MDAC first listen (part IV)

[TwoSeventy]

What is the correct output level for running the mdac into an integrated amp (mine's an avi lab series). I am currently running it on +3db but for some reason 0db makes more sense to me What level would compare to a CD player output?

 

[John_73]

You should be able to get a proper 2v and 0db output from M-DAC by putting it into pre-amp bypass mode.

Turn off M-Dac. Press/hold the Menu button down and turn on power. Select pre-amp disabled. Then press the menu key again. (Page 21 of the manual )

- John

 

[elnero]

What is the correct output level for running the mdac into an integrated amp (mine's an avi lab series). I am currently running it on +3db but for some reason 0db makes more sense to me What level would compare to a CD player output?

Setting the volume at 0db is the same as bypassing the preamp.

 

[arthur]

Lo John. I was trying not too, but I'm inherantly nosey. Can you say who it is that you are designing the new dac for?

Is it a secret?

 

[TwoSeventy]

You should be able to get a proper 2v and 0db output from M-DAC by putting it into pre-amp bypass mode.

Turn off M-Dac. Press/hold the Menu button down and turn on power. Select pre-amp disabled. Then press the menu key again. (Page 21 of the manual )

- John

Thank you. For some reason I missed it in the manual. I assumed that sort of info would be near the beginning.

It's a really great unit though

 

[TwoSeventy]

mmm.... Just tried set the mdac to fixed volume level but when it reboots it reverts to preamplifier mode. I'm guessing this is a software bug.

 

[John_73]

mmm.... Just tried set the mdac to fixed volume level but when it reboots it reverts to preamplifier mode. I'm guessing this is a software bug.

Mine works fine and I haven't heard of any other units with that particular problem. Are you sure you selected the correct setting and pressed the volume control/button in, then pressed Menu?

 

[TwoSeventy]

Mine works fine and I haven't heard of any other units with that particular problem. Are you sure you selected the correct setting and pressed the volume control/button in, then pressed Menu?

Thanks that works! I rotated the control knob to select the correct setting as per the manual. It doesn't say you then need to press it before rebooting

 

[TwoSeventy]

Just tried my Oppo BDP-83 with the M-DAC. I still get the first half-second or so of each track which either cuts out or starts again - the peak level indicators also (for a split second) read 'Encoded Bitstream' (shouldn't it be PCM?) when either starting a new CD, or skipping forwards (or backwards) to a track. I believe this is the M-DAC locking onto the digital signal each time. Never had this problem with any other DAC to date.

I got the encoded bitstream display (and muted output) from my Humax set top box on BBCHD this was down to the broadcast being in dolby digital 5.1 and me not having the latest firmware to fix a bug to make sure that the optical output delivered the PCM stereo stream. It may be that you need to adjust some settings on the OPPO? I wouldn't have thought the encoded Bitstream display should come up with CD replay. I am using a Pioneer BDP51FD as a transport and it works fine without any drops when skipping tracks etc.

 

[John_73]

I got the encoded bitstream display (and muted output) from my Humax set top box on BBCHD this was down to the broadcast being in dolby digital 5.1 and me not having the latest firmware to fix a bug to make sure that the optical output delivered the PCM stereo stream. It may be that you need to adjust some settings on the OPPO? I wouldn't have thought the encoded Bitstream display should come up with CD replay. I am using a Pioneer BDP51FD as a transport and it works fine without any drops when skipping tracks etc.

Well I get the same symptoms with my Rotel RCD-965BX CD player too, and that's a dedicated CD spinner with no options. Mind you it IS a bitstream CD player.

I'm get confused over PCM/bitstream - should one be outputting PCM and not bitstream, or vice-versa? Perhaps this explains the momentary 'locking on' symptoms I'm getting with M-DAC via coax.

 

[John_73]

Thanks that works! I rotated the control knob to select the correct setting as per the manual.

Jolly good!

 

[TwoSeventy]

I'm get confused over PCM/bitstream - should one be outputting PCM and not bitstream, or vice-versa? Perhaps this explains the momentary 'locking on' symptoms I'm getting with M-DAC via coax.

As I understand it you should try PCM. My guess is your player is putting out some additional Bitstream content. It's worth a try if you have the option. My Pioneer player is set to stereo PCM and this downmixes surround channels on Bluray movies but I've no idea whether it affects the output with CD content. The MDAC in my case displays the track numbers and time on it's display when using the Pioneer as a transport.

 

[John_73]

As I understand it you should try PCM. My guess is your player is putting out some additional Bitstream content. It's worth a try if you have the option. My Pioneer player is set to stereo PCM and this downmixes surround channels on Bluray movies but I've no idea whether it affects the output with CD content. The MDAC in my case displays the track numbers and time on it's display when using the Pioneer as a transport.

Unfortunately I can't select anything on the Rotel (and I want to use this transport - the Oppo was just wheeled in to check the lock-on of MDAC). It was a circa-1991 era CD player, and Bitstream was the latest 'in thing' in DAC design. It's worked perfectly with all DACs (vintage and modern) without any problems at all until MDAC so unfortunately I doubt it's to blame to be honest (I hope!). Stutters/silence at the beginning of tracks aside, it plays really nicely and passes the Audiolab bit-perfect test too. I just hope JohnW will find some cunning way around it with a firmware mod. It's not a huge problem as I mainly use USB and a Mac mini, but I would like to sort the problem out if possible, so it works as intended.

So far both my Rotel and the Oppo have this momentary (only half a second if that) locking-on problem with the very first track with MDAC, and also if skipping to another track, or backwards to another. Bar pressing play on the CD player for the very first time, it's glitch free if playing a disc straight through. It's only if skipping tracks, so must be as JohnW suggested a while back, it's locking-on again from scratch if a track is skipped, and on the very first track played. It needs to lock on and buffer the data perhaps to prevent this.

I'll see if I can find any other transports in the house with a digital out and see if it does it with all of them. I'll be a bit concerned if it does as I'd consider that a bit of a flaw in MDAC if that's the case.

- John

 

[JohnW]

Unfortunately I can't select anything on the Rotel (and I want to use this transport - the Oppo was just wheeled in to check the lock-on of MDAC). It was a circa-1991 era CD player, and Bitstream was the latest 'in thing' in DAC design. It's worked perfectly with all DACs (vintage and modern) without any problems at all until MDAC so unfortunately I doubt it's to blame to be honest (I hope!). Stutters/silence at the beginning of tracks aside, it plays really nicely and passes the Audiolab bit-perfect test too. I just hope JohnW will find some cunning way around it with a firmware mod. It's not a huge problem as I mainly use USB and a Mac mini, but I would like to sort the problem out if possible, so it works as intended.

So far both my Rotel and the Oppo have this momentary (only half a second if that) locking-on problem with the very first track with MDAC, and also if skipping to another track, or backwards to another. Bar pressing play on the CD player for the very first time, it's glitch free if playing a disc straight through. It's only if skipping tracks, so must be as JohnW suggested a while back, it's locking-on again from scratch if a track is skipped, and on the very first track played. It needs to lock on and buffer the data perhaps to prevent this.

I'll see if I can find any other transports in the house with a digital out and see if it does it with all of them. I'll be a bit concerned if it does as I'd consider that a bit of a flaw in MDAC if that's the case.

- John

Hi John,

I don't believe there's anything we can do to speed up the MDAC's locking time its already under 500mS.

Don't confuse the Rotel's which has a "Bitstream" DAC for the Dolby/DTS Bitstream setting on a DVD/AV systems. One's referring to the Bitstream DAC architecture (Rotel) while the second refers to the Data transmitted from the Digital output (Oppo).

The Rotel "Mute's" its digital output during any function apart from Play - while the Oppo reverts its output to 48kHz - both actions require a re-Lock advent.

95% of CD players will keep the DAC in lock upon power-up, your just unlucky with the Rotel.

John

 

[fusion5]

Hi Michael,

It sound like you need an USB Isolator - this will isolate your PC and Audio Grounds.

John

Hi John,

that was my first thought, too. The problem is that there is a HDMI connection between the HTPC an the AV-Receiver which would still be affected even if I would use an USB Isolator. Although I have to admit, the HDMI connection is less effected by a large margin.

I played around with a simple power meter and tried to find the exact source of the noise problem. These are my findings:

1. The HTPC draws about 50W when under full load and there is no noise at all!
2. When it's idle power consumption drops to ~28W. There is some noise.
3. Powered down the HTPC draws ~3W. This is because the VFD/IR-Receiver unit is still powered. Loud noise! Awful!!! But when I disconnect the VFD/IR-Receiver unit power consumption drops to zero and there is ... silence!

My guess is the 150W power supply provided with the case does have some problems with low load power. Or maybe it's just the ground connection.

I ordered a 120W Leicke NT03015 power supply to test it with my HTPC. The Leicke power supply isn't grounded. And all my noise problems are gone..

Finally I can enjoy my M-DAC again (and wait for the M-PAX and TRANSPORT to become available)

Michael

 

[JohnW]

Hi John,
Sounds like you've got a lot of projects on the go at the moment, and I've no intention of hassling you, but I'm really keen to hear how you're coming along with the SB Touch clock lock ?

The CDQ upgrade sounds very cool too. I'm sure you know what you're doing, but isn't this likely to reduce the demand for the M-PAX? I'm certainly reconsidering what path I should take now. Also, I can't help wondering what you're going to do with the discarded guts from the upgraded machine... throw it all in the bin?

Cheers,
Tim

Hi Tim,

I'll send you a new SBT to try Adrians software patch.

I think it's better to design an isolated USB Hub then messing with modifying units.

I would design the USB isolator for maxim isolation at RF - and also the USB 2.0 HUB enabling 24/96 with Async USB on the SBT - this would be a cheaper option then sending the units to us in CZ for internal modification.

John

 

[John_73]

Hi John,

I don't believe there's anything we can do to speed up the MDAC's locking time its already under 500mS.

Don't confuse the Rotel's which has a "Bitstream" DAC for the Dolby/DTS Bitstream setting on a DVD/AV systems. One's referring to the Bitstream DAC architecture (Rotel) while the second refers to the Data transmitted from the Digital output (Oppo).

The Rotel "Mute's" its digital output during any function apart from Play - while the Oppo reverts its output to 48kHz - both actions require a re-Lock advent.

95% of CD players will keep the DAC in lock upon power-up, your just unlucky with the Rotel.

John

I feared that might be the case John. Oh well - I'll make do with what I have until I get a new transport at some point. Not too much of a bother as I use USB 90% of the time anyway. By the way regarding the bitstream, it was the 'Encoded bitstream' message that briefly flashed up on the MDACs display when playing the Rotel that made me think it might be outputting bitstream via SPDIF.

Thanks,

- John

 

[dlcastles]

Hi Tim,

I'll send you a new SBT to try Adrians software patch.

I think it's better to design an isolated USB Hub then messing with modifying units.

I would design the USB isolator for maxim isolation at RF - and also the USB 2.0 HUB enabling 24/96 with Async USB on the SBT - this would be a cheaper option then sending the units to us in CZ for internal modification.

John

Can confirm that Triode's excellent work on the Squeezebox has it functioning as an asynchronous USB source for a CDQ. Works up to 24/96 with the addition of a cheap USB 2 hub.
I got it all up and running this afternoon and for the last three hours on various FLACs has been running flawlessly.
After a fair bit of messing around I even have Soundcheck's 3.0 Toolbox running on the Touch in tandem with Triode's USB modifications. They key here was to follow Triode and John Swenson's instructions to the letter - it did not work until I edited out the priorities as detailed in post 28 here.
http://forums.slimdevices.com/showthread.php?t=93310&page=3

Many thanks to Triode, John and everyone else involved for putting so much effort into this. Squeezebox streaming over USB is a really elegant solution.
- Duncan

 

[dlcastles]

As an added bonus, the CDQ's remote now controls the Squeezebox in the same way it does a laptop. Superb.

 

[AndyU]

Squeezebox streaming over USB is a really elegant solution.
- Duncan

No it most certainly isn't! (imo) It is a cascade of kludges, a pile of unsupported bodges.

An elegant solution would be if the MDAC could be fed directly from a network, either wired or wireless. UPnP renderers are appearing in everything; cheap bluray players, phones so it can't be difficult.

No spdif, no usb, no input jitter, no bother.