Author Topic: Mangler build with pregain  (Read 4881 times)

sgmezei

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Mangler build with pregain
« on: October 08, 2011, 07:09:42 PM »
Here is the Mangler I built. Can't wait to compare it with the Zygote and other fuzz boxes I have built. Running it with a road rage with some Small Bear transistors.

Thanks to aestoval for tipping me off to the pre gain mod. I realize this is built in to the zygote but I didn't at the time.

nzCdog

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Re: Mangler build with pregain
« Reply #1 on: October 09, 2011, 12:20:08 AM »
Friggin sweet looking pedal man... I love the look of this one

Bluestrat

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Re: Mangler build with pregain
« Reply #2 on: October 09, 2011, 09:36:29 AM »
Here is the Mangler I built.
Thanks to aestoval for tipping me off to the pre gain mod.

Cool looking pedal. I just built a mangler and think the pre-gain would be a great addition. How was that accomplished? Thanks!

bigmufffuzzwizz

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Re: Mangler build with pregain
« Reply #3 on: October 09, 2011, 11:29:08 AM »
You must have a nice fuzz arsenal by now  :)
That is one huge freakin knob..!
Owner and operator of Magic Pedals

sgmezei

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Re: Mangler build with pregain
« Reply #4 on: October 09, 2011, 10:56:51 PM »
Bluestrat

I got the idea from Aestoval on the thread here:

http://www.madbeanpedals.com/forum/index.php?topic=2782.0

Bean also has the same idea on his Zygote build. Check out the 50kb "strain" knob/pot on the build document. I used the idea from fuzz central but most of the pots rotation is useless so I hope to find a better value down the road.

Bluestrat

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Re: Mangler build with pregain
« Reply #5 on: October 10, 2011, 07:22:01 AM »
Bluestrat

I got the idea from Aestoval on the thread here:

http://www.madbeanpedals.com/forum/index.php?topic=2782.0
Hey, thanks for the response. I might give this a shot. Did you use the small resistor and cap before the pot as indicated on the Zygote pdf? I wonder if that would spread out the sweep of the pot. I'm also getting some RF interference when I turn down the guitar volume knob and I wonder if those two items would help with that as well.

sgmezei

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Re: Mangler build with pregain
« Reply #6 on: October 10, 2011, 09:30:19 AM »
Hmmmm I am not sure. I will have to line up my zygote and mangler and see. Maybe some of the veterans will chime in with some info.

JakeFuzz

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Re: Mangler build with pregain
« Reply #7 on: October 10, 2011, 10:12:10 AM »
Bluestrat

I got the idea from Aestoval on the thread here:

http://www.madbeanpedals.com/forum/index.php?topic=2782.0
Hey, thanks for the response. I might give this a shot. Did you use the small resistor and cap before the pot as indicated on the Zygote pdf? I wonder if that would spread out the sweep of the pot. I'm also getting some RF interference when I turn down the guitar volume knob and I wonder if those two items would help with that as well.

Is it RF interference or self oscillation (like a high pitch whine?). Self oscillation is common and you can do a few things to stop it. Try a small (100 ohm) resistor on the emitter of Q1 or a small capacitor (50-100pf) on Q2 from the collector to the base. 

Bluestrat

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Re: Mangler build with pregain
« Reply #8 on: October 10, 2011, 11:06:55 AM »


Is it RF interference or self oscillation (like a high pitch whine?). Self oscillation is common and you can do a few things to stop it. Try a small (100 ohm) resistor on the emitter of Q1 or a small capacitor (50-100pf) on Q2 from the collector to the base. 
[/quote]

Hi, Jakefuzz. Definitely RF, a really weird old music radio station, happens with a few of my other pedals as well.
Seems to vary depending on which of my strats I use. I have one with really low output Lollars and that gets the best reception :o Both guitars are well shielded. I have read that using a small cap on the input might help. I'm using an AB switch at the front of my effects and that seems like a good place to experiment. Any other suggestions?
 
The Mangler sounds great BTW. Really happy with it.

JakeFuzz

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Re: Mangler build with pregain
« Reply #9 on: October 10, 2011, 11:56:20 PM »
Hmm yeah that's strange. I have heard that coming from an old treble booster I once had. You are going to want filter out only very high frequencies so I would think a really small cap to ground on maybe the input would be a good experiment to try.

sgmezei

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Re: Mangler build with pregain
« Reply #10 on: October 11, 2011, 12:25:03 AM »
For RF interference I know there is a 68k resistor right at the input jack on most amps. Well the two fenders I have built both have them there and that is what I have read they are for.

k.rock!

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Re: Mangler build with pregain
« Reply #11 on: October 11, 2011, 09:11:14 AM »
You need an RC filter (Resistor/Cap) in order to filter out those unwanted frequencies. Most pedals already have a resistor in series with the input, if not, add a small resistor like Paul suggested (100Ohms) and then by just adding a 100pF cap from input to ground, it should help you out. Tie one leg from tip and the other to sleeve (If I'm wrong, someone please correct me :) I'm merely going with my instincts here haha)

If you would like to read more about electronic filters, here's a link: http://en.wikipedia.org/wiki/Electronic_filter

:) Great pedal btw! I love how it looks, good job!

-Kaleb
« Last Edit: October 11, 2011, 09:20:41 AM by k.rock! »

k.rock!

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Re: Mangler build with pregain
« Reply #12 on: October 11, 2011, 09:31:16 AM »
Actually...now that I think more about it...your guitar is already acting like the resistance in series with the input (you did say that it happens when the volume is rolled off...) so you only need a small cap from input to ground on your pedal. (I think!) haha

-Kaleb

JakeFuzz

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Re: Mangler build with pregain
« Reply #13 on: October 11, 2011, 09:38:01 AM »
You can look at the formula for the complex impedance of a capacitor Z=1/(JwC) and select a capacitor on the input that will give you a cutoff frequency above the acoustic range (20Khz=200001/s). What you are doing by adding the cap from the input to ground is just rerouting the very high (unwanted) frequency part of your input signal with a lower path of resistance to ground before it is amplified and fuzzed by your Mangler.

You can plot this impedance as a function of frequency and change the capacitance in something like excel (or if you want to go crazy you can do a 3d surface in matlab!). What you would be looking for is an appreciable drop in Z around 20Khz (remember w is in radians/second). Too far into the audible range and you are cutting off your high end. Or you can just start with really low value capacitor on the input jack and just start adding them in parallel until the noise goes away  :D

You don't really don't want to use and RC filter because adding a resistor in series (the low pass configuration) will change the input impedance of your FF and we all know what happens when you do that... (like the pre-gain knob).  

k.rock!

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Re: Mangler build with pregain
« Reply #14 on: October 11, 2011, 10:18:38 AM »
You're the man Paul!  :D

Thank you for sharing your knowledge with us

-Kaleb