Will RIGOL DG1022U be appropriate for audio repair and calibration work?

[vladc77]

Agree too! I need to learn about it more. I can see bunch of the apps even for iOS. However, it looks not promising at the first glance. Maybe my expectations are too high. The only concern about it is a possibility to damage the computer. I read about it in a few places that it is a possibility. I need to learn about proper connection options.

[rstofer]

I still want to find out if Kenwood FG 273 will be suitable for audio? Is anyone familiar with this one? Thank you!

Well, if the FG273 distortion actually is 1% it has 5 times as much as the DG1022A. 

BTW, are you sure about the 1022 'U' model?  I thought we were looking at the new and improved 'A' model even though TEquipment still lists (but doesn't have) the plain 1022 model.

The idea for the notch filter is to have sharp response around a single frequency and attenuate signals outside the passband.  So, if you wanted to test at 400 Hz, you would have a filter tuned to this frequency and signals outside the bandwidth would be greatly attenuated.  Then you need another filter for 500 Hz and 600 Hz and so on.

Here's a tunable notch filter but I would want to see the LTSpice output before discussing it:
https://www.bing.com/images/search?q=audio+notch+filter&view=detailv2&&id=CAD8CC1D0F257543D53E19F09F546D606A884614

There are filter designs all over the internet.

The DG1022A only has 0.2%, somehow I could live with that.  If it wasn't clean enough, I would consider building up some notch filters.  That way I would have a full featured FG for non-audio projects.  But that's just me...

[vladc77]

rstofer, yes, I was referring to Rigol DG1022U. This is what currently available. For example, http://www.ebay.com/itm/RIGOL-DG1022U-DG1022A-Arbitrary-Waveform-Function-Generator-AWG-25Mhz-2-chs-FG-/161131138600?hash=item25842a0e28:g:hc0AAOSwnLdWrLJt

Yes, the distortion is not that high. I misread something about the Kenwood 273. It is with even a higher distortion level. This is why I initially was looking for Rigol DG1022U. However, I got impression from here that it is still on a high side for audio. My understanding is that the acceptable distortion level is no more than 0.05%. I will be happy to get this one if that works. I guess I still do not have a definite conclusion on it and highly appreciate if more people will help to clear out on it.

[vladc77]

I am also leaning toward trying a software based approach. It is still not all clear to me about how I safely can do it. My understanding is that I have to have:

• Software like - VIRTINS Multi-Instrument, Tone Generator Software or Visual Analyser. Fortuantelly, There are many choices. Not sure which one is the best.
• A decent sound card - I believe I already should have it on my MacPro
• Connection cables. This is not fully clear to me yet. My understating, I should have 3.5mm Stereo to Composite RCA cable from sound card to the audio hardware. I also should have some intermediate filter to prevent damaging sound card. Do not know which one. I believe this approach is for replacing Audio Tone/Signal Generator with very low distortion level.
• I believe I also can have this connection via USB where I need to use an usb isolator and an USB device. This approach is even more unclear currently to me.
  I believe this approach is for replacing much more than only Audio Tone/Signal Generator. It can be suitable for Frequency Counter, Oscilloscope, Signal Analyser and more.

Can anyone share with more details? Any advice is greatly appreciated!

[funkyant]

My audio Sig Gen of choice is the NTI MR-PRO.

http://shop.nti-audio.com/pd_minirator_mr-procfm.cfm

The much cheaper MR-2 is also good value:

http://shop.nti-audio.com/pd_minirator_mr2cfm.cfm


The on-board sound on your Mac Pro, I'm sorry to say, is crap and I certainly would not use it to generate reference tones.

[vladc77]

Yes, they are good ones but cost as much as a decent modern Digital Function Generator. My understanding they carry only audio generator functionality. As a result, It may be then more reasons to buy something like Rigol DG1022U. I thought that if I am going to use a software based approach it will be a very cheap one. I may be wrong.

[funkyant]

Yes, they are good ones but cost as much as a decent modern Digital Function Generator. My understanding they carry only audio generator functionality. As a result, It may be then more reasons to buy something like Rigol DG1022U. I thought that if I am going to use a software based approach it will be a very cheap one. I may be wrong.

You're not wrong

But I have the DG1021 and as others have suggested, it just not up to spec as an audio generator for anything critical.

If you want to do it cheap as possible and get most bang for your buck then for sure a software solution will be best. Just start with the on board sound, and if you find you are hitting the limitations of that, there are plenty of cheap-ish USB soundcards with decent DAC's these days.

[funkyant]

Check out this software:

http://www.nch.com.au/tonegen/

[Lightages]

You still haven't mentioned how you intend to use the FG. Is it to inject anywhere on the circuit or just at the normal inputs? There are many things to consider. Common grounds, loading, voltages. You also mention that you have a Mac. Do you have a PC? I am only familiar with software for the PC. One of the best and cheapest (free) is:
http://www.sillanumsoft.org/

How you connect it to what you want to test is wide open depending on what the equipment is.
http://makezine.com/projects/sound-card-oscilloscope/
http://www.instructables.com/id/Use-Your-Laptop-as-Oscilloscope/?ALLSTEPS
That is for an input, but outputs are a different matter.

It is possible that all you need is the correct cabling with no extra components.

So, where are you planning to connect?

[vladc77]

Thank you funkyant. It is good Tone Generator.

Thank you Lightages for great links. I may need to have it for both reasons. I am running Windows on my MacPro. I also have a PC computer.

• Will injection at the normal inputs be OK with only 3.5mm Stereo to Composite RCA cable? Do I need anything else for safety? I believe it will be good for sending tone signal to the tape deck.
• Regarding injecting the signal to the circuit board, I believe you are saying I need to consider about common grounds, loading, voltages. Is any affordable ready solution I can get?
  

You said that I just may need the correct cabling with no extra components. What are you referring to? Is that a regular 3.5mm Stereo to Composite RCA cable or a special one?

Currently, I need to calibrate/analyze few tape deck. I also need to trace the problem on the circuit board at one of the decks. It is not working. One channel is dead. In addition, I just want to learn about the possibilities and be ready when I need it. Thank you again.

[Lightages]

Thank you Lightages for great links. I may need to have it for both reasons. I am running Windows on my MacPro. I also have a PC computer.

• Will injection at the normal inputs be OK with only 3.5mm Stereo to Composite RCA cable? Do I need anything else for safety? I believe it will be good for sending tone signal to the tape deck.

Yes

• Regarding injecting the signal to the circuit board, I believe you are saying I need to consider about common grounds, loading, voltages. Is any affordable ready solution I can get?
  

Too many considerations to post. Do some searching on the webs and you will find many circuits to take care of certain needs.

Currently, I need to calibrate/analyze few tape deck. I also need to trace the problem on the circuit board at one of the decks. It is not working. One channel is dead. In addition, I just want to learn about the possibilities and be ready when I need it. Thank you again.

Again, not enough information to know what you need. If it is to inject signals, that is one thing. If it is to look at signals, that is another. Google is your friend in this case.

[vladc77]

Thank you Lightages for great links. I may need to have it for both reasons. I am running Windows on my MacPro. I also have a PC computer.

• Will injection at the normal inputs be OK with only 3.5mm Stereo to Composite RCA cable? Do I need anything else for safety? I believe it will be good for sending tone signal to the tape deck.

Yes

Is that Yes for OK with no safety precautions?

• Regarding injecting the signal to the circuit board, I believe you are saying I need to consider about common grounds, loading, voltages. Is any affordable ready solution I can get?
  

Too many considerations to post. Do some searching on the webs and you will find many circuits to take care of certain needs.

Currently, I need to calibrate/analyze few tape deck. I also need to trace the problem on the circuit board at one of the decks. It is not working. One channel is dead. In addition, I just want to learn about the possibilities and be ready when I need it. Thank you again.

Again, not enough information to know what you need. If it is to inject signals, that is one thing. If it is to look at signals, that is another. Google is your friend in this case.

I understand. I need to look on google. I just wanted to get some sort of overview in general. I may need to inject and/or look at signals and experiment, not clear agenda at the moment. I wanted to gather information to create a PC based lab with all safety precautions, especially, preventing damaging computer or sound card. Thank you anyway!

[bson]

The DG1022A only has 0.2%, somehow I could live with that.  If it wasn't clean enough, I would consider building up some notch filters.  That way I would have a full featured FG for non-audio projects.  But that's just me...

My DG1022A measures 0.0100% across the audible spectrum on the HP 8903B, at slightly above typical line levels (500mV rms).   That's about the same as the 8903's internal source.  Compare this to the Siglent SDG2122X at 0.0060% (0.0045% using an external reference) and my HP 33120A at 0.0040%.

The instrument spec is just a max value and will be very conservative.  And even if it's 0.2% it's not that big of a deal since it can be subtracted from the total system THD+N measurement, as long as it can be reliably measured in isolation.

For repair purposes all of these are fine for test tone generation since even 0.01% is completely inaudible no matter what its nature.  For quantitative design analysis less is a little better so the system is dominated by the DUT.

[rstofer]

Isolating the ground loops can be done in at least 2 pretty simple ways:

1) Use a battery powered signal generator.  For troubleshooting, the 1022A is overkill and something with a couple of op amps and a 9V battery would be ideal.
2) Use an audio matching transformer (probably 1:1 ratio) to isolate the signal source and its ground from the DUT input and its ground.

You can just buy an isolating transformer setup, already built and in a box for about $9:
https://www.vminnovations.com/Product_48848/Boss-B25N-Ground-Loop-Isolator-Noise-Filter-.html?rd=gpf_48848&gclid=CMC1q7qy68wCFYZefgodrn0A7Q

Search the Internet for 'isolating ground loops in audio systems'.

There is no way in **** I would use my PC as a signal source for a circuit that was known to be defective.

The more I think about it, the more I like the OP AMP solution.  It's small, cheap, battery powered and expendable.  I would save my good equipment, and especially my PC, for things that are presumed to work.

[vladc77]

My DG1022A measures 0.0100% across the audible spectrum on the HP 8903B, at slightly above typical line levels (500mV rms).   That's about the same as the 8903's internal source.  Compare this to the Siglent SDG2122X at 0.0060% (0.0045% using an external reference) and my HP 33120A at 0.0040%.

Thank you bson! It is very informative and changes my view on it.

[vladc77]

You can just buy an isolating transformer setup, already built and in a box for about $9:
https://www.vminnovations.com/Product_48848/Boss-B25N-Ground-Loop-Isolator-Noise-Filter-.html?rd=gpf_48848&gclid=CMC1q7qy68wCFYZefgodrn0A7Q

There is no way in **** I would use my PC as a signal source for a circuit that was known to be defective.

The more I think about it, the more I like the OP AMP solution.  It's small, cheap, battery powered and expendable.  I would save my good equipment, and especially my PC, for things that are presumed to work.

Thank you rstofer! It is very helpful. I already ordered Boss B25N RCA to RCA Ground Loop Isolator. I wanted to clarify here. It seems like that using B25N will be 100% safe to send tones from a signal generator (computer or any), not need to follow options 1 and 2 above. Right?

However if I understood correctly, it is not safe for signal source for a circuit testing. Alternative for that is to have OP AMP solution. Is that correct? Please clarify.

I was looking for OP AMP solutions. I found mostly DIYs to maker it myself. I may do it but most likely later. Would you recommended something that available for purchase or appropriate kit to make it myself. I was looking for the options and did not find something within 20Hz -20kHz yet. Thank you again.

[rstofer]

Thank you rstofer! It is very helpful. I already ordered Boss B25N RCA to RCA Ground Loop Isolator. I wanted to clarify here. It seems like that using B25N will be 100% safe to send tones from a signal generator (computer or any), not need to follow options 1 and 2 above. Right?

However if I understood correctly, it is not safe for signal source for a circuit testing. Alternative for that is to have OP AMP solution. Is that correct? Please clarify.

I was looking for OP AMP solutions. I found mostly DIYs to maker it myself. I may do it but most likely later. Would you recommended something that available for purchase or appropriate kit to make it myself. I was looking for the options and did not find something within 20Hz -20kHz yet. Thank you again.

I didn't find a suitable 'kit' that covered the entire spectrum.  I didn't search eBay and I didn't spend a lot of time looking.  I kind of like the multi-range unit I linked to above.  But it is a DIY project - fun but time consuming.  I did find some fixed frequency signal generators but I don't see the utility in those.

For running a sound card, how about an old PC that is due for retirement.  I have at least 3 Dell OptiPlex systems that are expendable.  But you can absolutely bet on the fact I will never use my Surface Book as a signal source.

Technically, the isolation transformer should be entirely adequate for eliminating ground loop (hum) but what happens if you cross up 120V with the secondary of the transformer.  Well, it's still a transformer so the 120V appears on the sound card and the motherboard.  I'm just not going there.

No matter what it took, if I were doing debugging mains powered stuff where there was any possibility of getting into voltages above 5V, I want an expendable source.

Other people will scoff at my hyper-vigilance but that's the way I feel about troubleshooting stuff that could potentially destroy my equipment.  I started with one problem, now I have two!You could take every precaution and check every test point with a multimeter but still slip up and hit something that might not mix well with your source.

[vladc77]

Thank you rstofer! It looks like I can experiment with many things. I may get an older laptop for $50 and should be fine for a while.

[vladc77]

Another question, I tried Arta software based signal generator with sending test signal via sound card. For some reason, I cannot have a signal higher than 22Khz. I mean that even I set Sine waves with frequency more than 22kHz, the frequency counter never get measurement higher than 22kHz. I used Fluke 289 for this measurement. Does it mean the sound card has a limitation to output more than 22Khz. The spec on sound card states that it is 24bit, 192kHz capable sound card. Can anyone clarify what is wrong? Thank you!

[rstofer]

Another question, I tried Arta software based signal generator with sending test signal via sound card. For some reason, I cannot have a signal higher than 22Khz. I mean that even I set Sine waves with frequency more than 22kHz, the frequency counter never get measurement higher than 22kHz. I used Fluke 289 for this measurement. Does it mean the sound card has a limitation to output more than 22Khz. The spec on sound card states that it is 24bit, 192kHz capable sound card. Can anyone clarify what is wrong? Thank you!

A very brief look on the Internet shows that the upper frequency limit for sound cards is often on the order of 20 kHz.  Sure, they are 'sound' cards so why have an upper limit that is inaudible?

Are you sure the 192 kHz applies to the output frequency or is it the sample rate.  Got a link to the data sheet?

You could read the FAQs for your software and find out that this limit is quite common when the sound card has an anti-aliasing filter:
http://www.artalabs.hr/faqs.htm

[vladc77]

Thank you again rstofer! it all makes sense now. I believe the sound card just do not go over 22kHz. It seems like it is still workable for testing audio via sound card but need to realize about the upper limits. Thank you!

[The Soulman]

You could play around with this (free) software, I use it frequently and quite happy with it.
It's pretty cool actually.

http://www.sillanumsoft.org/ 

If the need arises you could always go with a high quality external sound card such as a RME or MOTU,
a isolation transformer would also be a good idea to use, depending on what you're doing.

[vladc77]

Thank you The Soulman! I may need to buy a good external sound card. I hope it wouldn't be as much as a decent audio/function generator.