Sound Technology 1701A

[jblmar]

Any hook-up suggestions for the Balanced Inputs to the gear under test?
Any advantage/disadvantage using bare wire as opposed to Bannana Plugs?
Pictures of your setup would be great.

Ron

 

[Jon_Logan]

I connect the DUT's out to '+' and common to '-', then I have a fat wire to ground on the Sound Tech and connect to chassis with a heavy alligator clip. With this connection, chassis ground currents are on the heavy wire path and don't muddy the '-' inputs signal ground. You get you lowest distortion with this connection. You could jumper the '-' to ground at the Sound Tech for simplicity, but don't forget to open that connection if working on a bridged/balanced output device. It seem to remember that if you connect the amplifier phase correct, the monitor output is phase inverted. .....but I'm just going from memory right now.

 

[jblmar]

Thanks, Jon.
Are bananna plugs necessary or do you use bare wire to connect to the Balanced Inputs on the ST?

 

[Jon_Logan]

I use banana's where possible. .....just make sure the screw is tight on the banana connector. ...the one that pinches the wire. I mostly use STP (shielded Twisted Pair) to connect the DUT to the test equipment, but I float the shield at the measurement end and just have the shielded twisted pair connect to the Audio Precision or Sound Technology, Then, I have my fat ground wire connect the chassis. I can land the ground at the DUT's chassis if I want, but it's not necessary. I like this aproach over using an unbalanced cable (Double banana to RG-58 to double banana, RCA, or whatever). Since the '-' is an input on the test instrument, I like to treat the signals the same. ....twisted and going into their own inputs. This will work for balanced and unbalanced equipment, so I never have to think of what type of equipment is being connected. So that's the signal wire to the test instrument. For the load, I use 14ga. twisted pair Belden. I connect the load to the amplifier output terminals and connect the wire to the test instrument at the amplifiers output terminals as well. Use banana's if you got'm. just make sure they're tight.

 

[jblmar]

Good advise.
I have a thin pair of double sheilded cable that I'm not too satisfied with.

 

[jblmar]

Jon,
What guage wire do you use from the speaker output terminals to the input of your test gear?
Figure a 200 WPC amplifier.

 

[Nakdoc]

I have a set of bare wires, a set of dual banannas, and a set of DIN speaker wires. On high power amp testing my wires get hot. I could probably stand to upgrade them someday. You'll find after dropping your ground clip off that the little chassis fuses will open. These have 10 ohm resistors in parallel, and these burn too. When this happens you get lots of hum. I suggest replacing the 1/8 watt 10s with 1/2 watt.

 

[Jon_Logan]

I use 14ga. Belden wire to the Loads. You can use any (small) gauge to the input of the Sound Tech. The Sound Tech's input impedance is 100k ohm, I believe. I tend to connect the loads to the output terminals, then connect the measurement wires to the output terminals too. ...I believe this will get you your cleanest measurements. I'd have to run a test matrix to figure that out. It's safe to say that this would be a 'good' setup.

DIN connectors (B&O etc) are kind of hard to stack the connector. I would have a DIN connector with short peices of wire, connect to some Banana jacks. Then you could connect to your load wires and your measurement wires. It's a good thing that most of those DIN connected amps aren't high power. Those little DIN wires might get hot if high current is going through a length of that. If your load wires are getting hot, you will want to up the gauge. As the wire gets hot, it's resistance will increase. I don't know what temperature will make what increase, but it's not ideal.