Moody Sounds Pratabas

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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Bernardduur
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Post by Bernardduur »

For the magazine I work for I ordered a couple of Moody Sounds kits. For the MusicMaker I reviewed and build a Muller Bass OD, for Bassplayer magazine I build and reviewed the Pratabas. As for this unit no schematic could be found on the website, I thought I shared it with you all!

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The unit has 2 switches; one to turn the unit on / off, one to switch between the OD and the fuzz section. Both units are controlled by the same potmeters; the gain of the OD stage is controlled with a LED / LDR stage.

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Post by Bernardduur »

And the schematic of the Hjart Muller Bass OD

Image
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Post by theehman »

Thanks for posting those!
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Post by andersom »

Thanks for this!
Dank je wel!

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Post by Magnus290 »

Hi!

Can anyone explain the symbol on top of the clipping didos of the prata bas overdrive??

// Magnus

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Post by borislavgajic »

It is LDR light dependent resistor (for controlling gain)...and it is near LED1 so it acts like optical compressor...

boris

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Post by Magnus290 »

Thanks Boris!

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Post by mictester »

borislavgajic wrote:It is LDR light dependent resistor (for controlling gain)...and it is near LED1 so it acts like optical compressor...

boris
There is also a small error in the circuit diagram: there should be a join at the emitter side of the second transistor as you need to provide bias for the first transistor! See attached corrected version:
Pratabas.jpeg
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Post by Bernardduur »

mictester wrote:
borislavgajic wrote:It is LDR light dependent resistor (for controlling gain)...and it is near LED1 so it acts like optical compressor...

boris
There is also a small error in the circuit diagram: there should be a join at the emitter side of the second transistor as you need to provide bias for the first transistor! See attached corrected version:
Pratabas.jpeg
I'm thinking of modifying this design and re-voicing it for guitar!
Whahaha, sorry! I'll fix the schematic!
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Post by mictester »

Bernardduur wrote:
Whahaha, sorry! I'll fix the schematic!
There's another error - the first switch can't be connected like that. Both circuit inputs must be fed at the same time - the "fuzz" circuit is used to drive the LED to add compression to the overdrive stage. S2 will select between the two available sounds (fuzz and overdrive), but I would change the circuit a bit to allow individual level settings for the two modes. The first switch should just be part of the overall bypass circuit.
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Post by borislavgajic »

No ...I made confusion.......LDR is not for compression function(there is noenvelope detector here).....it is there for GAIN controll.......with one pot you can controll gain of both circuits(and they are switchable :block: )


is this make any sense? :thumbsup
cheers

boris

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Post by mictester »

borislavgajic wrote:No ...I made confusion.......LDR is not for compression function(there is noenvelope detector here).....it is there for GAIN controll.......with one pot you can controll gain of both circuits(and they are switchable :block: )


is this make any sense? :thumbsup
cheers

boris
I see what you mean, but the brightness of the LED could be made to change with the level through the fuzz circuit! It seems a poor way of implementing a dual pot!
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Post by Bernardduur »

The gain control sets the gain of both the sides by simple gain setting of the fuzz (classic) as with varing the LED light on the LDR for the OD side. It is a single potmeter of 1k. The other 1k potmeter in the schematic is a trimpot to set the light of the LED to suit your needs. Another potmter (1k C) was added to control this as an extra.

Bypass switching was left out and was simple TB. The switching you see is for fuzz as OD.
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Post by dune2k »

Bernardduur wrote:And the schematic of the Hjart Muller Bass OD

Image
Hi,
I just did a vero layout for the bass od but haven't built it yet.
I'm not shure whether the pots are wired correctly, but it should work anyway.

Cheers,
dune
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Post by dune2k »

So, the layout is now verified. The one posted above has one little error, so here's the updated vero.

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Post by dune2k »

Forgot to remove something, could an admin/mod delete the post above?

Here's the verified vero layout. (The labels are NOT the same as in the schematic above!)
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hm_13ver.gif
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Post by RnFR »

done! how does it sound?
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Post by dune2k »

Really nice actually (on bass, don't have a guitar around).
Right now I'm experimenting with different diodes. The "stock" diodes, 1N4148, are cool and give a nice variety of sounds (mild OD -> fizzy fuzzy madness).
3 3.6V Zeners in a row are pretty nice (gain at max= fizzy high end and fat bottom, my cab rolls of lots of highs though), just as germaniums (AA113 I think) which don't have that much drive but give a nice warm & mild overdrive.
LEDs sound crappy and the IRF520+1N34A clippers from the Mightier Mouse Mods by beavisaudio aren't worth the effort (and space).
Gonna try germanium trannies and what else I can find tomorrow.

The tone control does what it's supposed to do, but is not that versatile. It's a Big Muff Tonestack, so that's normal. :)

It also holds the bottom end really nice and even adds some, at least with my setup (crappy Peavy 4 string P-Bass w/ Fender "Vintage" PUs).
At moody the say to run it at 12V, but to me it actually sounds better at 9V. The Bass Drive has less headroom, but to me thats fine since the OD sounds better somehow.
Also, right now, I have the OPA in the circuit but the TL071 is just fine. There's not much difference in the sound. I have to try it again though. :)
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Post by Pruttelherrie »

dune2k wrote:Forgot to remove something, could an admin/mod delete the post above?

Here's the verified vero layout. (The labels are NOT the same as in the schematic above!)
I built one over the weekend according to the above v1.3. Works like a charm.
Photo-2016-05-19-18-36-02_5666.JPG
Photo-2016-05-19-18-36-11_5667.JPG
Photo-2016-05-19-18-37-10_5668.JPG

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