36 watt tmb too much bass

[wafdaddy]

I just recently became a member of this site and built and 18 watt tmb from the layout I found here and it was magnificent! I have been building old fender tweed circuits for about 2 years now and the change to the marshall sound has been refreshing thanks to you guys. Anyhow I just completed a 36 watter tmb and problems have surfaced that I not that savy on, first off the set of matched jj's lasted about three days and now after changing the 125 ohm cathode resistors to 150 ohms the outputs have seemed to cool down some I think the bias is around 12.48 now is this ok? also the tmb channel has so much bass that I really don't find it useful as compared to the 18 watter and also it seems to me more gain would be nice too. where could I make some changes to acquire these results?

[rjgtr]

Here's a couple ideas. Try each one and then you could try them in combination if it isn't enough change.

For less bass and more gain, change the cathode bypass cap from 22uf to 1uf or .68uf. This will increase gain and emphasize the Marshally mids.

You could change the coupling cap from the 1st stage plate from .022 to .01 or even as low as .0022.

If you do both of the above changes you'll end up with a TMB channel that is more like the Bright channel of a Plexi. However, this might be too bright. I would do the cathode cap mod first and then try a .01 coupling cap. If that isn't enough try a .0047 (or in that range) and finally the .0022.

Hey is there an official schematic yet? All that's in downloads are the layouts.

[NitroLiq]

No schematic, just the layout.

[Plexi]

Quite a few things you can do if you want it brighter.. As was mentioned..change the TMB channel coupling cap to .0022 up to a .01
the .0022 having more treble. You can use the bright cap on the volume control.. maybe a 120pf.. Or the added cap across the 470k resistor going to pin 2 ov V2.. Just depends on how bright you want it to go.
You could also change the slope resistor to a 33k.

Richie

[Shad]

I think the bias is around 12.48

If you mean your dissipation I think you may be looking at toastng more tubes. I had the same thing. Toasted tubes in no time, and WAY too much bass. I think it is a long way from sounding as good as a stright up 18. My opinion based on two builds. The marshall thing is refrshing after years of Fendering it, however the 36 watter was a big let down for me, others seem to love it though. For the sake of keeping my sanity I have decided to stick to stuff that has been tried and trued over the years. I think the 36 watter really is more for those who want to do a lot of twekaing. Then again other say it suits them out of the box, so subjective it is I guess.

[NewGuitar]

I also had many problems with my 36 watter, BUT...

It is working VERY well now based 100% on the latest layout posted in the downloads area. It is a little heavy on bass, but I like that. It is a VERY, VERY nice amp. The problems I had may have been partly due to the old schematic (NOT the one posted by Mark in the downloads area), however IF that is true it was only 10% of the problem. I had huge problems with solder joints, layout, a few components, etc. I thought using a soldering iron was as simple as hammering nails. IT'S NOT! You have to use good soldering techniques and be very disiplined. Trust me. I've been through the pain and thought it was not me!!

I don't want to hi-jack this thread, so I'll post my experiences on another thread for newbies.

Regards...

Hutson

[wafdaddy]

yeah if you like overwhelming, wall shaking having to pick picture frames up off the floor bass this thing is for you, but after tweaking the thing for over a month and buying tube after tube I finally got it stabalized. I combined the fist channel preamp from one layout and the tmb from another and then changed the biased resistors to 150 ohms and oh yeah got rid of the choke. For god's sake don't even go there on the choke dilemma DON"T USE IT if you don't have alot of experience messing with these things because you'll just think you've did something wrong and spend alot of time chopsticking and reading and researching USE THE RESISTOR! at least to start out with and if you want to try a choke I have one I'll sell to you reasonably, besides the resistor is much lighter.
anyway my experience with the 36 watter won't be forgotten soon and my buddy just loves it... I gave it to him for christmas and his 56 strat really sounds awesome through it.. it does make the single coils boil and fill out any thing thin sounding but in my honest opinion I was somewhat let down with results after building the 18's tmb and regular versions they just can't be beat for tight crunch. I use a jensen neodymium 12" and a jensen p10r alnico in my tmb and a greenback celestion in the reg. 18 and I'm very pleased with results. try it you'll like it...