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The Sushi Box FX Secret Society

#10,002
Sushi Box FX said:
Hey everyone, I promise I'm still alive. Sometimes I work on things.

CAUTION: technical nonsense, skip if it's boring

The great capacitor debate will continue forever, and that's fine. In my research (I'm not an expert, but did go to school for this) the best answer I have found is "it depends." In low voltage, typical pedal applications running at reasonable room temperatures, I would not expect a difference in performance between MLCC (SMD) and film caps. When tubes get involved you have high voltages and high temperatures, both of which will affect the permittivity of the capacitor, and a capacitor's permittivity is dependent on the capacitor's dielectric. Multi-layer ceramic is cheap and easy to make small which is why we use it for everything these days. But its permittivity varies more over temperature and voltage than film dielectrics, which would cause the capacitance to fluctuate, which in an audio situation means your frequency response is changing.

"But Nathan, you've been using MLCC in your tube pedals for years!" I absolutely have. In MLCC dielectrics there are a number of grades. NP0/C0G are the most stable across temperature and voltage, and consistency is close to if not as good as film caps in high voltage and high temperature situations. Generally what I was taught in my day job designing circuits is to go with "X7R or better" dielectrics. NP0 and C0G aren't available in all values and all voltage ratings, but X7R can cover just about everything. X7R are rated to be within 15% tolerance of the stated value up to 125 C, which is pretty darn good.

So why bother with film caps/handwired versions when X7R and NP0/C0G can do the job just as well? There are a couple reasons. 1) with the pandemic electronic component manufacturing got weird and I noticed increased lead times for a lot of my specialty (high voltage) MLCC, but film caps seemed to be unaffected. 2) the factory that does my SMD assembly considers high voltage MLCC a specialty component and doesn't always stock them, I have to keep emailing them to make sure they're going to keep them in stock. 3) as noted in one of the links above, soldering them down is more consistent. I'm a lot less likely to have a bad solder joint on a through-hole film cap than an MLCC. The board house that does my assembly is pretty good, but every now and then I have bad connections and have to reflow them.

Tl;dr - both are cool, but my SMD caps are rated for 250V, film are rated for 400V or 630V, so I can run higher plate voltage.

Good reading from a reputable source, if you're into that sort of thing: Selecting capacitors to minimize distortion in audio applications
Click to expand...
Thanks for this!
Totally get that supply chain and production issues can also affect how things are built as I go through that daily.
What type of plate voltages do you typically run for SMT vs. through hole designs?
 
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#10,004
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#10,005
Jim C said:
Thanks for this!
Totally get that supply chain and production issues can also affect how things are built as I go through that daily.
What type of plate voltages do you typically run for SMT vs. through hole designs?
Click to expand...
Supply chain is nuts right now, at my day job "acceptable" lead time now means anything less than 52 weeks.

I use a regulated SMPS to generate the high voltages and it doesn't fluctuate much, so I don't need to leave big safety margins, so on the SMD versions with 250V caps I run 235-240V, and on the through hole designs with 400V (or lately 630V) caps I run 360V.
 
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#10,006
JKos said:
That stinks.
Click to expand...
Yup. So I've been doing a lot of reading, and I'm branching out of my analog comfort zone and into the deep end of DSP.

60wh9c.jpg
 
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#10,009
Sushi Box FX said:
Hey everyone, I promise I'm still alive. Sometimes I work on things.

CAUTION: technical nonsense, skip if it's boring

The great capacitor debate will continue forever, and that's fine. In my research (I'm not an expert, but did go to school for this) the best answer I have found is "it depends." In low voltage, typical pedal applications running at reasonable room temperatures, I would not expect a difference in performance between MLCC (SMD) and film caps. When tubes get involved you have high voltages and high temperatures, both of which will affect the permittivity of the capacitor, and a capacitor's permittivity is dependent on the capacitor's dielectric. Multi-layer ceramic is cheap and easy to make small which is why we use it for everything these days. But its permittivity varies more over temperature and voltage than film dielectrics, which would cause the capacitance to fluctuate, which in an audio situation means your frequency response is changing.

"But Nathan, you've been using MLCC in your tube pedals for years!" I absolutely have. In MLCC dielectrics there are a number of grades. NP0/C0G are the most stable across temperature and voltage, and consistency is close to if not as good as film caps in high voltage and high temperature situations. Generally what I was taught in my day job designing circuits is to go with "X7R or better" dielectrics. NP0 and C0G aren't available in all values and all voltage ratings, but X7R can cover just about everything. X7R are rated to be within 15% tolerance of the stated value up to 125 C, which is pretty darn good.

So why bother with film caps/handwired versions when X7R and NP0/C0G can do the job just as well? There are a couple reasons. 1) with the pandemic electronic component manufacturing got weird and I noticed increased lead times for a lot of my specialty (high voltage) MLCC, but film caps seemed to be unaffected. 2) the factory that does my SMD assembly considers high voltage MLCC a specialty component and doesn't always stock them, I have to keep emailing them to make sure they're going to keep them in stock. 3) as noted in one of the links above, soldering them down is more consistent. I'm a lot less likely to have a bad solder joint on a through-hole film cap than an MLCC. The board house that does my assembly is pretty good, but every now and then I have bad connections and have to reflow them.

Tl;dr - both are cool, but my SMD caps are rated for 250V, film are rated for 400V or 630V, so I can run higher plate voltage.

Good reading from a reputable source, if you're into that sort of thing: Selecting capacitors to minimize distortion in audio applications
Click to expand...

Good read, and interesting information! Thanks for sharing! :thumbsup:
 
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#10,010
Just opened ordering for February, thought everyone should know.

PSA: way too big of a portion of proceeds from February sales will probably go into figuring out how to develop my own DSP platform. At my school, the electrical engineering program focused heavy on software/firmware, but I ignored that and chose to focus on electronics/hardware design. I don't regret my choice, but sometimes I wish I had had a little more experience with programming stuff :P
 
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#10,019
el murdoque said:
Is there a pedal that has similar breakup to the Underground Accelerator which is not the Underground Accelerator?
Click to expand...
Yeah Space Heater or Finally should be similar.

Killing Floor said:
None of y’all had the awesome to try a Wrecking Ball X? Looks like it’s been dropped.
Click to expand...
Yup, I dropped it because you were the only person that ever tried it out. It's a killer circuit, but I don't want to keep something around jf nobody cares about it.

shoegazebass said:
Any clips of the Ambassador on bass?
Click to expand...
Nope, and frankly I don't really recommend it on bass. It's a little thin sounding.

Deleted member 360599 said:
Need to bring back the Lab Rat X! Please!
Click to expand...
I'm still thinking about it. If it comes back it will do so as a single channel pedal with no boost, and I would change the voicing a little to get better low end response.

But still no promises. Obviously.
 
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