USB audio converters

[craiggsmith]

Last week we used the following device:
https://www.amazon.com/Microphone-HOSON ... B07ZBZ62X9

I didn't notice any distortion during testing but there was distortion during the webcasts, with two different computers, so I assume it could only handle mic level. But now I see that the specs say it can handle 2.8V. So I'm not sure what's up; the specs are for both an XLR to USB and a TRS to USB. It does say something about 20db of gain though. Maybe we just need to turn the mic level down? I didn't know you could do that, thanks.

[russellhltn]

One thing I wonder about is using a mono vs stereo audio cable. I found two other similar devices on Amazon (https://www.amazon.com/gp/product/B07SSBHGP7 and https://www.amazon.com/gp/product/B01N905VOY) and both say the the microphone jack is not compatible with TS cables, only TRS. Yet it's mono. I can't imagine it expects a balanced input, and even if it did it wouldn't matter if the other channel had no signal. And with an unbalanced mono source it wouldn't matter which cable is used, the ring would just be grounded right. Right?

A mono "computer" microphone is TRS. Tip and Sleeve has the signal, the ring is power for electret mics. I'm not sure of the details, but apparently, shorting the power to ground by using a TS cable messes up the sound card. Using a TRS cable and leaving the R open on the other end might pick up noise, but otherwise doesn't cause issues.

[CalS201]

Thank you both for the recommendations. Where did you get the specs for the Sabrent device? I can't find max input level for any of the devices anywhere.

Sometime I can get specs by contacting the manufacturer, but more often I have to obtain the product and use my signal source, DVM, o'scope and the TrueRTA program to make measurements. The TrueRTA program works great for viewing a waveform (finding the point of distortion), but it's amplitude is not calibrated so I use a DVM or oscope paralleled with the input signal.

One thing I wonder about is using a mono vs stereo audio cable. I found two other similar devices on Amazon (https://www.amazon.com/gp/product/B07SSBHGP7 and https://www.amazon.com/gp/product/B01N905VOY) and both say the the microphone jack is not compatible with TS cables, only TRS. Yet it's mono. I can't imagine it expects a balanced input, and even if it did it wouldn't matter if the other channel had no signal. And with an unbalanced mono source it wouldn't matter which cable is used, the ring would just be grounded right. Right?

A TS cable should be avoided because it shorts the bias or the mic+bias signals to ground.

All of the TRS Mic connections I have seen on computers and USB adapters are unbalanced and either
T=mic, R=bias, S=Return
TR=mic+bias, S=Return
T=L Mic+Bias, R = R Mic+Bias , S=Return

If you are running a 50-75 foot TRS cable from the RecordOut jack it would be advisable to put a TS to TRS adapter (mono to stereo) at the RecordOut jack to prevent the "R" from becoming a 50ft antenna for noise. You may not need it but the adapter is only $2 and it's handy to have in your "bag of problem solving adapters"!

[craiggsmith]

A mono "computer" microphone is TRS. Tip and Sleeve has the signal, the ring is power for electret mics. I'm not sure of the details, but apparently, shorting the power to ground by using a TS cable messes up the sound card. Using a TRS cable and leaving the R open on the other end might pick up noise, but otherwise doesn't cause issues.

A TS cable should be avoided because it shorts the bias or the mic+bias signals to ground.

All of the TRS Mic connections I have seen on computers and USB adapters are unbalanced and either
T=mic, R=bias, S=Return
TR=mic+bias, S=Return
T=L Mic+Bias, R = R Mic+Bias , S=Return

If you are running a 50-75 foot TRS cable from the RecordOut jack it would be advisable to put a TS to TRS adapter (mono to stereo) at the RecordOut jack to prevent the "R" from becoming a 50ft antenna for noise. You may not need it but the adapter is only $2 and it's handy to have in your "bag of problem solving adapters"!

Thanks very much. I didn't know computers were capable of providing power for mics. Since most computers nowadays don't have separate headphone and mic jacks but rather a single TRRS jack, I assume the bias is applied directly to the signal? I certainly wouldn't want to short that to ground at any rate.

But this begs the question of what the input looks like for the Sabrent devices. I called them earlier today (they actually have a tech support line and picked up right away) to find out the max input voltage of that other device, but it took them a long time to come up with an answer and they said 3.5V, which seems highly unlikely. So I don't know if they will know the pin configuration or not.

[CalS201]

Thanks very much. I didn't know computers were capable of providing power for mics. Since most computers nowadays don't have separate headphone and mic jacks but rather a single TRRS jack, I assume the bias is applied directly to the signal?

Yes, Mic signal and bias voltage both appear on the "S" of a computer or modern phone TRRS jack.

But this begs the question of what the input looks like for the Sabrent devices. I called them earlier today (they actually have a tech support line and picked up right away) to find out the max input voltage of that other device, but it took them a long time to come up with an answer and they said 3.5V, which seems highly unlikely. So I don't know if they will know the pin configuration or not.

The Mic input for the SAbrent USB adapter is a TRS with the following pin configuration:
T=Mic+bias voltage
R=open
S=Return

The bias voltage is 3v open circuit, 1.5v when you attach a 10K source, and .5v when you attach a 2K source.

The maximum input is 550mv rms/777mv pk as I described in a previous post viewtopic.php?f=27&t=37755#p215749

[russellhltn]

The Mic input for the SAbrent USB adapter is a TRS with the following pin configuration:
T=Mic+bias voltage
R=open
S=Return

If R is open, then it seems like it should be happy with a TS cable.

[craiggsmith]

The Mic input for the Sabrent USB adapter is a TRS with the following pin configuration:
T=Mic+bias voltage
R=open
S=Return

The bias voltage is 3v open circuit, 1.5v when you attach a 10K source, and .5v when you attach a 2K source.

The maximum input is 550mv rms/777mv pk as I described in a previous post viewtopic.php?f=27&t=37755#p215749

Thank you. Yes, I saw your previous post, I was wondering about the other Sabrent device I listed. I don't like the one initially mentioned as it blocks the adjacent ports unless I buy a separate cable; the one I listed comes with a cable for the same price. But I'm not sure if it's the same internals or not. Most of the description is similar but it also says it "enables PC style 3.5mm headsets with microphone to be used on your Mac." Not sure how you could do that with separate mic and headphone jacks.

[craiggsmith]

Sometime I can get specs by contacting the manufacturer, but more often I have to obtain the product and use my signal source, DVM, o'scope and the TrueRTA program to make measurements. The TrueRTA program works great for viewing a waveform (finding the point of distortion), but it's amplitude is not calibrated so I use a DVM or oscope paralleled with the input signal.

Awesome.

If you are running a 50-75 foot TRS cable from the RecordOut jack it would be advisable to put a TS to TRS adapter (mono to stereo) at the RecordOut jack to prevent the "R" from becoming a 50ft antenna for noise. You may not need it but the adapter is only $2 and it's handy to have in your "bag of problem solving adapters"!

I see them from audio retailers but having a hard time finding one on Amazon. I'm only running a 6 foot cable but I'll try to get one eventually.

[russellhltn]

I see them from audio retailers but having a hard time finding one on Amazon. I'm only running a 6 foot cable but I'll try to get one eventually.

Here you go:

3.5mm Mono Plug to 3.5mm Stereo Jack

3.5mm Stereo Plug to 3.5mm Mono Jack Adaptor

[craiggsmith]

Here you go:

3.5mm Mono Plug to 3.5mm Stereo Jack

3.5mm Stereo Plug to 3.5mm Mono Jack Adaptor

Thanks!