MXR - Microamp  [schematic]

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

Re: MXR - Microamp

Postby lukatosh » 29 Apr 2012, 01:39

i've just complete the GGG micro amp... and the same thing :(

the effect takes a little time to act when I push the 3pdt...

i've used for the 15uF cap a 10 paralel with a 4.7 cap and for the 22M i used two 10M resistors in series...

i've changed the 3pdt and the same thing... what can be wrong?

i'm testing it with an electroacustic guitar!
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Re: MXR - Microamp

Postby Browser » 30 Apr 2012, 07:04

Same schematic and yes it is still correct.
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Re: MXR - Microamp

Postby daniel.t » 23 May 2012, 08:42

Browser wrote:Same schematic and yes it is still correct.


Made an account to see your schematic and also to thank you. Cheers man, cant wait to get this started. My project idea is to make this: http://www.dolphinmusic.co.uk/shop_imag ... 746344.jpg
starting with the MXR =D wish me luck
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Re: MXR - Microamp

Postby daniel.t » 23 May 2012, 10:08

^^^ Before anyone tells me it cant be done.. i realise this. but i can make the analog ones. Anybody know of some way to simulate a pitch/octave change without a microprocessor?
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MXR - Microamp, room for improvments?

Postby matt239 » 15 Feb 2014, 18:55

SO this is a classic circuit, and probably some other circuits are based on it.
It seems to work OK, but it's inexpensive/mass produced and has been around for a long while,
(Not that that's bad, but sometimes manufacturers make compromises that a d.i.y.-er might have the luxury to avoid, say spending $1 more on parts, etc..)
(and also perhaps the community has learned some things in 30 years.. and sometimes silly designs persist just because..)
;
Do any of you see any obvious problems with the circuit, or obvious room for improvement? Mods?
(Or perhaps subtle, less-than obvious ones?)

Can we, for instance, achieve lower noise?
Or do we think this is pretty much optimized?
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Re: MXR - Microamp

Postby Nocentelli » 15 Feb 2014, 20:08

I think the Mr Black Boost Tiger is an update on the Microamp design: viewtopic.php?f=7&t=22021&hilit=boost+tiger
brownwhopping wrote:How can I learn by reading threads an making circuits, when some day I can see a lawsuit or somebody beat me in the face for that?

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Re: MXR - Microamp

Postby Jack Deville » 15 Feb 2014, 21:00

Kinda but not really.
The Boost Tiger is an non-inverting opamp circuit, but that's kinda where the similarities begin to drift apart. It is a great lil low-cost, and highly effective circuit, at the same time it's nothing new under the sun. Build one up for yourself! I provided our schematic to prevent confusion.
I'm a "professional."
Buy my products and make me rich.

www.jackdeville.com

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Re: MXR - Microamp

Postby Bill_Mountain » 16 Feb 2014, 00:42

Well MXR just updated it with an eq. I love mine stock but I wish it went below unity gain. That would require redesign though.
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Re: MXR - Microamp

Postby drewl » 19 Feb 2014, 17:57

With good components and tidy layout, the one I built is very quiet.

Since it's very similiar to the Distortion +, I made it switchable between the two so it's two pedals in one.

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Re: MXR - Microamp

Postby caspercody » 29 Mar 2014, 03:46

Is there a vero for this in stereo?

Is this basically the same principle as their MXR headphone amp?

Thanks
Rob
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Re: MXR - Microamp

Postby Bernardduur » 19 Nov 2014, 20:45

Browser wrote:Same schematic and yes it is still correct.


I just got a rev B version of this pedal that is close to the schematic; only the 1M to Vref is a 10M resistor. IC's are the same. It sounds absolutely great, although the potmeter is shot :)
'No more....... loud music.......'
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Re: MXR - Microamp

Postby Karlaucas » 14 Jan 2015, 13:04

hello everyone. I have a problem with my Microamp. I built the compact circuit IvIark with all components in its exact value. Sounds great but the problem is that with Volume Pot turned to 0 the volume increases several Db. I have seen on video demos should not increase the volume. What could be the problem? Solders are clean, there is no connection between tracks and everything works. Help !! [smilie=a_hrm.gif]
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Re: MXR - Microamp

Postby Duckman » 14 Jan 2015, 18:32

Hi! Welcome here!... where all your doubts will grow eventually , but in a friendly environment :lol:
Your question is not clear enough to me. At first, looks like your pot is working in reverse, but I'm not sure... have you 0 volume at some point?
Check this out: http://www.electrosmash.com/mxr-microamp
no matter the position of the pot, the bridged pins must be 1 and 2, so when the pot is @"10", you have the less resistance (0k) and, inversely, when you pot is @"0", you have the maximum resistance (500k)
Hope it helps, at least, for a start :thumbsup
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Re: MXR - Microamp

Postby balokker88 » 26 May 2016, 02:06

Referring back to the OP's desire to get less than unity gain from his Micro Amp, I found an easy way to get a large attenuation at full CCW on the volume knob. Not silent, but many DBs lower. I put a 180 ohm resistor across R10, the 10k resistor on the output that runs to ground.
I now get unity just past 3 oclock, and still a large boost after that.
This is useful to me in the effects loop as a master volume for the amp. With a large 1.5" knob you can dial with your foot.
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Re: MXR - Microamp

Postby caspercody » 13 Nov 2018, 16:58

Does anyone have information on the Plus version? What type of tone stack did they use?
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