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

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

Post by mediatechnology » Tue Sep 15, 2020 8:32 pm

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

The intrinsic value matching of capacitors from the same lot sometimes comes up in design discussions of mic preamps and AC-coupled balanced line inputs. Capacitor value matching ahead of differential inputs affects low frequency common mode rejection.

Common mode rejection design limits should be based on the published tolerance but the actual relative matching of caps from the same lot are usually better. But how much better?


While recapping my Texar Audio Prisims I decided to measure the 4.7 uF axial lead caps as I installed them.
Since I was already measuring value I turned on the relative tolerance feature.
I used the first cap out of the bag to set the "standard."

48 of 59 caps, 81.3%, were within ±1%.
11 of 59 caps, 18.6%, were in the range of ±1 to ±2%.
Out of the 59 I measured none were greater than ±2%.

The value matching is much better than I anticipated.

The caps were Nichicon TVX1H4R7MAD 4.7 µF 50V axial lead that I purchased in 2018.

Your mileage may vary...
https://ka-electronics.com

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

Post by terkio » Wed Sep 16, 2020 12:06 am

Very interesting.
What was the tolerance of these caps to begin with ?

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

Post by mediatechnology » Wed Sep 16, 2020 5:49 am

They were ±20% tolerance.
https://ka-electronics.com

Plandemic Series: "Pland3mic - Indoctornation" https://proaudiodesignforum.com/content ... nation.mp4
Plandemic Series: "Plandemic - Doctors In Black" https://proaudiodesignforum.com/content/Plandemic.mp4

CDC: "For 6% of the deaths, COVID-19 was the only cause mentioned. For deaths with conditions or causes in addition to COVID-19, on average, there were 2.6 additional conditions or causes per death." https://www.cdc.gov/nchs/nvss/vsrr/covi ... /index.htm

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

Post by JR. » Wed Sep 16, 2020 8:51 am

Not surprising from production manufacturing. Chunka-chunk automated production lines won't wary widely, while tolerances specs are are mostly important for batch to batch variation. When designing for large scale manufacturing we ASSume the worst, and sometimes get it. (I won't bore you with bad capacitor stories).

I recall back in the day making a similar measurement of 5% carbon film (Rohm) resistors and they were likewise very close, IIRC much tighter than 2%.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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

Post by mediatechnology » Wed Sep 16, 2020 3:56 pm

Just received a shipment from Mouser to replace the power supply filter caps.
I only needed 4 but I bought 10.

The value is 2200 µF 40V ±20% Vishay MAL202117222E3 (Axial)

7 of 10 were within 1%.
3 of 10 were within 2%.

I used a test frequency of 100 Hz for the 2200 µF.
On the mF scale I could only read to 2 decimal places so ±1 LSD is an error of 0.47%.

So far 70-80% of the parts in the same lot - for values large and small - match within 1%.
https://ka-electronics.com

Plandemic Series: "Pland3mic - Indoctornation" https://proaudiodesignforum.com/content ... nation.mp4
Plandemic Series: "Plandemic - Doctors In Black" https://proaudiodesignforum.com/content/Plandemic.mp4

CDC: "For 6% of the deaths, COVID-19 was the only cause mentioned. For deaths with conditions or causes in addition to COVID-19, on average, there were 2.6 additional conditions or causes per death." https://www.cdc.gov/nchs/nvss/vsrr/covi ... /index.htm

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

Post by terkio » Thu Sep 17, 2020 6:53 am

In the 60's I was interested in 2R R ladders, so I sorted in a lot of 1K 5% resistors, they came out well matched, better than I presumed.
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 ?

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

Post by JR. » Thu Sep 17, 2020 8:12 am

I just got in 50 pieces of 33uF electrolytic caps, 20%. I only measured about ten of them but found a range of 33.5uF to 34.5uF, so roughly a 3% variation, nominally just above the specified value... not too shabby for (cheap) 20% parts. I think I'll use them. :lol:

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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

Post by JR. » Thu Sep 17, 2020 8:15 am

terkio wrote:
Thu Sep 17, 2020 6:53 am
In the 60's I was interested in 2R R ladders, so I sorted in a lot of 1K 5% resistors, they came out well matched, better than I presumed.
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 expect they are now tighter coming off the production machinery, but it may vary between manufacturers.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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

Post by AnalogJoe » Fri Sep 18, 2020 4:35 am

What about the tempco? heat them with a hot air gun and report back.

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

Post by JR. » Fri Sep 18, 2020 10:24 am

AnalogJoe wrote:
Fri Sep 18, 2020 4:35 am
What about the tempco? heat them with a hot air gun and report back.
Speaking of temperature, that reminds me of a production problem I encountered with potentiometers. The resistive element is generally a screened on carbon ink. The tolerance of the bulk resistance is around 20% but not widely known part of the production process involves curing the ink with elevated temperature. Cooking the substrates longer can pull in out of tolerance components. At Peavey we encountered one vendor (CTS cough) who's process was so far off, that they over cooked the substrates to pull in final resistive element resistance and in the process made the parts so brittle that they would break while being inserted into PCBs. I tried to work with them, they just needed to tweak the green resistance of their ink.

Almost humorously CTS decided to no-bid, dropping us as customer, because they said we were "too picky" :lol: .

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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