Unbalanced Hookup?

Allen

I have an amplifier with only unbalanced inputs. What is the correct way to hook it up to my dr260.

Do I tie pin 1 & 3, or just leave pin 3 open?

Thanks,

Allen

fotofx

Use an xlr to 1/4 adapter with a transformer. Available everywhere, even Radio Shack has them.

Steve

Dra

Only use a converter with a transformer if it is a matching transformer. You should not use a tranformer if it steps up or down the signal ( mic level to line level or line level to mic level). If you do it will greatly boost or cut you signal. Hosa, among others, sells transformerless adapters.

DRA

Gadget

Well I would just tell you to skip the balums altogether and hook pin 2 to tip, and if there is no hum issue just tie pins 3 and 1 together... if there is a hum issue open pin one at the unbalanced connector. This usually will keep any chassis issues out of the mix. The problem with cheap transformers is bandwidth, and frequency response.
Gadget

wolfgong

I agree with Gadget. I would start without the transformers.

I found a simple diagram in a crown owners manual if you like pictures. See figure 2.4 for unbalanced xlr connection in the manual.

http://www.crownaudio.com/pdf/amps/139441.pdf

Jack Hidley

Good transformers are going to be the best way to connect an unbalanced source to a balanced one.

The wiring diagram (figure 2.4) in the Crown manual linked above should never be used. It is one of the worst ways to do this. The proper way is to use the wiring method of figure 2.1 from here:

http://www.jensentransformers.com/an/an003.pdf

This will usually result in a 10-30dB lower noise floor depending on the design of the unbalanced equipment and the magnitude of current flowing in the ground loop.

Cobra2

If I use single ended(RCA->XLR-adapter) connection, and \"normal\" consumer level equipment, should I moove the jumpers on both input and output? (from 22dB to 14dB)?

Arne K

Gadget

I'd try it without it first...I haven't had any issues, the DR has lots of gain...an it shouldn't be a problem...
G

Cobra2

Thanks.

Arne K

Jack Hidley

Most consumer power amplifiers with RCA inputs require between 1 and 1.7V RMS to achieve full output power. This is a signal level of +2dBu (1V) to +7dBU (1.7V). There is no need to have the output of the DR to be able to swing all the way to +22dBu. Even set to +14dBu, you will have 7dB (14dBu-7dBu) to 12dB (14dBu-2dBu) of useless headroom. Running the DR with the output in the +22dBu setting is just going to give you 8dB (22dBu-14dBu) worse signal to noise ratio.

On the input side of the DR, things are somewhat different. Most consumer gear with RCA outputs have a maximum output voltage of about 2V RMS (8dBu). This is still plenty of headroom in the DR even if it is set for +14dBu input operation. There are some pieces of consumer gear that can output up to about 7V RMS (+20dBU), but they are fairly rare. If you are just talking about a typical receiver, it won't put out more than 2V RMS.

I would set both the input and output jumpers in the DR for +14dBu operation.

Gadget

Agreed... IF, you can set it and forget it...but in my case I use the DR for too many divergent tasks to take it apart and change the jumpers for each task, and I'm usually behind the 8 ball and have never had interface problems with pro or consumer/DJ gear...Granted, I do use the DRPA mostly for that sort of things though.. for what that's worth... 8)

Thanks Jack! pleased to have your contributions!
G

Jack Hidley

G,

Good point.

I also have an Shure P4800 that has a software controllable 20dB pad for the outputs. This makes it very easy to use for multiple applications. I wish it was selectable for 0, +10 and +20dBu though.

Cobra2

Thanks, again!
Then I can keep it at the 14dB setting ;-)

Arne K