Is this common for 36w???

kedsinger · Post by **kedsinger** » Sat 02/23/08 10:52 am

I'm finding the TMB side of my completed 36w has too much bass. I have to turn the Bass POT all the way down to make it usable. Before I go in and start changing values in the tone stack, I figured I'd ask if anyone else has found this to be the case.

Keith

pezed · Post by **pezed** » Sat 02/23/08 10:54 am

I don't think its a problem with only the 36watt tmb, the 18watt does it also. I think it depends on what cab you are using.. some speakers give more bass. you can lower the value of your coupling caps to roll off some of the bass.

kedsinger · Post by **kedsinger** » Sat 02/23/08 10:59 am

pezed wrote:I don't think its a problem with only the 36watt tmb, the 18watt does it also. I think it depends on what cab you are using.. some speakers give more bass. you can lower the value of your coupling caps to roll off some of the bass.

Yea, I was thinking of lowering c12(.022) only, because the normal side sounds just right. that's the only higher value on the TMB side that couples to the driver stage right after the tone stack.

kedsinger · Post by **kedsinger** » Sat 02/23/08 11:35 am

Oh by the way. Definfinatly not the cab. I have multiple cabs and if it was the cab both channels would be bassy. Any other suggestions besides coupling caps anyone??? Not that I won't try coupling value, I just want a few opinions first. Pezed, we do think alike though.

morcey2 · Post by **morcey2** » Sat 02/23/08 12:08 pm

As pezed said, it's a common problem on 18-watt TMB channels. You should also look at dropping the size of the 1st cathode bypass cap on the TMB channel from the normal 22µ to a 1 or 2µ. If that is still to much, then change the coupling cap value.

Matt.

kedsinger · Post by **kedsinger** » Sat 02/23/08 12:23 pm

morcey2 wrote:As pezed said, it's a common problem on 18-watt TMB channels. You should also look at dropping the size of the 1st cathode bypass cap on the TMB channel from the normal 22µ to a 1 or 2µ. If that is still to much, then change the coupling cap value.

Matt.

Actually, First half has no bypass just 1.5k, second has a 50u w/1.5k bias resistor. The schem. I followed is W@b@r 36w. I was thinking that 50u on this schem. is too high. I'll have to try changing. Thanks to both of you.

lovedat800 · Post by **lovedat800** » Sat 02/23/08 4:05 pm

Don't mean to hijack the thread, but my 18 has a overabundance of flabby bass, and it's a combo i've tried several speakers with and i know thats not it. I tore the pre out today to rebuild it as a 2204 high octane pre. Before i do, can anyone tell me if i will run into the same problem? I want a tight JCM800 tone, but while this circuit is supposed to be like that, i just want to know it really is and won't leave me with the same flab. If so, what pre circuit will give me that kind of gain w/o any flab? (by the way, i'm talking even low vol, so the flab WAS in the pre, not output)

morcey2 · Post by **morcey2** » Sat 02/23/08 4:29 pm

kedsinger wrote:
morcey2 wrote:As pezed said, it's a common problem on 18-watt TMB channels. You should also look at dropping the size of the 1st cathode bypass cap on the TMB channel from the normal 22µ to a 1 or 2µ. If that is still to much, then change the coupling cap value.

Matt.
Actually, First half has no bypass just 1.5k, second has a 50u w/1.5k bias resistor. The schem. I followed is W@b@r 36w. I was thinking that 50u on this schem. is too high. I'll have to try changing. Thanks to both of you.

If it was a BBQ amp, add 1-2µ bypass cap on the first stage and either remove the one on the second stage or drop it to the same range as the first. A friend of mine here had a BBQ 18-watt TMB that just didn't sound right. We changed that and it sounded much better. We added a MV on the TMB channel and got it the rest of the way there.

We went a little further and put 820 ohm cathode resistors on both stages and warmed it up a little. That's more of a flavor thing, but it sounded good there.

Matt

Alexo · Post by **Alexo** » Sat 02/23/08 7:45 pm

If it was a ***** amp, add 1-2µ bypass cap on the first stage and ... remove the one on the second stage...

We went a little further and put 820 ohm cathode resistors on both stages and warmed it up a little.

Wow, that is exactly the configuration I settled on after a lot of tweaking.

....So +1 I guess.

Post by **Plexi** » Sat 02/23/08 9:00 pm

one main this is to change the .022 that connects to the ,middle pot to a .01

Also the coupling cap,going to the vol pot, change it from .022 to a .015
You can also put a bright cap on the volume pot for even more crispness.
maybe a 120pf.

And as other suggested.. changes in the cathode bypass caps.
for the normal channel.. use a 1.5k with a 25uf bypass.

For the TMB.. the first gain stage for that tube try a 2.7k with a .68uf bypass cap or 1uf. for the second gain stage use a 820 cathode resistor with no bypass cap,unless you want more gain sound..use a .68 cap for the bypass.

I'd have to see the weber layout or schem to see whats going on with their version.

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Is this common for 36w???

Is this common for 36w???