MXR Microamp Vero Debug Weird Impedence

Started by vmazz38, July 21, 2014, 06:21:56 PM

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vmazz38

Hello All, Long time since I sought out help here, :-X hope someone might have some guidance. I built a Microamp on vero per fixed layout . It works but sounds muffled even used after all overdrive pedals etc. When i put it in the effects loop of my amp it sounds good/pretty transparent just a bit loud( usable  all the way down to half way). This made me think it was an input impedence issue. I know the micraomp is supposed to have a very high input impedence. Which helps it retain highs? WHen  i test on the vero it seems to be giving me off readings, where ther is a 22m resistor to ground  I get .3 ohms which spounds like something is grounded that shouldnt be. Any tips on testing input impedence on vero layout? I will try to link a pic of the layout. Here is a link im using the fixed one on bottom
http://www.diystompboxes.com/smfforum/index.php?topic=60733.0
Stompboxes are great , they usually can't kill ya like a tube amp!

duck_arse

the quickest test would be to lift one end of the 22M, see if the ".3 ohms" goes any higher. otherwise, you are looking for a solder-bridge short, or a vero-cut whisker. if you go to the "what to do when it doesn't work" page, follow instructions, come back with answers.
You hold the small basket while I strain the gnat.

vmazz38

DEbugging Checklist
1.was working briefly, tightened up bottom plate and then it went back to sounding muffled again. It worked ok in the effects loop to boost signal clean. In fornt of the amp it it muffled distorted.
2.Micro Amp
3.http://www.diystompboxes.com/smfforum/index.php?topic=60733.0
4.Slight mods to circuit? Trimput in place of 10k resistor in output
5.IC is a nte 857m equivalent to TL071
6.polartiy reverse?-NO

IC1 NTE 857m IC voltages DC

p1-.147
p2-4
p3-1.6
p4-0
p5-.147
p6-4.1
p7-8.8
p8-.02


Zener diode- Band side 8.8 other 9.4

Any suggestions are greatly appreciated :icon_confused:
Stompboxes are great , they usually can't kill ya like a tube amp!

duck_arse

Quote from: vmazz38 on July 22, 2014, 05:12:23 PM
DEbugging Checklist
1.was working briefly, tightened up bottom plate and then it went back to sounding muffled again.

so, did you test it working outta the box and only then install in box and screw down lid, to find it now muffled? or did you not test at all until in the box?

do you have it out of the box now, and it is producing those listed voltages? when you say "the fixed one on bottom"

is it this one? can you measure the voltage at the 100k//100k//10M please? and the cut under the input cap, is good/not missed?

and the next question, can we see photos of your work?

You hold the small basket while I strain the gnat.