MXR - Microamp  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
User avatar
salocin
Resistor Ronker
Information
Posts: 333
Joined: 02 Apr 2008, 00:27
Location: Dunedin, NZ
Has thanked: 4 times
Been thanked: 7 times

Post by salocin »

I missed this thread earlier, but going to have to build one now just because Jack put a layout together :thumbsup Nicest part layouts ever!

When are you going to spill the beans on your relay switching Jack?

User avatar
jay42
Information
Posts: 30
Joined: 06 Aug 2010, 00:36
Been thanked: 7 times

Post by jay42 »

dickierex wrote:What are Pauls pet peeves? I've had a Microamp for about 10 years now, and it's been the only pedal to stay on my board in that time - I love it.
If you look at the Buf V, you'll see two 9V batteries for ~twice the clean overhead. You will also see that the pedal is not bypassed. It switches between a unity gain buffer, which helps drive the line, and the gain setting. The 70's version of the microamp switched between boost and a load on the signal. I don't know if the new ones are true bypass.

While I can hear it color the signal a bit, it has the benefit that any coloring is there boost or buffer, so you can adjust it out at the amp. These Buf pedals were/are very poplular with studio guys in LA. Paul didn't have any real marketing reach at the time, so he moved on to other things. He had a series of them, but I don't recall what the other models did.

Try an LF351 if you have one.

User avatar
the3secondrule
Solder Soldier
Information
Posts: 216
Joined: 25 Apr 2010, 05:46
Completed builds: GGG Phase45
Fuzz Factory Clone
Shin Ei Companion Fuzz
EHX LPB
Fuzz Face
Zvex Machine
GGG Green Ringer
woolly mammoth
SHO
Microamp
Noise swash
Phaseur Fleur
Catalinbread SVT
valvecaster
CE2 Chorus
Aquapuss
Has thanked: 24 times
Been thanked: 13 times

Post by the3secondrule »

Hey IvIark -

on your layout where it shows a 22m, i'm guessing this is in fact a 2m2 as per the other schems?
I have used your layout as a bssis to do a vero layout to fit in a 1590a - not verified yet. once I've built it I will post it in this thread

Cheers,

Jeremy
IvIark wrote:Here's a vero layout I did for some axial components I wanted to use:

Image

There seems to be some differences between the schematic I used and the one Browser posted above. I've got 1K and 10M after the input cap, Browser has 10K and 1M, the voltage divider for Vref I have 2 x 100K, Browser has 75K and 100K, mine has a 15uF from the opamp output compared to 22uF.

Is yours based on the current model Microamp Browser?
"Rock music is mostly about moving big black boxes from one side of town to the other in the back of your car."

User avatar
Jack Deville
Resistor Ronker
Information
Posts: 403
Joined: 02 Apr 2009, 06:21
Completed builds: too many. too many.
Location: Portland, OR
Has thanked: 1 time
Been thanked: 86 times
Contact:

Post by Jack Deville »

salocin wrote:I missed this thread earlier, but going to have to build one now just because Jack put a layout together :thumbsup Nicest part layouts ever!

When are you going to spill the beans on your relay switching Jack?
Thank you for the compliment. I'm proud of that MicroAmp layout, and FWIW, it didn't come quickly.
If you use the layout, please post photos. I'd love to see it built up!

On relay systems:
Sadly, I'm not in a position to expose the double-black-magic-voodoo that makes the Click-Less™ system so quiet. Really though, there are only 12 parts. How complicated could it be? :twisted:

As I've stated in prior threads, I have quite a bit of development time invested into my commercial circuits. I try to contribute schematics when I can (see "Favorite Pedals You Built" thread for the most recent). The volume of emails I have received requesting schematics and design assistance, and the other competing products available indicate that exposure of the circuit could potentially hinder/cripple/damage my business; although I think a designer will be hard-pressed to come up with a cleaner, faster, smaller solution. Once I am ready to share them, you can all bet this will be the first stop.
:thumbsup
I'm a "professional."
Buy my products and make me rich.

www.jackdeville.com

User avatar
jb351
Breadboard Brother
Information
Posts: 119
Joined: 14 Jun 2009, 12:27
my favorite amplifier: Traynor
Completed builds: lots
Location: Nova Scotia, Canada
Has thanked: 92 times
Been thanked: 17 times

Post by jb351 »

A couple pics from my vintage Micro Amp. I picked it up used about 14 years ago.

I don't know if I put the socket in and replaced the opamp or someone else did. I don't remember. It seems like something I would have certainly done as I was just getting started and learning about this stuff back then.
Looking at it's guts again make me nostalgic for the bad old days when there was only 2 main sources of content. R.G.'s and Orman's sites. Which took forever to find on the 1 hour of internet time at school per week. Downloading the info on dial up and printing it out on a Dot Matrix printer (I still have some of the printouts). The only main source of parts were places like Mouser and Digi-Key where I had to mail in or phone in the order, the Canadian Dollar was only worth a little more than half of the U.S. dollar so it all cost way too much and I wait forever for the parts to arrive I could try to solder them in with an old wood burning tool. Anderton's book also cost me $50 and took over a month to arrive back then.
Hmm...After writing this I no longer feel so nostalgic.
Attachments
DSCF4955.JPG
DSCF4955.JPG (1.73 MiB) Viewed 6106 times
DSCF4954.JPG
DSCF4954.JPG (1.84 MiB) Viewed 6106 times

User avatar
IvIark
Tube Twister
Information
Posts: 2235
Joined: 01 Jan 2008, 23:59
Location: Manchester UK
Has thanked: 562 times
Been thanked: 586 times
Contact:

Post by IvIark »

Sorry Jeremy only just noticed your post. I used the GGG schematic here:

Image

I did think it was high but who am I to question these things :D so I just left it as shown. I'll change it to 2M2.
the3secondrule wrote:Hey IvIark -

on your layout where it shows a 22m, i'm guessing this is in fact a 2m2 as per the other schems?
I have used your layout as a bssis to do a vero layout to fit in a 1590a - not verified yet. once I've built it I will post it in this thread

Cheers,

Jeremy
"If anyone is a 'genius' for putting jacks in such a pedal in the only spot where they could physically fit, then I assume I too am a genius for correctly inserting my legs into my pants this morning." - candletears7 - TGP

User avatar
IvIark
Tube Twister
Information
Posts: 2235
Joined: 01 Jan 2008, 23:59
Location: Manchester UK
Has thanked: 562 times
Been thanked: 586 times
Contact:

Post by IvIark »

Here's a more compact version I also did which I've corrected the resistor in.
Attachments
MXR Microamp vero layout
MXR Microamp vero layout
MXRMicroamp-smaller.png (24.4 KiB) Viewed 4416 times
"If anyone is a 'genius' for putting jacks in such a pedal in the only spot where they could physically fit, then I assume I too am a genius for correctly inserting my legs into my pants this morning." - candletears7 - TGP

User avatar
earthtonesaudio
Transistor Tuner
Information
Posts: 1244
Joined: 28 Jan 2008, 04:00
Completed builds: Metal Simplex, Fuzz Factory, two Fab Echos-modded, Noisy Cricket, Earth & Space Wah, TS-7-modded, passive xover/splitter box, opamp fuzz
Location: Bloomington, Indiana
Has thanked: 11 times
Been thanked: 75 times

Post by earthtonesaudio »

roseblood11 wrote:The interesting point of this booster design is that the volume is at unity gain when the pot is turned completely ccw. That makes it easy to add a switch there - so you can switch between booster and buffer modes...
Here's something along those lines,

and an improved version.
rocklander wrote:hairsplitting and semantics aren't exactly the same thing though.. we may need two contests for that.

User avatar
the3secondrule
Solder Soldier
Information
Posts: 216
Joined: 25 Apr 2010, 05:46
Completed builds: GGG Phase45
Fuzz Factory Clone
Shin Ei Companion Fuzz
EHX LPB
Fuzz Face
Zvex Machine
GGG Green Ringer
woolly mammoth
SHO
Microamp
Noise swash
Phaseur Fleur
Catalinbread SVT
valvecaster
CE2 Chorus
Aquapuss
Has thanked: 24 times
Been thanked: 13 times

Post by the3secondrule »

IvIark wrote:Here's a more compact version I also did which I've corrected the resistor in.

Having seen a few schems in the last few days, there seems to be quite a few with that 22m resistor... could be right after all-
anyway, this is my *verified* layout for 1590a :thumbsup i built it with th 2.2m, but I may try the 22m for the sake of comparison
micro amp.gif
"Rock music is mostly about moving big black boxes from one side of town to the other in the back of your car."

User avatar
the3secondrule
Solder Soldier
Information
Posts: 216
Joined: 25 Apr 2010, 05:46
Completed builds: GGG Phase45
Fuzz Factory Clone
Shin Ei Companion Fuzz
EHX LPB
Fuzz Face
Zvex Machine
GGG Green Ringer
woolly mammoth
SHO
Microamp
Noise swash
Phaseur Fleur
Catalinbread SVT
valvecaster
CE2 Chorus
Aquapuss
Has thanked: 24 times
Been thanked: 13 times

Post by the3secondrule »

the3secondrule wrote: Having seen a few schems in the last few days, there seems to be quite a few with that 22m resistor... could be right after all-
anyway, this is my *verified* layout for 1590a :thumbsup i built it with th 2.2m, but I may try the 22m for the sake of comparison
micro amp.gif

noticed something interesting today, when i was messing around with my microamp. it seems to oscillate when the volume is at full, like a high pitched whine - but only in bypass, and happens whether i use battery or wall wart. I used my layout as above, and the only sub was a 22uf instead of the 15uf electro...

any thoughts? its not likely im going to be using this at full volume, so its not really a problem, but it'd be good to figure out whats going on here
"Rock music is mostly about moving big black boxes from one side of town to the other in the back of your car."

User avatar
minnow
Breadboard Brother
Information
Posts: 145
Joined: 30 May 2010, 03:51
Has thanked: 27 times
Been thanked: 16 times

Post by minnow »

the3secondrule wrote:
the3secondrule wrote: Having seen a few schems in the last few days, there seems to be quite a few with that 22m resistor... could be right after all-
anyway, this is my *verified* layout for 1590a :thumbsup i built it with th 2.2m, but I may try the 22m for the sake of comparison
micro amp.gif

noticed something interesting today, when i was messing around with my microamp. it seems to oscillate when the volume is at full, like a high pitched whine - but only in bypass, and happens whether i use battery or wall wart. I used my layout as above, and the only sub was a 22uf instead of the 15uf electro...

any thoughts? its not likely im going to be using this at full volume, so its not really a problem, but it'd be good to figure out whats going on here
I've had a somewhat similar issue with the oscillation, though not with the micro amp.
Try to play with your guitar's tone knob - it disappears when I play with mine!!
I am not providing any solution, just adding more questions to the puzzle :slap:

User avatar
the3secondrule
Solder Soldier
Information
Posts: 216
Joined: 25 Apr 2010, 05:46
Completed builds: GGG Phase45
Fuzz Factory Clone
Shin Ei Companion Fuzz
EHX LPB
Fuzz Face
Zvex Machine
GGG Green Ringer
woolly mammoth
SHO
Microamp
Noise swash
Phaseur Fleur
Catalinbread SVT
valvecaster
CE2 Chorus
Aquapuss
Has thanked: 24 times
Been thanked: 13 times

Post by the3secondrule »

minnow wrote: I've had a somewhat similar issue with the oscillation, though not with the micro amp.
Try to play with your guitar's tone knob - it disappears when I play with mine!!
I am not providing any solution, just adding more questions to the puzzle :slap:
Nevermind, i sorted it :slap: grounded the board input on bypass. problem solved :D
"Rock music is mostly about moving big black boxes from one side of town to the other in the back of your car."

User avatar
roseblood11
Tube Twister
Information
Posts: 1887
Joined: 23 Aug 2008, 14:21
Has thanked: 366 times
Been thanked: 313 times

Post by roseblood11 »

Having seen a few schems in the last few days, there seems to be quite a few with that 22m resistor... could be right after all-
a 22M pulldown resistor??!?

User avatar
the3secondrule
Solder Soldier
Information
Posts: 216
Joined: 25 Apr 2010, 05:46
Completed builds: GGG Phase45
Fuzz Factory Clone
Shin Ei Companion Fuzz
EHX LPB
Fuzz Face
Zvex Machine
GGG Green Ringer
woolly mammoth
SHO
Microamp
Noise swash
Phaseur Fleur
Catalinbread SVT
valvecaster
CE2 Chorus
Aquapuss
Has thanked: 24 times
Been thanked: 13 times

Post by the3secondrule »

roseblood11 wrote:
Having seen a few schems in the last few days, there seems to be quite a few with that 22m resistor... could be right after all-
a 22M pulldown resistor??!?
Yeah, i'm really not sure about that one hence the question mark on my layout :D - but it's on the GGG schem that IvIark used, and also on the pcb that Browers posted...

J
"Rock music is mostly about moving big black boxes from one side of town to the other in the back of your car."

User avatar
IvIark
Tube Twister
Information
Posts: 2235
Joined: 01 Jan 2008, 23:59
Location: Manchester UK
Has thanked: 562 times
Been thanked: 586 times
Contact:

Post by IvIark »

Sorry, I somehow managed to miss your post here. Cool layout, and I want to put one of these in a 1590A too because I've got a few sitting around doing nothing and it seems a waste to put this in a 1590B size box. I do love 1590A builds, although to be fair I should say I do love love other people's 1590A builds rather than it being me having to cram things in and show patience and drilling accuracy!) :mrgreen: Still at least this one only has one pot.
the3secondrule wrote:Having seen a few schems in the last few days, there seems to be quite a few with that 22m resistor... could be right after all-
anyway, this is my *verified* layout for 1590a :thumbsup i built it with th 2.2m, but I may try the 22m for the sake of comparison
"If anyone is a 'genius' for putting jacks in such a pedal in the only spot where they could physically fit, then I assume I too am a genius for correctly inserting my legs into my pants this morning." - candletears7 - TGP

User avatar
Setzer-Lynch
Information
Posts: 37
Joined: 18 Nov 2010, 18:58
Has thanked: 2 times

Post by Setzer-Lynch »

Hi all!
I resume this topic because I want to ask you something about this pedal.
I'm a novice with this kind of things, I know I've many things to learn, so I ask you to teach me! :lol:
Therefore, I've build it with this schematic:
http://generalguitargadgets.com/diagram ... amp_sc.gif

Today, when I was trying it, I've noticed that, when I use the clean amp, the volume of the boost was high when the knob was at 12 o'clock but, when I use the distortion of the amp, the volume of the boost wasn't so high.
When I put the max volume, the pedal is fuzzy and noisy.
It's a problem of the pedal? This pedal may work well only on the clean channel? How can I resolve those problems?
Thanks!

P.S. I'm sorry for my bad english, I hope you can understand :)

User avatar
Browser
Information
Posts: 24
Joined: 30 Mar 2009, 16:41

Post by Browser »

Setzer-Lynch wrote:Hi all!
I resume this topic because I want to ask you something about this pedal.
I'm a novice with this kind of things, I know I've many things to learn, so I ask you to teach me! :lol:
Therefore, I've build it with this schematic:
http://generalguitargadgets.com/diagram ... amp_sc.gif

Today, when I was trying it, I've noticed that, when I use the clean amp, the volume of the boost was high when the knob was at 12 o'clock but, when I use the distortion of the amp, the volume of the boost wasn't so high.
When I put the max volume, the pedal is fuzzy and noisy.
It's a problem of the pedal? This pedal may work well only on the clean channel? How can I resolve those problems?
Thanks!

P.S. I'm sorry for my bad english, I hope you can understand :)
Apparently my info is missing perhaps a copyright-based deletion. I posted a schematic and layout for the current version unlike what you have seen. PM

User avatar
Browser
Information
Posts: 24
Joined: 30 Mar 2009, 16:41

Post by Browser »

oops that was me :slap: Still PM if you want it.

User avatar
lukatosh
Solder Soldier
Information
Posts: 196
Joined: 04 Dec 2010, 02:55
Has thanked: 33 times
Been thanked: 186 times

Post by lukatosh »

I built this pedal today but i have a problem... when i press the 3pdt the effect take a time to start working...

What can be wrong?

User avatar
Steven_M
Resistor Ronker
Information
Posts: 386
Joined: 06 Jul 2009, 19:50
Has thanked: 59 times
Been thanked: 35 times

Post by Steven_M »

lukatosh wrote:I built this pedal today but i have a problem... when i press the 3pdt the effect take a time to start working...

What can be wrong?
Bad or backwards cap? Check the orientation.

Post Reply