Electroyltic Capacitors

It’s somewhat axiomatic that replacing all electrolytic capacitors in a DAP should be the first step in a refurb. They’re about 43 years old, and they deteriorate over time. Axial capacitors are still available, but they’re getting expensive, and the selection is not what it used to be.

It’s possible to eliminate three electrolytic capacitors on the Equalizer board. The output of each of the three channels is capacitively coupled to the next stage, which is a 2K pot followed by another cap. While there is a possibility that there could be a little DC voltage on the output of one of the 301 op amps, it’s not likely.

That being said, it has been recommended that you can remove C20 on Z1 (shown as 6uF), and you can. However, there will probably be an offset voltage on the output of Z1 if you do. That offset voltage will vary with the 301 in the circuit. While the offset is very low and not of much consequence, it will put DC on the 2K pot in the Compressor card that follows. DC on a pot can cause some nasty scratching noises. You decide.

DAP EQ Board-1920

Mike Phillips

2 Comments

  1. On all the three times I’ve rebuilt, I installed much larger filter caps in the power supply usually no less than 2200 UF, the small audio capacitor on the power supply board, I change out with a 20 UF or there abouts NPO cap.
    Also on the time and capacitors for the compressor cards I usually double all time constants so that would be 22uf, 10uf, 2.2uf but for some clients I’ve used as much as 100uf on the low 47uf on the mid and 22 on the high.

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