Depth mod/purple wire mode, need info

[Emetal]

Hey people can anybody tell me step by step how to preform that mode on a VH100R, from the info I found on the net I understand that it is done on the JCM 800, but people have done it on the Laney too.. I would like to try it and hear how it sounds

[Reeltarded]

Does someone have the resonance graphic handy? Search "resonance". There are two simple graphics. Both work the same.

You need a pot and a .0047 cap.

[Colossal]

Does someone have the resonance graphic handy? Search "resonance". There are two simple graphics. Both work the same.

You need a pot and a .0047 cap.

Here you go Emetal. Great and useful mod. Enjoy!

[Emetal]

Thanks for the info, now I do have a stupid request since I am not that good with this stuff, I understand that the action is happening in the lower left corner of this scheme around Resonance switch and Presence pot, but I am not shore which of these resistors is Negative Feedback Resistor, could somebody please just mark with two dots or just tell me exactly where does the pot connects. Sorry

[Emetal]

Is this correct, is this basically replacing my resonance switch and those two 100k resistors? Should I disconnect them, take them out?

[Colossal]

Emetal,

The switch marked resonance is actually just changing the negative feedback. Notice that it is either 50k/4k7 or 100k/4k7, depending on the switch's position. This will change more of the character of the amp from aggressive in the 100k position (switch open) to slightly more refined in the 50k position (switched closed). If you want to retain the switch, insert the resonance circuit in between the switched portion and the 4k7. So in other words, move the right wire (as you have drawn it) to the left a little more. Leave the left wire where it is. You want the resonance circuit inside the feedback loop, so, 100k -> (1MA || 0.0047u) -> 4k7. Make sense?

[Emetal]

Well, why would I need that resonance switch when this pot will give me more options then just fixed 50K or 100K right? So I am thinking of removing that switch and in the same hole (on the face of the amp) maybe fitting the pot in its place. Then, just to make it clear:
1. IF I DO NOT want to keep the switch, my above drawing is correct?
2. IF I DO WANT to keep the switch the drawing would be like below?
Am I getting this right?

[Colossal]

Sorry man. I'm making it hard. See the enclosed drawing. You can keep the switch or remove it and just pick one value, depending on how useful the switch is to you. The switch SW1 is changing the negative feedback applied to the amp, not resonance. The pot/cap (VR1/C1) are changing the resonance.

[Emetal]

GREAT I understand now perfectly! Thank you so much for having patience with me, I am not a tech I'm just guitar player who knows basics of electronics Thanks again!

[Colossal]

GREAT I understand now perfectly! Thank you so much for having patience with me

Awesome, glad it helped. It's a very useful mod for high gain amps. Dial in your preamp then use the Presence to dial in your high end in the power amp, then bring in the Resonance to fatten up the cab and find the point where it starts to rumble but still stays tight. Sublime!

I am not a tech I'm just guitar player who knows basics of electronics Thanks again!

Stay safe and asking questions is good.

[Cameron]

Sorry man. I'm making it hard. See the enclosed drawing. You can keep the switch or remove it and just pick one value, depending on how useful the switch is to you. The switch SW1 is changing the negative feedback applied to the amp, not resonance. The pot/cap (VR1/C1) are changing the resonance.

This may sound weird.....It should not make much of a difference.....But to me it sounds better/different with it before the feedback resistor from the speaker taps. The amp seems .....to me..... to be more dynamic ...more bounce to it this way.

[Emetal]

Ok I have a problem when I try to do this in reality: R56, R57, R58 are all small miniature printed resistors on a PC board, and the connection between R56 - P48 - R58 is a printed line on the board.. I do not wanna just scrape printed lead line on the PC board and also I can't un-solder printed resistor on one end and take that part out of circuit? So how do I do this? Can I do it like this, after all of the printed stuff...

[Cameron]

Ok I have a problem when I try to do this in reality: R56, R57, R58 are all small miniature printed resistors on a PC board, and the connection between R56 - P48 - R58 is a printed line on the board.. I do not wanna just scrape printed lead line on the PC board and also I can't un-solder printed resistor on one end and take that part out of circuit? So how do I do this? Can I do it like this, after all of the printed stuff...

You need to take it to someone that can do this for you. Its very easy.....if you don't understand this or don't know what part is what...put down the soldering iron and take it to someone else...then go do some reading about what is what in amps

[Emetal]

Well Cameron you are right, I do need to learn a lot, and if you have any link or any reading on line please feel free to recommend, BUT right now since I have an open amp in front of me could you just tell me? The first part is easy I can just use the posts P47 and P48 to hook up the pot, what I can't figure out is how to eliminate the connection marked with red X below All the resistors and lines are printed on to PC board..

[Reeltarded]

You can just ignore the previous circuit and put the resonance control in series there. Bump and bump dump adump.