Replacing non-polarized electrolytics (other post broken)

[jordan s]

Sorry for the double post but for some reason, my first post broke when I added a schematic image and it won't load on any browser for me. I assume no one else has been able to load it from the lack of response.

What is the reason to use non-polarized electrolytic caps in a guitar preamp circuit? I have a Sunn Beta Bass amp here that is filled with 2.2uF non-polarized EL caps. This thing was due for a recap anyways so I bought a bunch of film type Wima's to replace them. I assumed since they were all in the signal path that replacing electrolytics with film caps would yield a sonic improvement. My guess is that these NP caps were used simply because the values were high so a larger and more expensive film cap wouldn't make sense, especially 30+ years ago.  Is there any other reason I should know about to use non-polar caps like the original instead of these Wima film caps?

Since I made the first broken post yesterday, I just decided to go for it with the Wima's. It works! I didn't play this amp before the recap so I can't say it what ways it does or doesn't sound different. I've only tested the preamp with headphones so far, we'll see how it sounds when I get the power amp section recapped and re-transistored. Please let me know if there any any considerations about the NP caps I should know about before blasting this amp.

Here is a link to the schematic since attaching the image seemed to break the original post:
http://s4.postimg.org/gjrli4frv/Sunn_Beta_Bass_AB_Channel.png

 

[PRR]

The opamps are powered +/-V. All the audio nodes sit at zero VDC. These caps have zero V DC both sides.

Traditionally, electrolytics work best with steady DC bias. And certainly hate reverse bias.

"NP" caps are optimized for no-bias uses such as AC motors and speaker crossovers. Film caps are an alternative but much too expensive to sell in a 90-day warranty consumer toy. I guess if it did not get junked in 30 years, it may be worthy of few-buck caps. I would not expect any "huge" improvement.

 

[gswan]

Gotta love the use of a 4069 CMOS hex inverter for distortion ...

 

[jordan s]

Thanks for the info PRR. These amps are well loved in certain circles and while I wasn't expecting to make a drastic tone improvement with the Wimas, I figured I might as well if I have to recap the whole thing. I also replaced the output transistors and put better heat sinks on the voltage regulators. So far it works and sounds alright. I will see when I get to blast it at the practice space.