• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Organic polymer caps for K bypass?

Is anyone using aluminum polymer caps for K bypass? They now have them in higher voltages, the ESR specs are great, the longevity is pretty incredible over electros, and the temperature rating is 105, and they are cheap. What's not to like, anything?

Example:

Polymer Aluminium Electrolytic Capacitor, 100 µF, 35 V, Radial Leaded, L8 Series, 0.025 ohm

https://www.newark.com/nichicon/rl81v101mdn1kx/aluminum-electrolytic-capacitor/dp/17W5849
 
Is anyone using aluminum polymer caps for K bypass? They now have them in higher voltages, the ESR specs are great, the longevity is pretty incredible over electros, and the temperature rating is 105, and they are cheap. What's not to like, anything?

Example:

Polymer Aluminium Electrolytic Capacitor, 100 µF, 35 V, Radial Leaded, L8 Series, 0.025 ohm

https://www.newark.com/nichicon/rl81v101mdn1kx/aluminum-electrolytic-capacitor/dp/17W5849
They sound awful
 
Check out page 6 (Figs 5-8) of one these
high ripple current aluminum (non-solid electrolyte) cap:

https://www.vishay.com/docs/28464/125als.pdf

It's capacitance is frequency dependent,
ESR varies with frequency => nonlinear element !

Would any "organic polymer aluminum" cap which
has a solid electrolyte be different ?


Interesting for sure. I think these caps were developed primarily for managing power across motherboards, I know that's where I see them, look at any motherboard. In that application they're just there as reservoirs near high speed chips, where small size is more important than analog bandwidth.
 
Yes capacitor discussions are always subjective, thats ok, some things cant be measured.

How capacitors actually sound can't be measured by anything except ears. A small minibox with a 6 position rotary switch and spring terminals to grab 6 capacitors, and a couple terminals to go across the Rk. That would be a handy device to have. I'd be very interested in actually hearing these little guys compared to maybe 5 other caps with a rotary switch I can just crank. Only then can a person know, by comparing its sound to some other references. A rotary switch would get you to the point of knowing they sound "different", knowing that is somewhat an objective judgement. Now going beyond "different"... which sounds "best" after knowing whats different is surely always a value and taste judgement.
 
Yes capacitor discussions are always subjective, thats ok, some things cant be measured.

How capacitors actually sound can't be measured by anything except ears. A small minibox with a 6 position rotary switch and spring terminals to grab 6 capacitors, and a couple terminals to go across the Rk. That would be a handy device to have. I'd be very interested in actually hearing these little guys compared to maybe 5 other caps with a rotary switch I can just crank. Only then can a person know, by comparing its sound to some other references. A rotary switch would get you to the point of knowing they sound "different", knowing that is somewhat an objective judgement. Now going beyond "different"... which sounds "best" after knowing whats different is surely always a value and taste judgement.

If you are going to do this add high value resistors (10X Rk)across the switch to keep the caps not selected charged to the same value as the UUT. This way, when you switch there will be no pop from the cap charging to the bias level of the tube.
 
If you are going to do this add high value resistors (10X Rk)across the switch to keep the caps not selected charged to the same value as the UUT. This way, when you switch there will be no pop from the cap charging to the bias level of the tube.

I see, thanks. I do have Chinese 4 relay with remote control board in my junk pile. It has 4 buttons on the remote, the board has a jumper for 3 different modes: 1 of 4 latched; n of 4 latched; 1 of 4 momentary. If I use the 1 of 4 latched mode I can actually sit on the couch and flip through them! Project scope creep, but Its nice to not waste a junkbox board.