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MDAC First Listen (part XXVII)

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Stefan

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Hello out there!

I upgraded to the latest Firmware a few moths ago and i noticed at least one "big" bug for me. I don't know if this occour with the stock Audiolab firmware, becouse i added one Spdif device:

I use a Bluelineo Bloutothdevice with a Wulfson SPDIF Transreciever, so not it's "cheapest" stuff and should meat the recomendations for the spdif protocol.

When I change the input channel from the optical spdif (BT) to USB, the Mdac denied to lock the Signal! I tried several different Filter and Jitter settings with no effect.

So in the Moment a I am forced to restart the DAC several times :mad: because of this bug.

I made a video, where you can see that the USB Stream must be running in the background without a any lock.


You wrote that the Left channel Bug should be fixed, but sometimes i can hear noise out of my Left Speaker. In the moment i am not able to provoce it.






As a Appendix the Teardown of the BT device, for 50bugs every penny worth.
gp97.jpg
 
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Stefan said:
Hello out there!

I upgraded to the latest Firmware a few moths ago and i noticed at least one "big" bug for me. I don't know if this occour with the stock Audiolab firmware, becouse i added one Spdif device:

I use a Bluelineo Bloutothdevice with a Wulfson SPDIF Transreciever, so not it's "cheapest" stuff and should meat the recomendations for the spdif protocol.

When I change the input channel from the optical spdif (BT) to USB, the Mdac denied to lock the Signal! I tried several different Filter and Jitter settings with no effect.

So in the Moment a I am forced to restart the DAC several times :mad: because of this bug.

I made a video, where you can see that the USB Stream must be running in the background without a any lock.


You wrote that the Left channel Bug should be fixed, but sometimes i can hear noise out of my Left Speaker. In the moment i am not able to provoce it.






As a Appendix the Teardown of the BT device, for 50bugs every penny worth.
gp97.jpg
Click to expand...

Hi Stefen,

Thank you for reporting the USB Bug, I'll forward to Dominik to resolve.

If you still have instances of the left channel locking bug, there is nothing more we can do to resolve - with MDAC2 we will totally bypass this section of the ESS DAC.
 
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JohnW said:
The only area where the MDAC2's "Original" headphone amplifier would have be less then optimal would have been into very low impedance loads where beyond about 100mA the output stage would drop out of Pure ClassA operation into ClassB.

This would never be be an issue with normal use - but very low impedance headphones current requirments could exceed 100mA - such as the HiFi Man ribbon headphones which really need a small power amplifier.

The idea is to design a "sliding class A circuit" where the heat dissipation can be kept under control - but if current is required beyond 100mA the circuit would insure the output stage remains in classA operation...

I'm also going to try using a MOSFET output stage... so ClassA Mosfet design...
Click to expand...

John, my understanding of the current MDAC design is that the headphone out is essentially the same as the rear single-ended out, just switched/routed by relays. Assuming the same thing in the MDAC2, would any improvements you make for the headphone out essentially benefit the regular single-ended and balanced outs likewise?

Leon
 
Stefan said:
Hello out there!

I upgraded to the latest Firmware a few moths ago and i noticed at least one "big" bug for me. I don't know if this occour with the stock Audiolab firmware, becouse i added one Spdif device:

I use a Bluelineo Bloutothdevice with a Wulfson SPDIF Transreciever, so not it's "cheapest" stuff and should meat the recomendations for the spdif protocol.

When I change the input channel from the optical spdif (BT) to USB, the Mdac denied to lock the Signal! I tried several different Filter and Jitter settings with no effect.

So in the Moment a I am forced to restart the DAC several times :mad: because of this bug.

I made a video, where you can see that the USB Stream must be running in the background without a any lock.

You wrote that the Left channel Bug should be fixed, but sometimes i can hear noise out of my Left Speaker. In the moment i am not able to provoce it.
Click to expand...

Hi Stefan, are you using OPT2 input for the BT box and it locks up when switching from OPT2 up one step to USB? Try moving it to OPT1 to see if the problem persists. Once locked up, can you go back to the OPT input and get lock?

Dominik
 
travelfotografe said:
John, my understanding of the current MDAC design is that the headphone out is essentially the same as the rear single-ended out, just switched/routed by relays. Assuming the same thing in the MDAC2, would any improvements you make for the headphone out essentially benefit the regular single-ended and balanced outs likewise?

Leon
Click to expand...

Yes, both the rear outputs and the headphone outputs are fed from the very same amplifier. The improvements discussed would extend Class A operating range into very low impedances which are only ever presented by (some) headphone loads. Even without any sliding bias, the line outputs are comfortably in Class A into any and all pre/power amplifier loads imaginable.
 
JohnW said:
Brian,

The MDAC2 will retain MDAC's +3dB option so can swing 3VRms... can I ask what application you need such a High level?

Analogue Gain scaling is a hat full of compromises - We plan too use "Gain Scaling" within the matching amplifiers where the extra Gain is used to improve performance rather then just being wasted as heat (as with analogue attenuation).
Click to expand...

Hi John,

I'm using the Sun Audio Amplifier with the MDAC. It has an input sensitivity of 1.5V so I have exhausted the MDAC +3dB and the volume is max out now. My system doesn't seem to have enough overall gain when using with this amplifier...performance seemed limited by gain, I think.

How to solve this ? Is it possible to have more gain with digital scaling ?
 
BrianC said:
Hi John,

I'm using the Sun Audio Amplifier with the MDAC. It has an input sensitivity of 1.5V so I have exhausted the MDAC +3dB and the volume is max out now. My system doesn't seem to have enough overall gain when using with this amplifier...performance seemed limited by gain, I think.

How to solve this ? Is it possible to have more gain with digital scaling ?
Click to expand...

At +3dB there is no gain scaling & your approaching the limits of the analogue section PSU rails - if you had balance inputs you could get an extra +6dB, as we are talking about tube electronics, maybe a transformer could help here?

At +3dB you have about 3VRMS output that's HUGH - your Tube amplifier appears to lacks Gain! Are you sure its correctly functional?

Which model do you have and did you DIY build it? maybe an incorrect component value (or is it one of the SE low power units? - what speakers do you use?)

If your using there singled ended designs then its a lack of amplifier power - the highest is only a claimed 8W, no amount of output from the MDAC can help at 3Vrms at +3dB its already well over the industry standard output level.

I've nothing against SE Tube amplifiers... only that its not the job of a DAC to provide such High output levels... I really believe the Amplifier design lacks Gain & maybe depending upon your speakers - power (unless you tell me that you have Horn loaded speakers :) )
 
On Optical Input 1 is my "Office PC" which use 96k 24bit.
Is there a hardware Difference betwenn those two inputs?
The special thing with the BT Box is, that the SPDIF Stream stops when no audio is send by the PC. So the Mdac's PLL has a lot of work to do in a youtubesession with my Notebook.

If there is anything I can test out for you, let me know.


The Left Channel Bug is not so often, so i can live with it.
 
A really good hp amp is something worth a couple of days extra, in my opinion.

John did you recieve my fusion resistors?
 
Taking the pre out is visually more appealing




AND I get to adjust the volume via remote control. The very slight hum has also completely disappeared :)

I would also get a couple of grand for the pre which would be very nice :)




BUT

No cigar. :(

I used the album Firecracker by the Wailin' Jennys, notably track 5, "Swallow" and the expression in the voices was better with the pre and it was easier to pick out each voice. There was also a slight loss of dynamics without the pre and timing wasn't as good.

This defies a certain logic but there you are!

A couple of grand would have been useful :(
 
Steven Toy said:
Taking the pre out is visually more appealing




AND I get to adjust the volume via remote control. The very slight hum has also completely disappeared :)

I would also get a couple of grand for the pre which would be very nice :)




BUT

No cigar. :(

I used the album Firecracker by the Wailin' Jennys, notably track 5, "Swallow" and the expression in the voices was better with the pre and it was easier to pick out each voice. There was also a slight loss of dynamics without the pre and timing wasn't as good.

This defies a certain logic but there you are!

A couple of grand would have been useful :(
Click to expand...

Should have gone for a Fusion then :D
 
PhilCTTE said:
Should have gone for a Fusion then :D
Click to expand...

From what I heard this morning I reckon even a Fusion would give more of itself via the pre. It isn't "added distortion" either because that doesn't bring more subtlety, enable you to hear more into the recording and hear more clearly three voices.

There is only one way to find out of course. MDAC2 will be Fusion...
 
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