Bypass Caps: Film or Ceramic (MLCC)

[jmsiener]

Hey y’all, I’m new here and just have a silly question- why all of the film caps?

I’m kind of new to guitar pedals, I’ve built about 3 pedals over the past decade but in the past 2 months I’ve built 4 from PedalPCB; I’ve got to say I’m hooked! Since 2016 I’ve built about 150 eurorack modules from panel/PCBs and have a relatively large stockpile of components.

The wisdom I’ve interpreted from the eurorack world is to use MLCCs for bypassing and film for any timing/oscillators/audio path stuff. If you have to use an MLCC for any typically film cap application then get a C0G/NP0 MLCC.

What has really spurred my question is that I’m building a low tide mini at the moment and the LFO/random board seems to call for film caps (after consulting the low tide documentation) for power bypass purposes. 100nF film caps between power and ground near an opamp, microcontroller , PLL, etc. Why not just use MLCCs for that application? After noticing this and looking back at my previous builds I noticed that some of the 100nF caps I had used were just power decoupling caps and nothing in the audio path. In any eurorack module I would just used a decent ceramic cap, probably something with an X7R dielectric.

Any and all wisdom is appreciated and thanks in advance!

 

[mybud]

I've used 100nF X7R caps for exactly the purposes you mention (PS bypass caps) for some time now without any obvious problems.

Saves a few bucks but I wouldn't do this in the audio path (as you note).

 

[jmsiener]

I've used 100nF X7R caps for exactly the purposes you mention (PS bypass caps) for some time now without any obvious problems.

Saves a few bucks but I wouldn't do this in the audio path (as you note).

Thanks for the confirmation of my thoughts. I suppose now I’m curious why film would be specified in the BOM. Makes me wonder if I’m not hip to something. Regardless, I’ll be using MLCCs for those bypass caps.

 

[GAStan]

I've spent many, perhaps TOO many, hours reading posts about various components and where to use what. Here's my thoughts on capacitors:

IMHO there are only a handful of hard and fast rules pertaining to Capacitors as used in pedals.
1. Never exceed rated voltage
2. Pay attention to polarity on electrolytic and other caps that have it marked.
3. Sometimes Size does matter (Low Tide Mini).

Other than these few rules one can use whatever suits them. If a person wants to use an electrolytic in the signal path they should try it (heed the rules above). If in their opinion it sounds good, great. If not then try something else.

Trial and error is what created the "guidelines", "common practice" or whatever a person wishes to call it. But these are based on various individual tastes and realize their taste may not match what you are looking for. Don't be afraid to socket a cap and experiment with various types or even compositions of same type ( i.e. X5F, X7R or COG ceramics).

Edit: Nevermind the Bullocks...

 

[Stickman393]

For what it's worth...

Film caps will do the job just as well as x7rs in our use cases. The most ideal setup here is something like a surface mount X7R with the shortest possible traces, but the stuff we fuck with just doesn't tend to be *that* sensitive

 

[GAStan]

I suppose now I’m curious why film would be specified in the BOM

My guess is that it may have been the type of cap used in the original pedal, but I'm curious too. Only the person that wrote the BOM would know for sure. What pedal? Maybe ask the question and flag Robert if it's one of his.

 

[Stickman393]

I would suspect that those were what was used to validate the build?