I have started measurement of the 100nF blue caps for the riaa filter section to find equal values close to 100 nF.
I have a Mega 328 alike tester. My idea was to take a number of readings as a quality control and then maybe take the average of 3 readings.
What I observed was that the reading of repeating readings was raising values. E.g. from 100.2 nF to 100.8 after 4-5 readings. My theory is that the cap charges a bit and then the reading after "confuses" the tester. If I take the cap out and discharge it and put it in again it starts again with a low value. Don't know if other has observed same behavior?
What I do now with a couple of repeated readings it that I take the cap out after each reading to discharge it before I insert it again for next reading.
I have a Mega 328 alike tester. My idea was to take a number of readings as a quality control and then maybe take the average of 3 readings.
What I observed was that the reading of repeating readings was raising values. E.g. from 100.2 nF to 100.8 after 4-5 readings. My theory is that the cap charges a bit and then the reading after "confuses" the tester. If I take the cap out and discharge it and put it in again it starts again with a low value. Don't know if other has observed same behavior?
What I do now with a couple of repeated readings it that I take the cap out after each reading to discharge it before I insert it again for next reading.
Discharging the caps between tests is the right answer. Also, for best consistency, power the Mega328 from a bench supply, not a battery.
Remember that any measured sorting of this type, and placing your closest caps in the critical positions will be beneficial over random placement. Basiscally it’s all good.
Remember that any measured sorting of this type, and placing your closest caps in the critical positions will be beneficial over random placement. Basiscally it’s all good.
I take a negative impression of this tester.
You can see the voltage of the 9V battery go down with subsequent measurements.
The tester says that 2SK170 JFETS are resistors.
It does identify the Collector Emitter and Base of a ZTX851.
Thanks DT
Mega328 does often get confused with out little small-signal Jfets, yes.
But as Jfet are actually quite rare anymore, and it does so many things very well, is that enough to have a “negative impression” of it?
I certainly don’t
Yes. That seems to be the point of battery monitoring…
But as Jfet are actually quite rare anymore, and it does so many things very well, is that enough to have a “negative impression” of it?
I certainly don’t
Yes. That seems to be the point of battery monitoring…
How large a difference would be heard if 1 channel was 100.2 and 1 100.8 vs both matched at 100.2 or both at 100.8?
@MEPER - I think you are expecting a degree of accuracy and repeatability not likely with most inexpensive testers, though the Mega328 and some other small, inexpensive testers offer some nice features and flexibility. I've noticed similar variability with all of my PEAK testers - capacitor, transistor, diode, etc. They aren't the last word in accuracy or capability, so about the best you can do is what 6L6 has suggested.
With capacitors, I've even noticed variable readings with my Sencore LC-102, which tests at rated voltages and has many useful features and characteristics. However, my readings have become much more precise with my new benchtop LCR meter, though it is getting to the opposite end of the cost spectrum compared to the cheap and cheerful handheld testers.
I built my Pearl 3 before getting my new LCR meter, so didn't bother with matching, but have used it now to select and match some film and electrolytic caps for another project. It should be understood that caps perform differently at different frequencies and voltages.
Discharge your caps before re-testing, and I think it's probably reasonable to be satisfied with a 0.6nF variance for a 100nF cap.
With capacitors, I've even noticed variable readings with my Sencore LC-102, which tests at rated voltages and has many useful features and characteristics. However, my readings have become much more precise with my new benchtop LCR meter, though it is getting to the opposite end of the cost spectrum compared to the cheap and cheerful handheld testers.
I built my Pearl 3 before getting my new LCR meter, so didn't bother with matching, but have used it now to select and match some film and electrolytic caps for another project. It should be understood that caps perform differently at different frequencies and voltages.
Discharge your caps before re-testing, and I think it's probably reasonable to be satisfied with a 0.6nF variance for a 100nF cap.
Hear? None. You’re talking about a difference of 0.6% in the split. Or in case of the matches, being 0.2% from perfect or 0.8% from perfect.
In every example you list, it is less than 1% away from perfect.
The real point of the optional matching is, 1) it’s fun, and 2) it’s an easy and cheap way to make a real difference regarding capacitors instead of dumping money at boutique caps that will likely be unmatched, of dubious benefit, much, much more expensive, and almost certainly better at picking up external hum and polluting the circuit.
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I have a bag of 1000 of these blue 100nF caps and it was suggested to try to match them as good as possible. So that I try to do.
But it seems these caps are much closer to 100 nF than the specs says. I think they are rated 5% but so far none has been below 99 nF and none above 101 nF so in real live they seems to be -+1% caps.
But it seems these caps are much closer to 100 nF than the specs says. I think they are rated 5% but so far none has been below 99 nF and none above 101 nF so in real live they seems to be -+1% caps.
The use of the Mega328 as recommended in the build guide was intended to allow builders to buy more commonly available, yet high-performing caps and match them closely for the circuit to perform optimally. It isn't necessary to spend a fortune on test gear and/or super-tight tolerance parts. It is fortunate that there are testers now available for such a low price that enable builders to perform very good matching and measuring without having to spend a LOT of money.
You can be confident that the parts as selected by Wayne will result in an excellent sounding and performing phono preamp.
Wayne talked about cap selection in his 2023 BAF presentation, and that video is now available to watch.
You can be confident that the parts as selected by Wayne will result in an excellent sounding and performing phono preamp.
Wayne talked about cap selection in his 2023 BAF presentation, and that video is now available to watch.
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From my bag of caps it is easy to find 10 that is within -+0.5% and then again easy to pair these so they are within 0.5% of each other.
The resistors that controls the bias of the JFETs and opamp which may be subject for a change to hit the spec'ed bias interval.......how likely is that to happen?
Probably difficult to answer but could it be recommended to just solder these two resistors so they are easy to change?
Something like solder them with longer legs and just beside of the holes (on the edge of the holes).
The resistors that controls the bias of the JFETs and opamp which may be subject for a change to hit the spec'ed bias interval.......how likely is that to happen?
Probably difficult to answer but could it be recommended to just solder these two resistors so they are easy to change?
Something like solder them with longer legs and just beside of the holes (on the edge of the holes).