Help me decide on DMM for Audio - Modern vs Vintage

[adamboon]

Hi,
We've got a few Fluke 7x series meters, they are great.  I have a Protek 506 listed on eBay - it's gotta go.
Right now I'm tossing up on 3 (or 4) options:

HP3468A - eBay US - "AS IS" But looks to be working. for about $50-100 US (plus about that in shipping)
HP3478A - eBay US - That is in good working order and in pretty close calibration - sold by a meter nut. for about $100-150 US (plus about $75-100 in shipping)
BK Precision 2712 - eBay US - Used, looks good - About $90 + $40
Greenlee DM-830A - New - Around $248 + Shipping

It's for mostly audio stuff.  I often need to test 10-15Khz sinewaves accurately - which is what I can't do with the flukes (or Protek).  I also need to match up pairs of resistors (and caps, inductors) but will probably get something like a DER EE DE-5000 for that purpose.  I'm strangly attracted to Vintage HP, TrueRMS and 4 wire resistance testing.  And whilst I occasionally need to move it to another location.  I'm not scared of the bench option (I'd probably be moving my DSO and AWG anyway).

I'm thinking option no 2.  What do you think?

[Wirehead]

Seems to me, to measure audio frequencies accurately.. You need a Spectrum Analyser, not a bench DMM. Maybe a pro audio interface with protection circuit in front of it.

[adamboon]

Hi,

No I've got a Couple of good AF Spectrum Analysers.  And at least a few Pro Interfaces - But what I need is something to accurately measure things like 1.228 V AC Sine Waves at 1K, 10K, 15K - The Fluke's drop a lot of level as the Frequency gets higher - and they're not True RMS (I don't know if they're measuring RMS at all - maybe what they're measuring is "Averaging" which is different?).

Measuring Resistance as (or more) accurately as the meters I have would be great too - as I havn't purchased the DER EE DE-5000 yet - and am flip flopping on it a bit, as we already have an Atlas ESR meter - if we had a good Ohmmeter perhaps that would do...

I am restoring an HP 403B (that I purchased to replace our HP 400E that the meter scale print got all flakey and lifted off the backing, preventing the needle from moving) but It seems a bit far off being useful, and even when i get it up and running, it would be nice to have something accurate-ish to calibrate it against.

[MosherIV]

It's for mostly audio stuff.  I often need to test 10-15Khz sinewaves accurately

I think you need a meter which can measure harmonic distortion. Keithley make one, Dave did a tear down
https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwiuuqD64_XNAhVIXiwKHRLrD5MQtwIIHzAA&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DMiXMKgxx_Oc&usg=AFQjCNHzkdF74BB2JX5UttmuUmDztY4pkg&bvm=bv.127178174,d.bGg

I also need to match up pairs of resistors (and caps, inductors)

Get the LCR meter.
If you want truly accurate resistance measurements, look to 5.5 digit or better bench meters

But what I need is something to accurately measure things like 1.228 V AC Sine Waves at 1K, 10K, 15K

Measure what exactly? Harmonic distortion, peak to peak, rms ?
Your best bet is an oscilloscope so you can see the waveform.
Someone else pointed out to me that most handhled DMM do not measure AC above 1KHz

[PedroDaGr8]

The Brymen BM869S (also sold at a higher price as the Greenlee DM-860A,brymen is the oem for many of Greenlees meters ) can do RMS up to 100kHz. The BM869S runs about the same price as the Greenlee you mentioned, though it only has a one year warranty instead of Greenlee lifetime warranty,  though you get more features and better accuracy as well . I forget which Brymen model the DM-830 is based on.

Sent from my LGLS992 using Tapatalk

[Gyro]

You might also want to check their capabilities at the bottom end of the range, a lot of meters are only specified down to 40Hz.

[Kalvin]

Have anybody used a good quality audio card for the audio signal measurements? Compared to the plain RMS-voltage measurement one can get other signal parameters too.

[linux-works]

emu 0404 usb was one of the 'go to' sound cards in its day.  it can do 24/96 iirc, and has decent pro and consumer i/o.

the other one that comes to mind is ancient (firewire): the m-audio firewire audiophile.  consumer unbal i/o only but very good and nearly measurement quality.

for cards, the pci (old style) card is also known to be very good: esi juli@ which can do 24/96 via pro and consumer i/o.

many of us use the free RMAA tool to do audio scans.


fwiw, I do have the keithley 2015thd and its audio is not meant for modern hifi audio; its not good enough for that, really.   I use mine as a simple 6.5digit dmm, only.

[RandallMcRee]

Another vote for the Keithley 2015P. Best thing I have for audio measurements--THD (20-20Khz only however), AC rms, frequency. It also includes a signal generator which is handy (but THD is 0.02% so a bit high). 6.5 digits.

Audio cards are pretty much a non-starter unless you're talking about a whole package including some good software to work around their limitations and/or the quantasylum QA400. But that is more expensive than the keithley, but, of course, better in some tasks.

Randy

[linux-works]

good 'audio cards' are measurement quality, these days.

don't ignore them - they are not your father's 'sound blaster' anymore

again, the ESI julia is a damned good card with top end a/d and d/a onboard.

arta is expensive but rmaa is not; there are quite a few software pkgs you can buy for audio analysis.

I would not go dedicated test gear for audio charts anymore; pc's do it as well or better.

[adamboon]

Get the LCR meter.
If you want truly accurate resistance measurements, look to 5.5 digit or better bench meters

Isn't that what the HP3478A is?  a 5.5 digit bench meter...

But what I need is something to accurately measure things like 1.228 V AC Sine Waves at 1K, 10K, 15K

Measure what exactly? Harmonic distortion, peak to peak, rms ?
Your best bet is an oscilloscope so you can see the waveform.
Someone else pointed out to me that most handhled DMM do not measure AC above 1KHz

Sorry that wasn't that clear.  I need to measure that I have 1.228 V AC RMS at a test point at 1KHz, then the same (or a different specific voltage) at a test point at 10KHz for example. whilst adjusting trimmers.

We've got a Rigol DS1054Z, but it's only 8-12 Bits, so the voltage measurements are fairly inaccurate I believe.

Audio Interfaces (eg soundcards) can be a great tool these days, no doubt.  Great if you want to do a frequency / phase sweep or whatever.  Not really appropriate for what I need out of this meter though.

The Keithley sounds interesting, if I can find one for not too much $.  We already have an HP 334 distortion meter.

The The Brymen BM869S (or Greenlee DM-860A) Looks like a cracker... any recommendations on where to buy one?

There's still somthing (Benchy &) interesting about that HP 3478.  The BM869S is probably the sensible choice.