My test area is right next to my computer monitors and a lamp. I wonder...

 

20 years agoa friend of mine would sometimes have a bit of a 30 H buzz on his radio signal as we talked. I would remind him that his microphone was too close to his computer monitor, and he would pull it back a few inches. That also happened when his mic was too close to his television, which was next to his computer monitor. I could usually tell the difference because the TV interference sound changed with the picture while the computer monitor sound did not change much. Of course those were both CRT devices, not flat screens. A CRT display has an electric field in front of the screen. On some displays that can be easily felt with the backside of a hand. At least, I can feel it.
Of course, many computers do generate lots of radiated and conducted noise.

 

What is the best type of non-polarized capacitor for audio? Say .1u size. My research suggests Polypropylene... just wondering.

 

Certainly PolyP is a good variety, stable and low loss and low leakage. The caution is needed while soldering because the poly plastic has a lower melting point. Price might be an issue if cost is more important than quality, (often seen in consumer electronics)
Others may have other opinions.

 

I use these ones, 0.2" lead spacing, 5% tolerance and 35V to 63V:

 

From post #199, I went with a center positive DC jack. But in the music industry this is uncommon, Boss style center negative is the norm. I want to add protection in case someone plugs in the wrong polarity. A simple diode, right? I would think right on the input jack? What type of diode do I need?

 

Use a 1N4002 rectifier diode in series with the center pole of the power input jack. It is rated for a max of 100V and 1A. It has a forward voltage loss of 1.1V max at 1A.

 

Blame Boss. When they came out with pedals back in the 70s/80's they were center negative and to this day 90% of all musical stuff I've ever seen are center negative. Although there are many companies who are trying to change the tide with center positive, it's hard (requires adapters) because most musicians just want it to be all the same standard Boss 5.5/2.1mm center negative.

Blame germanium transistors, with their negative power supplies.
Original pedals with germanium transistors have the centre pin negative, but the outer pin is connected to signal earth. Later pedals retained the centre-pin negative but the signal earth became connected to negative when silicon transistors arrived.
Connect two together and it shorts out your power supply.

 

What is the best type of non-polarized capacitor for audio? Say .1u size. My research suggests Polypropylene... just wondering.

NP0 or C0G ceramic (but definitely not any other type of ceramic).
Polyproplyene is good, a little better than polyester.

 

Use a 1N4002 rectifier diode in series with the center pole of the power input jack. It is rated for a max of 100V and 1A. It has a forward voltage loss of 1.1V max at 1A.

Ok I have a couple of these. I measured 0.56v forward voltage drop at 1mA. I’ve read to use 0.6v as a generic number for most diodes.

 

NP0 or C0G ceramic (but definitely not any other type of ceramic).
Polyproplyene is good, a little better than polyester.

NP0 or C0G, is that multilayered monolithic?

EEEEE 30 Value 300 pcs Multilayer Monolithic Ceramic Capacitor Assortment kit 10pf－10uF Individual Box Lid pf nf uf (300 pcs)

https://a.co/d/8kVL6SE

 

NP0 or C0G, is that multilayered monolithic?

EEEEE 30 Value 300 pcs Multilayer Monolithic Ceramic Capacitor Assortment kit 10pf－10uF Individual Box Lid pf nf uf (300 pcs)

https://a.co/d/8kVL6SE

If they are that cheap or if they don't specify, then they will be X7R, and they sound bad, and are microphonic. Avoid.
NP0 and C0G are multilayered. I only know them as surface mount. I don't know if you can get them in through-hole.

 

I’ve got some polypropylene and polyester caps coming from Amplified parts.

 

I’ve got some polypropylene and polyester caps coming from Amplified parts.

You'll not hear the difference. After all, consider the signal source!
The non-linearities are <-90dB, and you have only 50dB SNR from a condensor mic.

 

For protecting the device and operating from either polarity you could use a bridge rectifier, probably the smallest one you can find will be adequate. Of course with the outside connected to system common there might be a problem.