How can I integrate unbalanced gear in a "balanced studio" ?

Hi everyone !

I have an Ensoniq DP/4 in my studio, I like it very much but all the connections are unbalanced so I getting hum when I work with it. I use it thru the patchbay of my console, a DDA DMR-12, which is balanced.

How can I get rid off this noise ? Do I have to unbalanced the input signal and then balanced the output signal ? If yes, how can I do that ?

Best to all,

Ben.

You could put a balancing circuit on the output of the DP/2 but I doubt if it will solve your problem.

Check your wiring, you should have DP/2 Tip wired to Pin 2 (+) on the effects return and DP/4 Ring wired to Pins 3 (-) and 1 (gnd)

Rane has an excellent section on their site called "RANE NOTES", #110 covers system interfacing.

http://www.rane.com/note110.html

After that, it's down to gain staging.

Try turning down the input level on the DP/4 and turning up the send level on your console.

Mark

in my experience, and based on some advice from an old professor, I have a lot of unbalanced I/O on my console to interface with either balanced OR unbalanced, so I wanted to be prepared for both situations, so this is how I operated.

At the balanced connection, in my situation, on a patchbay, I wired it as normal balanced connection.  At the unbalanced connector, I would tie "pin 3" or the cold or negative of the 2 signal leads of a balanced signal, to ground.  As I was wiring my patchbay, I chose to lift ground at all inputs, so at an unbalanced input, it would just be the 2 signal conductors wired to the connector.  For an output, it would be pin 2 to tip, and pin 3 and the shield to the ground conductor.  I was told to wire all balanced ends as balanced, and make the change to tie pin 3 to ground on all unbalanced connections. 

Hope that helps.

Or you can get a Ebtech Line Level Shifter......... :-[

phishman13 said:

in my experience, and based on some advice from an old professor, I have a lot of unbalanced I/O on my console to interface with either balanced OR unbalanced, so I wanted to be prepared for both situations, so this is how I operated.

At the balanced connection, in my situation, on a patchbay, I wired it as normal balanced connection.  At the unbalanced connector, I would tie "pin 3" or the cold or negative of the 2 signal leads of a balanced signal, to ground.  As I was wiring my patchbay, I chose to lift ground at all inputs, so at an unbalanced input, it would just be the 2 signal conductors wired to the connector.  For an output, it would be pin 2 to tip, and pin 3 and the shield to the ground conductor.  I was told to wire all balanced ends as balanced, and make the change to tie pin 3 to ground on all unbalanced connections. 

Hope that helps.

Click to expand...

I've found just by using TRS/balanced connectors/leads throughout my studio I never have hum problems.

I had them sometimes years ago using unbalanced cables.

The only recent hum problem i had was off an old akai synth and it turned out to be due to a MIDI connection. Can't quite remember what I was doing but some sort of MIDI cable based earth loop was causing the problem. Proper head scratcher until i realised!

Incidentally I have a DP/2 which is largely similar i believe, and although it's generally quite noisy I don't get earth loops /hum.

Actually snatch, the Ebtech "Hum Eliminator" products will do the trick in smaller studios.  The gain is fine- they just went cheapo on the interface.
I have integrated DP4's directly in SSL, Trident, Harrison, Neve, etc. rooms with no problems, but the noise problems in a "huge chunk of metal console" are different than in "project studios".  Just a shield lift or something.
I bet that if you wire one of these in line with the inputs only you will be golden.  It still tests well even through a few cheaper upgrades.  It actually got rid of all of my "project studio" problems in the late 80's.  Unbalanced 16 track 1/2 inch machines- great idea, bad implementation.
Mike

sodderboy said:

I bet that if you wire one of these in line with the inputs only you will be golden.  It still tests well even through a few cheaper upgrades.

Click to expand...

I don't know if using that product is such a good idea outside cheapest consumer usage. It's a filter. it actually cuts down the 50hz/60hz in the audio itself. Very bad for any studio setup.

mOBiTh said:

I've found just by using TRS/balanced connectors/leads throughout my studio I never have hum problems.

Click to expand...

This is how I've wired all my studios over the years, kept it balanced through the console & patchbay, up until the actual piece of gear that is unbalanced, then wire as needed. I never bothered with TRS connectors on TS connections but it will accomplish the same thing as using TS with Pin 3 grounded.

Never had a problem doing it that way.

Mark

Biasrocks said:

mOBiTh said:

I've found just by using TRS/balanced connectors/leads throughout my studio I never have hum problems.

Click to expand...

This is how I've wired all my studios over the years, kept it balanced through the console & patchbay, up until the actual piece of gear that is unbalanced, then wire as needed.....

Click to expand...

much agreed.

I have a dp2 myself whcih is hummy when you put the transformer (external at dp2, not sure about the dp4) to close to your cables. So maybe check that first to see if that solves your problem.
With dp2 the cable is quite long so i can put away from the line cables without a problem..

Kingston said:

sodderboy said:

I bet that if you wire one of these in line with the inputs only you will be golden.  It still tests well even through a few cheaper upgrades.

Click to expand...

I don't know if using that product is such a good idea outside cheapest consumer usage. It's a filter. it actually cuts down the 50hz/60hz in the audio itself. Very bad for any studio setup.

Click to expand...

It is not a filter.  Ever take one apart?  It is 2 600:600 transformers in a plastic can.  It does has something of a rise starting at 10k, but otherwise it acts just like a "middlin" transformer.
It eliminates the hum not by filtering but by transformer isolating.  Search for it in the forum.  NYD uses them in some of his early projects.
If you want to go higher in quality, then Edcor makes some stereo transformer boxes.
Mike

From that website, a user review:

Item "almost" completely eliminated 60 cycle/ripple ground loop condition in my PC to stereo setup. It does reduce power (that's why some IPODS don't work with it) and 50-60hz tones that go to the stereo. It's a filter NOT an isolator and uses power absorption @ ~50-60Hz to eliminate hum. This freq. translates to a 4 string bass guitar. Readjust your stereo Freq. settings and you'll never notice the difference.

Bob Pease has a little circuit  that might help. You will have to click on the fig. # to see a very poorly drawn schematic

What's All This Noise-Rejection Stuff, Anyhow?
http://electronicdesign.com/article/analog-and-mixed-signal/What-s-All-This-Noise-Rejection-Stuff-Anyhow-21808.aspx

Kingston said:

From that website, a user review:

Item "almost" completely eliminated 60 cycle/ripple ground loop condition in my PC to stereo setup. It does reduce power (that's why some IPODS don't work with it) and 50-60hz tones that go to the stereo. It's a filter NOT an isolator and uses power absorption @ ~50-60Hz to eliminate hum. This freq. translates to a 4 string bass guitar. Readjust your stereo Freq. settings and you'll never notice the difference.

Click to expand...

The poster is wrong, unless they changed it in the month since I last bought one!  There are 2 transformers inside of it.  Really!
And if you look closely at the actual product, they have a two transformer schematic printed on the side.
I have been using them for 2 decades.
Mike

> It's a filter. it actually cuts down the 50hz/60hz in the audio itself.

Slit the label, squeeze the grommets, pull gently. It's transformers. It actually isolates grounds.

And, FWIW, the target market is Auto Sound, which has little 50/60Hz, but lots of alternator and other garbage in the frame.

Also a car-woofer application ought to pass LOTS! of 60Hz, a filter would be bad.

If you want a True Floating output, crack it open, find the bond from one RCA plug to shell, take the other side, re-wire to "balanced" connectors.

There's not a lot of turns, but if you drive from "600" outputs into 10K loads the bass and treble are fine, voltage transfer is unity-enuff. As 600:600 you will have some DCR loss, not a lot (I am not going to the garage tonite to measure one). They probably distort 30Hz at +18dBm, never tried that; nothing offensive happens at -10dBv nominal (2.8V peaks) of real music.

Yes, the RANE Note is excellent and may cure the problem without any tricks.

I thought it was a bit expensive for a mere filter, and wondered why the user review would state it is one. I'm familiar with benefits of ground isolation with transformers, but didn't expect to find it in little consumer gadgets like that.

This consumer gadget is even littler but I used them in an install with 40 odd synths and they work like a charm.  I knew levels would be low, and would not saturate smaller trannies.
Mike

> even littler

To my eye, it appears to BE the Radio Shed isolator, with someone else's label, and at a third the price (good find!).

Inside the transformers are smaller and saturate ≈3db lower than the RS, but for 70-80's era synths going into a programming mixer they drop noise floor down to clock artifacts.  No good for use with 600 ohm input stuff!
Mike

Hi everyone !

Thanks for all these answers !!! If I remember correctly, connecting  pin 3 to ground is already what I've done, I need to check it but I have too much work right now !!! And I also need to check if it's not the Aux circuit who are noisy.

Best to everyone,

Ben.