Dangerous Music Convert-2 technical measurements

Dangerous Music Convert-2 technical measurements

Standard Prologue
If you are unfamiliar with audio measurements please use a search engine with the query:
"audio measurements" or "audio measurement handbook"
Look for publications by Richard C. Cabot and also by Bob Metzler, both from Audio Precision. There are other useful publications as well. These will provide basic knowledge.
Interpretation of the following measurements is beyond the scope of technical measurements posts.

The data presented were collected as follows:

1. PrismSound dScope III, picoscope 5243B
2. DAC balanced (Bal) output XLR
3. Balanced cables Canare L-4E6S starquad (analog) and Belden 1800F with Neutrik XLR connectors (digital)
4. Single Ended cables Audioblast HQ-1 1.5 ft with Rean RCA connectors or RG6 with BNC connectors
5. 100 Kohm load used for measurements
6. dScope analyzer sample rate 48 KHz unless otherwise noted
7. DAC 44.1 KHz sample rate, 24 bit depth unless otherwise noted
9. Audioquest Forest and Schiit Pyst USB cables used for measurement equipment
9. Vaunix Lab Brick USB hub
10. Shielded 14AWG and 16AWG power cables
11. SRS FS725 10MHz rubidium time reference
12. Antelope Audio LiveClock (10MHz to SR wordclock)

Measurements performed with following Convert-2 parameters (unless otherwise noted):
1. Reference output set to +18 dBu
2. Output trim engaged and set for 0 dBFS = 2.8 dBu (1.07Vrms)
3. Internal clock

Measurements were acquired over several days.
Each day measurements commenced after 2 hours of warmup.
Each day measurements were performed over a period of 8 hours.


Index
Post 1 - measurement setup description, highlights
Post 2 - AES input - Balanced outputs part A
Post 3 - AES input - Balanced outputs part B
Post 4 - USB input - Balanced outputs part A
Post 5 - USB input - Balanced outputs part B
Post 6 - Internal Trim vs External Stepped Attenuator
Post 6 - Filter Response vs Sample Rate
Post 7 - Dante AES - gain linearity and inferred jitter int vs ext clock


Notable highlights:
Convert-2 has hot outputs, +22dBu with no trim engaged (9.76 Vrms)
Word clock input for external synchronization and disciplining
Distortion and residual noise exceptionally low
Excellent out-of-band noise rejection (see imaging measurements)
Slight channel imbalance when internal trim engaged


Setup picture:

 

AES input balanced output measurements part A

THD and THD+N spectrum at 1 KHz


THD and THD+N vs frequency


THD and THD+N vs amplitude at 1 KHz


IMD spectrum


IMD vs amplitude


Frequency Response


Frequency Response (y-axis zoom)


Inferred Jitter


1 KHz gain linearity


Imaging

 

AES input balanced output measurements part B

Dynamic Range


Crosstalk


50 Hz + 7000 Hz dual tone


600 Hz + 1700 Hz dual tone


1kHz @ -90dBFS

Due to trim adjust this -90 dBFS observation is actually over -100 dB relative
- an impressive performance.

1kHz @ -70dBFS


20 Hz square wave 0dBFS 4Vpp 10mS/div


20 Hz square wave 0dBFS 4Vpp 500uS/div


20 Hz square wave 0dBFS 4Vpp 100uS/div


Residual noise and interference

 

USB input balanced output measurements part A

THD and THD+N spectrum at 1 KHz


THD and THD+N vs frequency


THD and THD+N vs amplitude at 1 KHz


IMD spectrum


IMD vs amplitude


Frequency Response


Frequency Response (y-axis zoom)


Inferred Jitter


1 KHz gain linearity


Imaging

 

USB input balanced output measurements part B

Dynamic Range


Crosstalk


50 Hz + 7000 Hz dual tone


600 Hz + 1700 Hz dual tone


1kHz @ -90dBFS

Due to trim adjust this -90 dBFS observation is actually over -100 dB relative
- an impressive performance

1kHz @ -70dBFS


20 Hz square wave 0dBFS 4Vpp 10mS/div


20 Hz square wave 0dBFS 4Vpp 500uS/div


20 Hz square wave 0dBFS 4Vpp 100uS/div


Residual noise and interference

 

Internal Trim vs External Stepped Attenuator

Dynamic Range Convert-2 cal set to -14dBFS internal trim adjusted to 0dBu


Dynamic Range Convert-2 cal set to -18dBFS internal trim adjusted to 0dBu


Dynamic Range Convert-2 cal set to -14dBFS external Goldpoint SA2X adjusted to 0dBu


Dynamic Range Convert-2 cal set to -18dBFS external Goldpoint SA2X adjusted to 0dBu

Best performance achieved with this last configuration


Filter Response vs Sample Rate

20 Hz square wave 0dBFS 4Vpp 100uS/div AES Sample Rate 44 KHz


20 Hz square wave 0dBFS 4Vpp 20uS/div AES Sample Rate 88 KHz


20 Hz square wave 0dBFS 4Vpp 20uS/div AES Sample Rate 176 KHz


20 Hz square wave 0dBFS 4Vpp 20uS/div AES Sample Rate 44 88 176 KHz overlay

Higher sample rates result in less filter ringing and faster transition time
88 KHz is a reasonable compromise

 

Dante data transport to Convert-2 AES input
Gain linearity and inferred jitter - internal vs external clock

1 KHz gain linearity Convert-2 internal clock


1 KHz gain linearity Convert-2 externally clocked by rubidium time reference and LiveClock

Slightly better gain linearity with external disciplining from rubidium time reference + LiveClock combination

Inferred Jitter Convert-2 internal clock


Inferred Jitter Convert-2 externally clocked by rubidium time reference and LiveClock

Jitter reduced with external disciplining from rubidium time reference + LiveClock combination

 

reserved 8/8