Harrison Ford Filter Feeler

[slipperyflax]

16vdc will work but you wont have much headroom for any potential over voltage if your regulator gives out. 25vdc would be a big as you'd need to go if you decide to use something bigger then your 16vdc caps.

Thank you for that swift reply!

 

[niklasni1]

Does anyone have an up-to-date source for the pots in this?

 

[jensenmann]

If audiomaintenance.com doesn´t stock them anymore then Omeg might be the right place to ask. They used to do custom pots. If you´re in continental EU then you might want to try Potentiometer Service in Germany: PS Potentiometer-Service GmbH - Potentiometer, Steckverbindungen, Bedienknöpfe

 

[sweetbeats]

Greetings…I know this thread is old so I’m hoping to get some response…I’ve read the entire thread in detail and have a few questions:

1. The original Harrison circuit utilizes 0.1uF caps for C1 & C2. The BOM in the first post has this value for these parts. But then one version of the schematic shows the parts as 1uF, and @jensenmann mentions in a post about halfway through the thread 1uF parts partially resolved an issue he was encountering, but he eventually settled on 220nF parts and then I think later somebody else noted the BOM was updated with these values. The BOM in the first post does not reflect this. Is there somewhere besides post #1 I should be referencing for the BOM? And what is the end-all recommended value for C1 & C2?

2. What exactly is the impact on the performance of these filters when using 47K pots instead of 50K as in the original circuit? And…

3. Regarding pots in general, these continue to be hard to source IMO to match the pin spacing of the PCBs, and the specifications (47K or 50K reverse log dual-gang parts). I’ve found a couple options but both will need some tweaking of their pins to fit, and both are carbon-based element parts rather than conductive plastic. I see in pictures of the original Harrison 32C input/output module Harrison used precision pots, likely conductive plastic. Can anybody comment on the difference in performance, if any, when using carbon element pots vs conductive plastic?

Thanks.

 

[jensenmann]

3. conductive plastic is more expensive but doesn´t get scratchy
2. pots usually have tolerances of 20% which is much more than a change from 47k to 50k. It simply doesn´t matter.
1. my filters are still stuffed with the values I mentioned before and I´m happy the way they are. But that´s based on my taste. Other opinions may vary.

 

[sweetbeats]

3. conductive plastic is more expensive but doesn´t get scratchy
2. pots usually have tolerances of 20% which is much more than a change from 47k to 50k. It simply doesn´t matter.
1. my filters are still stuffed with the values I mentioned before and I´m happy the way they are. But that´s based on my taste. Other opinions may vary.

Thanks much for the reply…very helpful and I appreciate it!