LPD MegaDEN Bass Fuzz

Groovenut · Post by **Groovenut** » 10 Feb 2013, 01:02

Here's the schematic. I am still kind of on the fence about making the Fuzz pot 500kA. The switching on the schematic is the basic true bypass, I use Mictester's low current latching relay idea bent to my will in my pedal.

: LPD MegaDEN Bass Fuzz V2.1

b6a6r6n · Post by **b6a6r6n** » 28 Jul 2015, 20:55

EDIT: WRONG THREAD D'OH

this is cool guys, ta very muchly.

been playin about with buffers in there, thing is turns out i kinda like the combination tone/blend that a hardwired clean signal via a pot does when banged into the bazz fuss. at a low setting (low resistance on the clean) you get a very dynamic and responsive distortion, rather than the full-cocked blistering fuzz that lotsa peeps seems to dislike (about fuzz). i got a similar thing by running 2 BF circuits in series, with harsher diodes on the first than the second.

is cool!

next step on my to do list is to try a phase inverting buffer on the fuzz with a 2-in-1-pot (separate coils), see if it is the phase thats the problem. but then again, it doesnt sound like it... ah the mysteries caused by an only mechanical understanding of electronics...

and finally.... im using a roland jazz chorus amp which has only 1 gain/volume, no in, no out, just the one. and there were big discrepancies in volume when rolling the pot from no-clean down to full-clean. however when i took it to a large marshall stack these volume changes were all ironed out, no matter how low the input gain on the amp...

im guessing an impedance thing? but also i cant play 'at volume' in the house so the roland is always pretty low gain. ah, the mysteries etc...

snk · Post by **snk** » 04 Jan 2020, 22:25

Hi,
Thank you for the nice effect : I built it today, and it's indeed a nice sounding fuzz, with plenty output volume, a handy dry/wet section, and a nice, deep bass tone

If I wanted to tame the high a bit more and shape the tone further, which components should I try to tweak ?
Maybe changing the HARMONIC pot value to something else ? Or try with a different value for C4 (100nF) ?

snk · Post by **snk** » 05 Jan 2020, 00:06

Also, If i wanted the fuzz to have less "bite" and more "warmth", what could I try (What I am trying to achieve is a sound with less fuzz on the attack, at moderate fuzz settings) ?
I tested with various diodes (Germanium, silicon, leds... single, series and parallel), but it didn't seem to affect the sound much.
Should I try with other transistors ?

Nocentelli · Post by **Nocentelli** » 05 Jan 2020, 01:45

For a more effective treble control, you could swap the volume pot's lug 3 connection to the wiper/lug 2 of the harmonics pot (i.e. disconnect it from harmonics 3 and swap to the wiper). This will be more like the Rat filter, and you should probably reduce the cap value to 3n - 10n according to taste.

You can reduce the gain (and maybe reduce the "bite" / increase the "warmth") by replacing the bazzfuss darlington''s emitter connection with a 1k pot to ground or the standard fuzzface gain pot.

snk · Post by **snk** » 05 Jan 2020, 08:59

Thank you, Nocentolli, it's much appreciated.

For a more effective treble control, you could swap the volume pot's lug 3 connection to the wiper/lug 2 of the harmonics pot (i.e. disconnect it from harmonics 3 and swap to the wiper). This will be more like the Rat filter, and you should probably reduce the cap value to 3n - 10n according to taste.

I will try this mod, it's an easy one... and I like the RAT's filter

In fact, after playing a little while with the HARMONICS (Tone) control, I find the cutoff rather good enough at maximum settings, it's just that it seems to do nothing on at least half the course.
Do you think that swapping the 100K pot with a 25K (or 50K) pot would give me a more efficient range of control ?

You can reduce the gain (and maybe reduce the "bite" / increase the "warmth") by replacing the bazzfuss darlington''s emitter connection with a 1k pot to ground or the standard fuzzface gain pot.

It's the 3.9K resistor, right ?
I might also socket it, and try with various resistor values (or use a trimmer).

In fact, I like the way it sounds when the fuzz is maxed out, but at higher FUZZ settings, I find it gives me quite harsh attacks, and I wish i could tame this behaviour to have a softer sound at lower FUZZ settings.
By the way, if itsn't a GAIN, what does the 100K FUZZ pot do ?
Would the suggested 1K gain pot be the same than lowering the input level (I tried this, and it didn't change the fuzz's sonic character) ?

Nocentelli · Post by **Nocentelli** » 05 Jan 2020, 10:50

snk wrote: ...after playing a little while with the HARMONICS (Tone) control, I find the cutoff rather good enough at maximum settings, it's just that it seems to do nothing on at least half the course.
Do you think that swapping the 100K pot with a 25K (or 50K) pot would give me a more efficient range of control ?

Yes, if you like the sound but the first half of the pot rotation is useless, just swap it for a 50k.

snk wrote:
You can reduce the gain (and maybe reduce the "bite" / increase the "warmth") by replacing the bazzfuss darlington's emitter connection with a 1k pot to ground or the standard fuzzface gain pot.
It's the 3.9K resistor, right ?

The 3k9 sets the minimum level for the existing fuzz pot, which is simply an input level control. I was suggesting adding a 1k pot between the emitter of the lower BJT and ground, which will allow you to reduce the gain of the bazzfuss section.

: LPD_MegaDEN gain.png (38.52 KiB) Viewed 2038 times

snk wrote:In fact, I like the way it sounds when the fuzz is maxed out, but at higher FUZZ settings, I find it gives me quite harsh attacks, and I wish i could tame this behaviour to have a softer sound at lower FUZZ settings.
By the way, if it isn't a GAIN, what does the 100K FUZZ pot do ?
Would the suggested 1K gain pot be the same than lowering the input level (I tried this, and it didn't change the fuzz's sonic character) ?

The existing fuzz pot acts as an input level control for the fuzz: It will reduce the amount of fuzz when the input level is reduced, in the same way some fuzz circuits get cleaner when you roll down the volume control on the guitar. However, it is more accurate to call it a "fuzz" control than a gain control, since the actual gain of the fuzz circuit is fixed at maximum with the emitter grounded as in the stock circuit, and reducing the input level does not affect the gain of the darlington.

Adding resistance (or variable resistance with a pot) to ground reduces the actual gain of the fuzz circuit, and will reduce the amount of dirt. It may sound no different to the action of the original fuzz pot, or it might alter the quality of the attack in a way you like, so might be worth trying out. Alternatively, if you use the standard fuzzface "fuzz" (gain) control, you can try different capacitor values to see if this affects the attack in a way that you like:

: fuzzface gain pot.png (9.29 KiB) Viewed 2038 times

In the fuzzface, the cap value is nominally 20uF which effectively boosts the gain of ALL frequencies. If you reduce the cap value (e.g. to 1uF) it will increase the gain of higher and middle frequencies but without boosting the gain of the low end as much, i.e. it is a frequency selective gain control, acting as a high-pass boost, with higher capacitance = lower cut-off frequency.

snk · Post by **snk** » 05 Jan 2020, 11:52

It's perfectly clear, thank you Nocentelli

I wasn't sure if the FUZZ pot was a GAIN or an INPUT level control : adding a GAIN control might help shaping the sound further.

Now, I have plenty suggestions to experiment

snk · Post by **snk** » 05 Jan 2020, 16:08

Hi,
I must have done something wrong, as after my first try, adding the GAIN pot resulted in a huge loss of wet output volume, and a dirty sound (not in a good way).

This is what i did :
- I removed the Emittor (bottom) leg of the transistor, soldered it to a wire which got soldered to one side of the 1K pot.
- I soldered the other side of the pot to a wire going to ground.
(I didn't add the capacitor yet)

I am using this layout (by John K), and this is a rough sketch of what i did (consider that the purple led is actually soldered to the removed leg of the transistor, not to the transistor socket) :

Nocentelli · Post by **Nocentelli** » 05 Jan 2020, 22:11

You just need to connect lug 2, AKA the wiper (the middle one) to lug 1 (the one with the blue wire connected to ground).

At the moment, as shown below, you have the full 1k pot resistance between ground and emitter so you are hearing the minimum gain setting but you have no way to increase it. Linking lug 1+2 will allow the pot to operate as a 1k variable resistor and let you reduce the resistance as you turn the pot up, moving the wiper closer to lug 3 until you get back to maximum gain at full rotation/zero ohms.

: LPD_MegaDEN gain.png (25.49 KiB) Viewed 2021 times

If you're actually experimenting with a fully constructed pedal, I would suggest soldering a wire (a good few inches) from lug 2 to a croc/alligator clip (if you have one) and then just clip it to any ground point or directly to lug 1. If you get the new gain pot working and you're happy just remove the flying wire and put a small link between those lugs. If you want to experiment with caps, you can just detach the clip and use the flying clip connection to try out your cap-to-ground experiments - Here a second flying croc clip wire from ground would be useful as you could try out different cap values very easily by just sticking the cap between the two clips. Make sure if you use polarised caps for the larger values, you make sure to connect the negative leg to ground.

If you find a cap value you like, you can just solder it directly across pot lug 1+2.