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PostPosted: Sat Aug 20, 2011 10:00 am 
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Anyone know how to boost the volume output on the Leeds Fuzz? I need a much higher output. Can I just remove one of the resistors?
Thanks.


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PostPosted: Sun Aug 21, 2011 5:14 am 
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Pull the germanium diodes. Or, add a resistor in series with the diodes (ie 20k). The diodes kill the signal level. I don't notice much difference with/ without the diodes other than a huge increase in output level.

I ended up putting a 20k resistor in series with one of the diodes. I liked the asymetrical clipping which provided a bit more "crispness" and the increase in the output level.


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PostPosted: Sun Aug 21, 2011 9:44 am 
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Mandarine, I thought the germanium diodes were supposed to be a big part of the "fuzz" sound. I found the below on the internet, have you heard of this:

"If you have a circuit like the Jordan Bosstone or MXR Distortion+ or DOD overdrive 250 and others that have a diode pair creating the distortion at the end of a circuit, you can increase the output level of the circuit with the expense of a little distortion by putting two diodes where there were one. So instead of 2 diodes, you now have four.

This mod will increase the output level with the expense of a little distortion.

More diodes in series will also give you a wider range of clean to distorted sound but less distortion when the circuit is maxxed. Something to note is that a germanium diode "clips"at around .3V and a silicon diode "clips" around .6V so you need roughly 2 germanium diodes to equal one silicon diode. A good multimeter will allow you to measure the diode and find out what the forward voltage is. LEDs will clip even later and give you more range of clean to distortion.


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PostPosted: Mon Aug 22, 2011 11:56 am 
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Jimmy:

Thanks for that info. A moderators opinion would be helpful for more expertise.

All I can speak of is from my own experience with this beast. When I first built it, I had an intermittent output level. The output would drop about half after a few minutes. So I began the troubleshooting and researching "project". ( actually like this part about building pedals.)

Standard stuff, checking voltages, solder joints, etc. When I removed the diodes WOW!. Volume increased dramatically. I put sockets in the PCB where the diodes go and found really very little difference in tone with or without diodes. Just a lot more output volume. With the sockets in, it was easy to experiment with different diode combinations. Silicon gives much more output as well. I am no electronics guru but I guess this is due to the higher signal voltage the diode passes before shorting signal to ground. Silicon is ~ .5 where germanium is ~.2. So you are passing twice as much signal to the output gain stage before the diode shorts the signal to ground. It seems to me there is so much saturation from the transistor gain stages before it even hits the diodes, that their tonal effect is minimized.

I tried one silicon and 1 germanium diode which is nice. I also put a potentiometer in series with one of the germanium pair and "tweaked" the value until I liked the result. I think it ended up being ~ 20k Ohms. This gave me the output I wanted and hit a sweet spot tonally. Unity gain through the pedal is about 11:00 on the Balance knob now where before it was near maximum.

The other issue I had was trying to get the transistor voltages to what was considered "normal" from various builders and internet posters. So I bought a new set of transistors from Small Bear that had gains between 170 ~ 200 ( as opposed to the originals which were in the 300 range for gain). This didn't have much effect. I finally came across a respected builder of a Superfuzz clone, and looked at their schematic. Particularly the octave circuit. BINGo! When Univox inserted a trimmer in this part of the later circuit design , it just added to the resistance of the octave pair's bases to ground. The trimmer added an additional 5k Ohms! Maybe not a big deal, but when I swapped the 22k resistors for 17k resistors (well 16.9 metal film) the transistor voltages got to where It seems they should be. Using a balanced gain transistor pair here also brought the octave out much more. It also eliminated the harsh compression I was getting with higher output pickups and increased the sensitivity of the Expander knob.

I'm not sure if this is your issue or not, but if it isn't much trouble it is fun to experiment with. I would be very interested in your opinion of the tone of the Superfuzz with and without diodes. I have for all intent and purposes a cloned Superfuzz circuit with the addition of a 20k resistor in series with one of the clipping diodes causing asymmetry. It sounds really good to me ;-)


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PostPosted: Mon Aug 22, 2011 1:27 pm 
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Take a look at the schematic in the instructions: http://buildyourownclone.com/leedsinstructions.pdf.

The output section of the pedal is a BJT common emitter amplifier. The resistors that set the DC levels (bias) and control the gain of that amplifier are R26, 27, 28, and R29.

I ran a simulation with a 2n3904 transistor that should be fairly similar and it biases out to around 4.5V on the collector which is pretty much what you would shoot for. The gain is around 13.4dB.

You can increase the gain to around 23dB to boost the output more. Change R26 to 1meg, R27 to 150k and R28 to 470ohms.

That shouldn't change the characteristic of the fuzz like changing the diodes would.

Boosting that much might start clipping the output which you may or may not like.

Then I would replace R30 (100k) with a 100k volume pot. Remove the R30 resistor, connect lugs 1 and 3 where it was, lug 2 is the new output.


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PostPosted: Mon Aug 22, 2011 5:20 pm 
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Excellent well-detailed info all around. I'm getting to work experimenting and I'll post when I have some results. Thanks to both of you.


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PostPosted: Sat Apr 14, 2012 1:54 pm 
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Hi All ---- new to BYOC & just finished first build of LeedsFuzz - and actually worked first time?! genius. something to be said for followin directions, huh. great results.

I read mandarines' info re; tweakin/boosting the octave slightly, but I'm not too clever on electronic terms - like the 'balanced gain transistor pair' bit. Level is fine fr me - I'd like to bring the octave out some more (unless the level tweak does affect the octave?). I'm curious if all the 22k resistors need changing to 17k? and i'm not sure where to add a trimmer to change the 'resistance of the octave pair's bases to ground' on the board? i can see the 22k resistors but stumped on the trimmer bit....

guess i need to know what parts to put on a shopping list for the electrical store...and where they should go on the board. I apprieciate. yr patience in advance!

LeedsPedal pedal rocks - thnx to all @ BYOC for starting a new addiction.

any help much appreciated.

cheers JL.


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PostPosted: Tue Apr 17, 2012 11:54 pm 
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I'm wondering the same as Jimmy. Is there a confirmed fix yet? I'm up for swapping those resistor values, but just checking before I do.


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PostPosted: Thu Apr 19, 2012 7:31 pm 
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I thought I'd try something simpler than cracking open the pedal again, and just switched up where the buffer was in my pedal chain. I put the buffer, in this case a TU-2, in front of the Leeds and it made a huge difference. The volume is definitely up, and so are the mids and clarity. The sharp setting sounds so much better. Hard to believe that's all I had to do.

Anyway, I hope that helps anyone running into similar difficulties.


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PostPosted: Thu Apr 26, 2012 5:45 am 
That isn't too surprising, the Leeds Fuzz has a relatively low input impedance of 100K. Low input impedance is quite common with fuzz circuits, for one thing loading the guitar like that cuts input treble and helps reduce the amount of upper fizz that comes out of the fuzz circuit and it is often an attempt to make a fuzz 'interact' with the guitars controls.


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PostPosted: Mon Mar 13, 2017 6:35 pm 
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This was my first build, and I'm totally new but motivated to the DIY pedal world. After doing some resoldering a couple times the pedal is working and sounding great now!
Although I've noticed a signifigant volume drop with my favorite guitar... (which has really hot pickups.) I've tested with a couple other guitars and amps (always direct not in my pedal chain) and there's PLENTY of volume. So I'm assuming the hot pickups on my custom Tele isn't reacting as well as the not-so-loud guitars I've tried.
I'm really interested in trying this:

FF_Pedals wrote:
Take a look at the schematic in the instructions: http://buildyourownclone.com/leedsinstructions.pdf.

The output section of the pedal is a BJT common emitter amplifier. The resistors that set the DC levels (bias) and control the gain of that amplifier are R26, 27, 28, and R29.

I ran a simulation with a 2n3904 transistor that should be fairly similar and it biases out to around 4.5V on the collector which is pretty much what you would shoot for. The gain is around 13.4dB.

You can increase the gain to around 23dB to boost the output more. Change R26 to 1meg, R27 to 150k and R28 to 470ohms.

That shouldn't change the characteristic of the fuzz like changing the diodes would.

Boosting that much might start clipping the output which you may or may not like.

Then I would replace R30 (100k) with a 100k volume pot. Remove the R30 resistor, connect lugs 1 and 3 where it was, lug 2 is the new output.


anyone try this succesfully, and why the volume pot for R30?


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PostPosted: Tue Mar 14, 2017 10:20 am 
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eugenious wrote:
anyone try this succesfully, and why the volume pot for R30?


I haven't tried the mod (haven't had an issue with the output volume of the Leeds), but it looks like it makes sense. The R30 swap to a pot is to create a volume control. Since you would be increasing the gain of the output section, you may need a little extra control at the end. If you take a look at *most* of our schematics, you will see what is meant there, usually there is an A100k pot at the end of the circuit,
Lug 3 connected to the audio output from the circuit,
Lug 1 connected to ground, and
Lug 2 connected to the actual pedal output one way or another.

This allows you to control the resistance to ground, and tweak the output volume.

_________________
The tone is in my hands?!
Email: nick@buildyourownclone.com


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PostPosted: Fri Mar 17, 2017 8:09 am 
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I was going to build up the Leeds this weekend with a couple of these mods. If I want to add the volume control as described by Nwkenning, I would put the pot between the stomp switch and the #7 connection on the board correct? I assume if I put it between the stomp switch and the output jack (or connection #8) that it would control the volume of my signal regardless of whether it's running through the effect or not which wouldn't be desirable.

Or would replacing R30 essentially be the same thing?


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PostPosted: Fri Mar 17, 2017 6:10 pm 
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Just to clarify the volume mod as per an email exchange I had with Nick.

Remove R30. Wire lug 1 of a 100K pot to the south end of R30, lug 3 to the north end and then run a wire from the middle lug of the pot to lug 7 on the foot switch. You also forgo the the wire that connects lug 7 of the foot switch and eyelet #7 on the PCB.

I'll be doing this up this weekend and will post back with a follow up report.

Thanks to everyone at BYOC for just being awesome.


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PostPosted: Sun Mar 19, 2017 6:18 pm 
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Preliminary testing is looking good. The volume mod, as described above, works exactly as expected. I also added a very simple voltage starve which has opened up a bunch of new and messed up sounds. I think it would have been nearly useless without the additional volume. As less and less current gets into the circuit it starts getting more gated, then for a little while there's almost a reverse gate going on where the initial note flubs out but the octave slowly fades in and then increases in volume until you can't hear the initial note anymore at all. It's really cool.

Down towards the end of the dial though the fuzz just craps out entirely and and is almost useless ... except you've got some extra volume to play with so you can bring it back up to where you can hear it again. It's still pretty quiet but someone might find it useful.

I experimented with a 10K linear pot ended up going down to a 5K because too much of the larger pots sweep was useless. It would just stop making noise entirely.

Fun times for a Sunday.


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PostPosted: Sun Mar 26, 2017 9:03 am 
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Finally boxed it up.

Super pleased with the addition fuzz tones available with these mods.

Image


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