Thunderchief - Question for Gary /ROG

[gunther]

Hi Gary,
first let me tell you, that I love the Thunderchief (and the English Channel too) and have to thank you, that your work was very helpful for me to get my Guitarsound.
Now I think about a small improvement. I whould like to have a thunderrectifier. I thought about a lot of hours how to realize it and after all I think I will only need a bit more bass (bottom) coming out of the thunderchief.
To realize it by increasing the cap on the first stage is not the right way, this will change the overall sound - the same with the cap on the second stage.  I believe it has to happen on one of the next stages.
First - a Mesa cab is a bit bigger and sound bigger than a Marshall cab, so what do you think of increasing the 15n Cap on the output to 47n or 100n?
Then I thought about increasing the coupling cap (22n) before the last stage to 47n - maybe the same on before the third stage.
Any opinions / comments whould be helpful.

Best regards
Günther

[B Tremblay]

You could change the 22n coupling caps to 33n and/or increase the output cap.

You can also try a larger cap in place of the 680n at the source of the first stage.

[gunther]

You could change the 22n coupling caps to 33n and/or increase the output cap.

You can also try a larger cap in place of the 680n at the source of the first stage.

Hi Gary,
thanks for your reply. It took a bit time for me to answer, because i had to test diff. caps.
Here my opinions:
Replacing the 680n at the first stage will result in more "overall" bass. With 220uF you get the normal channel, with a lot of compression (and later on muddy bass) if you try high gain settings.
With the 680n you have the lead channel which sounds much better at high gain settings.

The 15n Cap at the output stage is worth to think about (maybe also regarding the Marshal Speaker Sim). With this cap you try to emulate the Bass of a Celestion Speaker. This may come close, but in case of Marshall Amps you have to emulate not only one Celestion, you have to emulate the whole Stack. And this Stack contains 8 Celestions which will have more bass than a single one. I tried a 47n and think this will do the job.

The 470p Cap behind the first stage cuts a lot of Bass, important for avoiding muddy bass in the distortion stage. For my personal taste it has been necessary to change the coupling cap befor the fourth stage (22n) to 47n to add deep bass.

I made these mods only on my Lead-Thunderchief, I left my normal-Thunderchief with 220uF at the second stage as it is, but have to mention that I use this version with "normal" gain.

The only thing i have to think about is that there is much much more noise (hiss) on my lead-Thnderchief than on the normal.

All resistor are Metall, could the first Fet or the 470p cap (quality) be responsible for the noise?

Best regards
Günther