Topic: USB hub vs Coax

Hi, I recently bought an ADI-2 DAC for my AV system. I need to connect 2 Macs, but there is only one USB socket. I am thinking about 2 possibilities. I already have an external USB to SPDIF converter (a Hag USB), so could connect one source via Coax. Alternatively I get a hub, to connect both sources to the one socket. I do not want to degrade the sound and ideally would prefer not to have to switch between the two sources on the hub.

Thoughts?

Also, I have changed none of the settings on the DAC. Assuming I want to optimise the sound quality and am looking for a flat frequency response, are there any must have adjustments? The RME feeds into a Pimare P30 pre-amp via balanced connections, in stereo bypass mode (so there is no reconversion to digital). I have active monitors, so everything has volume control.

2 (edited by bejoro 2020-04-19 07:26:32)

Re: USB hub vs Coax

You need an USB switch, no HUB. There are USB switches for 2 or 4 computers. They are used to share USB devices with more than one computer. I could not find an USB switch with a remote control, you will have to switch manually, a push-button at the device or push-button with a short cable.

You may have to try different devices and check whether all sample rates etc. are supported (bit test).

I am using an ATEN US424-AT for many years but I never tested it with RME devices, but I have a different USB DAC connected (AudioQuest Dragonfly) which works fine with Windows 10 and Linux.

Re: USB hub vs Coax

Thanks. That is a good answer.

4 (edited by bejoro 2020-04-19 07:43:44)

Re: USB hub vs Coax

Thanks. Sorry, I forgot: If the RME bit-test passes (see manual, forum) with all sample rates while connected directly to the computer or via USB switch then there is no sound degradation possible.

Try first without the USB switch, if all bit-tests pass with direct connection, connect the RME DAC to the USB switch, select the computer. If all bit-tests pass again you have perfect sound quality. Perform these tests also for the second (third...) computer.

Re: USB hub vs Coax

Thanks. I will try that. One other thing; white noise is quite audible from my monitors, more so at low volume levels as I then have to turn up the volume on my pre-amp. Is there any reason not to set volume to maximum and attentuate with the pre-amp? Sorry if this sounds obvious, but I am fairly new to this game.

Re: USB hub vs Coax

No one else seems to have an answer, so I try. It is not as easy as it seems.
In theory your setup would be correct.

Turn off the preamp and check the noise level of your monitors. If the noise level changes with the volume level, set the volume to a level with acceptable noise. Turn on the preamp and check again. If the noise level is signifcantly higher, bad preamp.

If the noise level of the monitors does not change with the volume level (preamp off), bad monitors.

Try to connect the ADI-2 DAC directly to the monitors, which I would recommend anyway.

There are many active monitors with high noise levels, audible at an ear distance of 1 meter (3 ft) or even 1.5 (5 ft) or more.

If your monitors have an integrated DSP, setting the volume level to maximum can cause clipping, DSP overload and hence high noise levels, distortion etc. Reduce the volume level step by step (try and listen) or ask the manufacturer for optimum settings.

With pure analog monitors mostly poorly designed integrated power amp modules are the reason for high noise levels (even in some expensive monitors). You have to reduce the max volume to levels with hopfully acceptable low noise. If this is not possible you have to live with it or purchase better designed monitors (try before buy).

Well designed passive speakers with a good power amp (or integrated amp) are very often much better than low-priced active monitors. Well designed active monitors have mostly also a high price.

Re: USB hub vs Coax

bejoro, thanks for your reply. detaching the dac from the processor is not really an option, as i need the 5.1 channel capability for movies. you are correct in saying that the noise originates from my speakers, a known issue with those genelecs (which are purely analogue). using the dac in my processor there is some noise, at an acceptable level. using the rme dac, going through the processor, the overall sound is better, but the noise level is higher, except when i turn up the dac volume to almost it´s maximum. the maximum is +13dBu/+6 but i guess setting it so high is not optimal. what level might be a reasonable maximum?  all said, it will be a compromise; the noise is only really an issue when listening to quiet classical music; it does not justify replacing my speakers.

Re: USB hub vs Coax

Do your Genelecs get quieter when you lower their little level controls at their backs?
Usually they do.
Bring them down and turn up the ADI-2 and/or the AV amp instead.


You didn't tell what AV-System you use, so level recommandation can only be generic:

Most Hifi amps can take up to 10V (+22dBu), but some are limited to 2V (+8dBu) at their input.
Easy to use a full scale digital sinewave played through the DAC and turn it up until you hear distortions.
This is the max. level to use.
You can keep the AV amps/speaker level low while doing so.

Re: USB hub vs Coax

The level controls on the Genelecs are set very low; the noise does vary with the level. The AV processor is a Primare P30, which is set to bypass mode to use the external DAC. As the Genelecs are 17 years old and, though good, probably the weakest part of the system, today I ordered a pair of PCM result6 active monitors, in theory a significant upgrade.

I am not hearing distortion even when the DAC is turned up to full. Maybe my ears don´t deserve expensive kit!

10 (edited by KaiS 2020-04-23 07:04:03)

Re: USB hub vs Coax

According to the schematic I found, the Primare P30 does not do hard wire bypass, just an ADDA/digital processor bypass.
It's analog electronics are always in the signal path.


P30 is built around a lot of FET-switches powered with +/- 12V.
So it's estimated (the schematic doesn't show resistor values, strange) max. undistorted audio input should be 8V or +18dBu. or +24dBu balanced

This is quite some level.
Your Genelec 1030A, at min. Input Sensitivity Control position, need just +11dBu for their max. 105dBSPL.
This is 7dB (or even 13dB balanced) less then the P30 can pass through from the ADI-2.


Conclusion:
Bring the Genelec's Input Sensitivity Controls full down for best noise reduction.
ADI-2 and P30 can still supply enough level to blow your head away.

If you still have noise problems then, there seems to be an internal jumper that activates a -12dB pad on the Genelecs.
It shift the input sensitivity further down 12dB.



Regarding Genelec 1030A vs PMC result6:
My bet is on the Genelecs to sound better.


BTW: the Genelecs selfnoise is specified with only 10dBA SPL @ 1m.
This is, if the connected source does not feed in some noise.
If you can hear this, congratulations for the good health of your hearing and for having a very quiet room.

11

Re: USB hub vs Coax

Thanks KaisS. Your conclusion seems to be correct, i.e.

Conclusion:
Bring the Genelec's Input Sensitivity Controls full down for best noise reduction.
ADI-2 and P30 can still supply enough level to blow your head away.

You say: According to the schematic I found, the Primare P30 does not do hard wire bypass, just an ADDA/digital processor bypass. If you are correct there appears to be no point to include the RME DAC. I am not an electrical expert, but the P30 manual says very clearly:

¨The P30 provides a Bypass mode, which bypasses the digital processing stages for the purest possible reproduction of conventional two-channel music sources. ¨ This is backed up by the people at Primare. Are you sure what you say is correct?

My Genelecs are 1029a, the smaller brother of the 1030a you mention. I am surprised you expect them to sound better than the PMCs, which are very well regarded in their price bracket, about twice that of the Genelecs, and 17 years younger for what that matters.

Regards

12

Re: USB hub vs Coax

Sorry KaiS, I now understand that ADDA/digital processor bypass is consistent with the manual and means the RME DAC will be the only thing doing a DA conversion; and that there is no subsequent AD conversion

13 (edited by KaiS 2020-04-23 11:19:52)

Re: USB hub vs Coax

dil wrote:

...My Genelecs are 1029a, the smaller brother of the 1030a you mention. I am surprised you expect them to sound better than the PMCs, which are very well regarded in their price bracket, about twice that of the Genelecs, and 17 years younger for what that matters.

Genelec has a 5 decades track record for building excellent studio monitors.
Even their earlier ones like the S30 from 1992 are still highly regarded.


I know and have worked on most of the smaller ones, specially the 1031 and 1030, and always liked them very much.

The 1029 is a negative exception.
Although astonishing for it's size, it lacks resolution where size isn't the limiting factor to keep the quality - in the treble:
Shakers, hihats, cymbals, even vocal sibiliants: they all sound the same and do not separate in the mix.

My nearfields are Tannoy 600A, and the 1029 can't hold a candle against them.
Still, tonality-wise the 1029s are correct.


At the price asked for the PMC result6 I would have a very close look at the new Genelec coax monitors, the 8341.

Nothing beats a coax system in the nearfield, where you are sitting too close for drivers from multiple locations to properly mix.

Get both models at the same time and do a shootout, even try to mix on them and compare the results.

14

Re: USB hub vs Coax

mine are the 1029a, not the 8000 series.  the price of the 8341 is around £2,400 each, way beyond my budget. the PMCs will cost me £850 each

Re: USB hub vs Coax

Sorry, I mixed Genelec's old and new line numbering, changed my post accordingly.


£1,700 a pair sounds like a reasonable price, Musicstore.de asks 2,850.-€.
Genelec 8341 are 2,799.-€ per piece, more then double your price.

Musicstore confused me, some prices, as usual with speakers, per piece, some per pair.


Genelec 8331AP are 2,059.-€ a piece, and more comparable to the PMCs, with H 305 x W 189 x D 212 mm size.

As beeing equipped with digital input, comprehensive DSP room correction and such these are heading into a different direction.
I'd give them a shot if you can imagine paying their price.

16

Re: USB hub vs Coax

Thanks, but they are still way too expensive. One of the things I like about the PMCs is that they focus on the basics, without digital input etc.

17 (edited by KaiS 2020-04-23 22:43:57)

Re: USB hub vs Coax

It's the result that counts, and studio monitors are quite personal, less so then headphones, but still.


No matter what you choose, you have to get used to them to create good results.


When I had to get rid of the Yamaha NS 10, which never made it for me, I made some test mixes on the then already preselected candidates.
Next step turned out to be easy - there was a clear winner where the mixes perfectly translated to the outside world.


It was very disapointing for my dealer - one of the cheapest under selection made it.
The Tannoy Systhem 6 NFM II costed some 500.- DM, a pair, nice!
Coupled with a powerful stereo pair of active subwoofers (Canton AS30) nothing stayed hidden during tracking and in the mix.


The final approvement of that decision appeared when I started to hear my mixes in radio broadcasts here and there and they perfectly fitted like intended.


Later I switched to the even better active version, the Tannoy System 600A in a 5.2.1 arrangement.
A bit more refined, but same characteristics, still my main workhorses where the results of an 8h mix session does sound the same when you listen to it the next morning or at the clients home.

Cheap, still, but Tannoy built-in many decades of condensed experience in creating top notch studio monitors.
And none of them ever broke during the last 15 or so years.


Dual Concentric rules!

Nowadays Tannoy places shitty sounding super-tweeters on top of their concentrics, what a heresy.

Fortunately even the pure Dual Concentrics are still available from them.
Guess what - still cheap, the active, biamped Gold 7 cost 195.-€ a piece.

18 (edited by dil 2020-04-29 13:55:03)

Re: USB hub vs Coax

Just to let you know, I bought the PMC result6. In my opinion, in every respect they sound superior to my 1029a. After a few seconds of comparison my wife agreed; a clear improvement.