Master molume and harsh disto.

[Colas LeGrippa]

Hi buddies !


I have troubles designing a preamp section (4 stages) that will have a pleasant smooth distortion. Everytime I add a MV the disto. is harsh. I 've tried and I've tried but it seems that a clean amp like mines don't like a MV. I tried to reduce the guitar signal with voltage dividers, replace the values of the grid leaks and grid stoppers, even to look at other amps schematics but I am only obtaining shitty tone.
My amps are nice sounding ones, stable, no parasitic oscillation. Seems that I was born to play clean in a country band. I was banned from rock n roll. 😭😭😭😭😭

[Papa Jim]

Any way to show your schematic or what amp and what master volume scheme you are using or else describe it as well as possible

[shooter]

so without the MV it's like this?

nice sounding ones,

[Papa Jim]

Hi buddies !


 but I am only obtaining shitty tone.

I probably will be no help because you describe most of my amps. Lol 

[Colas LeGrippa]

I could draw a schem but I don t have time  nor the software to do it. The specific amp I am working on is a PP cathode biased , 4 stages (2 x 12ax7) , last plate of the 4th half driving a 12AU7 long tail pair. If I send the signal coming out of the last 12ax7 plate to a 1MA pot b4 returning it to the PI , the distortion is horrible. The amp is very stable good voltages everywhere, good grounding and polished pot knobs as well....


Thanx

[Colas LeGrippa]

...Would it help to add a CF before the PI ?

[Colas LeGrippa]

The clean amp tone is excellent even wth 4 stages of gain. I should get some crunchy tone at higher volume that I didn t try, the baby of the girl next door ( could be my own child, I dont know. for now....)  was sleeping.


Could be the high voltages at the plates of the

12ax7 too high resulting in more headroom ?


Anyway I  always got distortion cascading amp heads or using a pedal


In this case, I need nice rock disto in one head.


Thanx again

[Colas LeGrippa]

Hello it is me again, the woodstock tribute guitarist from canada...


The power tubes (2x) are gold lions 6550 and biased just under the max watt diss. permitted.
( never fought the law, it would have won !!!!)

[Colas LeGrippa]

....and I know they don't break up as easily as 6CA7 but even though when I swap the tubes, I am getting the same harsh sounding disto.
(I think I could have had the time to draw rhe sches instead of writing all those posts😁).

[Papa Jim]

I could draw a schem but I don t have time  nor the software to do it. The specific amp I am working on is a PP cathode biased , 4 stages (2 x 12ax7) , last plate of the 4th half driving a 12AU7 long tail pair. If I send the signal coming out of the last 12ax7 plate to a 1MA pot b4 returning it to the PI , the distortion is horrible. The amp is very stable good voltages everywhere, good grounding and polished pot knobs as well....


Thanx

That is not how to do a master volume at all. I am messaging you a really good transparent way to do one.

[sluckey]

What's the matter Colas? Girlfriend on spring break? 

[Colas LeGrippa]

I think you know me by now Sluckey...

[Colas LeGrippa]

I should concentrate on amplifiers stuff if I wanna succeed!

[Colas LeGrippa]

Papa Jim, I am talking about a pre PI master volume

[PRR]

> I could draw a schem but I don t have....the software to do it.

Soft like crayons?

[Papa Jim]

Papa Jim, I am talking about a pre PI master volume

Yep. this one is pre pi built into the LTP

[Colas LeGrippa]

PRR ,  just love your post 

[Papa Jim]

Hears a nice way to do it   Whoops i attached it twice.

[Colas LeGrippa]

Interesting, papa Jim.  And this MV sounds better than the one I described, ?

[Papa Jim]

Interesting, papa Jim.  And this MV sounds better than the one I described, ?

[Papa Jim]

Interesting, papa Jim.  And this MV sounds better than the one I described, ?

Yes this one worked perfectly without producing shitty tone. 

[Colas LeGrippa]

You re laughing too much I 'm suspicious....

[Papa Jim]

Okay it will be cool. I will change that. 
Did you get my message I sent.

[Papa Jim]

No shit it works. 

[tubenit]

Colas,

Always good to see you on the forum!  My experience using four gain stages for overdrive (mostly Dumblish inspired stuff) is that there are numerous factors in getting a pleasant overdrive & distortion beyond just the master volume allowing the overdrive/distortion.

Looking at all the Dumble schematics,  some of the Mesa Boogie schematics, some of the Cornford schematics …..
there is something of a pattern that shows up.

-  smaller value coupling caps with 4 gain stages then 2 or 3 gain stages
-  smaller value cathode caps with more gain stages
-  smoothing caps

In addition in the D-inspired amps like the D'Mars,  Tweed Overdrive Special, Tweed BluezMeister and Carolina Overdrive Special,  things like  the type of caps used  (Orange Drop polyester) and plate resistors (such as Vishay-Dale RN65 or larger wattage metal film) and cap orientation all seem to play a factor in smoothness.

Other thoughts to allow overdrive and distortion are the different type of master volumes.   Pre-LTPI,  PPIMV,  the type shown by Papa Jim,  using a VVR with cathode biased amps (just on the power tubes and LTPI but not preamp tubes), and DaGeezer's great cathode-attenuation method are all considerations given the amp design and other factors. 

So, in my opinion,  I don't find the master volume to be the issue.  I find the right values and types of caps, types of resistors, cap orientation, plate voltages and other factors to be the context that the master volumes work well or poorly.

Just some thoughts to ponder. 

I've heard your guitar playing (including that incredible Johnny Winter cover you mailed me years ago & the Alvin Lee impersonation).   I wish I had 1/10 of your talent because IF I did then I'd be twice as good of a player as I currently am.  Needless to say, I am a big fan of your playing.

I'd love for you to have an amp that gives you the overdrive/distortion tone that is a good match for the phenomenal talent you have been given and honed. 

I think IF you don't factor in other variables and you are just wanting a master volume to dial in the tone you're looking for that you may be chasing your tail.  Again, just some thoughts to ponder.

With respect,  Jeff 

[tubenit]

Colas,

Without even a neatly pencil drawn schematic provided to us, we're somewhat in the dark in offering suggestions.

You may or may not like this overdrive/distortion, but here is an example of the Tweed Overdrive Special I had using a VVR on the phase invertor and power tubes. I don't remember whether I had 5881's or 6V6's in there?

https://www.soundclick.com/html5/v4/player.cfm?songID=9488477

NO pedals were used for the overdrive at all.  The live volume when I recorded it was almost at conversational levels where we could have conversed above the guitar playing. I added delay and some compression in the mixing of the recording but NO OD or distortion.

I don't know if you would consider the overdrive tone smooth or buzzy/shitty?  I think it sounds reasonably smooth.  And I like that tone.

I am wondering IF you used 5881's instead of the 6550's that you could get more overdrive at lower volumes?

With respect, Jeff

[Papa Jim]

I could draw a schem but I don t have time  nor the software to do it. The specific amp I am working on is a PP cathode biased , 4 stages (2 x 12ax7) , last plate of the 4th half driving a 12AU7 long tail pair. If I send the signal coming out of the last 12ax7 plate to a 1MA pot b4 returning it to the PI , the distortion is horrible. The amp is very stable good voltages everywhere, good grounding and polished pot knobs as well....


Thanx

That is not how to do a master volume at all. I am messaging you a really good transparent way to do one.

That is a really nice tone @tubenit. I think you are correct about the values and types of components for sure having an affect on it. What about the method Colas, used for his master volume described above. Could it of messed with the tone/distortion the way he tried to achieve it. I have not seen it tried like that.

[sluckey]

If I send the signal coming out of the last 12ax7 plate to a 1MA pot b4 returning it to the PI , the distortion is horrible.

You must have a cap between the pot wiper and the grid of the PI tube. Do you have such a cap?

[Colas LeGrippa]

Of course I put a cap b4 returning to the pi...there is like 100v at the pi grids to be tsaken care of !  It s the kind of error I could have committed when I first joined this forum and as a matter of fact I think I did it once


I read articles written by Rob Robinette last night until 2 o'clock, ignoring the calls of a female searcjing for her man. The lady wasn't happy when I woke up this morning you can imagine. But my guitar tone sometimes takes a really big importance, fellows, to prefer RobRob more than Rubrub. Sorry for my bad english but i am sure you know what I' m talking about.
Like Rick Derringrr said in a songg: the way she wiggles that thing really lnocks me out....

[Papa Jim]

Did you ever do any kind of MV yet?

[Colas LeGrippa]

No I didn't. The amp is sounding very good witjhout one. It takes my disto pedal ( hot cake) very well and is perfect to play in my small apt with a very nice crunchy tone!. In clubs at higher vol  yields a rich overdriven tone.


Colas