How to do a diode toggle on the Parentheses?

[bengarland]

I hope this isn't too much of a newbie idea, but part of the Parentheses uses 2 "GE" diodes and I have 2 different types: 1N270 and 1N34 (not 1N34A if it makes a difference). I'd like to add toggles between these two types.

The anode side is common to Q2 (2N5089), but the cathode sides go to different places, so switching between them isn't quite as straightforward as if they were in parallel. Here's the relevant part of the circuit:



Instead of someone just giving me the answer, I really want to figure this out on my own, BUT...

Can someone just answer these yes or no questions to help me?

1) If I do this mod, will it give me different sounds / is it worth doing? Or do all GE diodes affect the circuit in the same way?

2) Is there any risk to modding it such that 1 of the 1N34 and 1 of the 1N270 are active at the same time?

3) Is there anything that I might be overlooking / be aware of?

My basic idea is to install 2 SPDT switches so I could have the following config:

a) 2 of the 1N34 active
b) 2 of the 1N270 active
c) 1 of the 1N34 + 1 of the 1N270 active

Thanks!

 

[Chuck D. Bones]

1a) Probably not
1b) Probably not
1c) Should be pretty much the same, but see B below

2) No

3) Yes, see B below

Because you said you wanted to figure this out on your own, I'll add these two thoughts and then shut-up:
A) Try this out on a breadboard and see for yourself.
B) There is discussion in the Troubleshooting forum pertaining to the Parenthesis octave diodes.

 

[bengarland]

Thanks! Even if it's the same, it'll be worth exploring simply for the experience.

Is there any good resource that gives a list of what components are good for swapping?

e.g. "If the circuit calls for Diode Type X, you can substitute Diode Type Y for a different sound." Maybe this applies to different transistor types too?

To be clear, I'm interested in substitutions which will give different sounds without much other circuit modification needed (maybe something simple, like also needing one different resistor or capacitor which is a direct "neighbor" in the circuit, and can easily be in-lined) -- not substitutions which don't affect the sound (e.g. for hard to find parts).

I'd really like to get into modding more of these pedals now that I feel confident about building them "as is", but I really have no idea where to start, which parts are easily (commonly) modified, etc. I really like reading about this stuff in real books (even if it's just a PDF) versus on websites because I find books to be better organized and easier to follow.

 

[Barry]

Overdrives are where you can get some difference swapping diodes, LED's have more headroom, symmetrical VS asymmetrical....

 

[Chuck D. Bones]

Understanding how the circuit works and what you want it to do different is the best basis for modding. Otherwise, you're just shooting in the dark. Sometimes, not often, but sometimes trying something way outside the box can yield interesting and useful results. You wanted to try different diodes in the Parenthesis Octave section. Why? Do you not like the sound? Diode-based octave circuits are pretty simple. To get the cleanest octave, the diodes need to be balanced, otherwise too much fundamental tone leaks thru. The Parenthesis has a BLEND control to add fundamental back in, so there's really not much point in deliberately unbalancing the octave diodes.

The problem I struggle with is knowing too much (or thinking I know) about how a circuit works and that causes me to not try things because I think they won't work. Your best bet is experimentation. Take lots of notes so that a week or a month from now, you'll know what you did. Learn to read a schematic. Obtain and use a prototyping board to build circuits so you can easily try out mods. Those of us who design and mod pedals need to be real good at troubleshooting because it's all too easy to break a circuit with mods, either because the mod idea is crap or we just plain built it wrong. I troubleshoot my own stuff all the time, I just don't do it here where everyone can see.

 

[Nostradoomus]

Spot on, Chuck. I’m the opposite as far as my knowledge base goes (I just put in a solid day with EasyEDA today for the first time so you may get a message or two ). I hardly know shit from shinola about how things work BUT experimentation has led me to the same functional place, I don't need to ask for help very often.

There’s no mod that will give you a specific sound that’s applicable to every circuit which is why no such list exists. Over time of studying schematics and playing around you WILL however find that many blocks inside the circuits are similar enough that you’ll get the ideas flowing for sure.

 

[Fantasticky]

Hey Bengarland,

check out this link to help get some more intel on your diode mods, good stuff in this article. https://www.guitarpedalx.com/news/gpx-blog/a-brief-hobbyist-primer-on-clipping-diodes
I have completed many builds with some switches activating different diodes set to clip, remember you can double GE diodes in series to increase Vf, also add it to silicon. Recommend to wire to a bread board for plug and play, you will get a good ear for what works, pick your favs, have fun. Remember law of balance, for every thing you add from somewhere, you take away from somewhere else. Meaning, you add more into this circuit you will take some element away from the original signal and you will hear it. Sometimes the simplest adjustments like changing the high frequency filtering from 33pf to none or up to 200pf will greatly help your tone. Have fun, life is too short for bad audio.

 

[Fantasticky]

Here are 2 pics of a strip board mod I set up to use with a rotary switch. I would have 15 combos to use. Basic board for one strip per each position of the switch and the common base for the other.