Need some mod help/ideas

Hi,

I'll post the schematic below.
This is a bass amp 2x12AX7s and 2x7189s. Ss rectifier. 8 ohm output.
Being a bass amp there is not much sparkle/highs/treble on tap. There is also a lack of gain/volume. I'm assuming the design choices are to enhance the use for bass and no regard for guitar use was factored in. Now, I don't play bass I play guitar and therefore would like to mod this circuit to bring out the upper frequencies and increase gain/volume to better suit guitar use.

Without gutting the amp what are some mods that can be done to achieve the above objectives? Any and all ideas welcomed.

Thanks

http://i280.photobucket.com/albums/kk163/pchilson/Custom_Kraft_Electra/C_K_model-800_schematic_web-3.jpg

Coming off V1a plate there is a .02 cap, 47k resistor and a .01 cap that is bypassing the bass pot. What would be the theoretical effect of changing any or all of these values? Is there something in here that is draining all the high frequencies off to ground?

Thanks

try going to this website
http://www.tone-lizard.com/Table_Of_Contents.htm

Pay particular attention to the section titled Mods and Odds.
hope this helps

The first thing I see is the .0015Uf cap between the outputs of the PI, get rid of it. Then strip out the bass and treble networks and install something more guitar oriented. Once that is done, then think about changes yoiu want to make to get it right for what yoiu want from it.

The first thing I see is the .0015Uf cap between the outputs of the PI, get rid of it. Then strip out the bass and treble networks and install something more guitar oriented. Once that is done, then think about changes yoiu want to make to get it right for what yoiu want from it.

Lifted one leg of that .0015 and... WOW!
It was like lifting three big wet, heavy horse blankets off this thing...

Lifted one leg of that .0015 and... WOW!
It was like lifting three big wet, heavy horse blankets off this thing...

Your welcome.

Yeah, that really just jumped out at me. Glad it made a dramatic change for such an easy mod.

Hey celeste, I was so excited about the difference I totally forgot to give you a thank you, my bad. Thank you!

Quick question. On the inputs the are grid stopped with 47k resistors and a 680k to ground. Most of the Fender and Marshall inputs I see and probably many others use 68k and 1m to ground.

What should I hear change if I were to go to these values?

Hey celeste, I was so excited about the difference I totally forgot to give you a thank you, my bad. Thank you!

Quick question. On the inputs the are grid stopped with 47k resistors and a 680k to ground. Most of the Fender and Marshall inputs I see and probably many others use 68k and 1m to ground.

What should I hear change if I were to go to these values?

You will likely hear very little. The differences in values are not that great.

Of course the lower the grid reference resistor, the more signal gets blad off to ground, the lower impedance will increase the load on the preceding stage and drag it's gain down. The differences in value not all that huge to make much of an issue there.

The grid stopper forms a low pass filter with the miller capacitance of the triode, so the lower the value, the brighter the tone, assuming the corner frequency is in your passband.

Back to the .0015 cap spanning the PI outputs.

Celeste or anyone. Can you explain why that was there and what it adds or removes by taking it out of circuit?

Back to the .0015 cap spanning the PI outputs.

Celeste or anyone. Can you explain why that was there and what it adds or removes by taking it out of circuit?

The cap kills treble. It is a bass amp. I am going to guess here, any post tone stack high order distortion is removed by the cap.