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ADA Microcab

Started by Yazoo, January 14, 2008, 01:37:21 PM

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Has anybody had a go at building an ADA Microcab speaker simulator? They go for lots of money on eBay, otherwise I'd buy one - same old story!  :-\

I've had a look at the schematics and it doesn't look completely out of the question. There are 4 or 5 TL074 quad opamps and 2 (I think) 5532 dual opamps.


can you point me to the schematic?

I would like to see the schematic of the ampulator and the monster cab also.

I have a pcb for the marshall/groove tubes SE100 , is not tested.




I've spent the last few days feverishly looking at the schematics  :icon_eek:

I've realised if you don't need two channel input/output - I will only ever need 1 channel - you can almost halve the work involved. The schematics for the two channels duplicate each other. This knocks the chip count down to where it's definitely doable.

The switches used to select the cab model you want to use look complex, but hopefully with one channel only again, the complexity should be reduced.

There are a couple of components whose values are not listed. There are two resistive networks marked as RN100 and RN200. Does anybody know what values these are?


for me a good cabinet simulator must have a high order low pass filter this one is just 2nd order, the se100 is 5 order if I remember well, the sansamp use 4 or 5 I can`t remember. that is specially important if you will put a lot of armonics on it (distorted sound).

the ampulator look a lot more interesting, the power supply and the power amp simulator is very interesting .


Just about a year ago I had planned to build a single channel copy without all the switches (I always used the same settings) - so I pulled the resistor network from my ADA unit and measured it as I  couldn't find the values listed anywhere. I redrew the channel schematic with discrete resistors and used 5.6M in the schematic. I don't remember now if that is exactly what I measured or if that was the closest I could find. The resistors I ordered were 5.62M so I feel confident that 5.6 is what I measured. (I still haven't built it)


they seems to be "anti pop" resistors.


I've been working through the switch mechanism which selects the different cab models and here is what I've got. I'm describing Channel B, which I thought would be easier to trace through.

Output from IC U200 (TL074) is filtered though capacitors C200, C201, C204, C205, C207, C208, C210, C211, C212 and C213. This feeds into the positive input of U101C. The switching mechanism switches in and out the outputs from these capacitors in different combinations. Non-used outputs go to ground through the resistive network.

This is what I've worked out:

Open Cab 1x12            C212
Open Cab 2x12            C200, C204
Open Cab 2x12 Vintage          C201, C205

Sealed Cab 1x12           C213
Sealed Cab 2x12           C200, C207
Sealed Cab Vintage 2x12         C201, C208
Sealed Cab 4x12           C200, C204, C207, C210
Sealed Cab Vintage 2x12         C201, C205, C208, C210, C211   

Please let me know if I've got this wrong.

If anybody knows the values for the HI Balance (Crunch) and Thump pots, I'd be grateful if you could let me know. These are the only values which aren't listed on the schematics.


HI Balance (Crunch) = P101 = dual B50K
Thump = P102 = dual C10K


Dear DocHeavy,
Many thanks. This really is an excellent forum and the response time knocks me out. I repaired a Quadraverb a while ago and needed some capacitor values. Thanks to a poster in this forum it's now up and working.

So thanks again!


I've just finished my one channel version of the ADA Microcab. It's taken me about 5 weekends, but I'm really pleased with the results. I built the main board and meter on stripboard and built the cab selection switches on copper board. I've never etched any boards and I'm a chicken when it comes to dangerous chemicals so I just used a knife to cut the tracks I needed.

Initially I thought there might be a problem with the switching mechanism because in the original, only 1 switch was meant to be on at a time. However, it turns out there is a well known trick where you deliberately have no switches pressed or combinations of switches so it turns out to be a bonus to be able to do this.

This project is definitely worth a go. A while ago I tried the Marshall speaker simulator, but it wasn't what I wanted. The Microcab sounds much better and gives you at least 8 different speaker simulations to choose from.


Quote from: Yazoo on February 17, 2008, 02:57:01 PM
I've just finished my one channel version of the ADA Microcab.

Cool, congrats  ;D

Sound samples? Layouts?


Here are some pictures of the one channel Microcab and my schematics. I'm in the process of putting everything into an old 1U rack box, but I've got one or two more holes to drill yet, not my favourite part.

This is the whole board

Here is the switching assembly

This is my layout of the main board - TL074 filtering and 5532 chip

and here is the separate meter board with the clipping indicator

Please let me know if I've made any mistakes. The clipping led isn't doing anything at the moment. This could just be because there is no clipping (I hope).


I was reading through this thread and it got me thinking. Could a rotary switch be used like the ones that were utilized in those LPT1 port switchers to switch between 4 different printers? Those are a dime-a-dozen at Goodwill/junk stores.

thoughts?  :-\


I think if I ever get around to building one, I'll use 10 mini toggles - one for each filter section. It will be easy enough to create a little "cheat sheet" to dial in the ADA presets, but there are 1024 possible filter combinations with an on/off for each of the 10 filters.


I'd love to see a layout and schematic of this when one is available...
Jim Rodgers


Hello all!

This is my first post here and I am anything but a DIY builder...

However, I would love to know if anyone has successfully built a DIY Microcab and what the results were...

Any sound clips available?

And do you guys sell your products or is that a no no?


I finished the single channel version of the microcab and I've got it fitted into my rack. I have to be honest though, I usually use another cab simulator based on the Celestion V30 speaker. There is a thread in this board about this

I can do some sample of the Microcab if you like. I'll just record something I'm playing at the moment, "Start me up" if that's OK.


Hi Yazoo!

Thanks for the quick response on an old thread!

I'd love to hear a sound clip of both the Microcab copy/clone you made and the cab sim based on the Celestion V30 (I'm a fan on Eminence myself...)  I lean toward high gain tones just to let you know...

I am a BIG fan of the Microcab.  I have one and would love a back up, but I don't need all of the options as I run it with all the buttons out.  I run the MC with my ADA MP-1 but love to run the MC with an old lovely Gallien-Krueger 2000cpl - in stereo for both - so I can use the chorus on both preamps.

I'd love to see a pic of both cab sims if you've got 'em!



Here are the samples, Marshall JMP-1 through Marshall EL84 20/20 into Microcab or V30 emulator

Microcab - all buttons out

Microcab 1x12 open back

Microcab 2x12 open back

Microcab Vintage 2x12 open back

Microcab 1x12 sealed cab

Microcab 2x12 sealed cab

Microcab 2x12 sealed cab vintage

Microcab 4x12 sealed cab

Microcab 4x12 sealed cab vintage

V30 cab simulator

The Microcab is in a standard 1U rack with my own DIY buttons for the different options. I couldn't find commercial buttons. I was also unable to do the spring assembly which would normally only allow you to select one cab type but this hasn't been a problem for me.