Hi
I own a SPL Volume 2 and wanted to check how it measures.
So I tried.
SPL (Sound Performance Lab) is a German company, specialised in Pro audio electronics.
They are not new comers in that market (they say they're in the business for 30 years).
They offer analog preamps, channel strips, control room volume and control switches, headphone amps, and some interesting effects devices.
Personnaly, my first SPL device was the SPL Transient designer 4.
This very special (unique) analog device which, although looking simple, is doing some magic inside, allowing you to modify the transient attack of live instruments.
It can do magic indeed, as an example on drums in live events.
Back to the Volume 2:
One may find doc and manual (including serious Audio Precision measurements) for this device here.
The volume 2 is a 1/2 rack wide, and some 2U high.
It's also approximatively as deep as wide. Not a small box.
The big volume knob is smooth and pleasant to use.
It's labelled from 0% to 100%.
There is also a Mute button, which lights in RED if active.
The device doesn't look cheap, for sure, and weights some...
List price is below 400€. I bought mine new, for less.
Back panel has XLR connectors only. Target is Pro audio.
Inside the box, everything is proper and neat.
Measurements
(Measurements all performed with Virtins Multi Instrument 3.8 and RME ADI-2 Pro fs.
RME DAC > Volume2 > RME ADC.)
Red: SPL Volume 2,
Black: RME ADI-2 Pro fs in loopback (DAC > ADC) for reference.
Volume matched to get same input level on the ADC
At Max level (100%) position, when fed with +15dBu (4.36Vrms), we have a SINAD of 103dB
That's a bit lower than the RME, due to a higher distortion.
We see some H2, H3 and H4. Level is very low though (THD around 106dB below signal level).
Note that SNR (un-weighted), at above 107dB, is indistinguishable from the RME, which is very good.
This is all above the specs, which are
THD & N (@ +15dBu Input Level) ›-100dBu
S/N A-weighted -102dBu
Also note that, even at Max level, there is some attenuation (around -4.3dB).
It never reaches unity gain.
The Volume 2 always provides attenuation.
Looking at the attenuation vs volume setting, we see the following
X is the volume setting, from 0% to 100%
Y is the ADC input level, where 0dBFS is +19dBu
DAC output level is 4Vrms or +14.3 dBu
Left channel is black, Right channel is red: We see a pretty good channel coherence.
Also, the attenuation is smooth from around 90% to 20%, with 40dB more attenuation at 20%
But such a volume control is rather used at lower volume settings:
Here is a trend of THD+N and THD vs volume setting
X is the ADC input level (ie the level at the output of the Volume 2)
Left channel in Black and Right in Red.
THD (dashed), under a certain level, can't be measured correctly.
THD+N (solid), mainly follows the noise.
Except at the highest level settings, where it shows a bit more distortion, the Volume 2 measures the same than the RME, when we match the levels.
(More to come...)
I own a SPL Volume 2 and wanted to check how it measures.
So I tried.
SPL (Sound Performance Lab) is a German company, specialised in Pro audio electronics.
They are not new comers in that market (they say they're in the business for 30 years).
They offer analog preamps, channel strips, control room volume and control switches, headphone amps, and some interesting effects devices.
Personnaly, my first SPL device was the SPL Transient designer 4.
This very special (unique) analog device which, although looking simple, is doing some magic inside, allowing you to modify the transient attack of live instruments.
It can do magic indeed, as an example on drums in live events.
Back to the Volume 2:
One may find doc and manual (including serious Audio Precision measurements) for this device here.
The volume 2 is a 1/2 rack wide, and some 2U high.
It's also approximatively as deep as wide. Not a small box.
The big volume knob is smooth and pleasant to use.
It's labelled from 0% to 100%.
There is also a Mute button, which lights in RED if active.
The device doesn't look cheap, for sure, and weights some...
List price is below 400€. I bought mine new, for less.
Back panel has XLR connectors only. Target is Pro audio.
Inside the box, everything is proper and neat.
Measurements
(Measurements all performed with Virtins Multi Instrument 3.8 and RME ADI-2 Pro fs.
RME DAC > Volume2 > RME ADC.)
Red: SPL Volume 2,
Black: RME ADI-2 Pro fs in loopback (DAC > ADC) for reference.
Volume matched to get same input level on the ADC
At Max level (100%) position, when fed with +15dBu (4.36Vrms), we have a SINAD of 103dB
That's a bit lower than the RME, due to a higher distortion.
We see some H2, H3 and H4. Level is very low though (THD around 106dB below signal level).
Note that SNR (un-weighted), at above 107dB, is indistinguishable from the RME, which is very good.
This is all above the specs, which are
THD & N (@ +15dBu Input Level) ›-100dBu
S/N A-weighted -102dBu
Also note that, even at Max level, there is some attenuation (around -4.3dB).
It never reaches unity gain.
The Volume 2 always provides attenuation.
Looking at the attenuation vs volume setting, we see the following
X is the volume setting, from 0% to 100%
Y is the ADC input level, where 0dBFS is +19dBu
DAC output level is 4Vrms or +14.3 dBu
Left channel is black, Right channel is red: We see a pretty good channel coherence.
Also, the attenuation is smooth from around 90% to 20%, with 40dB more attenuation at 20%
But such a volume control is rather used at lower volume settings:
Here is a trend of THD+N and THD vs volume setting
X is the ADC input level (ie the level at the output of the Volume 2)
Left channel in Black and Right in Red.
THD (dashed), under a certain level, can't be measured correctly.
THD+N (solid), mainly follows the noise.
Except at the highest level settings, where it shows a bit more distortion, the Volume 2 measures the same than the RME, when we match the levels.
(More to come...)
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