Installing a "Resonance" control in my Bugera 333xl. Assistance please?

[Jack Tone]

Hi,

This sounded like a simple mod, so I ordered a 1 meg pot, took the chassis out of my Bugera 6262, and found that the R42 resistor seems to be connected to the crunch switch on the clean channel. After re-reading the page, I realized you were referring to the 333XL. Does anyone have any idea where this mod would go in the 6262? Thanks.

[Jazz P Bass]

I don't see it as simple.
Doable, maybe.
It appears the idea is to copy the Peavey circuit.
A schematic would be helpful, although I do not have access to one.
This is the only link that I could find.
Link: http://music-electronics-forum.com/t14088/
Unfortunately,it does not come to conclusion.

[tedmich]

other worthwhile things to try on a JSX (or "JSX inspired" design!) include:
1 larger values for the 56k R6 after the 2nd gain stage (Ultra has 220k)
2 increasing C3 (1nF) to 1.5-2.2nF
3 upping C2 (470pF) to 1.5-2.2nF
4 upping C31 (0.47uF) to 1uF
5 removing (or increasing) the shrill C35/10nF cathode bypass cap before the master volume

Mod (1) decreases the amount of signal going to ground and can GREATLY increase gain! (you have been warned!
The 2-5 mods tend to darken the amp and emphasise more bass; try one at a time!

[ejc6stringer]

I don't see it as simple.
Doable, maybe.
It appears the idea is to copy the Peavey circuit.
A schematic would be helpful, although I do not have access to one.
This is the only link that I could find.
Link: http://music-electronics-forum.com/t14088/
Unfortunately,it does not come to conclusion.

It's actually quite simple, remove the resistor located at R42 and solder one wire from one of the remaining holes (left by the now absent resistor) to terminal 1 of a 1 meg pot, then solder another wire from the other remaining hole to pot terminal 3. If I remember right, you also solder terminal 2 of the pot to either terminal 1 or 3, whichever one you like.

[ejc6stringer]

Tedmich,

Would it be worthwhile to replace these resistors with pots or switches? It would be nice to switch between stock and modded or blend between values.

[tedmich]

Tedmich,

Would it be worthwhile to replace these resistors with pots or switches? It would be nice to switch between stock and modded or blend between values.

4/5 mods I've mentioned are cap changes, and switched coupling caps are to be avoided usually, or you might be able to do something with optoisolators.
Switched cathode bypass caps can work but can be noisy. I did put a switched 76k resistor over my Ultra's 220k (56k R6 on JSX) to give the JSX value but I never used it as the 56k value had no balls. IME blending is difficult to implement and of little value, I change things and if I don't like them I change them back. I bag the old parts and tape them internally with a note so it can always be "restocked" by me or the next owner.

As long as you're careful (and don't peel up a PCB trace!) PVs mod nicely,

[ejc6stringer]

4/5 mods I've mentioned are cap changes, and switched coupling caps are to be avoided usually, or you might be able to do something with optoisolators.
Switched cathode bypass caps can work but can be noisy. I did put a switched 76k resistor over my Ultra's 220k (56k R6 on JSX) to give the JSX value but I never used it as the 56k value had no balls. IME blending is difficult to implement and of little value, I change things and if I don't like them I change them back. I bag the old parts and tape them internally with a note so it can always be "restocked" by me or the next owner.

As long as you're careful (and don't peel up a PCB trace!) PVs mod nicely,

Sorry, I overlooked that most were cap changes, I saw "R6" and couldn't help but think "resistor" for the rest of the post. Would replacing R6 with a pot work well as an additional gain tweak? Like, say, a 250K? I've done some mods with amps and guitars, but am no expert by any stretch of the imagination. Your knowledge is appreciated.

[tedmich]

Adding pots to existing amps is can work but you gotta drill a hole and stick it somewhere on the chassis, and this destroys amps resale value and seldom works well IME. Sadly the only real way to do this is mod the fixed value components internally and then accurately judge which way was better.

Unfortunately if you take 1.5 weeks to listen/disassemble/ change out a component/reassemble/listen its nearly impossible to judge which was better. Similarly guys who ship their amp off to FJA/Voodoo for 3 weeks and shell out +$500 for them to do their "magic" can seldom fairly judge the impact on the amps tone. In a perfect world you'd record the exact same guitar/cable playing the same riff with the same miking before and after the mod then judge from the recording. Amp designer often have "test mule" amps setup with switches and pots for various values and then dial in the amp sound they want. But they replace these extraneous parts with fixed values for any production amps. Some amps do allow for a huge variety of adjustment but MANY owners can never dial in a sound they like. Sometimes amp designers go for maximum flexibility figuring this maximizes their customers, while most customers want one specific sound.

A personal experience of mine may help to illustrate this conflict. I adapted the resonance circuit from the PV JSX into a dual pot and put it in the feedback circuit for my Ultra
where it replaces the 3 position toggle switch. I love the way it sounds with its two controls at their extreme, so I NEVER use those knobs. Might as well pop in two fixed resistors and put the toggle back...and that dual pot was expensive and hard to find...

[ejc6stringer]

Adding pots to existing amps is can work but you gotta drill a hole and stick it somewhere on the chassis, and this destroys amps resale value and seldom works well IME. Sadly the only real way to do this is mod the fixed value components internally and then accurately judge which way was better.

Unfortunately if you take 1.5 weeks to listen/disassemble/ change out a component/reassemble/listen its nearly impossible to judge which was better. Similarly guys who ship their amp off to FJA/Voodoo for 3 weeks and shell out +$500 for them to do their "magic" can seldom fairly judge the impact on the amps tone. In a perfect world you'd record the exact same guitar/cable playing the same riff with the same miking before and after the mod then judge from the recording. Amp designer often have "test mule" amps setup with switches and pots for various values and then dial in the amp sound they want. But they replace these extraneous parts with fixed values for any production amps. Some amps do allow for a huge variety of adjustment but MANY owners can never dial in a sound they like. Sometimes amp designers go for maximum flexibility figuring this maximizes their customers, while most customers want one specific sound.

A personal experience of mine may help to illustrate this conflict. I adapted the resonance circuit from the PV JSX into a dual pot and put it in the feedback circuit for my Ultra
[ATTACH=CONFIG]26904[/ATTACH] where it replaces the 3 position toggle switch. I love the way it sounds with its two controls at their extreme, so I NEVER use those knobs. Might as well pop in two fixed resistors and put the toggle back...and that dual pot was expensive and hard to find...

I don't mind adding pots and drilling holes in the amp, I've already done that with the Resonance knob and I don't plan on selling the amp down the road anyway.

[Jack Tone]

I'd like to add the resonance control to a 6262 and I found a schematic. Doing it on the 333 sounds simple, replace R42 with the 1 meg pot. Here's a view of the 6262 schem:



and the 333xl:



on the 6262, there are two resistors in series, R27 and R26. Would you replace just R26, the one in parallel with the capacitor, or both with the 1 meg pot?

Thanks for your help.

[b.arzaga]

just to make sure, thats the one right?

and this is like a soldano depth mod? i have the jetcity hdm100

[splintertheory]

Fury, what mod did you do to increase the gain on the lead channel? I can't seem to find anything on it

[splintertheory]

other worthwhile things to try on a JSX (or "JSX inspired" design!) include:
1 larger values for the 56k R6 after the 2nd gain stage (Ultra has 220k)
2 increasing C3 (1nF) to 1.5-2.2nF
3 upping C2 (470pF) to 1.5-2.2nF
4 upping C31 (0.47uF) to 1uF
5 removing (or increasing) the shrill C35/10nF cathode bypass cap before the master volume

Mod (1) decreases the amount of signal going to ground and can GREATLY increase gain! (you have been warned!
The 2-5 mods tend to darken the amp and emphasise more bass; try one at a time!

In mod 1, would you have to bias the amp if you change the value of the r6 resistor?

[tedmich]

In mod 1, would you have to bias the amp if you change the value of the r6 resistor?

I did not, bias is (largely) for power tubes and this is a preamp mod.

[Danglin' Fury]

Jack Tone... Just the R26... The one in parallel with the cap...