DC5AB Frankenstein

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sKenDread

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Hello,
Im currently studying the DC5A and B version schematics seeing the differences between the two and yup yup its the clean channel that was changed, so I am looking into a switchable conversion. It looks pretty simple from a distance but has anyone had any experience in doing this?

I want to make it switchable rather than a straight conversion. So can I add switching relays to swap between the 2 different components whilst performing live or would this be a power down > switch > power up > GO!

Secondly,
Whilst I am digging deeper into the power section I see the possibility of a simul-Class type conversion (class A + AB) also but my concerns are with the OT and PS. If anyone has done this I would love to hear from you.

Why am I doing this rather than buying a MK4 or other?
Because I want to. I understand all you Mesa Boogie purists out there would probably look at me in disgust for even thinking of modding like this and I fully understand where you are coming from (if its not broke don't fix it)

Please be nice
 
Should be do able. You can use this for a switching relay:

http://www.hoffmanamps.com/MyStore/perlshop.cgi?action=template&thispage=Lamps&ORDER_ID=401215545

http://www.el34world.com/projects/relay_switch.htm

My relay switched reverb setup:

EE48D58A-53D2-4ACD-A083-760B1208DC62-4375-000004FB43FE8397_zps68cdb324.jpg



I used this for my reverb foot switch setup on my DC3, with this, you will be able to make it foot switchable. Otherwise, it would just need an DPDT switch to switch between the different resistors/caps included in the circuit. You will also likely need to make a board to hold all of the components, or you can wire it point to point with a simple eyelet board.

You should be able to switch it on the fly as it's just some resistors and caps. Just like the voicing switches on the other Mesa amps.

I would look at the schematics for one of the Rectifiers with switchable voicing per channel. That should give you a really good blue print to work off of.
 
Hi there thank you kindly for the input,

I'm wondering if by switching in and out the components would cause drastic popping.
E.g
swapping out a simple low pass filter value seems OK but what about swapping out the actual HT to the tubes from 287V(DC-5A) to 420V(DC-5B) could this cause some serious damage?

what gets me is the power supply to these are coming from different places and the components that were changed are very subtle so why did they change the HT supply? Would it be best to leave it at 450V and just swap out the different caps and resistor values?
 
sKenDread said:
Hello,
Im currently studying the DC5A and B version schematics seeing the differences between the two and yup yup its the clean channel that was changed,


just wondering what exactly have been changed and the influence on the final tone . . . :)
 
Vigo1999 said:
sKenDread said:
Hello,
Im currently studying the DC5A and B version schematics seeing the differences between the two and yup yup its the clean channel that was changed,


just wondering what exactly have been changed and the influence on the final tone . . . :)

Hello, there was only a change made to the clean channel. In the original the clean channel was more like a compressed class A sounding channel when the whole amp came together at volume. There is an obvious difference in brightness, sparkle and mostly compression between the two versions.

When sat side by side with an A and B and set all params to 5 except the gain put that to about 7. Pull the boost out and plug in a strat. no fx.
You will hear the difference instantly. Unfortunately there were complaints made about the version A not being clean enough??!?!!%%!?? like WTF!@^%#*

I would have to admit yes it wasn't exactly transparently clean like a pure amplified original tone from the guitar kind of clean. It was REAL clean with some lovely harmonics and compression. Fair enough to Mesa Boogie for making the decision to listen to their customers. I really do admire the team, they make us owners feel like we've bought something well worth buying. But to all you moaners out there. If you don't like a Boogie tone... go buy a Rockit... oh hang on that was based on a MK2 oh well we can't always win haha!

Obviously I prefer the A version
 
thanks skd!!

asking cause i have the 'a' version and i have the chance to have a b for a short period of time for comparison, but it wasnt a fair one, since the 'b' was heavily modded by Monsta.

but, one thing that i notice is that the B has more gain and is brighter, but i dont know if it was the modds or not . . . :?

i love DC3s also. planning to get another head and make a cool mini stereo rig. it will be nice!! :D
 
When you're A/B'ing 2 amps - keep in mind that even the same circuit will sound different - variables in tubes, speaker, current draw, etc can often contribute to a bigger difference than the circuit changes.
 
Hey AB, thanks!

sure. in that specific case, ive used 2 1x12 mesa open cab with MS12s to be a fair comparision and used a similar set of tubes (al JJs).

but, sure enough you're right about those variables.

off topic, but i'll take the opportunity . . . wondering if i can use KT88s on my stiletto to have more bottom end out of it.

thanks in advance! :D
 
So looking over the schematics more. The main concern I have is switching the HT (B+) from 287v(DC-5A) to 420v(DC-5B). I can now see how this HT voltage would contribute to a darker tone (DC-5A) it seems that the lower the HT voltage the darker(browner)the tone so I will definitely be doing this mod.

But again lies my question?
switching voltages from one to another would be done via relay. Actually there will be a number of relays (about 8 so far)

Would there be any damage caused (spikes) while the transition from one voltage to another is taking place?

Or should I just give up and just hard mod the channel in question loosing the DC-5B changes
 
It sounds to me like an A is what you really want. In the interest of reliability, and ease of modification, I would just mod it to an A and be done with it.
 
sKenDread said:
So looking over the schematics more. The main concern I have is switching the HT (B+) from 287v(DC-5A) to 420v(DC-5B). I can now see how this HT voltage would contribute to a darker tone (DC-5A) it seems that the lower the HT voltage the darker(browner)the tone so I will definitely be doing this mod.

But again lies my question?
switching voltages from one to another would be done via relay. Actually there will be a number of relays (about 8 so far)

Would there be any damage caused (spikes) while the transition from one voltage to another is taking place?

Or should I just give up and just hard mod the channel in question loosing the DC-5B changes


on both A and B models (B+) is 450v and (D+) 287v

i think you missed something .. read twice

Regards
 
BlackBoxy said:
sKenDread said:
So looking over the schematics more. The main concern I have is switching the HT (B+) from 287v(DC-5A) to 420v(DC-5B). I can now see how this HT voltage would contribute to a darker tone (DC-5A) it seems that the lower the HT voltage the darker(browner)the tone so I will definitely be doing this mod.

But again lies my question?
switching voltages from one to another would be done via relay. Actually there will be a number of relays (about 8 so far)

Would there be any damage caused (spikes) while the transition from one voltage to another is taking place?

Or should I just give up and just hard mod the channel in question loosing the DC-5B changes


on both A and B models (B+) is 450v and (D+) 287v

i think you missed something .. read twice

Regards

Sorry I quoted the US standard B+ As the HT line not the B+ and D+ supply on the schematic. Yet still lies my question can I safely switch these supplies via relay while still operating?
 
Ok I've narrowed down my wants.

DC5B Clean channel to DC5A
I've decided to revert the clean channel back to DC5A version without switching as I know I wont be using the newer version anyway. Looking at the comparison between both versions, the changes wont be that difficult to do.

Additional Crunch channel
I'm going to add additional Gain pots and Master pots to the crunch channel so I can have a effectively have 2 variations of crunch and volume for that channel.
Replace the stock gain and master pots with dual concentric pots. Switch between the 2 pots(actually 4) via relay.
Question
Why did mesa boogie use LDRs? I'll need to check the voltage across these pots. What relays would be recommended?

Solo Boost
Looking into an additional boost switch so I can just jump right on that for solos to give me maybe a 6dB boost.
I'm thinking... for simplicity sake, rather than boost on push attenuate when not in boost?

Midi Implementation
To allow switching of all functions via midi

I'm open to suggestions :wink:
 
^ my suggestion?... with all those mods you're pretending to do, it would be better and cheaper to get another amp.
 
crguti said:
^ my suggestion?... with all those mods you're pretending to do, it would be better and cheaper to get another amp.

Thanks for the input. I'm doing it because I can and I have what I have. I'm in two minds about the simul-Class thing though. I will give that one a miss. But the multi-gain per channel in my opinion is worth it. Hell if it was good enough for R. Smith to mod a fender, I'm more than happy to mod a boogie. I love boogies and I love tinkering around with things.

I've learnt quite a bit so far and I take my hat off for the way this amp ultimately sounds. Why buy something that everyone else has?

The switching matrix is still a bit of a mystery but I will work it out.

Regarding the cheaper? I don't think it would be cheaper to buy a new one really. I modded my own Marshall Anniversary mod myself but had guidance from a Marshall tech. I was alot cheaper than sending it in to do and I could say. I did this myself :)
 
I thought i'd jump back on this to keep it updated.

I've worked out a MIDI switching matrix using the original switching matrix with a few tiny mods for the extra gain, extra volume pots and the new components for the midi and PIC. The PIC programming was surprisingly easy!

Does anyone have any opions regarding using analog muxer/swith ICs vs relays? Im thinking of using ICs instead but how reliable are they compared to mechanical relays? I'm not keen on LDRs
 
Hey SKD,

Interesting thread, man. Kudos to you for trying mods to make it suit you better ...heck, that's how Randall started it all! :)

I have an A, and long ago was drawn to a B thinking it was some "upgraded" version ...nahhh! I evntually came across a B, heard it, and said no way! While I like the added brightness, it's not anything I can't really get with the treb and pres knobs on my A. And it is precisely the smooth, creamy texture of the semi-clean A that is so addictive and musical, IMHO. I never play "spanky clean" so keeping it "A" was my final result.

I am very interested, though, in your modding the pull boost to make it switchable ...as in making it footswitchable! I brought this subject up here long ago, but it was said the dramatic difference in volume would make it unusable in live use ...my concern. Please let us know here if you get a footswitchable pull-boost feature going, how you balanced the output volume, and what your tonal impressions are. Rock on, man!
:)

Edward
 
Hey Edward,

Thanks for the positive words dude. As far as I can see so far. The pull boost is part of the tone stack stage. So by pulling the boost, it removes the tone stack from the signal chain allowing more gain, plus more volume as well.

I can't see why it would be unusable in a live situation ay? That would be sweet in a live situation if thats what you really wanted.
And as far as the volume boost issue.. thats not an issue either

You know? what you could do if you really wanted to have both options available on the floor.

  • Replace the switch with a relay.
  • Tie the switch to relay for manual switching
  • Add a stomp to the tied end for floor control
  • Throw a dual ganged volume pot in the mix for control over both boost and un-boosted states
  • Tie relays to the volume pots to toggle those as well via the pull boost.

DUDE! Nice! I didn't think of this!

Im currently working on the new switching matrix using the built-in matrix and extra switching circuits at once. They will be controlled via MIDI and foot stomp. It's a bit of a headache TBH. I'll add this switching too!
 
Alrighty SKD, if you are willing to do the deed, I'll have my ears on! FWIW, when I had a MkIII, I modded the R2 channel to add a volume control ...that made all the dfference; now totally usable and switchable! And that's where I got the idea for the footswitchable boost for my DC5. But I'm no electronics maven ...just know enough to get me into trouble...lol!
Let me/us know when you get up a working model, then give us your impressions ...really curious about this. Thanks man!! :D

Edward
 

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