NDX and digital out

Posted by: naimUnT on 07 September 2011

I tried the NDX digital out into a Benchmark DAC (BNC to BNC). As some may know, the Benchmark DAC is of studio quality and is well known for its jitter rejection. When there is a high amount of jitter, the Benchmark input light will blink 64x before going out. Interestingly, the NDX digital feed into the Benachmark indicates a very high amount of jitter! I tried another DAC and the signal light blinks occasionally, indicating higher than normal amount of jitter. I am very preplexed by these observations and wonder if it would be correct for me to conclude that the NDX is the culprit! If so, and at its price point, I would be very surprised indeed. BTW, my humble Squeezebox Classic (digital out to Benchmark) shows a steady blue light indicating that jitter is well within threshold.

Posted on: 07 September 2011 by AMA
NaimUnT, isn't it a reason to ... do a service for NDX?  

 

or fix a bulb on Benchmark DAC 

Posted on: 07 September 2011 by naimUnT

Good one Ama!

 

Well, I doubt the NDX is defective given that it is only 2 months old but I guess its possible!

 

As for the Benchmark, the lights are working fine. I tested the Benchmark with another source and the blue light was continuous and strong.

Posted on: 07 September 2011 by Simon-in-Suffolk
This does sound bizarre, and my suspicion is a fault somewhere. However transmission jitter in spdif can come from the interconnect and connection quality so as to avoid reflections  and earthing quality, so.....

Are you using 75ohm terminated interconnect. Is the Benchmark DAC specced at 75 ohm input? And are using BNC and not RCA?

Does the Benchmark DAC use a galvanic isolator? If not you might have a earth loop and hum on the spdif which would cause jitter.

Both of these points would cause distortion of the spdif signal and therefore jitter as remember the clock is recovered from the bit stream spdif, however if the Benchmark is of high quality I would expect the answer is yes, but worth checking....

Simon
Posted on: 08 September 2011 by naimUnT
Thanks for your suggestions Simon! I am using BNC from NDX to Benchmark BNC input. You have raised some good points about the cable being the cause of high jitter. I am not sure if the Benchmark has a galvanic isolator but Benchmark are very particular about jitter in their DACs. I will try to borrow a Naim digital cable to try and see if it is able to solve the problem.
Posted on: 08 September 2011 by rhr

I don't know if the benchmark has a toslink connector, but could you use an optical connection to test the hypothesis of an earthloop? 

Posted on: 08 September 2011 by naimUnT
rhr: thanks for your reply. The Benchmark has a Toslink input but unfortunately the only connection for NDX's digital out is BNC.
Posted on: 08 September 2011 by AMA
NaimUnT, can you do yourself a favor -- pls, run NDX to BM with hi-res staff and see if the jitter is paced.
 
One of the reasons can be NDX  SW.
Posted on: 08 September 2011 by rhr

Sorry, assumed the connector on the back was an output, like the HDX.

 

Does changing the 'Signal Ground Switch' have any effect?

Posted on: 08 September 2011 by naimUnT
rhr: good point! I have not tried that. I am now using a very old Wadia Digimaster DAC which is reputed to be very sensitive to jitter but with digital out from NDX to Wadia, I have had zero problems!
Posted on: 08 September 2011 by Simon-in-Suffolk
Rhr, I am sure there was a comment from Naim on this forum saying that the grounding switch only affected the ground on the audio outputs.
Simon
Posted on: 09 September 2011 by naimUnT
I just discovered that the NDX signal into the Benchnark DAC only causes the Blue light ob the Benchmark to fade off when playing Internet radio streams. When listening to the NDX analog radio stations, I get a solid blue light. In other words, the data only becomes questionable when using mP3 format. Am I correct to conclude thus? However, if I use my Classic Squeezebix Internet radio, the Benchmark's blue light is constant. I am still somewhat puzzled!
Posted on: 09 September 2011 by Hook

Hi NaimUnT -

 

What is the goal of your experiments?   Are you trying to decide whether or not to use the NDX's internal DAC versus using it as a digital source for the Benchmark?

 

I auditioned a Benchmark DAC1 before buying the Naim DAC a couple of years ago.  I thought it sounded very clean and very detailed, but for me it placed a distant second when it came to natural midrange warmth and bass articulation.  But that's just my ears, and perhaps you are hearing it differently?

 

Please don't misunderstand me -- if you are simply experimenting for fun, and trying to understand how things work, then that's cool!  I am enjoying reading your posts.   It is just not clear to me what it is that you are trying to eventually accomplish.  

 

Thanks!

 

Hook

 

Posted on: 09 September 2011 by DavidDever
Does the Benchmark DAC1 support 32 kHz playback?
Posted on: 09 September 2011 by naimUnT
Hi David, the Benchmark can handle input frequencies from below 32 to 192 KHz. When there is an invalid sampling, the blue LED will flash rapidly 64 times before the LED goes off.