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Happy 4th of July.... Mesa Boogie Cabinet Emulator Schem, PCB, and Layout

Started by Bob N, July 02, 2006, 10:47:32 PM

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Bob N

Ok guys!

Being a Vet, there are certain holidays like Memorial Day, 4th Of July, and Veteran's Day that mean a WHOLE lot to me. What does this have to do with guitars, amps, and music in general? Well, outside of the fact that music is what got me in a zone whenever my unit was in a "Hot Zone", absolutely fooking nuthin'.

I know you've seen the Marshall Cabinet Emulator... Some may have even tried it... An amplifier is only 1 part of an overall sound. The cabinet is the other part. Speakers and cabinets work together to give you an overall tone.

In Short... Here's the Boogie...

Triaxis Cabinet Simulator Schematic

Cabinet Simulator Parts Layout


PLEASE... Double check the schematic to make sure I have everything right. I need an extra set of eyes.... If there's anything I need to adjust, let me know and I will do what I can.... I'm not the greatest PCB designer as this is only my 2nd or 3rd from scratch, so it is a bit large for the component count.... Comments, criticisms, bitches, etc... shoot me a PM or leave me a post....

1 thing I do plan on this weekend is putting in bigger pads to solder to.... When I printed it out, they were thin... That will be updated on the final PCB....

Bob N

Ok... here are the new files... Same basic setup, just easier for you to read and solder to.... I tried out a new piece of software and like it so far....

Cabinet Simultor Layout and Parts List

New PCB (PCB size 3" x 1.5")


Don't know whether it makes a difference or not in this case but it is a common measure to "terminate" the unused opamp sections: Non-inverting input to ground, output and inverting input tied together. According to Texas Instruments whitepapers (http://focus.ti.com/lit/an/slyt166/slyt166.pdf) "Improper termination can result in greater power consumption, more heat, and more noise in op amps on the same physical IC." Shouldn´t be too tricky to re-route couple of traces. The opamp might need some decoupling between the rails too. A small cap in close approximity of the IC should do it. Otherwise oscillations might lurk out.

Bob N

Thanks for the input Teemuk! I'll take a closer look at that documentation on Wednesday and make adjustments to the circuit board as needed. I will post what I come up with just to confirm. I plan on building this into my Solid State using the DR Boogie as the preamp, just to see what happens.

Is everyone in a wait and see mode to see what this will do sound-wise? or no interest?


It will be good for running direct perhaps, but may be funky into an actual cabinet. That's been my experience with cab sims.

I do, however look forward to your report.


Bob N

I'll post a new thread with the entire build process of the amp with sound clips. If worse comes to worse, I'll use the sim as a line out feature on the amp, but I will record a bunch of clips so you can hear everything through the build both mic'd and direct. My donor amp is the Crate MX15R practice amp that I despise so much, but I'll be keeping the circuit board intact to play frankenstein with again if this experiment goes awry.

Now, off to reading the documentation that Teemuk forwarded. looks like it could be some cool reading...

Nicht Bernd

J M Fahey

Hi nicht.
As I see it BobN hasn't posted anything since 2006, and way back then "he still had to correct a couple mistakes", so I guess you'll have to design your own.
Even better, build the Marshall simulator for which there is a lot of info, including PCB.
Besides that, personal opinion, the Boogie simulator is quite poor, and the inductor makes it harder to build..

Nicht Bernd



Plus 1 on last post,, I can't see anything either?

Re Teemu's comment,, Yes absolutley ground un-used pins of opamps as I've had fisrt hand experience with that and took me quite a while to catch onto what the hell was happening.
Arrh but slowly we all learn not to take short cuts.
Re the sim stuff I've had good success with 2 circuits.
1/ Ed Rembolds Marshall sim (lifted from Marshall JTM 30/60 Valve Amps)
2/ the cab sim inside the Nobels SST1.
Schematics still on the Nobels site AFAIK?? if not search for my postings as I built a cut down version of the SST 1 and posted it here a while back.
PhAbbTone and  DDC circuits.

Kaz Kylheku

If you're itching for cabinet simulator schematics, not necessarily these ones, download the ADA Microcab ones from ADA depot: http://www.adadepot.com/adagear/gearpages/cabsims/ADA-Microcab.htm

The Microcab is based on op-amp resonant cicuits (gyrators).  Gyrators simulate inductance, eliminating the need for hefty inductors in the circuit:


The Microcab has something like five of these circuits. I think the one connected to the "thump" control is intended to represent the basic speaker driver resonance and the others do some cabinet resonances.

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