your V1 tube (that makes the most dramatic impact in shaping the tone) what did you end up using instead of stock 12AX7? I’m thinking 5751 slightly less mu than 12AX7, 12AT7 or ECC81 (70% mu) or even 40% mu 12AY7 equivalent (6072A for musical applications).
Thanks.

[marcwhy]

[of course, many things "depend" on the amp, but ...] Yes, 5751 or 7025 could work. I like TAD or JnJ.

[vinnyv1k]

+1 TAD 5751 or 7025. NOS Jan 5751

[wzpgsr]

5751 is the ticket.

[Joeontheguitar]

Swapped my 12AX7 for a 12AY7 to get more clean headroom in a 5 watt Elfring Little Gem. Works perfectly: I do get more headroom and the tone is superb.

[Arya44]

Thanks a lot for the feedback.

[TedBPhx]

Put a 5751 in V1 of my Peavey Classic 30. That along with an Eminence Cannabis Rex speaker smoothed it out into a respectable jazz amp.

[jazzkritter]

5751 in my Princeton. Smooth as you could want. NOS JAN vintage.

[Arya44]

Put a 5751 in V1 of my Peavey Classic 30. That along with an Eminence Cannabis Rex speaker smoothed it out into a respectable jazz amp.

Thanks. I’m actually doing this change for Peavey Delta Blues 210 and since the circuitry is similar to Classic 30, hopefully it can do the trick to make it work better for jazz. Right now it is actually good for single string solo lines but for chords it has too much kick which I’m hoping it gets tamed with 5751.
I was tempted to make the amp a bit more bedroom friendly by changing the V1 to 12AY7 but if I can smooth things out with 5751 which power-wise is a little less than 12AX7 then why not!

[NEWCITY]

I switched out my 12AX7 to a 5751 in my preamp circuit. In my opinion the amp tone has less sharpness and is smoother. It depends on what you intend to play and of course your own personal taste as far as a "jazz sound".

[Arya44]

Thanks everyone for the feedback. I noticed I had bought a couple of NOS 5751 (Phillips Mullard) and I thought I try it out for V1. I’m thinking to also change V3 while I’m at it. I have 7025 and also a couple of 12AT7 options, one NOS and one recent production. What is your opinion for using 12AT7 for V3 (phase inverter)?

[marcwhy]

Thanks everyone for the feedback. I noticed I had bought a couple of NOS 5751 (Phillips Mullard) and I thought I try it out for V1. I’m thinking to also change V3 while I’m at it. I have 7025 and also a couple of 12AT7 options, one NOS and one recent production. What is your opinion for using 12AT7 for V3 (phase inverter)?

Uh-oh, now you're heading down the rabbit hole of tube swapping! Stop while you're ahead -- you've been warned!!

[ruger9]

5751 NOS is a fantastic tube. AY7 can also be good, less gain than 5751. However the AT7 isn't really a "tone" tube, it's more of a "function" tube- it's used alot for phase inverters and reverb pans. I have never had a 12AT7 (even NOS) sound good in V1 (or any position that "makes tone")- they are thin sounding.

If you decide to start tube swapping various positions, you really need to know what each half of each tube does in your amp: for example, sometimes 1/2 of a tube is used as a reverb send or return. You don't want to swap that tube out for a different gain value because you'll also be changing the reverb sound as well (could be too weak, or too strong/harsh).

Gain values of A_7 preamp tubes:

[jim777]

I use a 5751 in V1 in my '80 Acoustic G100T, which is a 100 watt / EVM 12, and it completely changed the amp. It's just a warm and beautiful 90 pounder now and I couldn't be happier.

[Arya44]

Uh-oh, now you're heading down the rabbit hole of tube swapping! Stop while you're ahead -- you've been warned!!

[vinnyv1k]

Remember for your V3 Phase Inverter the triodes MUST be certified balanced.

[Arya44]

5751 NOS is a fantastic tube. AY7 can also be good, less gain than 5751. However the AT7 isn't really a "tone" tube, it's more of a "function" tube- it's used alot for phase inverters and reverb pans. I have never had a 12AT7 (even NOS) sound good in V1 (or any position that "makes tone")- they are thin sounding.

If you decide to start tube swapping various positions, you really need to know what each half of each tube does in your amp: for example, sometimes 1/2 of a tube is used as a reverb send or return. You don't want to swap that tube out for a different gain value because you'll also be changing the reverb sound as well (could be too weak, or too strong/harsh).

Gain values of A_7 preamp tubes:

Thanks for the heads up. I'm attaching Delta Blues block schematic as well as detailed schematic here. Looks like the reverb is not related to the tubes. V1 is shared as input tube, V2 added for the drive mode, and V3 as phase inverter. I have 3 supposedly high quality Tube Store 7025 called Preferred which I think means they selected from a bunch to be their best ones for strength, clarity, etc. Detailed schematic shows 4 halves for the pre-amp on the top (V1 and V2) and two halves in the middle on the right side that feeds the power section (V3). Can you please look into the schematic and let me know what you think? Thanks a lot.

[wzpgsr]

I’d be wary of this tube rabbit hole if your intention is to make music. If you are swapping tubes just for geeky curiosity (guilty as charged here) have at it, but I think there are many other places in the signal chain I’d be looking to start with in order to change the sound: string choice, pick thickness, speaker all will likely have a much more profound effect on tone than the phase inverter tube. Also: just because something sounds different doesn’t make it sound better.

[ruger9]

Thanks for the heads up. I'm attaching Delta Blues block schematic as well as detailed schematic here. Looks like the reverb is not related to the tubes. V1 is shared as input tube, V2 added for the drive mode, and V3 as phase inverter. I have 3 supposedly high quality Tube Store 7025 called Preferred which I think means they selected from a bunch to be their best ones for strength, clarity, etc. Detailed schematic shows 4 halves for the pre-amp on the top (V1 and V2) and two halves in the middle on the right side that feeds the power section (V3). Can you please look into the schematic and let me know what you think? Thanks a lot.

I can't read schematics. I do discover, usually from techs in online forums, what the tube assignments are, for the amps that I own. What tube is tasked with doing what. So I can't help you there.

But in general, V1 is easiest way to tailor the tone and headroom of your amp, and it's completely safe to put any 12A_7 in there, including a 5751. I just know from years of various amps, the 12AT7 tubes do not sound good in positions where tone is being created... especially V1.

And as for the phase inverter, that tube does not have to be balanced. As a matter of fact, most people don't even consider such a thing when choosing a PI tube, and some people actually prefer an unbalanced tube there.... balanced or unbalanced, either works, you may not even be able to tell the difference. But you're not going to hurt anything either way.

[jazzkritter]

5751s (which I love) are a lower gain tube than any if the 12s. Hence more headroom and less harshness in the preamp. No reason in your schematic not to pull the pre amp tubes and replace with 5751s. But i would stop there, cause you will get nothing but more gain/sharpness in tone going up the 12 route. (7025s were an industrial version, much cheaper back then. Leo as usual was balancing cost/sound/profit)))
As to phase inverters the balance question can be debated and only settled on an INDIVIDUAL amp’s PI circuit with an oscilloscope. Its splitting the signal into two signals 180 degrees apart. If the two signals are not aligned perfectly well thats pretty normal. Its very hard using consumer grade parts to achieve 100% symmetry given value tolerance s. The entire PI circuit will effect the symmetry of the wave forms. If you want to truly balance a PI you need to take all components used on either phase side and replace with exact matches in value. Then you can worry about a balanced PI tube.
Is it worth it? IMHO no, as its the funky tube amp characteristic of everything not lined up gnats-rear end perfect that we all love. If you want signal line perfection its 100% solid state time. A whole ‘nuther argument.
Review: put the 5751s in, relax and go play and enjoy.
jk
(Hope this made sense)))

[citizenk74]

I switched out my 12AX7 to a 5751 in my preamp circuit. In my opinion the amp tone has less sharpness and is smoother. It depends on what you intend to play and of course your own personal taste as far as a "jazz sound".

[TedBPhx]

I’d be wary of this tube rabbit hole if your intention is to make music. If you are swapping tubes just for geeky curiosity (guilty as charged here) have at it, but I think there are many other places in the signal chain I’d be looking to start with in order to change the sound: string choice, pick thickness, speaker all will likely have a much more profound effect on tone than the phase inverter tube. Also: just because something sounds different doesn’t make it sound better.

Of the two changes I made to the PV C.30 swapping in the C.Rex speaker made a bigger impact. Effectively the 5751 moved the breakup point from 6 to 8 on the volume knob. Same db at breakup, to my ears, just a little more control range not more headroom.

[ruger9]

5751s (which I love) are a lower gain tube than any if the 12s. ))

This is incorrect- please see the chart above. 5751 is less gain than a 12AX7, but not all the 12's

[Arya44]

Thanks all of you for your input. As wzpgsr mentioned, I didn’t want to go to the headache of tube swapping and I noticed I need extra budget for changing Peavey Delta Blues speaker to make it sound more acoustic, etc and decided to sell the amp and stick to my Fender Bronco. On Rumble mode with zero bass, medium to low mid-range, and relatively high treble it gives a good tone for jazz. It’s a modeling amp so the speaker has a good range. I found it is much less headache to stick to solid state. I had those days of my life spending money and chasing tubes but not anymore. I’m too old for that.

[ruger9]

There's alot to be said for "dancing with the one who brung ya".... as long as your happy, that's ALL that matters!