Boss - ME-5 - Distortion Section

[FloPoeKo]

Hi guys,

can anyone explain the circuit of the distortion in the Boss ME-5? I´d like to mod it, but I´d like to know what does what first instead of soldering by some other guys´ numbers... Which doesn´t mean that I´d not wildly applaude any suggestions...

Cheers!

[FloPoeKo]

First impression: The distortion is far from being detailed, rich and complex. Also, I guess there is too much bass going in, making it really fuzzy at high gain settings on the lower strings. And lastly, it has this strange "pseudo-fixed-wah" quality to it. Any thoughts?

[Dirk_Hendrik]

A quick glance suggests the circuit you're looking at is the DS2 circuit. That means that, other than your own inventions, all mods known to DS2's are a starting point for your ME5.

The Overdrive 2 circuit in the full schematic appears to be an OD2

[FloPoeKo]

A quick glance suggests the circuit you're looking at is the DS2 circuit. That means that, other than your own inventions, all mods known to DS2's are a starting point for your ME5.

The Overdrive 2 circuit in the full schematic appears to be an OD2

Thanks, I´m embarassed for not noticing that...

I already looked into the OD-2. What puzzled me was that a big part of the OD2-Circuit is missing in the ME-5. Is that the turbo-section?
Same seems to apply to the DS-2 the ME-5 (plus there are 2 back-to-back diodes missing from the feedback-path of the compact DS-2). I will take a look into the mods... But again: Thanks for clearing that up...

[Ice-9]

The Boss ME-5 I quite sought after , the effects inside are all from the old vintage schematics of the original pedals CS-2, DS-1, OD-2, RV-3, EQ-1, CE-1, DD-2, BF-2. Any mods to any of these pedals should all apply the ME-5.

[Ice-9]

RTHat is meant to say DS2 not DS1

[Nocentelli]

EQ-1

[Dirk_Hendrik]

The Boss ME-5 I quite sought after , the effects inside are all from the old vintage schematics of the original pedals CS-2, DS-1, OD-2, RV-3, EQ-1, CE-1, DD-2, BF-2. Any mods to any of these pedals should all apply the ME-5.

CS2, RV3, CE-1, DD2, EQ-1 (?? indeed)
err..

Not really
And I did not check the BF2

[Ice-9]

The Boss ME-5 I quite sought after , the effects inside are all from the old vintage schematics of the original pedals CS-2, DS-1, OD-2, RV-3, EQ-1, CE-1, DD-2, BF-2. Any mods to any of these pedals should all apply the ME-5.

CS2, RV3, CE-1, DD2, EQ-1 (?? indeed)
err..

Not really
And I did not check the BF2

Yes Indeed apologies, I should have actually checked the information before posting.

[NegationOfNegation]

Hi guys,

can anyone explain the circuit of the distortion in the Boss ME-5?

Hi,

An overview:

It starts with a little clipping stage (R102, D10, D11) without
preamplification (at least on the screenshot there ist no
preamplification).

After a stage with a low dynamic and asymetrical clipping (Q25)
signal passes an second order 1kHz low pass (Q22, with resonance
peak?) and, in parallel, a bypass. So, via R84 & R85 a midboosted
signal will be sent to a discrete (none integrated) operational
amplifier (Q16, Q14, Q13 and, as a buffer Q10.) This kind of
discrete OA could be found in some BOSS devices like blues
driver or similiar.

OA is used in non-inverting scheme---negative feedback and
amplification depends of the value of one of the resistors
R48-R56. I assume, that 4051 is an binary to parallel-decoder.
That means, looks like, the 3-bit-control DIST-A to DIST-C
controls, which resistor is activated for negative feedback of
the discrete OA. So amplification of OA could be switched from 2
up to 250.

Low cut frequency of discrete OA depends on the value of C16 an
R58---1k and 0,22mu means 700 Hz approx.

The output signal goes via C37 to a standard clipping stage
(R103 and diodes). May be, that Q28 is clipping too, but it
depends of the voltages between uparrow icon and downarrow icon
on your schematic sheet. Don't know, which voltage is on uparrow
icon or on downarrow icon.

After Q26 via a low cut top end will be deminished.

So as main ingredents we have a midboost, an amplification stage
with 700-Hz-lowcut (like in many distortion boxes) and a standard
diode clipping. Distortion could be controlled by a digital signal.

Thats all from me.

Hi guys,

I´d like to mod it, but I´d like to know what does what first
instead of soldering by some other guys´ numbers...
Which doesn´t mean that I´d not wildly applaude any suggestions...

Cheers!

BTW: I.M.H.O it makes absolutelly no sense to tune something
without any idea of problem or goal---think, before you tinker

Hope that helps

Torsten

[Dirk_Hendrik]

Torsten!
Someone who signed up mor than 4 years ago should know by now that a goal is not required. When a device is modded it's, per definition, always better. And because we are musicians (and the designers of musical equipment are, ofcourse, not), w have a far better sense of what's right sounding and all we do will sound better.

[Fender3D]

amen

[FloPoeKo]

Torsten!
Someone who signed up mor than 4 years ago should know by now that a goal is not required. When a device is modded it's, per definition, always better. And because we are musicians (and the designers of musical equipment are, ofcourse, not), w have a far better sense of what's right sounding and all we do will sound better.

Guys, may I kindly refer to post nr. 2 in this thread in which I expressed my dismay over the character of the effect ... My first issue would be the "fixed wah" sound, the second its two-dimensional clipping and the third the somewhat fuzzy-farty sound at high gain levels, which leads to the following ideas and why I asked for what does what:

a) midboost somewhere
b) too much bass somewhere before clipping
c) in which elements does the clipping occur

btw, Torsten, many thanks for the explanation, that gives my a hint where to look...

[EddieTavares]

Guys, may I kindly refer to post nr. 2 in this thread in which I expressed my dismay over the character of the effect ... My first issue would be the "fixed wah" sound, the second its two-dimensional clipping and the third the somewhat fuzzy-farty sound at high gain levels, which leads to the following ideas and why I asked for what does what:

a) midboost somewhere
b) too much bass somewhere before clipping
c) in which elements does the clipping occur

btw, Torsten, many thanks for the explanation, that gives my a hint where to look...

FloPoeKo

a) midboost somewhere

If you consider the schematic of DS2 you can realize that there is a mid boost just after the input and a mid scoop next to the tone control. They work together when the turbo is set on.

This arrange (Mid Boost -> Distort -> Mid Scoop) intend improve the distortion definition by reducing the intermodulation.

But in the ME5 there is a mid boost but there is no mid scoop. Why?

I don't know why they cutout that portion of this circuit but it makes the "fixed wah" on, maybe the engineers thought that the user could cut this mid excess in the eq. I think that someone who design the blocks told to the technician to cut the tones out and he does it! Let us consider that the Q12 and Q13 in DS2 is in exactly portion of the circuit of Q26 and Q28 in ME5.

Possible solution:
1 - Change the values of R84 and 85 control the amount of "wah" that goes to the effect, you can change this two resistor with a 20k trimpot.
2 - Implement the mid scoop in a small board and replace C41 with the mid scoop, this is not necessary if you cut the mids on eq but if you want to keep the eq more flat so try it.

Mid scoop.png (2.43 KiB) Viewed 2013 times

b) too much bass somewhere before clipping
- Change C36 and C26 to smaller values, 10n would be fine

c) in which elements does the clipping occur
- Mainly D12 and D13 but if you use the compressor as a booster you can get some overdrive in D10 an D11.

[roseblood11]

I started a similar thread in german here:
http://musikding.rocks/wbb/index.php/Th ... iterungen/

Is it true that "NegationOfNegation" translates to "Graue_Theorie" in german?