RFI Issues. CJ ET3SE

[Markhh2]

Just purchased a used ET3SE. The unit was at CJ for a check and replacement of some indicator lights.

Got it home, hooked it up and I’m getting a ton of RF interference. It’s a mix of mid frequency hum and 1 or more radio stations! I live about 2 blocks from some high power transmission lines, and I had this issue once before with another tube preamp. At the time I assumed it was because the pre, a blue circle, was hard wired with an attenuator made up of individual resistors. Since then I’ve had another tube pre from Manley and several DACS that I’ve run straight into my amps with no issues.

I’ve switched out IC’s and power cords with no audible effect. The pre came with come RCA covers that I added with no improvement. These are NOT shorting RCA’s just caps. I swapped the tube, took the cover on and off etc with no improvement. The sounds stops when I mute the pre, and is pretty consistent across all the inputs.

Any other suggestions? Shorting RCA Caps, copper foil on the inside of the chassis? I guess I could build a faraday cage!

[admin]

I would just make sure it's not the interconnects (by trying a different preamp). If it's truly isolated to the ET3SE, I would look at position (maybe stacking it between other components).

I know you were joking about the faraday cage, but in your specific situation it may actually be a viable solution. You can probably build one yourself for not much money or purchase one specifically for your application. Some googling found this and you may want to call them and discuss it:

https://hollandshielding.com/Faraday-ca ... enclosures

Let us know what happens, I'm curious to your solution.

[Markhh2]

Wasn’t at all joking. More interested in solutions that have worked before I spend any more $. I’ll also be moving soon, so this won’t be a long term issue.

[AnotherJohnson]

My suggestion is to call CJ.

They’ve seen it all.

Regarding interconnects, take a cheap pair of RCAs from Walmart or similar. Generally they’re well shielded. If that solves the problem, at least you know where to put your effort.

https://www.amazon.com/Cmple-Stereo-Aud ... _id=597546

[Markhh2]

I emailed Jeff at CJ. Still waiting on a response.

[AnotherJohnson]

Folks say that communications are difficult these days.
Small shop. Small staff. COVID precautions. Etc.

Phone usually works better than email.

May still lead to the need for several attempts.

This is pretty much an industry wide issue at this point.