Stuff you wanted to know but were afraid to ask

[cdwillis]

C11 is going to get 18v, so 16v won't be enough. C22 is going to get 15v, but I still wouldn't stick a 16v cap there. I usually use 35v rated electrolytics in the power section even if I'm not planning on running higher than 9v, just in case I (or anyone) uses a 18v power supply on accident.

On the octave fuzz I'm guessing that the R6 and C4 are filtering out high frequency noise. Using a larger cap might make it sound like it's got a blanket over it. Someone else may have a better answer.

If it were me I would just order the correct components and wait to finish them as annoying as that may be. It's better than getting it done later and wondering if it sounds right.

 

[Chuck D. Bones]

While you're at it, be sure to buy spares because chances are good you'll use them sometime soon. Most vendors offer quantity breaks and there's the cost of shipping, so buying extras is a no-brainer.

 

[ICTRock]

on the octave fuzz r6 and c4 form a RC Filter ... so you can use a different cap if you compensate with a different resistor too otherwise you are going to be playing with the tonality of the pedal for good or bad

on the electrovibe, keep in mind that the values there provide filtering for the 18 and 15v supplies ... you don't want to go lower (noise potential) and I don't have a good handle on what the upper limit should be on going larger at 2AM on a Monday morning. you could probably get away with 220uf but I wouldn't be surprised that there be monsters I didn't consider

 

[masonlewisdiesel]

on the octave fuzz r6 and c4 form a RC Filter ... so you can use a different cap if you compensate with a different resistor too otherwise you are going to be playing with the tonality of the pedal for good or bad

on the electrovibe, keep in mind that the values there provide filtering for the 18 and 15v supplies ... you don't want to go lower (noise potential) and I don't have a good handle on what the upper limit should be on going larger at 2AM on a Monday morning. you could probably get away with 220uf but I wouldn't be surprised that there be monsters I didn't consider

okay thank you, what your saying makes perfect sense on the octave fuzz. i'm breadboarding it as i type this, so perfect time to screw around.
Yeah on the electrovibe I was kinda guessing that so i got 50 of them coming at 25v to backstock. thank you!

 

[lowpitch]

Let's say I have a JFET source follower where the drain is connected through a 100R resistor to a regulated 24VDC (+/-1%). Am I cutting it too close if I'm using FETs that are rated for 25V max drain-gate voltage, like 5457, J211, etc or are these rated rather conservatively?

 

[UtilityBeltFX]

You know how something like a phase 90 or the BOSS PH3 requires a matched set of 4 JFETs for the phasing? How are these companies going about matching all these JFETs for their thousands and thousands and thousands of phase pedals made and sold? Even in the early days when they weren't as massive as they are now. Do they just have a dedicated person matching JFETs all day every day? Am I missing something?

 

[giovanni]

You know how something like a phase 90 or the BOSS PH3 requires a matched set of 4 JFETs for the phasing? How are these companies going about matching all these JFETs for their thousands and thousands and thousands of phase pedals made and sold? Even in the early days when they weren't as massive as they are now. Do they just have a dedicated person matching JFETs all day every day? Am I missing something?

Do they use discrete transistors? If they got 4 of them fabricated on the same substrate they could get a very high rate of matched quads and they may also be easier to test if they are all on the same chip. That’s what I would do.

 

[ICTRock]

You know how something like a phase 90 or the BOSS PH3 requires a matched set of 4 JFETs for the phasing? How are these companies going about matching all these JFETs for their thousands and thousands and thousands of phase pedals made and sold? Even in the early days when they weren't as massive as they are now. Do they just have a dedicated person matching JFETs all day every day? Am I missing something?

I once had this very question and found the answer from Mark Hammer and others on diysb

lots of questions on fet matching for phasers

lots of questions on fet matching for phasers

www.diystompboxes.com

 

[ICTRock]

on the octave fuzz r6 and c4 form a RC Filter ... so you can use a different cap if you compensate with a different resistor too otherwise you are going to be playing with the tonality of the pedal for good or bad

on the electrovibe, keep in mind that the values there provide filtering for the 18 and 15v supplies ... you don't want to go lower (noise potential) and I don't have a good handle on what the upper limit should be on going larger at 2AM on a Monday morning. you could probably get away with 220uf but I wouldn't be surprised that there be monsters I didn't consider

re: octave fuzz and 2AM ... my answer was so incorrect. anyways the series resistance with the cap keeps the gain down and the response linear. this is the helios console preamp part of the octavia circuit. if you want to be a super genius like roger mayer you can change R5 to 100K and R7 to 220R and claim you've optimized the circuit to run on 9v instead of the 24V the console preamp ran at.

 

[Guardians of the analog]

You know how something like a phase 90 or the BOSS PH3 requires a matched set of 4 JFETs for the phasing? How are these companies going about matching all these JFETs for their thousands and thousands and thousands of phase pedals made and sold? Even in the early days when they weren't as massive as they are now. Do they just have a dedicated person matching JFETs all day every day? Am I missing something?

Boss PH-3 is digital so that luckily saves Boss/Roland a ton of time on matching

 

[UtilityBeltFX]

Boss PH-3 is digital so that luckily saves Boss/Roland a ton of time on matching

Ahh yeah you're right! I built the Aion Emerald which is the three knob PH-1r but with an additional volume knob making it four knobs and my wires got crossed.

 

[Erik S]

What's up with the number 47?

I get that you'd use multiples of 10 in component values for ease of math, but why is everything 47, 470, 470k etc?

 

[Betty Wont]

What's up with the number 47?

I get that you'd use multiples of 10 in component values for ease of math, but why is everything 47, 470, 470k etc?

Prefered numbers E series and logarithms.

 

[Erik S]

Prefered numbers E series and logarithms.

Thanks!

Excerpted from the AI search results:

• Preferred numbers are based on a logarithmic series, meaning the ratios between successive values are constant.
• The number after "E" indicates the number of steps (or values) in the series per decade (a tenfold increase in value).
  
  
• For example, the E12 series has 12 values per decade, while the E24 series has 24 values per decade.
• The goal is to have a limited number of readily available values that can approximate a wide range of desired values, simplifying inventory and manufacturing.

Very cool. I feel like I should have learned that long time ago!

I met my future wife in math class the third time I failed Geometry, so my experience with Logarithms before I got into pedals was limited, but now I know at least two things they're good for!

I'm gonna guess that 47 in particular comes up extra because it's the E12 approximation of 50 which would make sense to me as a useful common value.