I swear i'm done with the tweaking....

[daz]

Kinda ! LOL! Really, i zipped it up and was just playing it and intended to leave it....BUT....along came another realization. I have the V2A grid as u can see at 220k but theres a switch on the back that i have hooked up to parallel a 100k with the 220 for about 70k total. Heres the thing...i use it in the 220k position and i like the amp but i found that if i use the 70k position and crank the gain knob up to where it has about the same gain as i use with the 220k load, the tone gets super harmonically rich especially when i boost the amp with a clan boost. It just kills. But i know 70k is a really major load there and typically not normal. Would you guys suggest i leave the 220k load and drop the gain elsewhere? Maybe a 4.7k in place of the V2A cathode or something else? Or do you think it's not just about the lower gain that makes it sound so rich but that it's the WAY it's accomplishing that low gain and another method likely would not work as well?

[eschertron]

Chart out the loadlines on V1B to see how THAT triode is affected by your switch (plate load). That's where the magic is happening.

[daz]

I'm no tech so i have no idea how to do that or the first thing about it. But i'm glad to know where to focus any changes.
Are you suggesting i lower the plate resistor?

[Russ]

The 220k attached to V2A grid is not a load resistor, it's a grid stopper. It act as a hi-cut filter. When you reduced it to 70k you just reduced the amount of hi-cut that the grid stopper caused. So you just made the amp brighter by reducing its value. Any value from upwards of 1M to no resistor at all can be used. The larger the resistor the more hi cut (less treble) you get.

[Chuck H]

As Russ said, the grid stop acts as a cut filter. The actual load you mention would be the load on the plate feeding that grid. And that is a significant consideration as well. I'm not going to go into all the ins and outs of what happens with a lowered plate load. But I will try to put your mind at ease about it since you mentioned it...

Just look at any black face Fender amp with reverb (many of them) and notice that due to the "vibrato" circuit there is a plate load for the mix circuit that feeds the PI of less than 50k!!! I don't see many people here or on other gear forums acknowledge this but it's worth noting that the "vibrato" channel (rather than the "normal" channel) is the preferred input for these amps. There is something to be said for the tone of guitar amps that put a significant load on at least one stage of the preamp arrangement. My own favorite design does it. As does the Suhr Badger and other Suhr circuits and the TrainWreck amps. Taxing preamp tubes with some current in operation is fine as long as it doesn't exceed safe operating parameters. You are well within safe with your design and you don't need to worry about it. Enjoy the tone you've achieved. There is no problem with what you are doing. In fact it demonstrates that you're able to hear a phenomenon that has been "exclusive" to some really respected designs. Roll with it

[daz]

The 220k attached to V2A grid is not a load resistor, it's a grid stopper. It act as a hi-cut filter. When you reduced it to 70k you just reduced the amount of hi-cut that the grid stopper caused. So you just made the amp brighter by reducing its value. Any value from upwards of 1M to no resistor at all can be used. The larger the resistor the more hi cut (less treble) you get.

No, i didn't touch that. I was talking about the other 220k thats coming from the coupling cap at the V1B plate to ground.

[daz]

As Russ said, the grid stop acts as a cut filter. The actual load you mention would be the load on the plate feeding that grid. And that is a significant consideration as well. I'm not going to go into all the ins and outs of what happens with a lowered plate load. But I will try to put your mind at ease about it since you mentioned it...

Just look at any black face Fender amp with reverb (many of them) and notice that due to the "vibrato" circuit there is a plate load for the mix circuit that feeds the PI of less than 50k!!! I don't see many people here or on other gear forums acknowledge this but it's worth noting that the "vibrato" channel (rather than the "normal" channel) is the preferred input for these amps. There is something to be said for the tone of guitar amps that put a significant load on at least one stage of the preamp arrangement. My own favorite design does it. As does the Suhr Badger and other Suhr circuits and the TrainWreck amps. Taxing preamp tubes with some current in operation is fine as long as it doesn't exceed safe operating parameters. You are well within safe with your design and you don't need to worry about it. Enjoy the tone you've achieved. There is no problem with what you are doing. In fact it demonstrates that you're able to hear a phenomenon that has been "exclusive" to some really respected designs. Roll with it

I will have to read this a few times but i always looked at that like a load on the next grid in addition to the other 2 resistors. I wouldn't have thought of it as a plate load from the previous stage because it;s after the coupler. But hey, i've said it many times, i know very little about exactly how amp circuits work.

[Chuck H]

I will have to read this a few times but i always looked at that like a load on the next grid in addition to the other 2 resistors. I wouldn't have thought of it as a plate load from the previous stage because it;s after the coupler. But hey, i've said it many times, i know very little about exactly how amp circuits work.

Well whatever passes through the coupling cap is being loaded by the following circuits. Since the plate current under conduction is predominantly swing voltage it qualifies as AC. Which the coupling cap passes. So it IS precisely the load following the coupling cap (parallel to the plate resistor) that qualifies the plate load for that previous stage. At least at such frequencies as the coupling cap passes. And, hopefully you already got this, a heavier than ideal plate load can result in a good tonal effect in many cases. And to reiterate, your amp does not appear to be over taxing any operating parameters. So if it sounds good it IS good. Its important to remember that guitar amps aren't "reference" amps. So whatever distortions are a byproduct of less than ideal (but still safe) operating conditions that sound good are entirely acceptable. Guitar amps are signal processors. Not audio reproduction tools.

[The Dude]

I had to "like" the first post purely for the irony of the thread title.

[daz]

Well whatever passes through the coupling cap is being loaded by the following circuits. Since the plate current under conduction is predominantly swing voltage it qualifies as AC. Which the coupling cap passes. So it IS precisely the load following the coupling cap (parallel to the plate resistor) that qualifies the plate load for that previous stage. At least at such frequencies as the coupling cap passes. And, hopefully you already got this, a heavier than ideal plate load can result in a good tonal effect in many cases. And to reiterate, your amp does not appear to be over taxing any operating parameters. So if it sounds good it IS good. Its important to remember that guitar amps aren't "reference" amps. So whatever distortions are a byproduct of less than ideal (but still safe) operating conditions that sound good are entirely acceptable. Guitar amps are signal processors. Not audio reproduction tools.

Ok, i get that. What i am wondering now is that since it's NOT lower gain that got me that harmonic complexity i'm hearing, then i should be able to bring the amount of gain it's capable of back to where it was somewhere else in the circuit. Think so? Because they way it is now the gain is all the way up for my vintage output teles and i like to have a range there where i can go both lower AND higher. Before i ran the gain about 1 to 3 o'clock and now it's on 10 all the time. So where would you raise the gain? Remove the 220k grid resistor at V2A? I don't know theres any other way that wouldn't change the voicing

[The Dude]

I might try a larger coupling cap off the V1A plate if you're after a more centered gain pot.

[daz]

I might try a larger coupling cap off the V1A plate if you're after a more centered gain pot.

i had a .022uf there but the lows were kinda woofy and the .0047uf just barely got it to where it didn't bother me much anymore. But still not perfect. Maybe with the change it will now be ok, who knows. I don't think that will up the gain much tho because i didn't notice any less when i went to the .0047uf.

[Chuck H]

I don't see any good way to raise the gain and still keep the 'through circuit' EQ profile AND keep the 70k load on v1b plate. One thing I try to do with amps on the bench is to simply maximize them for what they can do and then let it go. This, as you know, is harder to do when you own the amp and have it available all the time. But if I were you I would just concede to having to switch out the 100k (so you're on the 220k load) whenever you want more gain and accept that this is the tone when more gain is desired. And use the 100k switched in (70k load) at the expense of some gain when that tone is desired. In other words, the amp has now been idealized as much as possible for for you within the design, circuits and components available. Button it up and try to enjoy it that way.

And, FWIW, I often play my own favorite amp on ten. It irks me a tad that I don't have more gain than I need because I too like to have more than I need on the off chance that I may want it some time. But whenever I'm playing that doesn't actually happen. I just play and the tone is right enough that I don't think about the amp, but just playing. And that is the goal of getting an amp tweaked in for a player. Get it to where they think about playing instead of their amp or their tone.

JM2C

[daz]

I don't see any good way to raise the gain and still keep the 'through circuit' EQ profile AND keep the 70k load on v1b plate. One thing I try to do with amps on the bench is to simply maximize them for what they can do and then let it go. This, as you know, is harder to do when you own the amp and have it available all the time. But if I were you I would just concede to having to switch out the 100k (so you're on the 220k load) whenever you want more gain and accept that this is the tone when more gain is desired. And use the 100k switched in (70k load) at the expense of some gain when that tone is desired. In other words, the amp has now been idealized as much as possible for for you within the design, circuits and components available. Button it up and try to enjoy it that way.

And, FWIW, I often play my own favorite amp on ten. It irks me a tad that I don't have more gain than I need because I too like to have more than I need on the off chance that I may want it some time. But whenever I'm playing that doesn't actually happen. I just play and the tone is right enough that I don't think about the amp, but just playing. And that is the goal of getting an amp tweaked in for a player. Get it to where they think about playing instead of their amp or their tone.

JM2C

I think you're right. I'll just leave it. Or i might even try a different combination of resistors to get 70K then more resistance but not all the way to 220k. Maybe a couple 68k's in series and see if switching to 136k adds enough gain w/o compromising the tone as much as the 330k does. But like you i think i'll find myself never needing more aide from fluid hot solos which i get with a pedal anyways. And wow, i can't believe the tone i get now when i do that ! It gets overtones i have never had before with any amp and have sought forever. Come to think of it, i have a clean boost pedal that i never use that has bass treble gain and level with a mid boost/fat boost switch. And with the way the amp sounds now with a front end boost i bet it will kill with the gain lowered and the boost as an always on pedal hitting V1 enough to get whatever gain i need. Gonna try that today. I'm pretty excited because i may be onto the best tone i've ever had as far as my own personal taste at least.

[Chuck H]

I'm pretty excited because i may be onto the best tone i've ever had as far as my own personal taste at least.

That was a great day for me too. And...

I'm still tweaking that design Though I'm very careful about it so I can always put it back just exactly as it was.

I think experimenting with various loads following the .0047 cap is a good idea. Suppose you find that a 136k (or 150k or 120k, etc.) allow you to keep the harmonic balance you like and still give enough more gain. MMmmmm cake (have it and eat it too).