Mesa 20/20 Deep Mod

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francm
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Mesa 20/20 Deep Mod

Post by francm » Wed Jan 07, 2009 10:26 am

A lot of people want to do this mod on their 20/20 but info can be hard to find.

Basically, the deep mod consists in removing the high pass filtering on the input stage on the 20/20 amplifier. Its is very simple. All you need to do is remove the C1/C3 capacitors on the tube board. The image below shows an original 20/20 tube board. To perform the mod, you need to remove two yellow capacitors with the tapered end on the "+" marking of the PCB.

The Ch B capacitor is the first device on the lower left hand side.
The Ch A capacitor is the 3rd device after the ch b tube socket (the first tube socket from the left) on the lower part of the board. Right under the ChA marking, between the two 12AX7 sockets.

I hope this is clear enough.

Image

sir riff a lot
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Re: Mesa 20/20 Deep Mod

Post by sir riff a lot » Tue Jan 27, 2009 6:02 pm

has anyone here done the mod ?

did you like the results?

I'm curious about doing mine, but I already like the 20/20 and dont want to mess with it.

but then again, if it gives a bit more "thump" , I would be keen

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crane
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Re: Mesa 20/20 Deep Mod

Post by crane » Wed Jan 28, 2009 2:56 am

Mine is still under warranty, but I'll do the mod in a few month. I will simply use a switch to bypass the capacitors, so the mod could be reversed with a simple "clic"
PRS McCarty Soapbar with BKP Pigs90, PRS custom 22 with BKP Rebel Yell
Mark V Head, 1x12" Mesa 1/2 closed (EVM-12L)
Triaxis 2.0 noFat - Quad preamp
Deep modded 20:20 - Bias modded 50/50 - SimulClass 295
Home made amps/speakers/pedals

BECOS
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Re: Mesa 20/20 Deep Mod

Post by BECOS » Wed Jan 28, 2009 12:33 pm

What is the result of this modification? How it will affect the sound?

francm
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Re: Mesa 20/20 Deep Mod

Post by francm » Sat Mar 07, 2009 1:18 pm

BECOS wrote:What is the result of this modification? How it will affect the sound?
Ummm.... did you read the first post?

Gives you more bass AND makes the amp appear to sound less nasally because of the better frequency response

Monsta-Tone
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Re: Mesa 20/20 Deep Mod

Post by Monsta-Tone » Tue Mar 17, 2009 7:12 am

Do you have any clips?

How much more bass does it have after the mod?
I've been looking at a 2:90, and while I realize that the 20/20 will never have the thump that 8 6L6's will, can it come even close?
Elvis said.......
Amp techs do get shocked. :shock:

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MusicManJP6
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Re: Mesa 20/20 Deep Mod

Post by MusicManJP6 » Tue Mar 17, 2009 8:52 am

This may be a stupid question, but does this mod apply to a DC-3 as well?
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francm
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Re: Mesa 20/20 Deep Mod

Post by francm » Sun Mar 29, 2009 11:14 am

Monsta-Tone wrote:Do you have any clips?
How much more bass does it have after the mod?
I've been looking at a 2:90, and while I realize that the 20/20 will never have the thump that 8 6L6's will, can it come even close?
No clips.

The modded 20/20 does have some thump BUT it compresses at band volumes. The extra bass is definitely noticeable and to me, it made a big difference. With the mod, its a great small amp that can definitely get loud. It has a great vocal quality to its sound. Great combination with a Strat, esp. if you play blues/rock and some 70's classic rock. It would make a neat little jazz amp too.

Does it come close to the 2:90? No. I replaced the 20/20 with a 2:90. I prefer the 2:90's more transparent sound, extra high end and overall balls. Its just way too loud for most situations. I always run it in 1/2 power mode. The 2:90, when run louder, provides more definition and less compression. Great for fast, articulate rhythms.

tofisi
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Re: Mesa 20/20 Deep Mod

Post by tofisi » Sun Mar 29, 2009 2:18 pm

Because my plate is not the same like a picture above. For moding my mesa 20/20 shoud I remove this two yallow capacitor? thanks for replay

PICTURE

Image

francm
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Re: Mesa 20/20 Deep Mod

Post by francm » Sun Mar 29, 2009 2:37 pm

tofisi wrote:Because my plate is not the same like a picture above. For moding my mesa 20/20 shoud I remove this two yallow capacitor? thanks for replay
Yup, those would be them.

tofisi
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Re: Mesa 20/20 Deep Mod

Post by tofisi » Sun Mar 29, 2009 3:09 pm

francm wrote:
tofisi wrote:Because my plate is not the same like a picture above. For moding my mesa 20/20 shoud I remove this two yallow capacitor? thanks for replay
Yup, those would be them.
Thanks

Dewdman42
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Re: Mesa 20/20 Deep Mod

Post by Dewdman42 » Sun Jun 07, 2009 3:05 pm

I am thinking about doing the deep mod, or possibly making it switchable. here's the question though, if the deep mod simply removes a high pass filter being executed by the electronic component, would it not be possible to deep mod the 20/20 and then when you want to have your sound be more stock, just apply an EQ to the end of the preamp chain just before sending to the 20/20 in order to accomplish essentially the same thing?

My guess is that for lead sounds I'm gonna prefer without the mod and for chunky rythmns I'm gonna prefer the mod.

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crane
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Re: Mesa 20/20 Deep Mod

Post by crane » Mon Jun 08, 2009 1:02 am

It is a filter, so it cuts frequencies. Applying an eq won't help.
But you can make the deep mod using switches, as I plan to do, so you can apply or remove it as you want.
PRS McCarty Soapbar with BKP Pigs90, PRS custom 22 with BKP Rebel Yell
Mark V Head, 1x12" Mesa 1/2 closed (EVM-12L)
Triaxis 2.0 noFat - Quad preamp
Deep modded 20:20 - Bias modded 50/50 - SimulClass 295
Home made amps/speakers/pedals

Dewdman42
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Re: Mesa 20/20 Deep Mod

Post by Dewdman42 » Mon Jun 08, 2009 2:39 am

Uhmm, An EQ can cut frequencies too. The right kind of EQ could probably do close to the same thing couldn't it? Advantage would be that I could control it from my floorboard.

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crane
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Re: Mesa 20/20 Deep Mod

Post by crane » Mon Jun 08, 2009 3:18 am

On the triaxis group on Yahoo there's a deep mod controlled by.. the triaxis ! it works the same as the 2:90. Schematics and pic availlable on the group.
PRS McCarty Soapbar with BKP Pigs90, PRS custom 22 with BKP Rebel Yell
Mark V Head, 1x12" Mesa 1/2 closed (EVM-12L)
Triaxis 2.0 noFat - Quad preamp
Deep modded 20:20 - Bias modded 50/50 - SimulClass 295
Home made amps/speakers/pedals

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