Iron Bell Noise Gate

[squirrels]

So I just finished up an Iron Bell and like most Big Muffs I've built or played, it's got quite a bit of background noise. I looked up some mods and found one about adding a 100k trimmer as a variable resistor in parallel with the base to ground resistor in the second stage. So to implement this would I add the trimmer to the 100k resistor on Q3? Any help would be appreciated. Thanks. W

[Muadzin]

I think I did that once to one of my Muffs. It did cut some noise, but it also cut some gain. Don't expect any miracles from it. Maybe you should look into adding a dedicated noise gate circuit to your pedal instead? The average Muff board is not that big that you can't squeeze in a noise gate board beside it. Maybe not if you're using a 1590B, but in a 125B, easily.

[squirrels]

Thanks for the advice. It's not overly noisy so I still would like to try it out since it's an easy mod. A noise gate could definitely be another option.

[induction]

squirrels wrote

So I just finished up an Iron Bell and like most Big Muffs I've built or played, it's got quite a bit of background noise. I looked up some mods and found one about adding a 100k trimmer as a variable resistor in parallel with the base to ground resistor in the second stage. So to implement this would I add the trimmer to the 100k resistor on Q3? Any help would be appreciated. Thanks. W

To be clear, Q3 in IvIark's Iron Bell layout is the third stage, but it's the second clipping stage. Without a link to your mod, I can't say which of those is correct.

Here's a link to an FSB thread where pinkjimiphoton discusses his BMP noise reduction mod. It involves paralleling (replacing would work just as well) one of the clipping diodes in the second clipping stage with a Ge diode (a schottky would probably work just as well). In the thread, mictester mentions that similar results can be gotten by messing with the emitter resistors in the clipping stages. Based on that, I'm guessing that your intended mod should have a similar effect to this one, but again, I can't be sure.

In any case, you can test jimi's mod easily by paralleling D4 with a Ge diode; you can test it without any permanent mods by just touching the legs of the existing diode with the new one. If it doesn't work try D3. Make sure your new diode is oriented the same as the one you're paralleling. If it works and the gain reduction is ok with you, you can make it permanent.

[squirrels]

I used the schematic and info from Kit Rae's site:

http://www.kitrae.net/music/Big_Muff_Mods_and_Tweaks_Page.html

I tried it out and it works but it dropped the volume and gain substantially, so I didn't use it. I have my diodes on an on/on switch  so I tried using a 1N5817 on the middle lugs which also helped a bit but caused a slight octave up, didn't like that too much either. I also have mine wired up like a Pharaoh with the input switch (tried a pot, wasn't all too useful honestly) using a 30k and 82k resistor to clean it up a little bit. That seemed to help the most with the hum. Honestly I only have the switches on there because I'm using a recycled box with extra holes. They're fairly useful though to tame the Iron Bell a bit more. Thanks for the help. 

[squirrels]

After using my LSTR (which is in another board) and realizing how quiet that one actually is, I switched it with the Iron Bell and it is actually super quiet. I did a little experimenting with the board the Bell is normally on and realized it is interacting with the starve pot on my Algal Bloom. I've had issues with starve pots in the past interacting with pedals but they were with Dwarfcraft clones and a Fuzz Factory. I fixed past problems with 4PDT switches, disconnecting the power supply with the fourth pole, I guess the Algal Bloom is no different.