Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jackplug1 on February 11, 2022, 11:42:44 am

Title: Blue coloured HV ceramic capacitors in a tone control circuit
Post by: jackplug1 on February 11, 2022, 11:42:44 am

Is there any reason not to use this type of small capacitor in a tone control circuit? - they are usually 1or 2 Kv
They are cheap and easily available where as the silver mica type are not.
Usually used in snubber circuits.

Title: Re: Blue coloured HV ceramic capacitors in a tone control circuit
Post by: st on February 11, 2022, 01:53:51 pm

Mojo

Title: Re: Blue coloured HV ceramic capacitors in a tone control circuit
Post by: pdf64 on February 11, 2022, 05:06:30 pm

What’s their specification, eg temperature and voltage coefficients?

Title: Re: Blue coloured HV ceramic capacitors in a tone control circuit
Post by: PRR on February 11, 2022, 11:07:14 pm

"Blue" is a dip-coat? What is inside? Wax paper? Formica? Dried lark-tongue?

Can you point to a catalog page?

The 1KV rating is a good sign that they won't blow-up easy, and I am not tooo concerned about Voltage Coeficient on a 1KV cap in a guitar amp, but historically audio-people want to know more than just "Blue 1KV".

Title: Re: Blue coloured HV ceramic capacitors in a tone control circuit
Post by: jackplug1 on February 12, 2022, 05:15:23 am

Blue dip ceramic - 471 2kv printed on the surface, no other information
For use on a guitar amplifier tone circuit.

Title: Re: Blue coloured HV ceramic capacitors in a tone control circuit
Post by: pdf64 on February 12, 2022, 05:24:57 am

In the absence of anything more than the most basic info, the only way for your query to be answered is for you to try it  :icon_biggrin:
Temperature coefficient might be assessed by monitoring the cap’s capacitance value whilst holding a soldering iron in close proximity, so as to warm it up.

Title: Re: Blue coloured HV ceramic capacitors in a tone control circuit
Post by: Esquirefreak on February 12, 2022, 06:11:45 am

I've been using those (100pF-500pF) blue caps here and there in guitar amps. Like bright caps and on tone stacks. Not that I've done a proper shootout against more expensive parts, but they've been working just fine for my purposes.

/Max

Title: Re: Blue coloured HV ceramic capacitors in a tone control circuit
Post by: jackplug1 on February 13, 2022, 10:48:40 am

Seems like the are probably okay to use in a guitar amplifier

Title: Re: Blue coloured HV ceramic capacitors in a tone control circuit
Post by: thetragichero on February 13, 2022, 08:42:01 pm

i like em because they're cheap and pretty and usually come in high enough voltage ratings to be useful either in the signal path or as snubber caps on rectifier diodes
how do they sound? when i play guitar through an amp with em in the signal path it sounds like a guitar... maybe i'm not a tone connoisseur but as long as it's not leaky and of an appropriate voltage rating a cap's a cap to me