Hi!

Can you please offer some advice on how to go about measuring the
output voltages on my converters, gear etc. What exactly do I need to
do this? an RMS voltmeter?

Also, if I want to perform tests on preamps (S/N, THD+N, etc) , how do
I go about setting up a load on the input (simulate a mic connected).
Does anyone make a product, say an XLR with with user-selectable
resistance?

Appreciate your input

Harry Houdini wrote:

Can you please offer some advice on how to go about measuring the
output voltages on my converters, gear etc. What exactly do I need to
do this? an RMS voltmeter?

Do you need to measure peak or average levels? Your best choice might
just be an old-fashioned VU meter. There are a lot of commercial
audio test sets out there... HP made a nice one that shows up surplus
a lot.

Fair Radio Sales often has the HP units with a reference oscillator
and a level meter in the same box, for around a hundred bucks.

Also, if I want to perform tests on preamps (S/N, THD+N, etc) , how do
I go about setting up a load on the input (simulate a mic connected).
Does anyone make a product, say an XLR with with user-selectable
resistance?

No, but it'll take you less than a minute with a fixed resistor and
a soldering iron. You can, in fact, just jam a resistor into the holes
on a female XLR in a pinch. Don't forget to have lots of clip leads
around!
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Harry Houdini wrote:

Can you please offer some advice on how to go about measuring the
output voltages on my converters, gear etc. What exactly do I need
to
do this? an RMS voltmeter?

What context do you want to measure in? Do you want to measure
real-world audio signals (voice, music) or do tests with continuous
sine waves?

Measuring a steady 400 Hz tone is easy, just about any cheap DVM can
do a wonderful job of it. Most cheap DVMs have low pass filters that
can serious impact the accuracy of measurements above 500 Hz-1 KHz.

OTOH, my Fluke 83 has 0.1 dB (or so) response up to 20 KHz. I have a
Protek 506 True RMS DVM that is just a little worse, which is to say
its good for most audio purposes. As a plus the Protek has DB ranges.

Generating a really-pretty good 400 Hz tone is easy - just about any
computer sound card can generate a cleaner, steadier 400Hz tone at up
to 1 or 2 volts, than the really expensive stuff from yesteryear.
Software like Goldwave (shareware) or Audition ($$$) can generate just
about any test signal you can conceive of.

A more modern high end audio interface like a Card Deluxe or a
LynxTWO can generate more than 5 volts up to 100 or 200 KHz
respectively, with 0.1 dB or better flatness over the audio range, and
stunningly low residual distortion and noise. You still need a
voltmeter to set the output voltage.

IME, the most economical way to accurately and meaningfully measure a
varying voltage is to record it with DAW sofware, and analyze it
using DAW software like the analysis feature built into Adobe
Audition.

You can do a variety of audio equipment tests with a good audio
interface and the Audio Rightmark freeware. Spectra Lab costs money
but adds a ton of flexibility.

You can see the results of a lot of technical tests done this way at
www.pcavtech.com .

Also, if I want to perform tests on preamps (S/N, THD+N, etc) , how
do
I go about setting up a load on the input (simulate a mic
connected).

Usually a 150 ohm resistor is considered to be a adequate simulation
of a mic. Wire one into an XLR from pin 2 to 3.

Does anyone make a product, say an XLR with with user-selectable
resistance?

I doubt it, but it should be easy enough to modify a variable mic
attenuator. I don't know why one would do this, theory aside.

The Fluke 8060A is a great universal meter. True RMS with good accuracy
in the audio band. It has a frequency counter and a db mode that's
handy as well.

As to an analyzer, the Audio Precision will do anything you want
including selectable souce and destination impedances. Just be prepared
for sticker shock. Rent one to save mucho bucks.

Jim Williams
Audio Upgrades

If you are measuring sine waves, you don't need a TRUE RMS responding
meter...most any meter is calibrated to read the RMS value with sine
wave input. You do need a TRUE RMS responding meter If you are
measureing complex waveforms and want the RMS value.

Mark

wrote:
The Fluke 8060A is a great universal meter. True RMS with good accuracy
in the audio band. It has a frequency counter and a db mode that's
handy as well.

Mine served me well until someone stole it a few years back.

I bought one of the new 189's and I have to say it (and the 187) are
truly *wonderful* for audio. Dual numeric displays (so you can see dB
and frequency or AC and DC components of a signal, duty cycle, etc.)

http://us.fluke.com/usen/products/features.htm?cs_id=26864(FlukeProducts)

Thanks so much for your help guys! Really appreciate it.

I must say I've been very impressed with the support in this forum.
I'll try to return the favor by helping those just starting out in
this crazy, fascinating world of audio.

Harry

In article writes:

Can you please offer some advice on how to go about measuring the
output voltages on my converters, gear etc. What exactly do I need to
do this? an RMS voltmeter?

Why do you want to do this? Curiousity? Test? Just want to find out
what you have? For mostly useful audio measurements, I recomment the
NTI Minilyzer, and the companion Minirator as a source. They don't
cover the analog levels you'll encounter at full scale digital level,
but they're good for general measurements.

Also, if I want to perform tests on preamps (S/N, THD+N, etc) , how do
I go about setting up a load on the input (simulate a mic connected).
Does anyone make a product, say an XLR with with user-selectable
resistance?

This is the sort of thing that test technicians make themselves. It's
not rocket science. I usually make noise measurements of mic preamps
with the input shorted.




--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo