Suggested test and measurement gear for DIY API-like console build?

[grievousangel]

Suggested test and measurement gear for DIY API-based console build? I like the CAPI stuff.

eBay is loaded with China-based test gear, but .... ? Not concerned with room yet, just power supply & noise, calibration and trouble-shooting of modules,. etc.

Does CAPI deal with Aux Sends, Bus selection and master section features?

Thx

Billy

 

[pucho812]

you need a scope, you need a DMM and you need an AP or equivalent device.

 

[grievousangel]

Yes I understand that. I was looking for suggested brands that were cost effective.

Thx
Billy

 

[Audio1Man]

What is your basic budget for your lab? This is needed as a DVM is  $10 however a good on may be $100 or more.  A scope could be a sound card or a  used Tek $2k. Some new DSO are now under $300. A signal gen &  analyzer can be Heathkit $150  or AP or similar for $2k-3k to 30K. What equipment do you now have?

 

[Bo Deadly]

For a "spectrum analyser", the super low-budget solution is just use a conventional audio interface box (used for $50 on Ebay) with the right software (DSSF3 from ymec or "Room EQ Wizard"). One step up from there would be a Quant Asylum QA400 or QA401 (there's one on Ebay right now for $75 and IIRC they originally cost ~400 USD) which on the surface doesn't look much better than a conventional audio interface but the software is what is important and it's not bad.

 

[rackmonkey]

...eBay is loaded with China-based test gear, but .... ? ...

Yes I understand that. I was looking for suggested brands that were cost effective.

Thx
Billy

The Chinese ebay gear is all over the map in my experience.  Some of it is very high quality.  I wouldn't measure my Johnson with some of it. For less than $300 you could get a Hantek or Siglent scope and do very well with it. The specs/features on even the lower end of those brands surpass some of the high end Tektronix scopes from 20 - 25 years ago. I still use my old Tek 2221 for lissajous curves, but usually pull out the light little Hantek for most other things.

DMMs. Be careful buying used unless you like fixing DMMs. Some of the ebay sellers have pictures of testing that they've done and let you return something that doesn't work as advertised.  I've gotten four or five years of good service out of an old Keithley bench MM I got from one of those guys. Think I paid around $75 plus shipping. Can't speak to handhelds or the chinese stuff here, except to say I've had no issues with a Mastech bench MM that I bought new for under $130. I like it.

Before you drop 2 Gs on an AP, try out one of the PC/Mac-based audio analysis programs. Getting levels right can be tricky at first, and you're limited by the frequency response of your sound card, but I'd venture a guess that most people here use sw for the purpose. Some names that come up are RMAA, Arta, REW, TrueRTA, etc. Plenty of options, some of it free.

And do yourself a favor and get one of the many ATmega/PIC based digital LCR/transistor checker meters out there for a few bucks. Most are based on an open source project that's been around quite a while and are basically the same under the hood. Some of the cheapest ones are poorly executed and pretty bad. But for around $20 - 40 you can get one that's good. You won't check transformer inductances with these, but for quickly checking resistors/caps/diodes/transistors you can't beat em. I've tried a few and like a little no-name labelled MK-328 that's been a real time saver.

Lastly you might want to have a function generator around. No cheap ones have completely pulled me away from my patina'd antiques yet, but I'm sure someone's got some good low cost options for you here.

BT

 

[Khron]

The cheapest (and arguably simplest) solution would indeed be a lowly 2-channel audio interface (think Focusrite Scarlett 2i2, or the myriad of ones in that class from all the other manufacturers). 

Audacity is free (and cross-platform), and there are plenty of free tone-generator plugins (to produce a test-signal) as well as spectrum analyzers or oscilloscope plugins (to view the signal coming out of your device-under-test).

On the other hand, in case you have / want to test signals from other than the output of your device-under-test, only THEN the utility of a stand-alone oscilloscope starts to come in, imho.

Regarding multimeters, Brymen actually make some really nice (and impressively well-built) handheld ones, even the smaller ones in the 100$ range.

 

[cyrano]

Audacity is free (and cross-platform), and there are plenty of free tone-generator plugins (to produce a test-signal) as well as spectrum analyzers or oscilloscope plugins (to view the signal coming out of your device-under-test).

Audacity also has the Nyquist scripting language (Dannenberg, CMU). It's worth exploring, as it is made for audio. Makes stuff like DTMF a breeze:

http://wiki.audacityteam.org/wiki/Nyquist_Generate_Plugins

Regarding multimeters, Brymen actually make some really nice (and impressively well-built) handheld ones, even the smaller ones in the 100$ range.

Thx for the tip. Didn't know that brand. Neither does Google...

 

[Khron]

It doesn't? Then what's with this? ;D

https://www.google.fi/search?client=opera&q=Brymen&sourceid=opera&ie=utf-8&oe=utf-8&channel=suggest&gws_rd=ssl

Thx for the tip. Didn't know that brand. Neither does Google...

 

[cyrano]

Well, of course Google knows the brand and can find the corporate website. But some of their models seem te be available... nowhere...

It seems this is a bit typical for some Taiwanese companies. They make good products, but 90% of their production is OEM for other, more known brands.

Any idea if this is true in this case?

 

[ruffrecords]

I use REW coupled to a Scarlett 2i2 for most of my tests. However, to make this more pro audio specific I have added my own interface box that adds a number of features:

1.  Buffers the generator source with a 600:600 Sowter transformer - this prevents badly wired phantom powered mic inputs from blowing up your signal source - and yes it DOES happen.

2. 40dB and 60dB signal source attenuators for testing mic inputs -  you cannot rely on a digital interface producing a low noise -60dBu signal

3. Zero ohm and 150 ohm input loads for measuring noise performance.

4. 600 ohm load with switchable 20dB pad so you can measure output levels up to +20dBu

It is 100% passive amd is built in a tin box with XLR ins and outs.

Cheers

Ian

 

[rackmonkey]

Like Ian, I recently added a sound card interface to my setup (REW). I got tired of constantly having to fiddle with input levels or use a sub-optimal DI box to get signals into the sound card at the right level for the task at hand.  I just built a kit that hi-fi guru Pete Millett sells and it works nicely.  Also has a little panel voltmeter built in, which is handy. Description/BOM/Schematic here:

http://www.pmillett.com/ATEST.htm

BT

 

[gswan]

With test equipment, reliability and confidence in the measurement is everything.

There are a few key pieces of equipment worth spending extra $ on. The DMM is one. Get a Fluke, Agilent etc. It will last for a long time and give a measurement of which you can be confident.

As for scopes, you might be able to find a bargain on a used Tektronix analogue 100MHz unit. A lot of places are literally throwing these out and replacing with DSO's. Otherwise there are some reasonable Chinese units (eg Siglent, Rigol etc) that will allow you to view and examine waveforms. The DMM will be a better tool for accurate measurements of these waveforms though.

Another useful piece of equipment is the Noise/Distortion meter. Some old AWA/HP etc boxes can be had for a bargain. I have a nice old AWAF242A unit which gets a lot of use, came calibrated from an old test lab and cost about $100.

A good analogue signal generator is also a requirement. Look for old HP units.

And the bench PSU. Plenty of these to choose from. Get one with at least a bipolar output with current limiting and OVP. The Rigoil DP832 is not bad, but you may be able to find a cheaper one.

 

[grievousangel]

I ended up getting a PICO PC Scope 4262, it does a great job on audio measurements, including spectrum stuff. Includes a low distortion signal generator.

Is's fast and detailed enough for analog audio, ie., 16 bit @ 10MS/s Resolution, 5 MHz Bandwidth, 16MS Memory. Check it out.

Also got benchtop Rigol DMM, 5-1/2 digits.  Does db measurements. Great for price.

They are doing an excellent job on what I have needed so far.

Later.

 

[user 37518]

I ended up getting a PICO PC Scope 4262, it does a great job on audio measurements, including spectrum stuff. Includes a low distortion signal generator.

Is's fast and detailed enough for analog audio, ie., 16 bit @ 10MS/s Resolution, 5 MHz Bandwidth, 16MS Memory. Check it out.

Also got benchtop Rigol DMM, 5-1/2 digits.  Does db measurements. Great for price.

They are doing an excellent job on what I have needed so far.

Later.

Nice setup, I've seen the PICO scopes in magazines but never tried one,  I'm currently relying on my QA401 , for the price it is a bargain I think. Sometimes I also need to do acoustic measurements either testing a speaker or a room, I-ve found that the Dayton Audio Measurement Mic is the best thing you can get for the money, it is around $50 USD, it comes with a calibration file, the file can be imported to the QA401 and correct for frequency response.

 

[Newmarket]

Like Ian, I recently added a sound card interface to my setup (REW). I got tired of constantly having to fiddle with input levels or use a sub-optimal DI box to get signals into the sound card at the right level for the task at hand.  I just built a kit that hi-fi guru Pete Millett sells and it works nicely.  Also has a little panel voltmeter built in, which is handy. Description/BOM/Schematic here:

http://www.pmillett.com/ATEST.htm

BT

I don't really get the bit about:

"One could scale all the input resistors by a factor of 10 and get a 1 megohm input impedance.  This might seem desirable as it would allow using 10x or 100x scope probes, which provide very little load to the circuit under test.  The problem is that the input noise and offset would also go up (maybe also by a factor of 10), as the input bias current and current noise of the amplifiers will turn into nose and offset voltage."

That's true in itself wrt resistor values with no input source connected.
But with a signal source connected the high resistance is in parallel with the source impedance so the overall resistance is much lower - reducing the noise / offset problems.

 

[grievousangel]

I finally got (at least to me) a 'top drawer'  2 channel ADA box, a RME ADI-2 Pro FS. I found one at a discount since a newer model (I think) is out.

It made a significant listening difference even on MP3's! It opened up the music! It's like I could imagine space between the instruments. Also a big plus is it's use as a quality audio measurement tool, even at very low levels ... way down there where nothing seems to exist!

Later.

 

[abbey road d enfer]

I don't really get the bit about:

"One could scale all the input resistors by a factor of 10 and get a 1 megohm input impedance.  This might seem desirable as it would allow using 10x or 100x scope probes, which provide very little load to the circuit under test.  The problem is that the input noise and offset would also go up (maybe also by a factor of 10), as the input bias current and current noise of the amplifiers will turn into nose and offset voltage."

That's true in itself wrt resistor values with no input source connected.
But with a signal source connected the high resistance is in parallel with the source impedance so the overall resistance is much lower - reducing the noise / offset problems.

When the attenuator is in circuit, the input sees the shunt branch of the attenuator. A typical scope probe in x10 position has a 10 Meg resistor that is the series branch and the shunt branch is the scope's own input impedance. In short, the input is practically unloaded.
If you use that with an audio analyser that is optimized for typical line impedance of 10-50kiloohms, the EIN is bound to go over the roof.

 

[Whoops]

Test Gear:

- 100€ Sound Card with REW (Room EQ Wizard) free software

DMM
UNI-T UT136A Digital Multimeter
https://www.ebay.co.uk/itm/UNI-T-UT136A-Digital-Multimeter-Auto-Data-Hold-DMM-AC-DC-Volt-Ohm-Freq-Hz-Teste/112646171863?hash=item1a3a3c2cd7:g:z4AAAOSwFypZeFzA


Component Tester
MK-328 Tester
https://www.ebay.co.uk/itm/1PCS-MK-328-TRLCRESR-Transistor-LCR-ESR-tester-semiconductor-device-analyzer-M/191873654353?hash=item2cac8f9e51:g:afUAAOSwboVXOWKc


Oscilocope
Rigol DS1054Z
https://www.rigol-uk.co.uk/product/rigol-ds1054z-50mhz-digital-oscilloscope/


Bench PSU
TENMA Bench Top Power Supply, 0-30V 3A with Single Output
https://pt.farnell.com/tenma/72-10480/power-supply-1ch-30v-3a-adjustable/dp/2251946