I need help.

[ju.stin]

I had a friend suggest that I remove the 470k resistor from v1-7 to ground, for improved clarity on my Mesa Dual Caliber 50. This is what he said:

The 470k input resistor on the gain-channel is not a fundamental part of that channel. To be precisely, the 1M 500pf combination of the clean channel is still active when the gain channel is activated and the additional 470k in parallel will indeed result in a 391k 500pf combination. This may sound dull. One could remove it or replace it with a 5M resistor.

The Lead channel is too dark or muddy, lacks character & harmonics. This is caused by an unusually low input impedence on the Lead channel of about 319K ohms. To fix this simply remove the 470K ohm input grid to ground resistor on the Lead channel (V1b-7).

Well, I did it.(after much brain racking, as I am a noob, and the amp has been modded prior to this, and the resistor I was looking for was not a 470k. lol Took a verrrrry long time to say "I know this is where it is supposed to be, but that isn't it, oh hell, just do it..." lol)

Now here is where I run into a problem. The lead channel lost all it's luster, has hardly any gain, and pretty much sounds dull x's 1000. The kicker though, is when I use a overdrive pedal, it sounds like it did with a boost prior to this mod. Is this an impedance issue? Any help would be greatly appreciated!!! Thanks in advance

[IMG489]http://i.imgur.com/eQ1Ed.jpg[/img]

[Phil_S]

I'd call that a grid lead resistor, not an input resistor. It's function is to help balance that tube. IMHO, there is very little meaningful difference between 390K and 470K, but I can't see if that's even true because the schematic is chopped off. If the amp lost it's luster, you know the thing to do is to undo your "mod."

[chief mushroom cloud]

pics would help

[jjman]

You guitar pickup is now the grid leak/resistor. If you unplug from your guitar the grid will have no reference to ground and will float up and the tube will do bad things. Put it back. Use 1meg if you want a hair more signal strength.

[Reeltarded]

Or 2M if you want crazy.

[ju.stin]

Alright guys, thanks for the help.

I went with a 1meg to see how that sounds. In the process though, one of my two 6l6's went bad. I don't have any spares, so I can't even test it. lol The luck... Damn it.

[tictac]

Your friend says the lead channel is too dark... the fix is to get rid of that .001 on V2a grid. That cap is bleeding high frequencies to ground...

TT

[surfsup]

Your friend says the lead channel is too dark... the fix is to get rid of that .001 on V2a grid. That cap is bleeding high frequencies to ground...

TT

Yes, the 330k/1n has a knee of about 480Hz attenuating everything above it. A 100pF would be better at 4.8kHz as speakers don't reproduce much above 5kHz and at the second stage input a third harmonic is at ~4k of the highest frets of the high e string. (if you still wanted a cap there)

[ju.stin]

Thanks for the input. I have a two different friends hooking me up with a matched set of Sovtek 6l6's and Winged C 6l6's later on tonight. So, my wife is just going to have to deal it once I get them. lol