MXR - Custom Audio Electronics - Boost/Overdrive MC-402  [schematic]

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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402

Postby analogguru » 27 Jul 2010, 17:28

Gila_Crisis wrote:this is another schem of the boost section, it comes from an italian forum.
the guy who traced it, reverse-engineered it from the MC401 Boost-Linedriver and it's verified!
oh well forget the flip-flop bypass section an build it with a normal true-bypass
the boost pot is a 100k lin, and R12 100k


Insane construction if it is really using a 1k/1k bias divider instead of using the second half of the op-amp as a buffer with a 100k/100k bias-divider for less overall current consumption (4mA only through the bias divider itself).

BTW, the schematic can´t be verified, only have a look at the wrong Led-orientation (beside others).

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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402

Postby ryanuk » 28 Jul 2010, 08:30

Gila_Crisis wrote:this is another schem of the boost section, it comes from an italian forum.
the guy who traced it, reverse-engineered it from the MC401 Boost-Linedriver and it's verified!
oh well forget the flip-flop bypass section an build it with a normal true-bypass
the boost pot is a 100k lin, and R12 100k


Could some explain the switching for this schem - I'm interested to know howit operates. For starters wheres the switch? What type of switch is it?

RyUK

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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402

Postby Dirk_Hendrik » 28 Jul 2010, 11:29

+1.
Don't have a clue how those FET's should switch between in and out and have even trouble understanding which terminal is the Gate, source and drain. I can hardly imagine that schematic is verified as working if it includes the switching.
Sorry. Plain out of planes.

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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402

Postby ericsabbath » 29 Oct 2010, 07:55

any news on the overdrive section schematics?

any tips on how to make the overdrive section smoother and a bit more middy (like a screamer)?
I love this pedal as a booster in both sections, but the overdrive sounds more like a distortion pedal
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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402

Postby okgb » 29 Oct 2010, 15:29

I don't think anyone feels it's worth the time to trace it
is it just an Dist + ? or worse , diodes to ground type
look at an ocd style conversion maybe
I agree , i like the clean boost section , but the dist side
is unusable that i gotta get rid of the one i have
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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402

Postby Dirk_Hendrik » 29 Oct 2010, 17:21

okgb wrote:I don't think anyone feels it's worth the time to trace it
is it just an Dist + ? or worse , diodes to ground type


Isn't a Dist+ a diodes to gnd type ? ;)

But yes, I agree. Not worth the bother. :mrgreen:
Sorry. Plain out of planes.

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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402

Postby okgb » 29 Oct 2010, 19:06

I meant or worse then an dist+ which IS a diodes to ground type
i got the guts if anyone wants a go
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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402

Postby Bill_Mountain » 23 May 2012, 14:08

Sorry to bump but...

This thread is relevant to my interests because I’m looking to build a boost into a D+ pedal. If that’s really what this is I can save myself some time and energy.
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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402

Postby okgb » 23 May 2012, 14:17

Bradshaw had responded to ONE email from me , claiming it was capable of sounding good , [ curiously he c.c the his response to someone at dunlop - i think ]
you should be able to find one used for a reasonable deal , [ I have one that i started to socket the I.C. to try others in it ] someone had claimed being able to
get a reasonable santana sound , but you know neck pick up with allot of gain homoginizes anything , most other can't find a satisfying sound from it , I do like
the clean boost though
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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402

Postby Bill_Mountain » 29 May 2012, 17:38

Just tried one.

It was terrible. It seems like the boost is after the overdrive channel???

And the overdrive tone was :slap: What were they thinking? They could have poached one of the many successful MXR designs. That boost was nice and clean though.

I had so much hope for this. I didn't want to believe any of the reviews. :(
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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402

Postby mikebud » 07 Sep 2012, 00:18

I agree, more research is needed into this pedal.
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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402

Postby roseblood11 » 07 Sep 2012, 08:45

Why? The boost section is the same as in the MC-401, which was retraced in another thread. And the overdrive is just crap...
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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402

Postby mikebud » 07 Sep 2012, 20:20

roseblood11 wrote:Why? The boost section is the same as in the MC-401, which was retraced in another thread. And the overdrive is just crap...

Why in order to make it better that is why.

I want somebody to mod this one, it just looks so cool, and is excellent build quality (at least exteriorly), like true bypass, upgrade components to better caps (if any) etc.

I'm not sure though, really, I'm not that technical in this department.

But the distortion is unique, not like others. If it could just be made cleaner it would be far more useful, better tone frequencies/cutoff, better response? In some cases it almost sounds like a speaker-blown effect.
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Re: MXR MC-401 CAE Boost / Line Driver Pedal ?

Postby Lorenzo-m05 » 21 Feb 2015, 08:17

Steven_M wrote:[ Image ]


Hi, I'm sorry for this necroposting, but could someone say me the value of C12 and C10 C11 C18? (in the link above)

Thank you in advance for your kindly replies.
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Re: MXR MC-401 CAE Boost / Line Driver Pedal ?

Postby giudis » 10 Nov 2016, 14:51

Lorenzo-m05 wrote:
Steven_M wrote:[ Image ]


Hi, I'm sorry for this necroposting, but could someone say me the value of C12 and C10 C11 C18? (in the link above)

Thank you in advance for your kindly replies.




They are all 47nF :D
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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402

Postby Victor Nery » 12 Apr 2018, 01:37

Greetings,

I've got one of these and had a chance to mess around with it. The overdrive section has a blatting sound problem, so when trying to fix it, I took the opportunity to trace the circuit (actually part of it till now). [img][https://lh3.googleusercontent.com/proxy/Y9m3HKRz7RO-UQiuctJfeBC6oOciaOzvj2JTPVkrUpRG9beyriXHPF-zDzpWzNLImHpFrmilccT0IzMx4TqY8eBfWppwcExilu7Igrf0ow=w540-h960-p-k-rw/img]

Following the signal with no power supply connected there's is no blatting sound, signal passes as it should (R2/R3 connection) but when I insert the power supply it starts blatting from the very input till a almost cracking sound at this point. Sits someone have any clue of what is happening? Thanks in advance.
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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402

Postby Victor Nery » 12 Apr 2018, 01:54

Sorry, I don't know how to upload the images here. Here's the link for download: https://www.4shared.com/photo/ch79All5ei/402.html# I removed the fets that connect to the input and output. Problem remains the same as described. Here are the voltages. My power supply has an output of 7.98V.

1 - 2,76V
2 - 2.80V
3 - 2,53V
4 - 0V
5 - 2,53V
6 - 2,64V
7 - 2,90V
8 - 5,37V (that's the same as measured after R1).

Thanks.
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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402

Postby alexradium » 12 Apr 2018, 07:07

The overdrive in reality is a fuzz, made with opamp with a starving supply to imitate a dying battery.
Values look appropriate for the circuit, you could swap the opamp with a good one to see if it changes.

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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402

Postby Victor Nery » 12 Apr 2018, 12:13

I've already tried other opamps (TL072 and NE5532). I shorted R1 (470r in series with power supply) and got the same problem. I've also made sure to disconnect all the FETs (removed them) from the signal so they're not the cause. The signal with no power supply connected is strong as it should till it gets to the opamp. The thing is when I connect the power supply, the signal gets blatty at the first input (even when I tried a jumper instead of R1). Thanks.
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Re: MXR - Custom Audio Electronics - Boost/Overdrive MC-402  [schematic]

Postby Victor Nery » 12 Apr 2018, 15:39

I just finished the drive side of the circuit. Here's the schematic so far. Why can't I edit my posts so I don't flood the topic with updates?
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