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[scottoliphant]

something I've been wondering for a while, is it possible to use a computer to generate a 1k test tone (or a 10k test tone for bias) at the equivelent of 0vu (+4dbu)? Is it as simple as adjusting the level of the 1k tone generated on the computer to read approx 1.23 volts at output? would the same apply for a 10k "0vu" tone? (don't remember the voltage of this one of the top of my head). thanks in advance

[JGreenslade]

You can get a handy shareware generator here: http://www.audiotester.de/

You have to re-launch the program after 15 minutes of use if you don't unlock it (35 Euros).

If you don't have a calibrated dB meter, you can use an RMS voltmeter in conjunction with a converter such as This One to check the voltage coming from your soundcard.


Justin

[scottoliphant]

cool
i can generate a 1k tone at 1.23 volts (if i check with a voltmeter) from the computer, i just wanted to see if it was "usable" to fine tune my tape deck / lay down test tones (and then go on to generate a 10k tone to set bias and rec eq and stuff). The oscillator in my console is getting a bit wonky and i don't trust it

[JGreenslade]

Maybe I'm missing something here, but I can't grasp why a tone coming from the analogue buffers on your soundcard should be any less useful than one generated by a dedicated analogue generator.

Providing your soundcard is happy to drive the input-stages of your tape machine (no problem, unless you have an unusual vintage tape machine or very weedy op-amps on your soundcard), I can't see a problem.

Am I missing something?

Justin

[Andy Peters]

scottoliphant wrote on Mon, 14 August 2006 11:12

something I've been wondering for a while, is it possible to use a computer to generate a 1k test tone (or a 10k test tone for bias) at the equivelent of 0vu (+4dbu)? Is it as simple as adjusting the level of the 1k tone generated on the computer to read approx 1.23 volts at output? would the same apply for a 10k "0vu" tone? (don't remember the voltage of this one of the top of my head). thanks in advance

It'd work, assuming that you actually measure the amplitude of the tone with a 'scope or a true-RMS-reading DMM.  I can't think of any soundcard that lets you set its output voltage.  (Actually, though, it's not difficult; if you know the DAC's reference voltage and any post-DAC gain, then you can figure the output voltage easily.)

Make sure your meter has decent bandwidth; mamy cheaper meters read accurate AC at only low frequencies.

The voltage corresponding to 0 dBVU is the same regardless of frequency.

-a

[scottoliphant]

thanks for the info
I've got an RME multiface, and my idea was to measure the voltage with a voltmeter coming off the end of an xlr that was plugged into one of the output channels of the box (and feeding the 1k tone from the software into that output). maybe i've got it all screwed up and i should just buy a good trustworthy tone generator.

[JGreenslade]

Quote:

maybe i've got it all screwed up and i should just buy a good trustworthy tone generator.

A soundcard with the right software is a tone generator - where's the difference?

A battery-powered generator will avoid ground-loops - that is one pro.

Andy makes a salient point regarding frequency @ 0dBVU


Justin

[scottoliphant]

just doubting myself =) never really took the time to really sit down and think about the inboard oscillator, and how it actually worked, just plugged in my tones and went, being a novice when it comes to the electronics side of things.

Quote:

The voltage corresponding to 0 dBVU is the same regardless of frequency.

won't a 10k tone at 0vu read differently on the voltmeter? or no? this bit has confused me. you guys rock, thanks again

[Andy Peters]

scottoliphant wrote on Mon, 14 August 2006 19:16

won't a 10k tone at 0vu read differently on the voltmeter? or no?

Why would it?

-a

[Brian Roth]

As mentioned earlier, the quality of your meter can lead you astray.

Inexpensive digital meters are designed to accurately measure frequencies at or below 400 Hz.  Above 400 Hz the frequency response rolls off.

Bri