DC-3 Lead Channel lifeless

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Balint

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Oct 9, 2013
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Hello,

I'm a happy owner of a DC-3 combo amp (REV B). I'm OK with the Rhythm Channel but I find the Lead Channel quite lifeless. I miss some highs that helps cut thru in band. I mean some extra brights or a little fuzz type high, in a good way.

I've found many theoretical possible mods, but I want to implement only few to achieve what I want. The options I can see:
- increase the V1b grid resistor from 470k to 1M
- remove the .001 cap in front of V2a
- remove the .001 cap at the end of the Lead preamp after the Master pot
- play with the tonestacks (fixed and adjustable): slope resistors, etc.
- add a bright cap like in the Rhy channel to the gain pot

Are there any more to take into this list? What do you think about the above listed mods? Which one is the most promising for my needs? Which ones did you try?

Two more questions:
1. I found the REV A schematic of DC-3 on the net, but not the REV B. Does anybody have it?
2. In the DC-3 Lead channel's adjustable tonestack there is a 6k8 resistor between the mid and bass caps. This is not so common, I've never seen in other designs. What this resistor is doing?

Thanks,
Balint
 
Hello Crguti. I would prefer not to have any pedals between guitar and amp, just pure sound from the amp. I think it can be modified for my needs quite easily. This afternoon I'll try to implement few of these changes and see the results.

br
 
crguti said:
why you don't try with a treble booster pedal.
I used to think this also, but.......with the band I'm playing with right now, I need to frequently make instant changes between rhythm and lead sounds, and it is only a flawless change if I can do it by stomping on just one switch, not two or three pedals. Besides, if his DC3 rev B is like mine, he has a footswitchable graphic EQ, so shouldn't be any need for a treble booster pedal.
 
I would check your guitar as well. Maybe your guitar/pickups combo is the one that needs more treble.
 
Hello all,

Yesterday I had some time to try few of my modifications - focusing only on the Lead Channel. Here comes my first, low volume experiences about the mods and its effect on the sound:

1. Pull out on leg of V1b grid resistor (470k): more harmonics and a little less muddy sound. Not so dramatic change. The circuit is still stable without any grid resistor but finally I put in 2M2 just not rely on V1a grid resisor to set the input of this stage. I would score this mod as a good one, but not enough for my needs at the moment.

2. Pull out one leg of V2a grid capacitance (.001): this resulted a non stable circuit. Depending on where the treble and gain pot was set I had weird tones from the amp without hitting any string. Definitely not what I was looking for - immediate unmod (of course it was the hardest component to reach on the PCB).

3. Replace the treble cap (500p) from ceramic disk to Silver Mica 680 pF (this was th closest value what I had at home) in the adjustable tonestack. I like the sound of SM caps in tonestacks. More high, more high-mids. I would score this mode as a good one, the actual cap value might be adjusted later, but I keep it now.

4. Remove the .001 cap after the Master pot. I didn't notice difference, probably just a very tiny one. But I'm ok with this mod. As I saw this cap is represeneted only in DC3, not in DC5.

5. Put a bright cap between Gain pot's wiper and end terminal (shunt the higher ferquencies). I used only a 33pF SM cap directly soldered to the pot (like the clean channels has its own 120pF). This is just a very small cap, hard to hear at low volumes, but I keep it now.

All together, I prepared the amp with the mods 1, 2, 4, 5 and will see and hear it in our rehearsal this afternoon - as I sad, all the above listed experiences were with quite low volumes.

I will keep you informed about the sound if you are interested.

Regards,
Balint
 
Some details and intorduction to add:

I play a Casio MG510 guitar (strat like with s/s/h pus) from the 1980's. I play mostly rock and blues songs with my band. I play this type of music for 20 years and I had so many amps (Fender, Rivera, Peavey, Laney, etc...) and also modded few of them. I really want to have "the one" amplifier for my needs. I usually use a slight crunch for rhythm and a drive sound. Plus need a little volume boost for solo works on both sounds. I don't like using many pedals, only a good wah. DC3 would be a perfect choice for my needs (two channels, EQ for boost or attenuate).

Here comes a picture of my beauty DC3:

263303_20120627000810.jpg
 
...

Actually the amp is running with TungSol 12AX7s and Sovtek EL84 tubes.
The V30 speaker was replaced with a Fane Medusa (my favorite speaker in combos), I am planning to install a beam blocker to reduce ice picking.

That's all for now. Back to work :|
 
Casio MG510 guitar? :lol:

I think that's the problem with your tone. Don't blame the amp.
 
sounds funny? most likely you know hardly anything about these guitars.

I don't use the midi at all, just the guitar. In a contest between my old Fender strat vs. Ibanez Artist vs MG510 definitely MG is the winner. But I'm not the only weird guy using this japan masterpiece from FujiGen Gakki guitar factory. See JJ Cale as an example, or google it.

focus on the amp friend.
 
crguti said:
Casio MG510 guitar? :lol:
I think that's the problem with your tone. Don't blame the amp.
I understand completely why you say this. I've never bonded with anything I had that said Casio on it, but that was 25 years ago.

Balint said:
sounds funny? most likely you know hardly anything about these guitars.

I don't use the midi at all, just the guitar. In a contest between my old Fender strat vs. Ibanez Artist vs MG510 definitely MG is the winner. But I'm not the only weird guy using this japan masterpiece from FujiGen Gakki guitar factory. See JJ Cale as an example, or google it.

focus on the amp friend.
If you say so....... but if your Casio guitar beats out your Fender and your Ibanez, then either you got the 1 in a million super freak Casio guitar, OR........your Fender and your Ibanez guitars are super lame. Not trying to insult you at all, just that over here we get all the cheap budget $59 dollar Casio gear and none of it sounds like anything worth keeping. You got lucky if you like yours better than the Fender and the Ibanez! But I still would not recommend modding your gorgeous Mesa amp just to make it sound good with your Casio guitar. :wink: 8)
 
Perhaps I can try to bridge the gap here as I own a Casio MIDI/synth guitar and play Boogies

cgruti - I respectfully agree you should ignore the name on the headstock. :? The Casio MG-510 and PG-380 were, in fact, made in the Fuji Gen Gakki factory in Japan. This is the same factory where Ibanez were made. I've owned a Casio PG-380 since the late 1980's and it is a superbly made guitar. The only difference between the MG-510 owned by Balint and the PG-380 is the midi/synth electronics package. The MG-510 had MIDI capability without the built-in synth, while the PG-380 had both.

Now that we've put that issue to bed, let me also say that I've played Boogies since 1987. I used the stock pickups in my Casio for a long time. However, I was never totally happy with the sound of it through my Studio 22 or my DC-5. There was no bottom end and an overall lack of sustain. I eventually decided to replace the magnetic pickups. I went with a DiMarzio Tone Zone in the bridge and 2 Kent Armstrong single coils in the neck & middle positions. I also used black pickup covers so the guitar looks completely stock.

I must say that I am much happier with the tone of my Casio PG-380 after the pickup swap. I always suspected that the combination of the Floyd and the significant body routing for the MIDI/synth electronics robbed the guitar of some sustain. In addition, the ebony fretboard also probably tooks some bottom end, though I love ebony! In my case, I think the pickup swap was what I needed. I get better tone from both of my Boogies. :D

Hope this helps!
 
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