To mod or not to mod...?

[thom]

3. Bypass the 220 k resistor that feeds stage 2 (drive stage) of Channel 2 with a 470 pF capacitor. This copies the Channel 2 "Edge" mode of the Mark V, if you happen to like this sound, which is a brighter distortion useful for on-the-verge of breakup sounds.

Chris (or anyone else!), do you know what the circuit reference is of the 220K resistor, or could you help point out where it is? I would quite like to try this mod but don't know which resistor it is. I am actually pretty happy with my LSS but still curious to try it anyway.

Thanks

Tom

 

[Ylo2]

Hello Tom. Sorry for the slow response. I have not been visiting the Boogie Board very often lately and just saw your message.

Find the schematics for the Mark V and Lonestar on the web and compare the CH 2 signal paths. They are almost identical in the preamps. The EDGE mode in the Mark V adds a 500 pF capacitor across the 220 k resistor that feeds the additional tube stage used for drive in CH 2.

In the Lonestar or LSS, locate the center pin (wiper) of the CH 2 Drive pot. Trace the wire to the circuit board, and follow the trace to the 220 k resistor. The opposite end of the resistor connects to a .005 (input) coupling capacitor. Carefully solder a 470 pF (500 pF is close enough) capacitor across the 220 k resistor. Do this carefully so you can unsolder or clip it without making a mess of things if you do not like the sound. I think this mod sounds great for blues!

Chris

 

[thom]

Hello Tom. Sorry for the slow response. I have not been visiting the Boogie Board very often lately and just saw your message.

Find the schematics for the Mark V and Lonestar on the web and compare the CH 2 signal paths. They are almost identical in the preamps. The EDGE mode in the Mark V adds a 500 pF capacitor across the 220 k resistor that feeds the additional tube stage used for drive in CH 2.

In the Lonestar or LSS, locate the center pin (wiper) of the CH 2 Drive pot. Trace the wire to the circuit board, and follow the trace to the 220 k resistor. The opposite end of the resistor connects to a .005 (input) coupling capacitor. Carefully solder a 470 pF (500 pF is close enough) capacitor across the 220 k resistor. Do this carefully so you can unsolder or clip it without making a mess of things if you do not like the sound. I think this mod sounds great for blues!

Chris

Thanks Chris. Much appreciated. I have actually, just two weeks ago, soldered bright caps (250pf Silver Mica) across the drive pot and both channel gains. Probably a bit OTT, (may substitute the 250pf for 150pf) but its great having to tame the highs rather than to try to coax them from nowhere. I also find myself playing just on the clean channel with a bit of compression quite a lot now, sounds very good, but then I always did like a bright sounding amp! Anyway thanks for the info, I will surely try it out at some point.

Tom

 

[ja22y]

Thanks Chris. Much appreciated. I have actually, just two weeks ago, soldered bright caps (250pf Silver Mica) across the drive pot and both channel gains. Probably a bit OTT, (may substitute the 250pf for 150pf) but its great having to tame the highs rather than to try to coax them from nowhere. I also find myself playing just on the clean channel with a bit of compression quite a lot now, sounds very good, but then I always did like a bright sounding amp! Anyway thanks for the info, I will surely try it out at some point.

Tom

I've haven't been here lately but came across this. There's a 120pF bright cap on each channel already, controlled by a 82k resistor. By adding a 250pF (or other value) in parallel, all you're doing is extend the lower end of the bright bypass. In other words, it won't be brighter but rather you get more 'high-mid'. And the effect diminishes once the pot is at 2:00 and higher. But when you open the amp, trace the circuit board and you'll see that Channel 1 actually has 3 caps in its bright bypass. I think it's done to get somewhat of a stepped brightness, very unique and I think it's quite nice. Just some foods for thoughts.

 

[thom]

Thanks Chris. Much appreciated. I have actually, just two weeks ago, soldered bright caps (250pf Silver Mica) across the drive pot and both channel gains. Probably a bit OTT, (may substitute the 250pf for 150pf) but its great having to tame the highs rather than to try to coax them from nowhere. I also find myself playing just on the clean channel with a bit of compression quite a lot now, sounds very good, but then I always did like a bright sounding amp! Anyway thanks for the info, I will surely try it out at some point.

Tom

I've haven't been here lately but came across this. There's a 120pF bright cap on each channel already, controlled by a 82k resistor. By adding a 250pF (or other value) in parallel, all you're doing is extend the lower end of the bright bypass. In other words, it won't be brighter but rather you get more 'high-mid'. And the effect diminishes once the pot is at 2:00 and higher. But when you open the amp, trace the circuit board and you'll see that Channel 1 actually has 3 caps in its bright bypass. I think it's done to get somewhat of a stepped brightness, very unique and I think it's quite nice. Just some foods for thoughts.

Interesting. I realise the effect of the bright caps diminish as you turn the pot up. I like to use lowish gain and push the amp with drive pedals. The 250pf caps make the amp pretty bright in my experience. It also makes the amp work very well with humbuckers which it didn't really do well, (for the sounds I like), before this mod. Anyway it's an easy mod to do and easy to reverse and I am enjoying the amp more than ever. I still find I run the bass very low and the mids almost off.

I did also try Chris' 'edge mode' mod but ended up taking it out. It sounded a bit 'raspy' to me, possibly too much with the other caps I already added.

As an aside, for anyone wanting to try any of these mods, please ensure the filter caps in the amp are drained. I found a very effective way is to play the amp, and then switch it off using the power switch only, and leaving the standby in the play position. I always then measure the caps with a volt meter just to make sure.

Tom