MXR - Microamp [schematic]
- RnFR
- Old Solderhand
Information
thanks for adding that! i'm surprised we didn't have that circuit covered already.
"You've converted me to Cubic thinking. Where do I sign up for the newsletter? I need to learn more about how I can break free from ONEism Death Math." - Soulsonic
Blog-APOCALYPSE AUDIO
Blog-APOCALYPSE AUDIO
- lolbou
- Old Solderhand
Might be because it's readily available everywhere else. But now it's here indeed!!RnFR wrote:i'm surprised we didn't have that circuit covered already
I like this booster (built two from tonepad's layout)...
- Are you a mod or a rocker?
- Uh, no, I'm a mocker.
- Uh, no, I'm a mocker.
- IvIark
- Tube Twister
Information
Here's a vero layout I did for some axial components I wanted to use:
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?
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?
"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
- okgb
- Diode Debunker
It is a little different but you may want to check out the
CAE / MXR schemo in the booster thread in this section
viewtopic.php?f=1&t=10060
CAE / MXR schemo in the booster thread in this section
viewtopic.php?f=1&t=10060
- Attachments
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- boost.jpg (32.29 KiB) Viewed 7125 times
Bought it new last year from Musicians Fiend. I pulled the resistors to verify check values. Busted a lead because they are paper-thin.IvIark wrote:Is yours based on the current model Microamp Browser?
This is all I saved if you want the actual layout:
Purple is top, blue is solderside
@ IvIark I left out the zero but the input cap is 0.1uF just in case.
- IvIark
- Tube Twister
Information
Cool thanks for that. They make small changes like this from time to time, so I wondered if yours was the modern version schematic and the one I had was older, and that seems to be the case.
"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
Information
- Posts: 2
- Joined: 11 Aug 2010, 07:20
I changed the op-amp in my microamp to a JRC4558.Sounds a lot better know.
- Jack Deville
- Resistor Ronker
Information
Here'a a layout I knocked up for dual opamps.
Total PCB size: 2" x 1.2" Layout is unverified.
Total PCB size: 2" x 1.2" Layout is unverified.
- Attachments
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- Schematic
- ma_scheme.png (10.71 KiB) Viewed 6957 times
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- Parts layout
- ma_layout.png (4.41 KiB) Viewed 6957 times
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- Transfer
- ma_transfer.png (4.34 KiB) Viewed 6957 times
- marshmellow
- Cap Cooler
Two things:Jack Deville wrote:Here'a a layout I knocked up for dual opamps.
Total PCB size: 2" x 1.2" Layout is unverified.
- The unused opamp will be happier, if you tie it to VCC/2 instead of ground. Here and here is why.
- You could use it to buffer VCC/2 for the main circuit by configuring it as a voltage follower and then connect the output to R2. Still the same parts count, but improved.
- Jack Deville
- Resistor Ronker
Information
Doh.
You're right. So much for that pretty tracking, eh?
Thank you for catching that, marshmellow.
Here is a quick and dirty revision.
You're right. So much for that pretty tracking, eh?
Thank you for catching that, marshmellow.
Here is a quick and dirty revision.
- Attachments
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- Rev. B Transfer
- ma_rev_b.png (4.82 KiB) Viewed 6697 times
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- Rev. B Scheme
- ma_rev_b_scheme.png (11.01 KiB) Viewed 6697 times
- roseblood11
- Tube Twister
Hi,
i´d recommend to use a better IC (OPA134) and a 18V power supply, it really improves the sound and the headroom.
Or use a voltage doubler:
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...
The Micro Amp is one of my ugliest designs:
http://forum.musikding.de/cpg/albums/us ... design.jpg
i´d recommend to use a better IC (OPA134) and a 18V power supply, it really improves the sound and the headroom.
Or use a voltage doubler:
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...
The Micro Amp is one of my ugliest designs:
http://forum.musikding.de/cpg/albums/us ... design.jpg
- minnow
- Breadboard Brother
Tonepad's got a couple of MicroAmp layouts.
I'm interested in the dual microamp (i'd like to have stereo out) and I have a question.
How should I wire the input signals? - can I just solder two wires to the input jack, each end to IN1 and IN2 respectively?
Or should I feed the signal into a splitter first (like the AMZ JFET Splitter) before soldering onto the FX board?
I'm interested in the dual microamp (i'd like to have stereo out) and I have a question.
How should I wire the input signals? - can I just solder two wires to the input jack, each end to IN1 and IN2 respectively?
Or should I feed the signal into a splitter first (like the AMZ JFET Splitter) before soldering onto the FX board?
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. I just made one from a GGG board, and in my initial testing it sounded great, too. I noticed it spec'd a TL061 IC, whereas the original had a UA741CP. I've only briefly compared them, but they seemed to be very very similar. Considering they both seem to be general purpose opamps, I guess this should be expected. Does anyone have any info regarding the differences in these? My limited research (and knowledge on the subject) seems to indicate a better slew rate on the 061 - was this maybe the reason for this chip rather than the 741? Does anyone have a more recent model of Microamp, and does it have a different IC now?jay42 wrote:I only post this because Paul Rivera's set of pet peeves about the MicroAmp are evident from the Buf series he produced in the late 70's. Before the gig at Fender he was doing all sorts of things to make a living. Modifying MXR boxes was one of them.