Grounding and Hums - DP32 SD

[davey]

Hi all, I've recently started using my DP32 SD, mainly to record guitar. I've been greatly troubled by various hums when a guitar is connected. I've tried several guitars and all are affected to some degree.

Classic symptom is a hum that gets worse when I'm close to touching the strings and all but goes away as soon as I do actually touch them (or if I touch the Tascam's chassis). Same problem if I'm using a jack direct to input or via a DI with or without it's ground lift engaged.

I can reduce it by shutting down everything in the house - right down to fridge / phones / wifi / water treatment plant / lights... everything. That reduces the hum, but it's still usually there and intrusive.

I've read up and it seems that some DP32 SD / 24s etc. have a ground connection point on the back next to the power socket, it's shown in lots of promo pics of the machine. Mine doesn't have that, and it's 'wall wart' adaptor has no ground (plastic pin).

As a fix, I got an old 3 pin plug, removed live and neutral pins and run a lead from earth, captured it in one of the Tascam's chassis screws. When I plug in my home brew ground it reduces the hum considerably.

Final fix is a copper plate connected to the shield on the guitar lead, I stick my foot on that and everything's nice and quiet.

I've checked the mains ground with a plug in tester, and all connected equipment is plugged in on the same set of mains power sockets. Oh, and I'm in the UK, and I bought my DP32 new within the UK rather than import.

I'm sure this set up is as safe as can be. As some of these machines have a ground point I can only assume it's alright to add one, and if something goes wrong and I get a shock from my copper foot plate I'd get same from strings anyways.

Do any of you more knowledgeable and wiser souls know different? I'd be interested in any neater fixes or any risks I haven't forseen with my setup. I also wonder why some DP32s have ground point and some do not - I assume regional?

Cheers for now, davey.

 

[-mjk-]

Hi @davey and welcome to the Tascam Forums

The DP-32 has the ground lug. The DP032SD does not.

Studio grounding is a topic so large that it could have a dedicated site. Single coil guitar pickups can be notorious for picking up hum (hence the development of the humbucking pickup). Spinning around in your chair can often help find a "null" in the noise. Noise can also be picked up by cables. There may be something in your environment that is creating a particular noise. You can try using some kind of snap-on choke on the cable, or even a wireless guitar transmitter to eliminate as much of the cable as possible. You may want to do some research on "star grounding" and also ground lifting.

 

[davey]

Thanks mjk for your advice, much appreciated.

I do indeeed have a sad liking for single coil pickups! That said, my one guitar that has a humbucker still picks up a decent level of background hum. It amazes me how many guitars come with no internal shielding. I bought a fender strat recently which is reasonbly quiet so I've not investigated as I assume it must have some shielding, but a new and quite high end Squier has no shielding at all, and it really showed! Copper tape lining to the main control cavity made a huge difference.

I have indeed tried moving around the room. It does make a difference when the other electrics in the house are not shut down, but main background noise remains.

I'm in a very rural location and I suspect problem was / is a milking parlour half a mile up the road as with the whole house electrics shut down, the mains noise usually followed a repeating 9 seconds low level / 13 seconds high level repeating pattern. I say was, I carried down the whole house shut down two weeks ago, and the electric people came out by chance last week and replaced the main transformer and cable throughout the village so I'll recheck at next daylight opportunity. Fingers crossed that may have helped.

Interesting that the 'SD' version of the Tascam has no lug. I'd imagine it cost more to modify tooling to remove the facility than it cost in components (if indeed there are any) to include it.

I don't think ground lift will help as my DI box has that facility which made no difference. I will indeed read up on star grounding and I've ordered a box of those chokes (cheap enough to be well worth trying).

Wireless is a good idea that I hadn't thought of, might be a neater solution than my guitarist earthing plate.

One solution I did find worked rather well is an Electroharmonix Hum debugger pedal. Not a noise gate, but a pedal that seems to analyse mains hum and introduces a reverse wave to conteract it. Does a very good job too. It's a great sticking plaster fix, but I'd be happier to minimise the problem to start with, so I shall continue in my quest!

All the best and thanks again for taking the trouble to write,

davey.

 

[-mjk-]

In situations where you've done your best but you still have noise, you can record anyway and use Izotope RX Advanced to remove spectral noise. Sometimes people send me tracks for mixing and they are noisy. RX does an amazing job.