Any recommendations for a new (budget) USB audio interface (+ USB filter?) and a pair of monitors

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bgravato
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Re: Any recommendations for a new (budget) USB audio interface (+ USB filter?) and a pair of monitors

Post by bgravato » Thu May 13, 2021 7:03 pm

I've tried the powered USB hub, the noise is 10 times louder!

And the funny thing is that the noise level actually got quieter the more I raised the volume of the output!

bgravato
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Re: Any recommendations for a new (budget) USB audio interface (+ USB filter?) and a pair of monitors

Post by bgravato » Thu May 13, 2021 7:24 pm

Another interesting experience... I tried unplugging the other USB devices I have connected to the PC (mouse, keyboard, etc...) and the pitch of the hiss changed everytime I unplugged/plugged a device.

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Re: Any recommendations for a new (budget) USB audio interface (+ USB filter?) and a pair of monitors

Post by Paul2 » Fri May 14, 2021 8:27 pm

My 2c worth, if I may.

USB filters do help, but......there is a "gotcha".

All USB chips/interfaces, have a certain power up sequence that is dependent on the slew rate (rise time) of the supply.

A USB filter (essentially a DC filter) will use inductance and capacitance to form a low pass filter and these two will cause a delay and slow down the rise time of the DC before it reaches around 3V which is the legal "absolute low" of USB's 5V levels.

Because of this slow rise, some USB chips will not initialize whilst others will become very erratic.

So what you have, is a catch-22 situation, the more filtering there is, the less the noise but greater the chances of the USB chip/interface not initializing and responding.
The less the filtering, well I'm sure you can guess.

(BTW that is also one of the reasons why the 2 power connections on USB are slightly forward relative to the data pins.
This guarantees that the DC is applied before data to initiate the turn-on sequence and data is disconnected before DC when connecting and disconnecting a USB interface.
Have a look at your USB lead, the two outer pins are the power pins).

Over and above, what Koz wrote in a previous post is very true, in general MAC's are much cleaner than PC's/laptops.

Another big contributor to audio noise is the charger used with laptops.
As an experiment (if you are using a laptop), disconnect the charger and see if the noise drops.

If your PC/laptop has built-in bluetooth, you could try that and feed the audio in to an external bluetooth transmitter which your computer will pickup.
Keep in mind though, that bluetooth audio does have some latency, depending on your situation/use, this may or may not be a problem.

Please note however that the audio levels for bluetooth transmitters, are normally designed to be line level.
If you are using mics, then you will need a mic pre-amp in series and if your mic needs phantom power,
then ensure that the pre-amp can supply this too.
It goes without saying that the mic pre-amp should not be USB powered. :D

For the interface box, my personal favourite is the Scarlett, but of course your milage may vary.

As for monitors, the Presonus 3.5 and 5 are good.
I have a pair of each and I'm happy.
Of course they are not in the same league as Genelec, but in my opinion better than Yamaha, whose tweeters are very harsh and sound like nails on a blackboard.

Hope this is of some help.

Paul.

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Re: Any recommendations for a new (budget) USB audio interface (+ USB filter?) and a pair of monitors

Post by Paul2 » Sat May 15, 2021 11:10 am

Another idea, have you considered using optical/Toslink?

It may take you a bit over your original budget but I suspect you won't have any noise issues.

By the time the audio gets transferred via USB to the computer, it has already been digitized
onto Toslink and hence will have much more immunity to noise.
There is also no physical connection between your computer and the analog audio parts.
The Toslink feed acts as an optical barrier to DC and therefore no common earth/ground.

Note that the U24-XL is only needed if your soundcard/computer does not have optical input.
Very few have.

I have not included any direct links to the products as that may be viewed as advertising or endorsing them.
A quick Google search and you will find them, of course there must be others.

Something like this:
Screen Shot 2021-05-15 at 1.22.44 PM.png
Screen Shot 2021-05-15 at 1.22.44 PM.png (185.07 KiB) Viewed 162 times

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Re: Any recommendations for a new (budget) USB audio interface (+ USB filter?) and a pair of monitors

Post by kozikowski » Sat May 15, 2021 6:04 pm

the two outer pins are the power pins
I knew that part.

It's a good idea to get the USB connector in straight when you connect or disconnect a cable. Ask me how I know that.

Oblique Question.

Do you know the power negotiation sequence for USB-C? It's not just five volts. That's so last year.

Google will admit there is one.....

Koz

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Re: Any recommendations for a new (budget) USB audio interface (+ USB filter?) and a pair of monitors

Post by kozikowski » Sat May 15, 2021 6:09 pm

included direct links to the products as that may be viewed as advertising or endorsing them.
Unless a forum elf asks you to.....

What are typical products in this area?

Koz

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Re: Any recommendations for a new (budget) USB audio interface (+ USB filter?) and a pair of monitors

Post by Paul2 » Sat May 15, 2021 6:39 pm

Do you know the power negotiation sequence for USB-C? It's not just five volts. That's so last year
Here you go, happy reading: :D

https://www.ti.com/lit/ug/tidudn6/tidudn6.pdf

https://www.ti.com/lit/an/slva842/slva842.pdf

The above is for Texas Instrument devices but it's pretty much the same for others.
Most USB chip sets are very similar and often made under license and used by many manufacturers.
What are typical products in this area?
There aren't actually that many.

The ESI-Audio unit:
https://www.esi-audio.com/products/u24xl/

This one has Toslink input and USB-C output.
https://audient.com/products/audio-inte ... /overview/

I'm sure there may be a few more.

Going from Toslink to RCA (Analog Audio) and vice versa, there are plenty.
However Toslink to/from USB, are more difficult.
I know that Teac used to make but that was a while back and could not find anything on their site now.

Here are some misc analog to Toslink and vice versa:
(Note however that some will be better than others, have more available sample rates etc).

https://www.amazon.com/USB-Optical-Audi ... io+Adapter

If you want to experiment with Toslink in your own circuits, DigiKey (and others), stock plenty of modules:
https://www.digikey.com/htmldatasheets/ ... -Guide.pdf

Getting really technical and if you would like to design your own ADC and feed that into a Toslink TX module,
Texas Instruments make many different models, you just need to choose one that has the same output protocol as Toslink.
Of course designing the PCB and all the important decoupling and filtering that goes with mixing analog and digital is part of the fun. :D
https://www.ti.com/audio-ic/converters/ ... ducts.html

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Re: Any recommendations for a new (budget) USB audio interface (+ USB filter?) and a pair of monitors

Post by Paul2 » Sat May 15, 2021 9:16 pm

For those that may be having noise problems and are using a computer (not a laptop) as it uses PCI-e and are on Windows,
found this soundcard that has optical input and output.

It costs around USD 100 and can do 24 bit up to 192Khz sample rate, so they claim...read the fine print just in case.

Must stress that I have never used one, so therefore cannot vouch that is does what is says, but it does look very interesting due to it having optical ports.
I'm assuming that the default input and output can be set to them as opposed to the 3.5mm analog inputs and outputs.

In theory by connecting an analog to optical converter to it's optical input and the opposite to it's optical output, one would have a completely isolated (DC wise) audio system.
These converters are pretty cheap and cost about 10-15 bucks each.

Official link:
https://us.creative.com/p/sound-blaster/sound-blaster-z
Screen Shot 2021-05-15 at 11.27.40 PM.png
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Another interesting item I found was a USB isolator:
It supports USB 2 but not full speed (480Mb/s), just up to 12Mb/s which is what audio interfaces use.
Not sure what the isolation is in dB's and frequency response but interesting none the less.
Found it on amazon and for that price, decided to order one to experiment with.
Screen Shot 2021-05-15 at 11.57.05 PM.png
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The tallish black rectangular item looks like an isolated DC-DC converter to power up the secondary side
and the multi-pin black item to the right of it, seems to be some kind of encapsulated transformers (or perhaps opto-couplers) to provide the isolation for the differential data pins.
Clever little product and may just be the solution to bgravato and others that already have existing external USB sound interfaces and have noise problems.
Also assuming it's O.S. agnostic so will work with Windows, MacOS and Linux.

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Re: Any recommendations for a new (budget) USB audio interface (+ USB filter?) and a pair of monitors

Post by bgravato » Sun May 16, 2021 1:00 am

Thank you Paul for all the valuable information!

These last few days have been quite hectic (tomorrow will be too). I'll analyze this in more depth during next week. But here are some quick comments in the meanwhile.

Optical link sounds like an interesting approach. One downside I see is one more piece of equipment cluttering my desk... which I'm trying to avoid...

I will be using this on a mini-pc (Intel NUC). I've tried a different power supply on the NUC, but I got the same noise, so either the PSU is not (one of) the culprit(s) or the ones I used, both have the exact same flaws... (I have a third one I can try, but no high hopes on that one either).

I used to have a PCI sound card when I was still using a "normal size" desktop PC on a mid-ATX tower. I've gone the mini-PC route about 6 years ago. Much less power consumption, much quieter and barely occupies any space. No PCI(e) slots though, so USB is the only way to go... It has one USB-C as well, but that's already in use for connecting the second monitor. So USB 3.1 is pretty much what I have available.

I've thought about connecting the USB ground to the "earth" ground, to see if it makes any difference, but I haven't tried that yet..

I have an older mini-pc (Gigabyte Brix). I plan on trying the Presonus Audiobox on it as well as on a laptop (both AC connected and on batteries).
But honestly if that works better it doesn't help me much anyway... I want to use the audio interface with the NUC (daily for listening to music while I work). I can use a different PC/laptop for the rare occasions when I need to record something from the mic, but for listening it must be on the NUC, which is my daily driver at the moment (and I'm hoping to use it for a few more years).

I'm an electronics engineer (though I work more with software than with hardware), so I could go the DIY route, but I know how that's going to end... About 9-10 years ago I bought a MIC-preamp chip, a bunch of japanese capacitors, etc... most of those components are still inside their original sealed bags...
I also meant to make a headphones amp, among other things... but I must be realistic, that's not gonna happen in a near future.

Please let me know how it goes with that USB Voltage Isolator. BTW that's probably USB 1.1. Yes it's compatible with 2.0, but 1.5 and 12 mbps is the (low/high) bandwidth for USB 1.1 (which should be enough for an audio device, so no problem with that).

You mentioned the Focusrite Scarlett... do you think it could have better filtering on the USB connection than the Presonus Audiobox or the Behringer UMC202HD? All 3 are within my budget.

Genelec studio monitors are out of my budget... Presonus 3.5 definitely seems like the better option under 100 euros. The cheapest Genelec I found is 245 and I think that's for 1 monitor only, not a pair.

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Re: Any recommendations for a new (budget) USB audio interface (+ USB filter?) and a pair of monitors

Post by kozikowski » Sun May 16, 2021 1:36 am

There is a fuzzy rule of thumb here. In general if your interface has this button.

Screen Shot 2021-05-15 at 6.26.27 PM.png
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Then it has some USB power filtering. There has to be a formal power supply there to make clean 48 volts for your condenser microphone. Some condenser microphones use that on the condenser element itself and any noise or instability would be the kiss of death.

Koz

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