Well this weekend I did exactly that ! The 50 uF cap does help. I'm also using a 12AU7 to lower the gain on the tmb. Those 2 mods improved the bass end a little bit but it's not to my taste.
I do like the normal channel, even when fully cranked it's tight but it doesn't have a lot of gain. So that's why I'm thinking about upgrading the OT
Upgrading your OT will probably improve the quality of your output sound, but not likely the shape of your sound. Follow these gents' advice and you'll find your way to happy tone.
One question: what kind of speaker are you using?
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'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
well spotted dave!
i'm very suprised at C5 being .0022 with your description of the bass especially with C11 being .0047 like dave mentioned.i would still replace the 1uf with a .68 polyester for better clarity.
i have .68uf and .022 and have good detailed bass with no mushiness but my tonestack is lite2b not TMB.
it might be worth checking the rest of your component values in the amp against the layout in case someone has done a previous mod.
Well it was bought brand new straight from ceriatone. Nik from Ceriatone told me that the bass mushiness is to be expected when driving the tmb channel at the max. Right now, with the AU7 tube and the 50uF cap in place, it's much better. The .68 cap and classic tone will probably solve everything hopefully !
I'm using g12h30 and vintage 30. I checked my amp and it's got a 0.0022uF cap in C5 so I don't need to change it.
I also ordered a classic tone OT yesterday so with all those changes, I think I'll get what I'm looking for
Are you able to try the amp with a different speaker cab? Something along the lines of a regular Greenback maybe? Is your current cab open or closed back?
The G12H30 some people say is heavy on the bottom end, but I haven't seen a tone curve of it, so I don't know. I know the Vintage 30 is typically too bright for 18 watters, but YMMV.
The benefit of trying another speaker and/or cab out is to make sure you're not modifying your amp to accommodate a speaker. Swapping a speaker is the easiest and one of the most noticeable mods you can make.
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'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
My gut feeling is that it may improve overall tone but maybe not solve your core issue with the TMB channel. Thinking about this a bit, on my 18W I would say that in general the TMB has a little bit more clarity than the normal channel, particularly with guitars that have humbuckers.
This is a bit opposite of what you are describing so it makes me think something else is a foot here especially since it looks as though you already have a pre-amp that has gone a fair way to limit bass frequencies early on. However, the TMB channel can be a bit over the top at full tilt, particularly if you are using active humbuckers. This is particularly the case with an 820R cathode resistor on both the first and second stages.
You also mentioned that you are using a 12AU7. I'm guessing that you replaced the first tube with this one? I have never used a 12AU7 but the data sheet would seem to suggest that a 100K anode resistor and 820R cathode resitor would not necessarily put you in an ideal spot on the load line with respect to bias. Perhaps it's o.k. with the existing values in the first position since there won't be too much signal on the grid? Anyway, lot's to consider when you get the new OT up an running.
I built a TMB about a year ago and it uses the cheapest parts known to man. Interestingly enough, It sounds really good and has plenty of balls. I kind of thought it was always a little stiff and that the highs were perhaps a little brash so I got some G12M Greenback 25 watt speakers to replace my G12T-75's. Not having totally broken in the G12M's yet, the sound did improve, but it still sounded brash and gritty, so I too thought that a better transformer would do the trick. Well, I put the Classic Tone transformer in and guess what? No difference at all...... The cheap plastic bobbin China made transformer sounds exactly like the Classic Tone replacement.
I had read many posts stating that OT's can change the tone of the amp, but like many things, it is the sum of all parts and the OT is just one part. I figured it would sweeten the sound up, round things out and just sound better, but that is not the case for me. I wanted to have a Name brand OT anyway and since it didn't get worse, I now have an OT for another project.
I don't think the OT will help in your case either. It may change the overall sound minutely, but I wouldn't expect it to be an outright paradigm shift in sound quality. You are likely going to have to use speakers or a cab with less bass response or dial back the bass by using smaller bypass and coupling caps.
The cheap plastic bobbin China made transformer sounds exactly like the Classic Tone replacement.
I agree with everything you said except this statement is only partially true. There are circumstances where you won't be able to tell the difference, and circumstances where it will be blatantly obvious. Unless you really push the amp, and play through dynamic range (with components that can handle that range), then swap transformers and record samples of both, it might be difficult to tell for some people.
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'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
