Peavey Triumph Signal Loss Or Gain?

[plexi50]

This is a 3 channel tube amp and i have been fiddiling with it for about 6 months now off and on. An experimental adventure. I have made many changes to the EQ-PI-Crunch & Ultra channel values. I think i have close perfection now in the Crunch & Ultra channels. The 50K Ultra Pre pot has been changed to a 1Meg to match the Crunch Pre 1Meg making both channels ramp up evenly

I have discovered some other changes that needed to be made to the EQ. The EQ Mid & Bass pots were interacting together rather than being completley independant of one another in their functions. Mid & Bass pots now function as a normal amp would and sounds 100% improved in Scooped & High mids along with a fuller Bass and pot sensitivity

The 3 channel mod has been done that links all 3 channels to the EQ / This was a weird tonestack and the Crunch & Ultra Mid & Bass pots did not function in these channels

The last think that is really bugging me is a 1Meg resistor just before the effects loop and to the PI Phase Inverter

I have forgotten something. Is the 1Meg damping my signal to the PI or increasing the gain to it?

The reverb is connected at this point on opposite sides of this 1Meg resistor

I wish they had connected the reverb back at the voltage dividers or had come up with a better place on the board for it

As i see it i will not be getting a clean and pure signal to my PI. If the 1Meg resistor is further increasing gain to the PI or damping i will  



  

[woolly]

the 1M and the 33k  form a voltage divider, lowering the 33k will send more signal to ground.

 increasing the 33k will incrase gain.

[plexi50]

Ok so increasing the 33K will increase the gain. But does not the 1Meg in place increase the gain as well or set the gain ratio?
  

I may be thinking to much about this but this amp has come a long way from a bee's nest to a very smooth and toneful machine. I dont like a circuit that had all this crap in it that this amp had. The amp sounds utterly fantastic compared to what it used to. The last step for me is to either disconnect the reverb and run my signal straight into the PI or come up with another idea

[sluckey]

The 1M knocks the crap out of your dry signal. In fact, you can get max dry signal by shorting out the 1M. BUT... doing so will kill the reverb. Or, you could increase the dry signal by decreasing the 1M, but the reverb level will appear to decrease since you now have a larger dry signal mixing with the wet signal.

If you have plenty of reverb to spare and you want more gain, just decrease the 1M. That 1M serves the same purpose as the 3.3M in a typical Fender reverb circuit. Why muck with it though since it sounds utterly fantastic?

[plexi50]

If i short out the 1Meg can i get rid of the 33K ground reference as well? It will no longer be serving as a voltage divider and the 33K would be sucking some signal to ground. Correct?

Ok that 3.3M in the Fender is what i thought the 1Meg resistor was there, for the reverb. Sounds fantastic but the point of this amps Crunch & Ultra channels was to clean them up and smooth them out as i could in a point to point build

The reverb is overwhelming and way to much even on 3 on the dial so lowering the 1Meg is the only tuning point i have left

If i could put reverb only on the Clean channel that would be great. Dont need it on the dirty channels

I will try both shorting and lowering the 1Meg / If you could hear this amp compared to what it sounded like before you would  

The clean channel has always been killer nice but the other two channels sucked and i was determined to get them sounding good / I cant count the number of times over 6 months that this chassis has been in and out of it's cab

UPDATE:
I removed the 1Meg resistor and put a 220K in it's place / Dropped the feedback resistor down from 68K to 1K

Reverb is present at full CW and just enough to spice it / Not too much not too little

Amp is much louder and full but wont rattle the windows until tommorrow. Wait it is tommorrow already!

Will have to wait for the rooster to give me the OK

 



  

[Dave]

If you reduce that 1 meg resistor you may find that it leads to some oscillation problems. It kills me because I really want to get rid of it too. I think it is single handedly responsible for the tone issues I have with those amps.

The best solution that I have been able to come up with is to bypass it with a small cap like Fender did with the 3.3 meg.

The problem with that resistor is that it squeezes off some of the signal, which is usually necessary to one degree or another, but it doesn't do it evenly. The high frequency content is the first to get squeezed. The bypass cap helps with that issue.

Dave

[plexi50]

Dave i put 1.5k grid resistors on the power tube board last month. The Triumph 60 didnt have them. This cured the osscillations at higher volume levels. The Triumph 120 shows 47K grids but i have never seen a 120 so im not sure it it follows the schematic or not

It takes some trace cutting and thinking to put the 1.5K grids on the board but it is well worth it

The 220K replacing the 1Meg has made this thing want to jump off the bench and it sounds like a Marshall on the dirty channels now with depth and crunch. No more buzz or grainy tone

A 470K may have been a little better for the reverb action but it's a 220K for now

As well at higher volume levels the clean channel breaks up nicely which is some thing i didnt expect and sounds great using varying pickup selection

The reverb is weaker now but is enough to be heard. Just a spot of reverb is good enough for this amp anyway.

Here is a board pic of what i did to the EQ: http://www.triodeamplification.com/Triumph60.html

I changed the 220K to 470K / Reverb is better and amp sounds great. I AM DONE!

[alerich]

Dave i put 1.5k grid resistors on the power tube board last month. The Triumph 60 didnt have them. This cured the osscillations at higher volume levels. The Triumph 120 shows 47K grids but i have never seen a 120 so im not sure it it follows the schematic or not

It takes some trace cutting and thinking to put the 1.5K grids on the board but it is well worth it

The 220K replacing the 1Meg has made this thing want to jump off the bench and it sounds like a Marshall on the dirty channels now with depth and crunch. No more buzz or grainy tone

A 470K may have been a little better for the reverb action but it's a 220K for now

As well at higher volume levels the clean channel breaks up nicely which is some thing i didnt expect and sounds great using varying pickup selection

The reverb is weaker now but is enough to be heard. Just a spot of reverb is good enough for this amp anyway.

Here is a board pic of what i did to the EQ: http://www.triodeamplification.com/Triumph60.html

I changed the 220K to 470K / Reverb is better and amp sounds great. I AM DONE!

I know this is a year old thread but my post is relevant to this thread so I opted not to start a new one.

--- Okay, scratch the part about the plate resistor. I was operating on too little coffee when I made this post. ---

Kudos to you for the 1M to 470K resistor change. I have been reading all sorts of threads on different forums about mods to this circuit to improve the gain side and that one little component change is the secret. I subbed in a 470K resistor with a 10pf cap across it and man, what a difference. Thank you for that. I have been scratching my head for days wondering why this circuit that looks like it ought to sound pretty good sounds like mud. That did it.