Re: [LAU] nice piece of USB hardware for 7.1 output

On 06/06/2013 01:32 PM, Jörn Nettingsmeier wrote:
> On 06/05/2013 10:57 PM, Fons Adriaensen wrote:
>> On Wed, Jun 05, 2013 at 04:25:56PM +0200, Jörn Nettingsmeier wrote:
>>
>>> in case someone is looking for a similar problem solver:
>>> i just received an esi gigaport hd+, which is a usb1
>>> class-compliant, bus powered audio interface that provides 8
>>> discrete unbalanced audio outs. at 135€, it's not quite a steal, but
>>> it solves one problem: to be able to listen to 5.1/7.1 content with
>>> a laptop.
>>>
>>> it works with jack out of the box and comes with two headphone outs,
>>> one of which plays outs1/2, the other plays a pair-wise mix of all
>>> eight outs. there is a row of flashing blue leds as "signal present"
>>> indicators, although their threshold is a bit on the high side.
>>>
>>> sound quality is appropriate, i gave it a quick listen and there is
>>> nothing obviously wrong.
>>
>> Interesting device... If and when you find the time, could you hook it
>> up to a Micstasy line input and Jaaa... ?
>
> ok. now running on my laptop at 64x4 w/o xruns but at very low load.
> for the measurements, i'm running off the battery to avoid hum issues,
> but plugging it did not make any noticeable difference to me.
>
> gigaport hd+ connected to a micstasy line in at normal Z (5.6kOhm
> unbalanced) with a crappy rca to jack cable.
> i chose 21.0dB amplification, because that should correspond to 0dBu at
> full scale. indeed, it makes a -1.0dBFS sine wave from the gigaport come
> out at roughly -14dBFS on the hdspm, which is what i'd expect going from
> consumer (-10dBV) to pro equipment (+4dBu).
>
> jnoisemeter reports -88.4 dB in flat mode with DC filter and slow
> averaging response.
>
> now if i feed it a white noise signal from JAAA at -1.0dBFS, the other
> end reports a flat noise level of -13.1 dB, which as a rough guesstimate
> gives us about 70dB of usable dynamic range. not great, but ok.
>
> the -1.0dbFS sine tone at 1kHz shows a first harmonic at -95dB, and the
> upper harmonics barely show in the noise, so we're fine here.
>
> however, there is a thumping DC impulse every few seconds which clearly
> shows up on the scope. it's clearly audible, not a show stopper, but
> needs looking into. it's signal-dependent: when you don't generate a
> sine-wave, it stops. complex signals either don't cause it or mask it
> completely. might be a power issue. here's what it looks like (peak hold
> and freeze, imagine this as a transient):
> http://stackingdwarves.net/download/GigaportHD+%20Thumping%20noise%20over%201kHz%20sine.png
>
>
> a white noise steady-state spectrum shows a slight raise of 2.5dB around
> 6khz, and another hefty boost of 3.5dB around 14khz.
>
> so much for a quick run-through. if you want specific measurements or
> have a pointer to proper measurement techniques, let me know.

some more measurements at
http://stackingdwarves.net/download/GigaportHD+/

-- 
Jörn Nettingsmeier
Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487
Meister für Veranstaltungstechnik (Bühne/Studio)
Tonmeister VDT
http://stackingdwarves.net
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