EQ based on Pultec EQP1 for bass guitar

[Bigorno]

What type of capacitor and brand is more suitable for the low frequencies?
Polyester? 716P?

Same question for the medium frequencies.

For the high, 7kHz @ 20kHz, I'm thinking Silver Mica.

Thank you for the Help.

 

[ruffrecords]

You should be thinking plastic film types for all frequencies.

Cheers

Ian

 

[Bigorno]

Hello Ian,

Thank you for your help.

Could you explain please?

Do you think of a particular brand?

Thanks.

 

[ruffrecords]

Some types of capacitor can be microphonic. Other types can produce significant distortion in an EQ circuit where they have significant voltages across them. Plastic film types as a rule do not have these problems and are suitable for use in EQ circuits at all frequencies. The most common dielectric is polyester. There is very little to choose between brands but Wima are well respected. Just make sure the voltage rating is more than adequate for the signal levels involved. It is difficult to get plastic film types in tolerance better than 5% (Wima tend to be 10% or 20% but Pansonic does a nice range of 5% types available from Farnell). For small values of capacitance (for high frequency stuff) polystyrene capacitors are available with a 1% tolerance but they are rather more expensive.

For your bass guitar EQ I would recommend Wima, Panasonic or Vishay types.

Someone on the group has already built a bass guitar EQ based on my poor man's EQP1A design so perhaps they will answer the thread.

Cheers

Ian

 

[Bigorno]

Thank you very much for Ian. 

 

[letterbeacon]

Just out of interest, what type of capacitors were used in the original Pultecs?  Paper-in-oil, or did they have plastic film in those days?