Mini-Mesa anybody?

[sean_thornton]

Well, our two resident "mad scientists" Geezer and Tubeinit have created some amazing amps, giving us "mini" versions of some great amps, and really pushing ahead the idea of great amps in small packages, so i had an idea. How about a "mini" Mesa Boogie Mark I or Mark II?
We could start out using the ECL82 again for power and PI, one tube reverb, and relay switching for channels. I would like to incorporate the 5-band eq, but it could just be optional just like on the original. For some reason the idea of playing "Europa" through a mini-mesa the size of a Kleenex box appeals to me.
Any interest in this idea guys?

[tubenit]

That is a very complicated build!     

http://www.el34world.com/charts/Schematics/files/boogie/boogie_mkii.pdf

Lots of stuff going on in that amp.

With respect, Tubenit

[sean_thornton]

Yeah there is !  I have started on a schematic, the original is kinda messy. Another schematic that might be worth looking at is the Mini Boogie 25, and come up with kind of a hybrid of the two. Worth a try?

[TIMBO]

Hey sean, Tubenits right, a lot of stuff happening. I started this http://www.el34world.com/Forum/index.php?topic=10485.0 awhile back and got the boards and chassis made up and started on a switching circuit that is on a multi pole rotary switch and it drove me insane   but it is all there I just have to find the enthusiasm to finish it.

I have found that SIMPLE is best as these are complicated circuit and the frustration that comes on completion when its starts buzzing and oscillating it takes all the fun out of the build.

Some of "Ts" low watt builds are great, I have built a one using the ECL82 and it sounds huge, so use the ECL82 or similar and stick a preamp amp in front and possibly a pedal and your there. Good luck.
  

[sean_thornton]

Timbo, thanks for the info. Maybe i should just buy a zendrive and run it through my Little Wing. I already get into SRV tones doing that with just my Bad Monkey, but that Carlos tone haunts my dreams. I am going to give it a try anyway guys, my sanity is questionable anyway so what the heck?
I may have some (lots) of questions, but I will plug away at it.

[TIMBO]

All I can say is go for it 

[Slimtim]

have fun with that,i went a little crosseyed just glancing at it.

[silverfox]

Here is a possible approach:

Try reducing the stages to simplified block diagrams and then reanimate the blocks to obtain the desired outcome. I can't say for sure but it looks like the input stage, the first thing that happens is the guitar input is square waved with the zener diodes placed back to back. The tone stack looks more complicated then the usual Marshall version- Are there bypass filters in there?. After that there may be sections where the harmonic content is developed.

Of special interest will be the purpose and effect of the TCR 5302 and 04. These are current limiting diodes connected to the tubes... Hmmm. What happens to the sine wave when the current is limited. Does it go square?? Peak chopped? That may be the real secrete weapon in the design. Is the diode adding some curve back into the wave so as to remove harshness?

What about an input stage with a 12AX or AU series that drives a Pentode to obtain the harmonic content and throw in one of those diode things??

Silverfox

[sean_thornton]

What about an input stage with a 12AX or AU series that drives a Pentode to obtain the harmonic content and throw in one of those diode things??

Silverfox

Thats an approach I had already been considering, but I am really going to have to take my time on this. I like the idea of breaking the design down into chunks, it does make it easier to deal with. Besides, it isn't the first i've bitten off more than i could chew.

[Jack1962]

I have built a few Mesa clones , shielded cable and ferrite beads are your friend with these amps , keep your lead dress very clean and very short. No part in a mesa can be removed and still sound like a mesa(unless you re-engineer the circuit) . I have never built a Mark series but it is a interesting idea .