Mallory 150 outer foil

[JuneauMike]

So this is not a big deal and I'm not going to sweat it. But I dragged an amp and guitar cable out last night and wanted to satisfy for myself that my coupling caps were going to be oriented in a way that minimizes excess noise in a couple of amps I'm working on.

I tested three brands of caps, all were .022uf and two of the three had markings indicating the outer foil direction. The Mallory's did not. I followed this method and my results were consistent with what he was talking about. The only difference was that I didn't use a bare input jack, I just unscrewed the casing of one of my 6-foot short guitar cables and plugged directly to the solder joints.



However, I couldn't detect a sound difference with the Mallory's. I thought I had read somewhere that some of these film capacitor actually has a foil shell wrapped around them that is disconnected from the inner layers, but I've never had the luxury of owning enough Mallory caps to actually cut one open.

Again, I'm not going to worry about it. Without any information I am going to orient the caps with the assumption that the outer foil is to the right as you read the lettering on the cap. If their advertising propaganda is to be believed than they are non polarized and so orientation shouldn't be an issue, right? I was really just curious. Is there another DIY method of testing this short of buying an oscilloscope or building another component that, lets be honest, I'm not going to build.

 

[Outlaws]

I did this and made the box. I had a Mesa Mark V with a 412 almost fully cranked to hear the difference for the test. Not saying it doesn’t matter, just that testing this way requires serious volume.

 

[JD0x0]

If their advertising propaganda is to be believed than they are non polarized and so orientation shouldn't be an issue, right?

Non-polarized caps will function in either direction, but that doesn't make outer foil orientation (if the cap has it) insignificant. If you have outer foil properly oriented in your amp, you will have better noise rejection. Obviously, it will make less difference in a 'lower gain' circuit compared to a high gain circuit.

 

[JuneauMike]

Yeah, no question they will function fine in either direction. Noise rejection is what I'm after.

 

[JuneauMike]

I did this and made the box. I had a Mesa Mark V with a 412 almost fully cranked to hear the difference for the test. Not saying it doesn’t matter, just that testing this way requires serious volume.

Hmm. There was absolutely no difference that I could detect. None. Maybe I'll use my Big Muff tonight. But I sorta think based on what I heard that no amount of volume is gonna make a difference. But nothing ventured ....

 

[Phrygian77]

I just did this with some 150s and there was a very noticeable difference. I used alligator clip leads on the end of a shielded cable, and I had the amp turned all the way up.

 

[sds1]

Can you find the noisy end more efficiently with an oscilloscope? If so, what's the procedure?

 

[JuneauMike]

My understanding is that yes, a scope would work better. As to the procedure:
Step 1: Spend a ton of money.
Step 2: Learn how to use the scope.
Step 3: Use it.
Step 4: Store it away for years and years until you need it again.

Thanks guys. Sounds like I should take another run at it. Gotta tell you, this approach seems very dodgy, but way cheaper than buying the right test equipment. Ha.

 

[D'tar]

Hold the cap over an ac power cord. I use the one to the amp i am testing with. This helps you hear the difference. The .022's are hard to hear sometimes

 

[Mr Green Genes]

Again, I'm not going to worry about it. Without any information I am going to orient the caps with the assumption that the outer foil is to the right as you read the lettering on the cap.

Yup. The easiest way to remember it is that the signal should flow in the same direction as the printing/lettering.

If their advertising propaganda is to be believed than they are non polarized and so orientation shouldn't be an issue, right? I was really just curious. Is there another DIY method of testing this short of buying an oscilloscope or building another component that, lets be honest, I'm not going to build.

Some people hear a distinct difference, others hear no difference at all.

As far as I'm concerned, it's no more effort to install them in one direction than it is the other, so why not just install them that way as a matter of course?

 

[Outlaws]

Yup. The easiest way to remember it is that the signal should flow in the same direction as the printing/lettering

Should was only correct in 4/5 of mine.

 

[JD0x0]

Yup. The easiest way to remember it is that the signal should flow in the same direction as the printing/lettering.

Sometimes the caps get flipped on the production line. Outer foil is not always inherently on one end relative to the printing on the cap.


The easiest way is to plug a 1/4'' cable into the amp, and touch one lead to the tip and one lead to the sleeve of the 1/4''
One direction will have notable hum, the other will be significantly quieter. The quieter direction will have outer foil to the 1/4'' cable sleeve. Connect outer foil of cap to the side of the circuit that has less impedance to ground.

 

[Mr Green Genes]

Should was only correct in 4/5 of mine.

If it's crucially important to you in a non-polarized capacitor, testing each individually is the only way to be certain.

For someone who doesn't want to go through and test every capacitor, it's a good rule of thumb, and will be right 80% of the time, according to the limited data available.

If the capacitor is being housed inside a Faraday Cage (like an amp chassis), I really don't think it's going to make a world of difference.

 

[dsutton24]

If the capacitor is being housed inside a Faraday Cage (like an amp chassis), I really don't think it's going to make a world of difference.

An amp chassis is not a Faraday cage. Tube amps are very noisy internally, and they're precisely the kind of place where you want to pay attention to cap orientation.

 

[JuneauMike]

My amp was not at an excessively high volume (because its annoying and I like my comfort) but I'll try tonight with the volume up and, failing that, with a muff pedal between them. If the casing is in fact manufactured in a way that separates the inner film from the outer casing (such as I described in my OP) is there a workaround? Touching the ends of the capacitor casing rather than the cylindrical surface wouldn't do it, right?

 

[JD0x0]

If the capacitor is being housed inside a Faraday Cage (like an amp chassis), I really don't think it's going to make a world of difference

There's internal interference going on in a tube amp. That's why shielded grid wires are often used and lead dress is extremely important in high gain amps. It makes a noticeable difference, in noise floor, IME.

 

[Mr Green Genes]

An amp chassis is not a Faraday cage. Tube amps are very noisy internally, and they're precisely the kind of place where you want to pay attention to cap orientation.

There's internal interference going on in a tube amp. That's why shielded grid wires are often used and lead dress is extremely important in high gain amps. It makes a noticeable difference, in noise floor, IME.

I stand corrected.

 

[Outlaws]

My amp was not at an excessively high volume (because its annoying and I like my comfort) but I'll try tonight with the volume up and, failing that, with a muff pedal between them. If the casing is in fact manufactured in a way that separates the inner film from the outer casing (such as I described in my OP) is there a workaround? Touching the ends of the capacitor casing rather than the cylindrical surface wouldn't do it, right?

I made it with a switch and a mute switch and had to listen closely. If i had to do it the other way with the volume and noise of flipping it around would make it very hard to hear the nuance in hindsight. It’s there, but it’s very minor.

 

[gourmetsaint]

I did this last night with six Mallory 150s using an old Marshall vs15 practice amp. When the outer foil end was connected to the tip of the guitar cable, there was definitely a different sound as I held and released the caps with my fingers. When the other way around, I could pinch and unpinch the caps and no difference was heard.

 

[Phrygian77]

My amp was not at an excessively high volume (because its annoying and I like my comfort) but I'll try tonight with the volume up and, failing that, with a muff pedal between them. If the casing is in fact manufactured in a way that separates the inner film from the outer casing (such as I described in my OP) is there a workaround? Touching the ends of the capacitor casing rather than the cylindrical surface wouldn't do it, right?

Don't touch anything except the cap. Pinch it in the middle with your index finger and thumb. Both ways will produce hum, but one way will be noticeably quieter, that's the foil side connected to ground.

Sometimes the caps get flipped on the production line. Outer foil is not always inherently on one end relative to the printing on the cap.

On the 716Ps I just tested, two 400VDC .022uF, and two 600VDC .1uF, the labeling was opposite for the different voltages/values.