3 Channel Recto Presence Mod....

[2CDR]

bump,please?

 

[fluff191]

can this be done on the old 2 channel DR?
will it make much of a difference,or not really needed on the 2 channel?
i have a 25k and a 50k pot.

Sure you could do it. Not sure it is needed, although changing to a lower value would cut down on some of the presence (would wouldn't be such a bad thing).

 

[2CDR]

can this be done on the old 2 channel DR?
will it make much of a difference,or not really needed on the 2 channel?
i have a 25k and a 50k pot.

Sure you could do it. Not sure it is needed, although changing to a lower value would cut down on some of the presence (would wouldn't be such a bad thing).

Thanks Fluff,ill give it a go and see if how i like it.not like it cant be changed back.

 

[2CDR]

well,i went ahead and changed the pot on my revG and i gotta say,its a night and day difference.it appears (to me at least) to have made the red channel ,say bigger in tone and sound?the other guitarist in our band described it as WAY ANGRIER than it was :? .really,the orange channel now sounds dull compared to the red.

 

[fluff191]

Cool glad it worked out!

 

[JCDenton6]

well,i went ahead and changed the pot on my revG and i gotta say,its a night and day difference.it appears (to me at least) to have made the red channel ,say bigger in tone and sound?the other guitarist in our band described it as WAY ANGRIER than it was :? .really,the orange channel now sounds dull compared to the red.

Were you able to record before/after clips of it? Really interested in hearing the difference!

What size pot did you use? Sounds like I should try this out :mrgreen:

 

[2CDR]

well,i went ahead and changed the pot on my revG and i gotta say,its a night and day difference.it appears (to me at least) to have made the red channel ,say bigger in tone and sound?the other guitarist in our band described it as WAY ANGRIER than it was :? .really,the orange channel now sounds dull compared to the red.

Were you able to record before/after clips of it? Really interested in hearing the difference!

What size pot did you use? Sounds like I should try this out :mrgreen:

no,nothing before or after.wont be for some time as the amp has shat it self in a major way.
i used a 25K pot.tech assures me it was nothing i did that made it die.its had a few problems for awhile now.
new cap job,new socket job or two to come and a few other issues .not sure when ill get it back.

 

[JCDenton6]

I gotcha. My 2ch Triple is in the shop as well, should have it back in the coming week.

 

[Nitrobattery]

Left a few messages with Mesa/Boogie during the past week or so...have yet to hear anything back. Was going to give this a whirl in my Tremoverb. Anyone know where else I can get the pot they use? I'm guessing it's not a standard 25k pot?

 

[StaggerLee]

I was just in touch with Mesa Boogie about this presence mod.

They told me that I should also change bass pot to get closer to orange channel with my red.

part numbers they gave me:

presence control pot part # 593737
Bass pot part # 593739

I will order them and later tell you all how it sounds


edit. manual says they already have same bass pot.. weird.

edit2. It seems that new reborn have different bass pots in channel 2 and 3. and perhaps that's why he told me to change it too..

 

[Shemham]

I was just in touch with Mesa Boogie about this presence mod.

They told me that I should also change bass pot to get closer to orange channel with my red.

part numbers they gave me:

presence control pot part # 593737
Bass pot part # 593739

I will order them and later tell you all how it sounds


edit. manual says they already have same bass pot.. weird.

edit2. It seems that new reborn have different bass pots in channel 2 and 3. and perhaps that's why he told me to change it too..

I had to check the bass pot values from the Reborn recto. They both were 590739 and both their in circuit values were around 850kohm. It seems the bass pot value difference was strictly original 3-channel thing.

BTW, both presence pots were dual ganged 22k/100k pots.

 

[StaggerLee]

I was just in touch with Mesa Boogie about this presence mod.

They told me that I should also change bass pot to get closer to orange channel with my red.

part numbers they gave me:

presence control pot part # 593737
Bass pot part # 593739

I will order them and later tell you all how it sounds


edit. manual says they already have same bass pot.. weird.

edit2. It seems that new reborn have different bass pots in channel 2 and 3. and perhaps that's why he told me to change it too..

I had to check the bass pot values from the Reborn recto. They both were 590739 and both their in circuit values were around 850kohm. It seems the bass pot value difference was strictly original 3-channel thing.

BTW, both presence pots were dual ganged 22k/100k pots.

This is weird cause if you look from manual the difference in bass pot is in new reborn mode and old 3-channel had same ones.
No idea what is truth then But manual says that you should have different bass pot in orange channel..

Btw. I just got great deal and I traded my old 3chan recto to new reborn model.. I love it.

 

[Shemham]

I had to check the bass pot values from the Reborn recto. They both were 590739 and both their in circuit values were around 850kohm. It seems the bass pot value difference was strictly original 3-channel thing.

BTW, both presence pots were dual ganged 22k/100k pots.

This is weird cause if you look from manual the difference in bass pot is in new reborn mode and old 3-channel had same ones.
No idea what is truth then But manual says that you should have different bass pot in orange channel..

Btw. I just got great deal and I traded my old 3chan recto to new reborn model.. I love it.

I don't know what's the deal with the manual, but this is what I found inside the actual amp:

http://postimg.org/image/swdk1anb3/
http://postimg.org/image/inl2vgz9b/

The pots above the dual-ganged pots are the bass pots on 2nd and 3rd channels.

 

[afu]

https://warpedmusician.wordpress.com/2015/02/07/understanding-the-mesa-boogie-dual-rectifier-3-channel-amplifier-presence-and-voicing/

 

[3124+]

When comparing the presence pot values, are you guys using vintage mode, or modern?

 

[afu]

When comparing the presence pot values, are you guys using vintage mode, or modern?

The value is independent of the negative feedback (mode), because the pot is mechanical and will always give the same comparison. The only thing I hear different is the way CH2 opens up at the end of it's taper. Otherwise, the rule of thumb previously noted is a good comparison.

 

[3124+]

In CH3 Vintage, the 100K presence pot actually sounds warmer than the 25K. Increasing pot resistance blocks signal through the .1uf presence capacitor to ground. This means less high frequency attenuation in the negative feedback loop and therefore less high frequency boost in the power amp.

In CH3 Modern, the negative feedback loop is disabled and the presence control becomes a treble bleed off the tone stack. Increasing pot resistance blocks high frequency attenuation through the .003uf cap to ground.

 

[afu]

Comparing the tapers between differing values will never be dead-on-exact as the maximum resistance of the pot affects the sound on it's own. However, rule of thumb, the approximate sound as described in the manual is close. The only major difference in taper I hear on mine is when peaking the presence in Vintage mode. Modern doesn't emphasize the mids the same way Vintage does, because of the difference in operation you have stated.

Maybe I'm misunderstanding your question. If someone swaps presence pots out to make CH3 like CH2, the mode doesn't matter. They'll be really close to each other in any mode.

 

[3124+]

The mode matters because on vintage setting the presence circuit works in the traditional way, by attenuating treble frequencies in the negative feedback loop to consequently boost overall treble in the power amp. When switching to modern mode on ch 3, the negative feedback loop is disconnected and the presence pot moves to control the r/c filter on the treble pot wiper.

 

[afu]

I think I understand what you meant, now. I think they're comparing the same modes, not modern vs vintage. That's apples to oranges as you pointed out.