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Re: How Closely Do The Values Of Electrolytic Caps From The Same Lot Match?

Posted: Fri Sep 18, 2020 10:14 pm
by mediatechnology
Annealing is a tricky process.
That's what makes some SMT resistors very low distortion and others horrible. https://proaudiodesignforum.com/forum/p ... ?f=6&t=401

Re: How Closely Do The Values Of Electrolytic Caps From The Same Lot Match?

Posted: Sat Sep 19, 2020 8:51 am
by JR.
That thread about smd resistors is pretty old and I didn't even share about my drama with operating high Z SMD resistors at high voltage, another case where larger package resistors were required to meet spec.

JR

PS: For my outlet tester I realized off scale >500M insulation resistance @ 500V (the 100M resistors in smaller SMD packages wouldn't meet the voltage spec.)

Re: How Closely Do The Values Of Electrolytic Caps From The Same Lot Match?

Posted: Sat Sep 19, 2020 6:24 pm
by montemcguire
terkio wrote:
Thu Sep 17, 2020 6:53 am
I was told, resistors were sorted at the end of the production line, so the 5% I got were those that did not make it in the 2%.
So I had those from the same of the two sides between 5% and 2%.
Does this make sense ? Is it this Now days ?
I think it depends on the manufacturer. I have measured and matched a lot of Susumu RG series SMD metal films, and there seems to be no 'hole in the middle' of their value distribution. They're all well within datasheet spec, but then again, I'm at 300ºK and the spec is good over a slightly wider range. Our local AES group got the Susumu rep out to make a presentation and I was able to ask some questions to the engineer.

Their process is unique in that they print the NiCr pattern then overcoat it with a 'mineral coating' instead of epoxy. They can laser trim through that, so it ends up making a very stable part, since no mechanical stress remains from trimming. The engineer said that they basically trim each part to tolerance, but what was more interesting is that they can trim for tempco as well! Not sure how they do that, and he wasn't about to tell me, but I have no reason not to believe it So, I think it's a tradeoff of taking more time to trim to result in a higher cost and tighter tolerance part. They might do some sort of magic on the lot level to exclude or more heavily anneal the raw blanks, but it was described more as a 'trim' process rather than a 'test and sort' process.

So, I think it depends a lot on whose parts you're using. The Susumu RG parts are not cheap, but they're not a fortune either. Panasonic seems to make something fairly close in quality (ERA series) at a slightly lower price with generally a better stock of offbeat values, but the Susumus might have a little better long term stability - not sure what the overcoat is for the Panasonics, and plain epoxy can drift with water over time as the epoxy expands and contracts.

Re: How Closely Do The Values Of Electrolytic Caps From The Same Lot Match?

Posted: Sun Sep 20, 2020 5:30 am
by mediatechnology
This is the report that Dave Hill shared with us on SMT resistor distortion sometime ago: http://www.waynekirkwood.com/images/pdf ... nesong.pdf

It is posted in the thread here: https://proaudiodesignforum.com/forum/p ... ?f=6&t=401

Image

Earlier in the thread there are some AP measurements comparing a couple of brands of SMT to TH. (includes Susumu).

Here's a link to the Susumu catalog: https://www.susumu.co.jp/common/pdf/n_e_all.pdf

Re: How Closely Do The Values Of Electrolytic Caps From The Same Lot Match?

Posted: Sun Sep 20, 2020 10:03 am
by JR.
is it fair to assume that his resolution floor is 0.0008?

Some parts may be better?

JR

Re: How Closely Do The Values Of Electrolytic Caps From The Same Lot Match?

Posted: Sun Sep 20, 2020 2:18 pm
by mediatechnology
I do think that might be fair to say.

Finding the better ones seems to be a good use of null testing.

Re: How Closely Do The Values Of Electrolytic Caps From The Same Lot Match?

Posted: Mon Sep 21, 2020 8:19 am
by JR.
mediatechnology wrote:
Sun Sep 20, 2020 2:18 pm
I do think that might be fair to say.

Finding the better ones seems to be a good use of null testing.
After designing the TS-1 I gained new respect for people who design test equipment, like the audio precision crew.

I would find it difficult to parse out distortion components that low (may be noise floor?).

JR

Re: How Closely Do The Values Of Electrolytic Caps From The Same Lot Match?

Posted: Wed Sep 23, 2020 5:02 am
by terkio
May I ask, why you care about matching electrolytics ?
What about matching film caps ?
Typically in microphone preamplifiers for phantom power isolation.

Re: How Closely Do The Values Of Electrolytic Caps From The Same Lot Match?

Posted: Wed Sep 23, 2020 6:38 am
by mediatechnology
terkio wrote:
Wed Sep 23, 2020 5:02 am
May I ask, why you care about matching electrolytics ?
What about matching film caps ?
Typically in microphone preamplifiers for phantom power isolation.
I don't, at least not for mic inputs for anything I'd do.

The subject has come up over the years for design customer's balanced line-level inputs and outputs as well as low-cost or space-constrained mic preamps.
The customers weren't interested in matching parts either but the question was always "how well do they match coming out of the bag?"
The answer is pretty good for units of the same lot.

Since I was checking the value of about 48 caps before I installed them I decided to look at tolerance out of curiosity.

Re: How Closely Do The Values Of Electrolytic Caps From The Same Lot Match?

Posted: Wed Sep 23, 2020 8:02 am
by JR.
If you look at the old Transamp mic preamp application notes, they included CMRR trim pots. IIRC there were two trims a HF and a LF trim.

FWIW I never used trims or selected parts in manufacturing.

JR