DC Mods that are easy to do!

DC-2, 3, 5, 10
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Monsta-Tone
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DC Mods that are easy to do!

Post by Monsta-Tone » Tue Feb 24, 2009 7:27 am

For quite a while now, I have been a bit of a mad scientist on my DC's.
I thought it would be a great idea to start a thread with a few of the mods I do on them.
Maybe we'll get lucky and enough people will chime in to get it made 'Sticky!'

These are the mods that I get asked about the most. I usually give the info away, as they are pretty easy and I figure everybody deserves to have their amp sounding the best that it can. Some of these I came up with, some of them are from other members here who have been gracious enough to share them with me.

Series Loop Mod: (I think this came from MJ Slaughter, hope he doesn't mind me sharing)
This basically changes the amp's FX Loop from parallel (which I hated with delays) to series.

I have a drawing for it, but it's a pdf and I don't know how to post it here. Plus, I don't have a long term way of posting it. Maybe someone can chime in and help with this.



Adjustable Bias Pot:
In the middle of page 5, you will see the Bias Supply.
Remove the 22k ohm resistor that leads to ground.
If I remember right, it's located on the lower left hand side of the board if the front of the chassis is facing away from you.

I use a standard 10 k ohm Bias Pot for a Fender amp: http://www.tubesandmore.com/scripts/fox ... E03=03_FOB
Their search engine was down when I tried it, but look for 'Original Fender Bias Potentiometer.'

I twist about 6" of wire together. I usually use 20 gauge wire.
I put 2 pieces of different colored wire in my drill and twist the hell out of it so that it is nice and tight and it looks like it was meant to be that way.

Then, I solder one end of the 2 wires to the solder tabs where the resistor used to be.
Make sure you know which one is ground. That will usually be the end that was toward you, but I've seen quite a few board revisions.

Place the pot in the 'Mix' pot's hole.
Solder a 15k ohm resistor from the Middle tab to the housing of the pot.
Solder the Ground wire to the housing of the pot.
Solder the remaining wire to one of the outside tabs of the pot.

If the pot seems to turn backwards, simply swap the wire to the other outer tab.


This works really well. But, make absolutely sure that your solder connections are good. Failed Bias can kill your amp quickly.




Master Volume mod: (not sure who told me about this one)
There will be a resistor in parallel with the Output Volume pot.
It is a 220k ohm 1/2 watt resistor.
Some older amps have them soldered directly to the pot.
Others have them placed directly behind the pot on the circuit board.
Make sure to use an ohm meter so that you don't accidentally cut the wrong resistor.
Simply snip it off or un-solder it from the board, that's it.

This will make the Output Volume have a much better taper and make it much more user friendly at lower volumes.



Footswitch mod: This one is a bit complex, but really makes the DC 'A' series much more useable on stage.
This mod makes the front footswitch jack on the 'A' series control the Channel Switching and the EQ!

You will need:
15" of shielded single conductor wire
1 - Stereo jack, insulated : http://www.tubesandmore.com/scripts/fox ... em=S-H601B

There are 2 ways to do this mod, the 1st of which is much more simple.

1. Simply remove the Reverb wire from the Reverb/EQ footswitch jack.
It is the middle tab usually.
Then, run the shielded cable from the middle tab on the jack to the front footswitch jack.
The tab that you will solder to on the front jack is the 'Tip.' You will see a grey or white wire going from it to the board.
That's it!

2. Remove the front footswitch jack.
Drill the hole larger so that your new insulated jack will fit.
Install the new jack. You will need 2 of the fiber washers that the jack comes with, so buy
an extra one. It only comes with 1.
Run the shielded wire from the 'Tip' of the Reverb/EQ jack to the middle of the new jack.
Replace the existing channel switching wire on the 'Tip' of the new jack, and the black ground
wire will go on the solder tab that is closest to the front of the chassis.
That's it!

You have to use shielded wire or your amp will hum like a motha.
You have to use an insulated jack or your amp will hum.
You have to ground only 1 side of the shield or your amp will hum.
I usually ground it at the side it starts from, the jack on the back.



Before you start, make absolutely sure that you know what you are doing and you know how to discharge caps.
The voltages in your amp can kill you or someone around you. I got careless once and it hurt so bad that it will never happen again!
http://www.aikenamps.com/SafetyTips.html


Anybody else have a few that are favorites?
Elvis said.......
Amp techs do get shocked. :shock:

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MusicManJP6
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Re: DC Mods that are easy to do!

Post by MusicManJP6 » Tue Feb 24, 2009 7:44 am

Awesome! I've heard of a different value reverb knob mod for better reverb as well...
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Monsta-Tone
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Re: DC Mods that are easy to do!

Post by Monsta-Tone » Tue Feb 24, 2009 7:47 am

I haven't been able to try this yet, but it makes sense in a way.
If you add a larger pot value, then less of the Reverb signal is being bled off to ground.


Another Reverb mod that makes a huge difference in the 'A' series is to simply change the circuit to the 'B' series spec.
This made a world of difference on mine.
I also use a really high gain tube in V5 to make the Reverb a little hotter.
Elvis said.......
Amp techs do get shocked. :shock:

mtnb1kr
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Re: DC Mods that are easy to do!

Post by mtnb1kr » Tue Feb 24, 2009 7:28 pm

Is there a mod to make the channel 1 push/pull switch on the DC-5 footswitchable? I realize there is a big volume jump but I still think it would be a nice feature. I also have an older Peavey Bravo which has almost the same thing in its channel 2, a push/pull to go from gain to ultra gain and that would be nice to make footswitchable.
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adam972
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Re: DC Mods that are easy to do!

Post by adam972 » Tue Feb 24, 2009 9:57 pm

there are a couple posts around about making the push pull switch into a footswith. its really quite simple as you are jut turning a pot switch into a jack. do a bit of searching and you will find it.

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Re: DC Mods that are easy to do!

Post by Green2002 » Wed Feb 25, 2009 2:23 am

Cheers for the adjustable bias mod :D :D :D
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Re: DC Mods that are easy to do!

Post by Monsta-Tone » Wed Feb 25, 2009 4:07 am

There is a pretty big volume difference when the pot is pulled, so I usually use a resistor in series with the 'On' position to equalize the sound.
I can't remember the value off hand though. I'll have to look through my notes.
Elvis said.......
Amp techs do get shocked. :shock:

mtnb1kr
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Re: DC Mods that are easy to do!

Post by mtnb1kr » Wed Feb 25, 2009 6:52 am

So with a resister to even out the volume can it be made footswitchable and then usable? What would I need to do?
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Re: DC Mods that are easy to do!

Post by LSC123 » Wed Feb 25, 2009 11:50 am

Why mesa didnt put the gain boost on the lead channel is beyond me. The one thing i've ALWAYS looked for in the mark series is Rhy = nice clean, Lead = high gain rhythm, and then either a cloned lead channel for a high gain lead, or a boost function to add a little more gain.

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Re: DC Mods that are easy to do!

Post by madryan » Wed Feb 25, 2009 3:33 pm

LSC123 wrote:Why mesa didnt put the gain boost on the lead channel is beyond me. The one thing i've ALWAYS looked for in the mark series is Rhy = nice clean, Lead = high gain rhythm, and then either a cloned lead channel for a high gain lead, or a boost function to add a little more gain.
I'm pretty sure that's the Mark V.
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MusicManJP6
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Re: DC Mods that are easy to do!

Post by MusicManJP6 » Wed Feb 25, 2009 3:37 pm

madryan wrote:
LSC123 wrote:Why mesa didnt put the gain boost on the lead channel is beyond me. The one thing i've ALWAYS looked for in the mark series is Rhy = nice clean, Lead = high gain rhythm, and then either a cloned lead channel for a high gain lead, or a boost function to add a little more gain.
I'm pretty sure that's the Mark V.
:lol: I was gonna say the same thing!
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Re: DC Mods that are easy to do!

Post by madryan » Wed Feb 25, 2009 4:00 pm

MusicManJP6 wrote:
madryan wrote:
LSC123 wrote:Why mesa didnt put the gain boost on the lead channel is beyond me. The one thing i've ALWAYS looked for in the mark series is Rhy = nice clean, Lead = high gain rhythm, and then either a cloned lead channel for a high gain lead, or a boost function to add a little more gain.
I'm pretty sure that's the Mark V.
:lol: I was gonna say the same thing!
My buddy will have his Mark V just as soon as they're available. He's going to get the first one the dealer gets in.

BTW... There's a nice DC-10 available over on HC (I think the same one is listed in the boogie classifieds) and it's a pretty good deal.
'02 Gibson LP Studio
'08 G&L USA Legacy
2009 Mesa Mark V Head (#375)
Avatar Oversized 212
Various pedals and whatnot


How to properly pack an amp for shipping...
http://forum.grailtone.com/viewtopic.php?f=12&t=39349

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Re: DC Mods that are easy to do!

Post by MusicManJP6 » Wed Feb 25, 2009 4:31 pm

madryan wrote:My buddy will have his Mark V just as soon as they're available. He's going to get the first one the dealer gets in.

BTW... There's a nice DC-10 available over on HC (I think the same one is listed in the boogie classifieds) and it's a pretty good deal.
Thanks, but i'm happy with my little shorthead DC-3...

I have a friend that works for a Mesa dealer and he's got one for him and one for the store coming so he'll have one of the first ones made as well. I'll have to check his out for sure!
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Re: DC Mods that are easy to do!

Post by MJ Slaughter » Wed Feb 25, 2009 4:46 pm

Great thread Monsta-tone. Regarding the rhythm channel pull switch, to make it foot switchable and most useful there needs to be another volume control you can use to change the level only when the switch in engaged. That way you can balance the engaged, pushed, volume with the disengaged volume so as not to take your head off. If that were possible I'd certainly do it. As it stands, I need/want my clean tones and use overdrives for adding a little hair and crunch. I'd rather utilize the pushed rhythm channel for classic rock crunch and be able to switch to clean without fiddling with controls in the middle or between songs. Is this possible?
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Re: DC Mods that are easy to do!

Post by Monsta-Tone » Wed Feb 25, 2009 6:44 pm

It is possible, but the problem is that you loose some of what makes the Boost what it is.
If you boost it, and then attenuate it, it sort of defeats the purpose. That's why I haven't done it yet on mine.


Another way to look at it is one of the mods that I do for Mark III's.
You could add an LDR and make the Negative Feedback adjustable.
Basically, I switch in a 100k pot that will make it so that you can have much less NFB.
I usually use the Reverb footswitch jack for this.


The NFB is fed back into the Phase Inverter so that it keeps the power amp a bit cleaner.
If you switch it out, the amp gains an intense amount of volume, so this is th reason for the pot. Without a way to adjust it, there would be no point in using it.


If you look at most of the higher gain amps that Mesa makes, they switch the NFB completely out of the circuit for the lead channel, but send a suitable amount into the PI for the clean channel.
Elvis said.......
Amp techs do get shocked. :shock:

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