DIY Verifying proper operation of gear with test equipment

[240sx4u]

This is a bit of an overwhelming ask for some reason for me but I am going to do it anyway. I have found over the years that I want to verify the signal output of various devices. Phono stages, amp outputs. whatever. This is usually because everything I run has some years on it, my ears aren't perfect and I can be a bit of an audio hypochondriac. Mainly I want to be able to say "gear is fine, must be something else".

I have a scope here, meter etc.. not much else. If I was looking for a channel imbalance that could be different in both audible volume and tone (I want to look at my phono stage) would a scope show me what's going on?

My scope is an admittedly old BK precision unit with a CRT screen so I'm not even sure it's in good enough condition to be useful. I do not have a lot of experience using test gear so I'm not sure I'd understand the results if I were looking at something.

Any guidance and suggestions are appreciated.

 

[Olson_jr]

I have zero background in this so this should prove an interesting thread.

To make sure I understand your issue, do you only hear this imbalance with phono? Can you swap cables left/right and have the issue follow the swap?

I only ask as I know I have a bit more midrange hearing loss in my right ear and can compensate for that at home, but sit in front of others' stereos for hours and not be sure if their system is off or if it is me. I know the listen backward trick.

 

[240sx4u]

I have zero background in this so this should prove an interesting thread.

To make sure I understand your issue, do you only hear this imbalance with phono? Can you swap cables left/right and have the issue follow the swap?

I only ask as I know I have a bit more midrange hearing loss in my right ear and can compensate for that at home, but sit in front of others' stereos for hours and not be sure if their system is off or if it is me. I know the listen backward trick.

Correct, phono only (in this case), The strange part is that the imbalance seems to go away when I swap channels. I don't trust my ears, at all, for actual troubleshooting and am hoping for a more binary solution. If the imbalance is me, I can live with that, but if it's something going on with my gear I'd like to rectify it.

 

[targeteye]

there is all kinda of equipment you can get for this sort of thing from audio analyzers digital scopes etc

There is even Software you can buy to use with an audio card.

Of the top of my head, if your familiar with scopes the easiest thing to do is get a decent new digital scope that can run FFT against both channels simultaneously coupled with a low distortion signal generator that also has sweep capability.

that should give you a good general idea. If you really wanted to get into the details you'd need a dedicated Audio analyzer / distortion analyzer.

 

[Faust3D]

This software works well with various mics and USB sounds cards. True Audio: Audio Spectrum Analyzer and Loudspeaker Design Software

 

[kirk57]

Any old dual trace scope can detect audio band differences no problem. They typically go well above audible range.

The challenge is identifying where to put the probes to detect the channel imbalance, and understanding what the output is at that node and adjust the scope range accordingly.

What device do you suspect has the channel imbalance?

 

[Rudy]

Similar/somewhat related--is there a good budget USB oscilloscope out there? I can justify buying something smaller if it works well. Buying an actual oscilloscope is out of the question.

 

[240sx4u]

Okay sorry guys, I have done a terrible job of staying ontop of this post!

At this point I just want to test the output of my phono stage and see if it's performing correctly. Upon further thought (which you guys sparked). I guess I'm willing to buy some equipment that's going to let me verify operation. Channel balance, tonally the same for both channels, distortion (I had not considered distortion before honestly)

I run older gear, and some DIY stuff, and like to tinker and do some repairs too so this does kinda dovetail with my current interests. I do have a Dayton Omnimic so I am able to do measurements of speakers.

I see lots of vintage test gear available, but I presume that's a whole other can of worms.

 

[Pat McGinty]

Similar/somewhat related--is there a good budget USB oscilloscope out there? I can justify buying something smaller if it works well. Buying an actual oscilloscope is out of the question.

I'm considering adding this cheap-o scope to my go-bag.

 

[Rudy]

I see lots of vintage test gear available, but I presume that's a whole other can of worms.

That is partly why I want to go with a USB scope--preferably one that won't die on me the fourth time I use it. Buying a used scope can be a can of worms in that we don't know how long it has been used, if it needs a calibration, etc. And in my case, I'm not going to have room to store one. If I could pop a handheld device into a tablet or computer with a USB connection so I have a nice, readable screen, that would be perfect.

Pat had a good option above, also. If the screen resolution works out to be sufficient, that might be a good alternative. Something contained all in one handheld package, rechargeable, ready to go at a moment's notice. Although as we get older, remembering where we put the test leads is another issue entirely. 😁 (I have that issue with my multimeter, and I own two sets of leads for it!)

Given that automotive diagnostics are often designed around task-specific tablets (look at the higher end Autel models), I could see something similar in electronics, if it hasn't been done yet already.

 

[House de Kris]

Sometimes it is more than just having the latest cool gear, good technique helps, too. Before I do any measurement, I verify the measurement gear setup, just to be sure I'm not fooling myself. For example, when checking channel imbalance, take both probes to the same signal to ensure the scope says they are the same. If not, you'll end up chasing you tail for way too long. Another thing, use a test record as your source. I know, many people insist that they listen to music and not test tones. But, for testing, test tones make the most sense. If you refuse to buy a test record, at least play a mono album cut before stereo was a thing.

If your BK scope is two channel and you have two matching probes, you may have sufficient gear on hand to accomplish what you are seeking. But, if the pressures of new are telling you otherwise, I have to say that I'm quite happy with my Digilent Analog Discovery 2 that I bought a few years ago. I see they have a version 3 now. The small portable scope listed earlier is also very cool. I had a Fluke 199 scopemeter when it first came out decades ago, and that was quite handy. You usually don't have to rely on the limited screen resolution of these portable devices, as they have built in measurements that will accurately tell you what's going on.

Good luck!

 

[RPMac]

I'm considering adding this cheap-o scope to my go-bag.

How easy is it to learn to use? Speaking for us ”not so inclined”.

 

[Rudy]

How easy is it to learn to use? Speaking for us ”not so inclined”.

👆 What he said. I learned the basics, but that was in high school. And we had a split of newer solid state scopes, and old tubed scopes that had drifted out of alignment (which had round screens). Interesting times.

 

[Pat McGinty]

How easy is it to learn to use? Speaking for us ”not so inclined”.

I haven't tried one, but it came to my attention when this vid appearing in my Youtube feed. Pretty much explains the functions.

 

[240sx4u]

I'm considering adding this cheap-o scope to my go-bag.

You know, this would actually be really useful for my purposes. I use my scope in the garage more often than not.

 

[240sx4u]

I'm considering adding this cheap-o scope to my go-bag.

Well this showed up yesterday, initial impressions are good. The screen is pretty small, so we'll see if this will work for me. I was able to test the output of my phone and a square wave at 600hz looked pretty nasty with lots of overshoot. Ill see if I can grab some screenshots and post them up for you guys to see.

The Auto button is pretty neat for a peon like myself.

 

[240sx4u]

I went ahead and tried it out using the calibration terminal on my B&K scope. There's obviously something wrong with the B&K..

 

[240sx4u]

So it seems to me there's something amiss here. I have both probes on the same source and both channels setup the same way but get a different voltage reading. I did flop the probes to see if the issue moved and it remained the same. Does this seem acceptable @Pat McGinty?