Wurlitzer 200A Aux Out Hum

[Drew9783]

Hello all, I have a Wurlitzer 200A, with a new Vintage Vibe preamp and a fully recapped/restored amplifier. I'm getting a great sound out of the speakers with a low noise floor, but I've noticed when I go to record my keyboard with the aux out, there is an annoyingly loud ground hum, which is present even when the Wurlitzer is turned off. This is only remedied when I plug into a DI with a ground lift. I've checked all grounds inside of the keyboard itself and everything seems like it is connected well... I can't find a missing ground anywhere! Why could my aux out be so noisy? I've even checked the output jack itself and the ground connection is secure. Any advice would be appreciated!

[pianotuner steveo]

I would ask VV what to look for since it is their preamp.

[Drew9783]

The preamp I was referring to is the preamp board mounted to the reed bar, not an external preamp. From looking at the schematic, the aux output seems correctly wired, with the sleeve of the Jack connected to the shielded portion of the cable, but it still sounds as if it is ungrounded. Can I safely add an additional ground going from the sleeve of the aux output jack to the chassis maybe?

[pianotuner steveo]

As long as you are sure where to put the extra ground wire, that should be fine, but the Jack may need replacing too. Rare, but possible.

[Drew9783]

As long as you are sure where to put the extra ground wire, that should be fine, but the Jack may need replacing too. Rare, but possible.

Thanks!

[Chris Carroll]

Drew,

It's quite possible that it isn't a missing ground that is the issue, but a ground loop between the Wurlitzer and the piece of equipment that you are plugging the aux output into.  I say this because you are able to remedy it by putting a DI in-between with a ground lift applied; hence, you are breaking the loop.  This is a very common issue when interfacing equipment together.  You are going about resolving it in a smart and efficient manner; it is also safer than using a cheater plug, for instance.

Best Regards