Mid-Fi Electronics - Demo Tape Fuzz  [traced]

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Nocentelli
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Post by Nocentelli »

I don't think the taper will cause/reduce any oscillation, I think it's just the design. I used a 100k log pot for treble, there's still plenty of bright on tap but it sounds about right at halfway up which is how I like it.
modman wrote: Let's hope it's not a hit, because soldering up the same pedal everyday, is a sad life. It's that same ole devilish double bind again...

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Post by VanPorter »

Nocentelli wrote:
pinkjimiphoton wrote:nocentelli, is your vero verified yet?
OK, this one is now verified:
Demotape_vero_nocentelli_verified.gif
In my actual build:

I used a C100k pot instead of the 25kB for trim, giving a wider range of lower gain sounds with humbuckers which tend to overload it. I also used log 100k pots for volume and treble, putting the most useful settings closer to noon.
Hello! I'm building this pedal for second time, for a friend, and this time I'll use 1micro electrolitic caps. I can't realize the polarity, could you help me, please?

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Nocentelli
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Post by Nocentelli »

Negative to connected to guitar for the input cap, positive connected to output of the chip (pin 1) for the middle one, and negative connected to trim lugs 1+2 for the gain cap at the top.
modman wrote: Let's hope it's not a hit, because soldering up the same pedal everyday, is a sad life. It's that same ole devilish double bind again...

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lippajad
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Post by lippajad »

is there a list of components somewhere?

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Addy Bart
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Post by Addy Bart »

I built this twice (using the milk fuzz boards at OSHPark) and strange enough, the second build does not squeal like the first when the trim is fully clockwise. I measured the pots on both builds and the first one is 24.8k compared to the second: 23.1k. I tried a 100k pot in there too and it still didn't squeal. I'm wondering what other parts of the schematic I can look at... Could the diode be responsible?

I already tried increasing the 470k resistor in the op amp loop but that made no difference.
Also changed the 100uF cap for the power to 47uF, as is there in the schematic that Doug confirmed to be 100% accurate.

Any ideas on what I can do? I'm making it for a friend who adores the Jesus & Mary Chain and he nearly wet himself when he heard the first build squeal like crazy.

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doug deeper
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Post by doug deeper »

So you want it to squeal?
Try some different op amps, I had a batch of 4558s at one point that squealed in this circuit (I changed to TL072s shortly after).
Shouldn't be hard to find an opamp that would be unhappy in this circuit!

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Addy Bart
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Post by Addy Bart »

Right! Thanks Doug, I'll give that a try.
Been enjoying MMOSS lately too.. Good stuff!

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jgriff1095
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Post by jgriff1095 »

I know this is an old thread but I cant seem to figure out my problem. I can pass signal through this circuit, but the trim pot doesn't do anything. And its definitely not as loud as it should be. I can't find anything missing, or any touching solder joints. Any one have any idea what is causing this?

I'm using this layout https://effectslayouts.blogspot.com/201 ... -fuzz.html

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Post by jrfox92 »

Bear in mind that "trim" isn't a trimpot, just in case you might've gotten that mixed up. Trim is the gain control.
I'd mess around with the values and tapers on it, but it sounds like there are probably connectivity issues there.
That or there are problems with whichever op amp you used.

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Post by garyg »

I've just built one of these on vero and I think it's basically working (bass and treble do what you expect, trim goes from clean to very fuzzy) but there's a kind of raspy noise (not sure of the terminology of fuzz :)) on top of the guitar sound, don't remember hearing it in any demo audio/videos.

It's not a constant noise, very much signal dependent, fades out with the sound but kind of stuttery as it fades.

Any ideas where I should look? I'm guessing the biasing or something?

Thanks.

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Post by Boba7 »

Try some other opamp, ne5532, lf353, op275. Its very much opamp dependant. Let us know what you find!

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Post by Boba7 »

I remember loving an opa2604 in it but its way too expensive an opamp haha!

JohnK found that the best opamp for the circuit is th MC33172 and I really trust his ears.

Otherwise I had good results with a classic ne5532 :)

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Post by garyg »

Thanks guys.

I feel a little foolish as I tried it again tonight with a better amp (ie. a proper guitar amp not my thrown together, workbench 1 watter...) and it sounded a lot smoother straight away... lesson learned there. :) (this is the first pedal I've tried to build since... hell, the early 90s I guess...)

I had a tl072 and ne5532 in my spares box and the ne5532 did seem a little smoother (tl072 I couldn't hear a difference).

So, yeah, sounding good. I think I'll play with the treble pot as that seems pretty much on or off then box it.

Cheers.

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