Modi MB technical measurements
Aug 16, 2016 at 12:25 PM Thread Starter Post #1 of 28

atomicbob

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The Modi MB data presented were collected as follows:
 
1.  PrismSound dScope III, picoscope 5243B
2.  DAC unbalanced output RCA
3.  100 Kohm load used for measurements
4.  44 KHz  sample rate, 24 bit depth
5.  USB input – Audioquest Forest
6.  SPDIF input - Tecnec B-B-6in with 75 ohm BNC to RCA adapters
7.  Toslink input - generic 12 inch toslink cable
8.  Unbalance cable DH Labs Silver Sonic Air Matrix RCA
9.  Vaunix Lab Brick USB hub
10. USB to SPDIF DDC - Gustard U12 XMOS
 
Modi MB - AD5547CRUZ resistor multibit 16 bit resolution DAC
Measurements were performed over a period of 6 hrs after 24 hrs warmup.
 
Notable highlights:
 
Substantially similar to Bifrost MB with the following differences of interest:
1. slightly lower resolution - see -70 and -90 dBFS sine
2. sligthly less dynamic range
3. higher residual noise floor as seen on jitter measurements
 
Excellent channel matching like the other Schiit MB DACs
Llistening evaluation finds the multibit magic of dimension and depth present
Incedible performance for a 16 bit resolution DAC at this price point
 
USB Input - Single Ended RCA output measurements
 
Frequency Response

 
 
Frequency Response (y-axis zoom)

 
 
Dynamic Range

 
 
THD+N

 
 
IMD

 
 
Crosstalk

 
 
Inferred Jitter

 
 
Inferred Jitter (x axis zoom)

 
 
1kHz @ -70dBFS

 
 
1kHz @ -90dBFS

 
 
20 Hz square wave -1.6 dBFS 5Vpp 10ms

 
 
20 Hz square wave -1.6 dBFS 5Vpp 500us

 
 
1 kHz gain linearity

 
 
Imaging

 
 
Measurement Setup

 
Aug 16, 2016 at 12:26 PM Post #2 of 28

atomicbob

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SPDIF Input - Single Ended RCA output measurements
 
Frequency Response

 
Frequency Response (y-axis zoom)

 
Dynamic Range

 
THD+N

 
IMD

 
Crosstalk

 
Inferred Jitter

 
Inferred Jitter (x axis zoom)

 
1kHz @ -70dBFS

 
1kHz @ -90dBFS

 
1 kHz gain linearity

 
Imaging

 
Aug 16, 2016 at 12:26 PM Post #3 of 28

atomicbob

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Toslink Input - Single Ended RCA output measurements
 
Frequency Response

 
Frequency Response (y-axis zoom)

 
Dynamic Range

 
THD+N

 
IMD

 
Crosstalk

 
Inferred Jitter

 
Inferred Jitter (x axis zoom)

 
1kHz @ -70dBFS

 
1kHz @ -90dBFS

 
1 kHz gain linearity

 
Imaging

 
Aug 16, 2016 at 12:26 PM Post #4 of 28

atomicbob

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USB to SPDIF and Toslink DDC (Gustard U12 XMOS) - Single Ended RCA output
 
When a DDC is connected to the Modi MB via SPDIF or Toslink the DAC measures very 
similar to the respective dScope III digital feeds which have been presented above. Here 
are the jitter measurements and noise floors obtained with the U12 DDC.
 
Inferred Jitter DDC USB - SPDIF

 
 
Inferred Jitter (x axis zoom) DDC USB - SPDIF

 
 
Inferred Jitter DDC USB - Toslink

 
 
Inferred Jitter (x axis zoom)​ DDC USB - Toslink

 
Aug 16, 2016 at 4:22 PM Post #6 of 28

XERO1

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Wow, thank for this!
 
Any idea why the jitter impulse measurements look so much better when using the USB-to-SPDIF converter versus using the coax or Toslink inputs directly?
 
Thanks.
 
Aug 16, 2016 at 5:31 PM Post #7 of 28

slex

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Just curious, does the BNC with RCA connector provide more accurately and stable 75 ohm compare with just RCA coax cable?
 
Aug 16, 2016 at 11:48 PM Post #8 of 28

atomicbob

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  Wow, thank for this!
 
Any idea why the jitter impulse measurements look so much better when using the USB-to-SPDIF converter versus using the coax or Toslink inputs directly?
 
Thanks.

Look at the residual noise floor for the two graphs. Note that the Toslink fed from the dScope has a residual of -140 to -150 dBFS. This is more revealing of very low level performance. Using the DDC to feed the MoMB shows a noise floor much higher of -120 to -130 dBFS. This higher noise floor masks the widening you see in the MoMB jitter when driven by the dScope. The widening is present in both but masked by higher residual noise floor when the DDC is employed.
 
Aug 16, 2016 at 11:51 PM Post #9 of 28

atomicbob

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Just curious, does the BNC with RCA connector provide more accurately and stable 75 ohm compare with just RCA coax cable?

In my acoustic laboratory I keep a number of stock broadcast / studio grade cables with great utility due to the type of connectors on them. Most are 50 or 75 ohm with BNC connectors on each end. The BNC to RCA adapters facilitates connecting non-broadcast or non-studio equipment to my measurement systems.
 
Aug 17, 2016 at 12:01 AM Post #10 of 28

slex

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In my acoustic laboratory I keep a number of stock broadcast / studio grade cables with great utility due to the type of connectors on them. Most are 50 or 75 ohm with BNC connectors on each end. The BNC to RCA adapters facilitates connecting non-broadcast or non-studio equipment to my measurement systems.


Ok thanks. btw, are those rca adaptor have a rating of 75 Ohm? I wanna to avoid using direct RCA coax and i believe only canare rca plugs Have the rating of 75 Ohm.
 
Aug 17, 2016 at 12:11 AM Post #11 of 28

atomicbob

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Ok thanks. btw, are those rca adaptor have a rating of 75 Ohm? I wanna to avoid using direct RCA coax and i believe only canare rca plugs Have the rating of 75 Ohm.

The BNC to RCA adapters are available in both 50 and 75 ohm versions. Likewise the BNC cables are available in both 50 and 75 ohm versions. In a laboratory situation it requires special care to avoid intermingling the two which results in sub-optimal performance.
 
Aug 17, 2016 at 12:12 AM Post #12 of 28

XERO1

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In your opinion, does a DAC having a relatively wide impulse base have any real-world negative impact on it's overall SQ?
 
Aug 17, 2016 at 12:24 AM Post #13 of 28

slex

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The BNC to RCA adapters are available in both 50 and 75 ohm versions. Likewise the BNC cables are available in both 50 and 75 ohm versions. In a laboratory situation it requires special care to avoid intermingling the two which results in sub-optimal performance.


Great to know thanks again. I will be going to use the matching 75 ohms BNC to RCA adapter from DDC to mimby.
 
Aug 17, 2016 at 5:49 PM Post #14 of 28

painted klown

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Thank you for the measurements and information. This is very helpful indeed...even if I don't understand a good deal of it.
redface.gif

 
Aug 17, 2016 at 6:58 PM Post #15 of 28

Mightygrey

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I'm commenting on this thread because eventually someone will be able to explain what this means to me like I'm 5 years old. Also, would be really keen to understand any advantages this has head-to-head with the Modi 2 Uber (4490). 
 

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