Direct Box from Phono Preamp

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I am trying with great difficulty to hook up a turntable to a Spirit by Soundcraft M12 mixer. I was told I needed a phono preamp, so the turntable feeds into a Rolls preamp, which then goes into the mixer via balanced 1/4" cable.

My problem is that there is an awful hum present at all times only on the channels coming from the preamp/turntable. The turntable does seem to be grounded to the preamp, as I have managed to get rid of a higher pitched humming sound. But I am still left with an even louder, constant hum.

After countless discussions with Soundcraft customer service reps, I have decided that a direct box with a ground lift switch is the next thing to try.

My question is should I be getting an active direct box, as opposed to passive? And do I just connect the phono preamp outs to the direct box ins, and the direct box outs to the mixer ins? Or maybe I don't need both the preamp and a direct box?

Perhaps I am missing something, and I'd appreciate any suggestions. Thanks.
 
What kind of lights do you have in your studio? if the're Fluorescent lights then, they can cause hum. And it myte be the turntable. is it old? It could also be in your cables if they've been steped on alot or if the're just bad. If the lights are giving of the hum noise, move your equipment around in the room until you find a place where it don't hum. that's what i had to do but the hum was in my bass amp.

Zeke
 
there is one halogen lamp. the turntable is a technics 1200 that is fairly new and in excellent working condition, and the cables are all monster cables.

my computer and computer monitor aren't helping, and neither are the power lines that come into my house not too far from my setup. regardless, i have tried several different locations and this awful hum is still there, so i figure the direct box is the next thing to try. i just want to make sure i get the right kind and use it the right way. hopefully that's where you guys come in. thanks.
 
What kind of preamp is that? You need an RIAA preamp for a turntable, not a mic preamp. They're very different. Also the turntable has to be grounded.
 
I've tried 2 phono preamps, just to make sure one wasn't defective: the Rolls VP29 and the Bellari (Rolls) VP129 Tube Phono Preamp, which has RIAA EQ.

I know I'm not the only one connecting a turntable to a non DJ mixer, so I'm curious how some of ya'll are doing this. Phono preamp? Direct box?
 
You said the turntable is grounded to the Phono Pre-amp? With the little gray cable that is usually in the middle of the RCA cables?

This was my problem when I tried it and the hum went away.

Does it sound like a 60 cycle ground loop?

Do you have a lot of gear connected that uses 3 prong plug ins?
 
>>>"You said the turntable is grounded to the Phono Pre-amp? With the little gray cable that is usually in the middle of the RCA cables?"

Yes and Yes. A higher ptiched hum went away when I did this. But there is still a more obnoxious, lower-pitched hum.

>>>"Does it sound like a 60 cycle ground loop?"

I don't know. I was told it sounds like a transformer hum, but it's not a transformer/power supply problem, since I tried multiple preamps and transformers.

>>>"Do you have a lot of gear connected that uses 3 prong plug ins?"

Yes - both connected to the mixer and plugged into the same power strip.

Help!
 
This advice may get me into trouble, but you can try it at your own risk.(I've never had problems)

Get a few of those ground lifting adapters, the ones that make a three prong plug fit a two prong outlet? Plug in all your 3 prong gear using them, and see if this breaks the loop.
 
maestro_dmc said:
Why?
Click to expand...

Well, if you're equipment isn't grounded then the nearest ground becomes the person touching the gear. Not a big deal unless something shorts out or you are holding a guitar and trying to sing into a 58, ouch.

Try plugging everything into the same power strip and see if that makes the hum go away. If not then try some ground lifting.
 
TexRoadkill said:
Well, if you're equipment isn't grounded then the nearest ground becomes the person touching the gear. Not a big deal unless something shorts out or you are holding a guitar and trying to sing into a 58, ouch.

Try plugging everything into the same power strip and see if that makes the hum go away. If not then try some ground lifting.
Click to expand...


Thats ok, just wear rubber soled shoes, and plastic lips whenever you record, that's what I do!:D :D :D
 
As a long time vinyl fanatic ( CDs suck :D ) the first thing I wonder is have you used that turntable recently thru a normal stereo that has a phono input? Because you can have a problem in the wiring in the arm, the wiring and/or connectors from the arm, the connection at the headshell if it's removable, the connections to the cartridge and even the cartridge itself. If it's any of those....you can change pre-amps and groundlifts forever and it'll still hum.
 
Everything is plugged into one of two power strips that come from the same set of wall plugs.

And the turntable is fine - just last week I used it with a DJ mixer, and plus I have two - I've tried both.

A friend let me borrow a ProCo DB-1, so I'm gonna try that tomorrow after I get an XLR cable. The DB-1 is a Passive direct box - should I also try an Active direct box? I Know a passive box isn't powered and won't amplify the signal, but why might I want those features? What are the advantages to an Active direct box as opposed to Passive?

Thanks, fellas.
 
Well.......I can give you one definite answer to your original questions. You would run the phono pre-amp outputs to the inputs of the direct box and then the direct box to the board. And the turntable would ground to the phono pre.

Yes you do have to have a phono pre-amp because it adjusts the RIAA equalization curve. Without one, you'll have little bass and a very tinny sound.

One last thought....it could be the phono pre-amp. I have a bunch of expensive pres 'cause it's my hobby but a few years ago I bought a couple of cheap phono pres similar to the Rolls just to have them....and they hummed like a bitch.
 
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