Karma Guitar Amplifiers - Capacitor Foil Test

This video shows how we determine the internal "outside" foil of capacitors.
Please note the URL for Karma Guitar Amplifiers has changed since this video was made. The correct one is: www.karmaguitaramps.com/
After many requests, the schematic for our testing box is available as a pdf from the online manual for our Karma 20T amplifier kit:
karma20tmanual.karmaguitaramps...

[@deanaf]

I just did this last night with an amp and an input jack. It worked, but this is easier. Wish I found it sooner. Thanks. I will be making one.

[@stratdude83]

Simple and easy, thanks!!

[@leedydrummer]

Wow man! Do these Karma amp kit amps go to 11? Nice to see a new product hitting the music market. Haven't been satisfied with the old, stodgy amps. Last great amp [and technician] until now was JB Labs [Akron, Ohio] back in the 60's......

[@karmaguitaramplifiers7967]

Thanks leedydrummer! Our first model, the Karma 20T, should be available around mid-summer 2017, initially as a kit. And I remember Joe Basile and JB Labs very well!

[@davidlong1786]

You do know that toggle switches connect the middle and opposite terminal on the switch I hope? If it's pointing to the right that means the middle and left terminal are connected. I wonder how many people have built this and wrongly identified the foil end of the cap because of this?

[@karmaguitaramplifiers7967]

Excellent point, David! I guess I assumed that anyone building this would know that, but it's an important point and I appreciate you bringing it up... thanks!

[@kilcar]

Test EVERY CAP for polarity, even if marked for polarity. I find mismarked caps all the time.

[@LifeBloodMarketing]

Sweet

[@karmaguitaramplifiers7967]

After many requests, the schematic for our testing box is available as a pdf from the online manual for our Karma 20T amplifier kit: karma20tmanual.karmaguitaramps.com/mark-outside-foil-of-capacitors Please note that our box shown in the video has an on/off switch. It's not really necessary and not shown on the schematic pdf.

[@andreastjahjadi476]

Can I buy the tools to determine the outside foil of capacitor?

[@karmaguitaramplifiers7967]

Sorry, no - we don't make the switch box shown here for sale.

[@ianaintsaying1625]

What about caps that don't make noise in either orientation? I've got a bunch of caps I've tried to identify. O-scope, amp input, amp input with a fuzz pedal. None of the caps I have tested make more noise in one direction over the other. In fact they hardly make any noise at all and that's with the amp cranked.

[@karmaguitaramplifiers7967]

Ian - I'm not sure what kind of caps you're checking, but assuming your testing methods are correct I'd say you don't have a problem!

[@ianaintsaying1625]

@@karmaguitaramplifiers7967 The caps are what's usually found in a guitar amp. Mallory, Sprague, Orange Drops, etc. I've just recently took up building tube guitar amps and trying to identify the foil end of these coupling caps has been driving me batty.

[@Bloodysugar]

@@ianaintsaying1625 They all got a polarity and make noise if used backwards. Noise being at least visible with an oscilloscope. If you can't see it on a scope it may be because you do the test wrong, for exemple you must keep the cap body between your fingers cause if you keep it hanging by probe's end without touching the body then it wont generate noise. kzbin.info/www/bejne/eJ-1kHeCmZaDeqs

[@karmaguitaramplifiers7967]

@@ianaintsaying1625 Ian, if you've just started building I wouldn't worry too much about this. I know of several high end boutique amp builders that don't bother with it at all.

[@ianaintsaying1625]

@@Bloodysugar I would build this if I were younger. My eyes are too old to work with surface mount circuits. If there is a thru-hole version I'd be all over it.

[@lingcod91]

Can the circuitry inside the mysterious "box" be shown. Otherwise there is no point in the video.

[@karmaguitaramplifiers7967]

Not so mysterious now. The pdf is available in the build manual for our Karma 20T amp kit. karma20tmanual.karmaguitaramps.com/mark-outside-foil-of-capacitors

[@lingcod91]

GREAT . . . Thanks . . . Just plug it into the XLR input jack of my DAW. What is my DAW ? If DAW is what I think it is, I know I don't have one. So I'm back to square one.

[@karmaguitaramplifiers7967]

You can plug the 1/4" output into your guitar amp and listen for the difference in hum, just know that the difference may be hard to discern with some caps. That's why I use a DAW (digital audio workstation - Pro Tools in this case) to visualize the difference. That and I'm not a big fan of listening to hum while doing a bunch of caps.

[@Bloodysugar]

Other solution : 20$ numeric pocket oscilloscope = very obvious noise waves and no need to listen to hum.

[@lingcod91]

@@Bloodysugar Huh? what is a 20$ numeric pocket oscilloscope? And how would such a device be a "solution" . . . ? . . . to anything? I have an oscilloscope. My problem is/was: the location of the noise (in the capacitor) is not identifiable. The object is to identify the correct "side" of the capacitor BEFORE inserting it into the circuit. Because I've got 3 amps to work on, this would be a sorting method . . . Do you understand now? Because your reply doesn't indicate that you grasp the situation, or are able to construct a logical sentence. [["noise waves" . . . indeed. isn't all sound a wave, and isn't every sound a noise? ]]. You're blowing shit out your ass.

[@Bloodysugar]

Nice but I prefer my scope, it is way more obvious and pleasant to use.

[@jeeplvr2000]

How do you do this with an oscciloscope? I have a dso but can't find any information on how to set up the scope.

[@Bloodysugar]

@@jeeplvr2000 Here is a good video about it : kzbin.info/www/bejne/eJ-1kHeCmZaDeqs Basics of using a scope starts at 8:07. It is very important you set it with the smallest volt by division you can get and it should be at least as low as 5 milli Volts / division. If you can't get as low as 5 milli Volts you wont be able to see the noise, 2 milli Volts is the sweet spot.

[@kwacz]

Scope is better but not everyone has a scope