Cable architecture conversions - Test Equipment

[earth tones]

Hello. I have an HP 400E AC Voltmeter that I plan to use for testing and calibrating an 1176 build. I'd like send an audio signal from the iPhone into the Voltmeter (to set the amplitude) and then into the 1176 circuit.

The iPhone output is 1/8" TRS-F, the Voltmeter input is BNC-F and the 1176 input is XLR-F. What I'm wondering is what kind of adapters and cabling I should use to create this audio chain (considering mono/stereo, balanced/unbalanced, etc...). Ideally, I'd like to split the signal at the BNC input, so that the same path is being metered by the Voltmeter and passed on to the input. As opposed to splitting the audio signal at the iPhone and having one sent to the Voltmeter and the other to the 1176.

Thanks!

[The Scum]

I have an HP 400E AC Voltmeter

Yow. Using vintage test gear to set up faux-vintage DIY projects.

The "old classic" doc for balanced/unbalanced insteconnetcion:
http://www.rane.com/note110.html

The whole thing will be essentially unbalanced.
Look at figures 13 or 14. You can treat BNCs about like RCA or TS connectors.
Treat the 1/8" headphone output as a pair of mono outputs, rather than balanced. Ignore one side of it.

You could build the thing using plain connectors and clip/alligator leads.

On my workbench, I usually have a number of adapters that have a regular connector on one end (XLRM, TRS, XLRF, BNC, etc, etc), broken out to alligator clips on the other. Then I can quickly assemble an "anything to anything" adapter.

If you want to do it really right, make an 1/8" to BNC cable, a BNC to XLR cable, and get a BNC T-joint. Put the T on the meter, and connect the cables as appropriate.

One concern I've got is the output capability on the iPhone. Any idea about the maximum amplitude it's capable of? I wouldn't be surprised if it can't drive more than 3Vp-p, which may or may not meed your needs.

[earth tones]

Thank you for linking that document....it's exactly what I needed to see.

Also, your point about the level output of the iPhone function generator apps is well taken. It took me a while to find a free generator app that actually had a dB-based output adjustment. I planned to hook it up to the AC Voltmeter to see what the actual level is. I will probably just end using Pro Tools to generate a tone and output the signal from a 002r.