Capacitor discharge large difference...ESR?

From circuitbending to homebrew stompboxes & synths, keep the DIY spirit alive!

Moderators: Kent, luketeaford, Joe.

jorg
Ultra Wiggler
Posts: 960
Joined: Fri Apr 03, 2015 9:38 am
Location: East Coast USA

Re: Capacitor discharge large difference...ESR?

Post by jorg » Mon May 03, 2021 8:16 am

neil.johnson wrote:
Mon May 03, 2021 6:01 am
guest wrote:
Sun May 02, 2021 8:15 pm
maybe we should make some bad filters that you sweep cutoff frequency by adjusting bias on the capacitors!
IIRC this was discussed on synth-diy several years ago.
At best you get about a 10:1 range, or about 3 octaves, using the worst possible capacitor formulation you can find. And it's highly non-linear so control could be, erm, interesting.

To avoid DC bias feedthrough you'd probably need some sort of balanced arrangement so the DC bias cancels out. Although if you're using such craptastic capacitors in the audio path you might find that getting a useful filter control response is the least of your problems.

Neil
You'd end up with extremely distorted audio, in addition to the sketchy and unstable control curve. In other words, Metasonix without the tubes. :sstorm:

User avatar
MikeDB
Veteran Wiggler
Posts: 680
Joined: Fri Feb 08, 2019 8:28 am
Location: UK

Re: Capacitor discharge large difference...ESR?

Post by MikeDB » Mon May 03, 2021 8:24 am

jorg wrote:
Mon May 03, 2021 8:07 am
If you replaced an electrolytic with a ceramic X7R (or even worse, Y5V) SMT capacitor, you will see huge performance problems. X7R and Y5V capacitors can have large value in a small space, but are completely unsuitable for signal handling; they are only OK for for power supply filtering (their one saving grace is low ESR). They cause massive distortion (not a few percent, but, depending on signal level, tens of percent). They are also extremely sensitive to temperature and to voltage level; capacitance can vary 2:1 or more, depending on voltage.

I've seen some pretty crazy and unexpected waveforms on these caps.
Whilst I agree there are a lot of really bad MLCCs out there, you shouldn't tar them all with the same brush. A decent X7R brand such as from Samsung designed for audio use and in the automotive packaging to avoid microphonics will cause negligable distortion, certainly less than 0.01%, when used properly. You can find them used all over the place in mobile phone or tablet audio systems and even in high performance mixers.
Always interested in innovative audio startups needing help and investment, just PM me.

transistorresistor
Wiggling with Experience
Posts: 450
Joined: Mon Apr 27, 2020 9:38 pm

Re: Capacitor discharge large difference...ESR?

Post by transistorresistor » Tue May 04, 2021 3:14 pm

Im hesitant to contribute to this discussion because I dont have any experience with the specific surface mount caps being discussed, however, in my experience both refurbishing vintage audio compressors and manufacturing new audio compressors, whenever I change the dielectric material in a timing circuit like the attack or release, the time constant is almost always effected.

If you have an old unit with a tantalum in there and replace it with an aluminum electrolytic, the time constant almost always changes. If you have a old tube unit with a paper in oil and you change it to a modern polyprop, the timing circuit changes. This has been such a consistent behavior in my experience, I have in the past put that cap on a switch on old tube units to get a different feel. Same values and voltage mind you, just different dielectric. And sometimes its not the overall time that changes but the curve. speaking specifically here about timing circuits in limiters.

Adding this just to generally say, the experience Ive had working with timing circuits in limiters suggests that the dielectric material has an impact on the discharge rate, more than ESR has ever been able to explain but Ive also not taken a deep dive on a further understanding. Will be curious to see where the OP winds up as a solution.

User avatar
devinw1
Super Deluxe Wiggler
Posts: 2213
Joined: Tue Aug 07, 2018 11:20 am
Location: Portland, OR
Contact:

Re: Capacitor discharge large difference...ESR?

Post by devinw1 » Tue May 04, 2021 3:29 pm

As far as a solution, I am running electrolytic basically everywhere they were electrolytic on the original schematic for the thru-hole version and all is well. For the SMT, I am having some new boards spun right now which for the few 1u and 2.2u electroltyics used for envelopes like this one I put a 1210 footprint in parallel with a little 4mm THT electroltyic footprint. I will hand add the 1210 X7R Samsung caps (since JLC didn't have any) and see how that goes. If it's still problematic for that ciruit, I'll just use electrolytics like the THT version. This isn't for super mass production so it's not a huge deal for me to hand add another couple caps as I'm already hand adding a smattering of THT film caps.

If in the future I decide to make it even more production friendly, I may attempt to shrink 2 PCBs into one, replace all the THT film caps with SMT film caps and use whichever version works properly and is the smallest for those 1u and 2.2u mentioned above. :tu:

User avatar
guest
Super Deluxe Wiggler
Posts: 6032
Joined: Mon Aug 19, 2013 11:49 am

Re: Capacitor discharge large difference...ESR?

Post by guest » Tue May 04, 2021 3:52 pm

if youre going to be hand stuffing, i find THMT electrolytics are slightly cheaper and easier to stuff. and how has your luck been with SMT film caps? i find they are really sensitive to soldering temps. i suppose if youre having them stuffed, the fab will have that all dialed in already.
openmusiclabs.com

User avatar
MikeDB
Veteran Wiggler
Posts: 680
Joined: Fri Feb 08, 2019 8:28 am
Location: UK

Re: Capacitor discharge large difference...ESR?

Post by MikeDB » Tue May 04, 2021 4:13 pm

devinw1 wrote:
Tue May 04, 2021 3:29 pm
As far as a solution, I am running electrolytic basically everywhere they were electrolytic on the original schematic for the thru-hole version and all is well. For the SMT, I am having some new boards spun right now which for the few 1u and 2.2u electroltyics used for envelopes like this one I put a 1210 footprint in parallel with a little 4mm THT electroltyic footprint. I will hand add the 1210 X7R Samsung caps (since JLC didn't have any) and see how that goes. If it's still problematic for that ciruit, I'll just use electrolytics like the THT version. This isn't for super mass production so it's not a huge deal for me to hand add another couple caps as I'm already hand adding a smattering of THT film caps.

If in the future I decide to make it even more production friendly, I may attempt to shrink 2 PCBs into one, replace all the THT film caps with SMT film caps and use whichever version works properly and is the smallest for those 1u and 2.2u mentioned above. :tu:
Note that JLCPCB will hand stuff some THT components now. $3 pull from stores charge plus 2 cents a pin but might be worth it.
Always interested in innovative audio startups needing help and investment, just PM me.

User avatar
MikeDB
Veteran Wiggler
Posts: 680
Joined: Fri Feb 08, 2019 8:28 am
Location: UK

Re: Capacitor discharge large difference...ESR?

Post by MikeDB » Tue May 04, 2021 4:42 pm

guest wrote:
Tue May 04, 2021 3:52 pm
if youre going to be hand stuffing, i find THMT electrolytics are slightly cheaper
Actually THT electrolytics are a lot cheaper for reasons I've never understood. The SMD ones need the lead spacer but they don't have the plastic insulating sleeve so one might think they'd be similar prices.
Always interested in innovative audio startups needing help and investment, just PM me.

User avatar
guest
Super Deluxe Wiggler
Posts: 6032
Joined: Mon Aug 19, 2013 11:49 am

Re: Capacitor discharge large difference...ESR?

Post by guest » Tue May 04, 2021 5:05 pm

i think that little injection molded plastic piece on the bottom would be costly (is this the lead spacer youre referring to?).
openmusiclabs.com

User avatar
devinw1
Super Deluxe Wiggler
Posts: 2213
Joined: Tue Aug 07, 2018 11:20 am
Location: Portland, OR
Contact:

Re: Capacitor discharge large difference...ESR?

Post by devinw1 » Tue May 04, 2021 5:56 pm

guest wrote:
Tue May 04, 2021 3:52 pm
if youre going to be hand stuffing, i find THMT electrolytics are slightly cheaper and easier to stuff. and how has your luck been with SMT film caps? i find they are really sensitive to soldering temps. i suppose if youre having them stuffed, the fab will have that all dialed in already.
Yeah I agree on the electrolytics. I put footprints for THTs on the board for those.

As for SMT films...that will be a new experience for me. I have some on the way from Mouser to try for another project. When you say sensitive to solder temp, I assume you mean they are easily damaged in soldering? This could be problematic..

I have used SMT Mica for TS0 and i never had a problem soldering those, but mica seems like it would be pretty durable compared to thin film polymers.

User avatar
devinw1
Super Deluxe Wiggler
Posts: 2213
Joined: Tue Aug 07, 2018 11:20 am
Location: Portland, OR
Contact:

Re: Capacitor discharge large difference...ESR?

Post by devinw1 » Tue May 04, 2021 5:57 pm

MikeDB wrote:
Tue May 04, 2021 4:13 pm

Note that JLCPCB will hand stuff some THT components now. $3 pull from stores charge plus 2 cents a pin but might be worth it.
I didn't know this! Thanks for the heads up! :tu:

User avatar
devinw1
Super Deluxe Wiggler
Posts: 2213
Joined: Tue Aug 07, 2018 11:20 am
Location: Portland, OR
Contact:

Re: Capacitor discharge large difference...ESR?

Post by devinw1 » Tue May 04, 2021 6:09 pm

Here's the Film SMTs I have coming. I shall heed this warning when applying!:
smtilm.png

User avatar
MikeDB
Veteran Wiggler
Posts: 680
Joined: Fri Feb 08, 2019 8:28 am
Location: UK

Re: Capacitor discharge large difference...ESR?

Post by MikeDB » Tue May 04, 2021 6:52 pm

devinw1 wrote:
Tue May 04, 2021 5:56 pm
As for SMT films...that will be a new experience for me. I have some on the way from Mouser to try for another project. When you say sensitive to solder temp, I assume you mean they are easily damaged in soldering? This could be problematic..
Yes you can happily change the capacitance as much as the applied voltage did The Y5V. Far better to put solder paste on the PCB and reflow it, either by a carefully aimed heat gun or a soldering iron touching the pad but not the component.
Always interested in innovative audio startups needing help and investment, just PM me.

User avatar
KSS
Super Deluxe Wiggler
Posts: 5571
Joined: Mon Jan 25, 2016 7:28 am

Re: Capacitor discharge large difference...ESR?

Post by KSS » Tue May 04, 2021 8:23 pm

transistorresistor wrote:
Tue May 04, 2021 3:14 pm
in my experience both refurbishing vintage audio compressors and manufacturing new audio compressors, whenever I change the dielectric material in a timing circuit like the attack or release, the time constant is almost always effected.

If you have an old unit with a tantalum in there and replace it with an aluminum electrolytic, the time constant almost always changes
. If you have a old tube unit with a paper in oil and you change it to a modern polyprop, the timing circuit changes. This has been such a consistent behavior in my experience, I have in the past put that cap on a switch on old tube units to get a different feel. Same values and voltage mind you, just different dielectric. And sometimes its not the overall time that changes but the curve. speaking specifically here about timing circuits in limiters
Preach! :agree: :tu:
Treat utility modules as stars instead of backup singers.
Treat power supplies like Rockstars instead of roadies!
Chase magic sound, not magic parts.

jorg
Ultra Wiggler
Posts: 960
Joined: Fri Apr 03, 2015 9:38 am
Location: East Coast USA

Re: Capacitor discharge large difference...ESR?

Post by jorg » Wed May 05, 2021 8:27 am


User avatar
guest
Super Deluxe Wiggler
Posts: 6032
Joined: Mon Aug 19, 2013 11:49 am

Re: Capacitor discharge large difference...ESR?

Post by guest » Wed May 05, 2021 11:17 am

wow, thats a well done wikipedia page.
openmusiclabs.com

User avatar
devinw1
Super Deluxe Wiggler
Posts: 2213
Joined: Tue Aug 07, 2018 11:20 am
Location: Portland, OR
Contact:

Re: Capacitor discharge large difference...ESR?

Post by devinw1 » Wed May 05, 2021 11:23 am

MikeDB wrote:
Tue May 04, 2021 6:52 pm
devinw1 wrote:
Tue May 04, 2021 5:56 pm
As for SMT films...that will be a new experience for me. I have some on the way from Mouser to try for another project. When you say sensitive to solder temp, I assume you mean they are easily damaged in soldering? This could be problematic..
Yes you can happily change the capacitance as much as the applied voltage did The Y5V. Far better to put solder paste on the PCB and reflow it, either by a carefully aimed heat gun or a soldering iron touching the pad but not the component.
Cool, yeah I was thinking of trying this. I have a hot air rework station and some solder paste. Hand applying for a big footprint like that should be pretty easy. :tu:

Post Reply

Return to “Music Tech DIY”