Hi Jesper,
A "Y" cable would indeed allow you to supply the UMC202HD from a separate +5V power supply instead of from the PC. But what I meant was a fully galvanically isolated USB interface. Search for ADUM3160 on Aliexpress. Such an isolator prevents ground loops and PC PSU noise from running through the ground wires of your audio interface and device under test. Some people claim a noise improvement, but I lost references. However, the DC/DC converter on this isolator is not capable of delivering the power required by the UMC202HD. It just did not work. And its output voltage may not be noise-free too. Admittedly, I did not measure it yet, but many cheapish DC/DC converters have some RF ripple on the output voltage. In the attached pictures, the DC/DC converter is marked by a green circle. Remove it and attach your 5V (or a little more) power supply to the terminals marked by a red circle on the second picture. It's an easy mod, I know, but I haven't tried it yet.
I'm curious if anyone ever tried this and whether it had any effect at all.
Cheers, Jan
A "Y" cable would indeed allow you to supply the UMC202HD from a separate +5V power supply instead of from the PC. But what I meant was a fully galvanically isolated USB interface. Search for ADUM3160 on Aliexpress. Such an isolator prevents ground loops and PC PSU noise from running through the ground wires of your audio interface and device under test. Some people claim a noise improvement, but I lost references. However, the DC/DC converter on this isolator is not capable of delivering the power required by the UMC202HD. It just did not work. And its output voltage may not be noise-free too. Admittedly, I did not measure it yet, but many cheapish DC/DC converters have some RF ripple on the output voltage. In the attached pictures, the DC/DC converter is marked by a green circle. Remove it and attach your 5V (or a little more) power supply to the terminals marked by a red circle on the second picture. It's an easy mod, I know, but I haven't tried it yet.
I'm curious if anyone ever tried this and whether it had any effect at all.
Cheers, Jan
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Nice, and something to do 
@jp8 Regarding usb isolator, I "can't" buy on Aliexpress, it's to expensive duo to tax etc... But they also sell this stuff here in EU.
@YashN Can you show the diy usb isolator you did ? - I actually think i have one chip left from another project.
Sometimes i repair some pcb for a company which do repair and service stuff on industrial kitchen machines. I never get paid for this, i just order stuff for my self, when ordering part, relays etc... for the repair.
Yesterday i was good darn lucky, ordering some relay's at RS Components, i stumpled over that they got two LT3045EMSE on stuck, which i ofcause did put in the basket - This is a very good reason to build a good say 5.1vdc supply.
Jesper.
@jp8 Regarding usb isolator, I "can't" buy on Aliexpress, it's to expensive duo to tax etc... But they also sell this stuff here in EU.
@YashN Can you show the diy usb isolator you did ? - I actually think i have one chip left from another project.
Sometimes i repair some pcb for a company which do repair and service stuff on industrial kitchen machines. I never get paid for this, i just order stuff for my self, when ordering part, relays etc... for the repair.
Yesterday i was good darn lucky, ordering some relay's at RS Components, i stumpled over that they got two LT3045EMSE on stuck, which i ofcause did put in the basket
- This is a very good reason to build a good say 5.1vdc supply.Jesper.
The USB insulator did not work. Not with the UMC202HD, nor with any other device. I'm afraid it's broken. 😞 I'm not going to spend any time and effort in this device anymore. Maybe if someone else achieves convincing improvements with an USB insulator, I'll try again with another device.
Jan
@MagicBus ...
I had suddently something to ask regarding this you wrote some day's ago :
You proberly allready have this in control ? - But you need to be sure that "Control input volume" is at MAX (near 1v) and to uncheck the box also.
Otherwise we got problems going <-6dB or so. (I have been there)
Jeper.
I had suddently something to ask regarding this you wrote some day's ago :
You proberly allready have this in control ? - But you need to be sure that "Control input volume" is at MAX (near 1v) and to uncheck the box also.
Otherwise we got problems going <-6dB or so. (I have been there)
Jeper.
Hi... pretty long time
Happy Easter (lucky me, going on vacation next week)
I am waiting to get this usb isolator here : LINK
Archimago is testing the thing : HERE
I know, that i might not getting any better performance, but still worth a try i think.
- Thing is that i can feed external power to it, and raise the voltage inside the Behringer to the codec (raise from 4.5vdc to 4.9vdc as discussed here recently)
Quistion is... Will i gain anything by using a linear regulated +5vdc psu here, or am i better off with a switcher (wall wart) ?
Jesper.
Happy Easter (lucky me, going on vacation next week)
I am waiting to get this usb isolator here : LINK
Archimago is testing the thing : HERE
I know, that i might not getting any better performance, but still worth a try i think.
- Thing is that i can feed external power to it, and raise the voltage inside the Behringer to the codec (raise from 4.5vdc to 4.9vdc as discussed here recently)
Quistion is... Will i gain anything by using a linear regulated +5vdc psu here, or am i better off with a switcher (wall wart) ?
Jesper.
The USB isolator seems like a cool little useful gadget and I am tempted getting one myself, but reading the feedback on Amazon it looks like rather dim when reading all the low rated comments, but one comment was interesting as it suggested to put the USB isolator in between the PC and an additional powered USB hub before plugging in the "sound module", it appears to be so the USB hub does something here, maybe conditioning the signals but it wasn't clear whether the problem lies in the communication signals or the power supply being poor.
The feedback from the link below reads:
https://www.amazon.de/-/en/ICQUANZX.../B07Z21RKMN/ref=psdc_1626220031_t2_B07GF6VMMK
The feedback from the link below reads:
https://www.amazon.de/-/en/ICQUANZX.../B07Z21RKMN/ref=psdc_1626220031_t2_B07GF6VMMK
Hi all,
today a former colleague was able to change the CD4066 switch between the TRS input and the XLR amp to a HC4066.
See pictures. Improved THD, but still high noise level. Input was 1 Vpp.
In the meantime I connected the TRS in parallel to the XLR by removing C78, C81, C83 and C85 and doing some connections. See photo.
If you use a mono TRS connector the unused input is shorted by the it. This is not the case for most XLR to cinch cables.
Alfred
today a former colleague was able to change the CD4066 switch between the TRS input and the XLR amp to a HC4066.
See pictures. Improved THD, but still high noise level. Input was 1 Vpp.
In the meantime I connected the TRS in parallel to the XLR by removing C78, C81, C83 and C85 and doing some connections. See photo.
If you use a mono TRS connector the unused input is shorted by the it. This is not the case for most XLR to cinch cables.
Alfred
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Hi...
@alfredr looking good, nice catch there.
So i recieved the usb-isolator thing, and did some test with it.
The attached screenshots are with 5vdc external switcher-psu & isolator. (-2dB & -6dB)
* The result's are the same without it, so i guess that duo to the balanced input's it does not matter much (but maybe it will be handy for some real DUT senarios?)
It look's that the sweetspot is around -6dB for my setup for now.
Well what confuses me right now is a thing i have with my usb cables (two ordinary A ---> B & one "Y" split cable):
When i feed the "Y" split cable with say 5.1vdc, i can measure that at PSU end. -But the other end of the cable, the voltage goes down to around 4.75vdc
(This is with the Behringer consuming ~400mA attached)
This is same senario with all three of them, that the voltage drop's in the cable (cables look's okay btw. not the thin ones here)
So maybee it's a usb thing i donno right now.
So my conclusion is, that if i would raise the voltage for the codec, i need to make an external psu connection, and at the same time also disconnect the usb + inside the Behringer or make a cable without the + connection. Donno if it's worth it!... But currious to see if i could get better THD numbers when going near -0dB.
Just some thought's
Jesper.
@alfredr looking good, nice catch there.
So i recieved the usb-isolator thing, and did some test with it.
The attached screenshots are with 5vdc external switcher-psu & isolator. (-2dB & -6dB)
* The result's are the same without it, so i guess that duo to the balanced input's it does not matter much (but maybe it will be handy for some real DUT senarios?)
It look's that the sweetspot is around -6dB for my setup for now.
Well what confuses me right now is a thing i have with my usb cables (two ordinary A ---> B & one "Y" split cable):
When i feed the "Y" split cable with say 5.1vdc, i can measure that at PSU end. -But the other end of the cable, the voltage goes down to around 4.75vdc
(This is with the Behringer consuming ~400mA attached)
This is same senario with all three of them, that the voltage drop's in the cable (cables look's okay btw. not the thin ones here)
So maybee it's a usb thing i donno right now.
So my conclusion is, that if i would raise the voltage for the codec, i need to make an external psu connection, and at the same time also disconnect the usb + inside the Behringer or make a cable without the + connection. Donno if it's worth it!... But currious to see if i could get better THD numbers when going near -0dB.
Just some thought's
Jesper.
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Thanks for sharing, Jesper, looks good.
Switcher vs Linear Reg would be good.
Then Switcher vs Battery.
Then Linear Reg vs Battery.
I'd keep the isolator in for all tests.
With the Battery, you get the AC isolation for free (here, the switchers pollute a lot), but batteries, depending on their internals have varying levels of internal noise too.
Then there are common Linear Regs which are good, but not as good as the very best Linear Regs. Many times, even the simplest, common Linear Reg can be better than the Switcher.
Switcher vs Linear Reg would be good.
Then Switcher vs Battery.
Then Linear Reg vs Battery.
I'd keep the isolator in for all tests.
With the Battery, you get the AC isolation for free (here, the switchers pollute a lot), but batteries, depending on their internals have varying levels of internal noise too.
Then there are common Linear Regs which are good, but not as good as the very best Linear Regs. Many times, even the simplest, common Linear Reg can be better than the Switcher.
@YashN :
I did try this quickly, dosen't make any change (with & without isolator)
But i still need to solve my issue with the USB voltagedropping cables.
I found this online here : LINK!
So there is something about this. If i feed power with an even better usb cable than the 3 i got, or using external input with thicker wire, i will properly have no voltage drop.
Behringer with @MagicBus balanced board + @alfredr filter are using ~400mA
Will report back when i figure something out.
Jesper.
Yep...
I did try this quickly, dosen't make any change (with & without isolator)
But i still need to solve my issue with the USB voltagedropping cables.
I found this online here : LINK!
So there is something about this. If i feed power with an even better usb cable than the 3 i got, or using external input with thicker wire, i will properly have no voltage drop.
Behringer with @MagicBus balanced board + @alfredr filter are using ~400mA
Will report back when i figure something out.
Jesper.
When I was looking around this I used a diy cable. It's very easy to build. You need to cut the red wire. The part that goes to the soundcard it takes the external connector. The part coming from the PC takes a LED/200 ohm resistor going to black wire to make an artificial load so to fool the PC. The black wire should not be intermittent as it's necessary for data too. Just scrap it and take another wire for the external ground connector. You can do this very close to the soundcard end so to avoid voltage drop.
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Yep, DC voltage drop is a thing. That's why for mains distribution, Tesla won and thankfully we have AC.
One day I decided to feed my mixer from +/-17V to +/-18V. However, that was before I checked the tolerances for op amps inside it, which was at around 17! I was wondering why the op amps weren't damaged. Of course, with the long DC lead up to the mixer and the internal DC leads, the op amps weren't seeing that much so that's why. I still dialled things down a bit just to be safe because maybe they can operate near their upper limits but most probably they won't operate long at these limits.
One day I decided to feed my mixer from +/-17V to +/-18V. However, that was before I checked the tolerances for op amps inside it, which was at around 17! I was wondering why the op amps weren't damaged. Of course, with the long DC lead up to the mixer and the internal DC leads, the op amps weren't seeing that much so that's why. I still dialled things down a bit just to be safe because maybe they can operate near their upper limits but most probably they won't operate long at these limits.
So... fiddling a bit with this USB-voltagedrop thing.
I'am getting good results with the voltages entering the Behringer now.
Only dropping from 5.18vdc ----> 5.04vdc. So now having 5vdc when Behringer is running doing some loopback to be sure, the switcher psu is loaded.
I now have the chance to test, raising the voltage for the codec to ~4.90vdc from the 4.50vdc it is now.
Let's see within next few day's if i can make it...
Jesper.
I'am getting good results with the voltages entering the Behringer now.
Only dropping from 5.18vdc ----> 5.04vdc. So now having 5vdc when Behringer is running doing some loopback to be sure, the switcher psu is loaded.
I now have the chance to test, raising the voltage for the codec to ~4.90vdc from the 4.50vdc it is now.
Let's see within next few day's if i can make it...
Jesper.