MDAC first listen (part XVIII)

[tull_hifi]

At present, really need 20dB. I have XLR attenuators, and I can attenuate the speakers slightly, but the attenuators I feel are slightly degrading the sound, and the speaker attenuation isn't quite enough... incidentally, I don't use the XLR attenuators at the same time as the speaker attenuation - it's just that these are the two choices I have...

Hi everybody,

This is my first post to this forum. Coming from a Musical Fidelity M1-DAC, i have recently changed this DAC to the audiolab M-DAC.
I m really satisfied with this device. The sound is great for me. i am waiting eagerly for the new M-PAX estension to improve SQ one step beyond. I use it with an classic QUAD 909 power amp.

Nevertherless, i meet the same situation as JTC (and probably Arthur) : the gain of the M-DAC is to high for the QUAD, since i listen to music with a level of -50 dB the most of the time.

I think that some good attenuators could help me to improve the SQ. That's why i've ordered two pairs of Harrison Labs attenuators (-6dB and -12dB). I will try the both and keep the one which best fit with my system.

Do you think my approach is a good approach ? What attenuator do you recommend for this situation ?

Thanks folks for your answers.

 

[Sober]

You probably need at least 20db of attenuation. 6db is not going to make any difference.

 

[Sober]

I'm only surprised it's taken this long - de-emphasis popping up! Yes, I can make the M-DAC apply de-emphasis, but this will only work when playing back an actual CD through a disc player. I'll include that in new firmware releases.

For computer playback, the only option is to grab and apply the filters offline. When doing so, make sure the output bitdepth is set to 24 bit and dithered properly.

Same goes for HDCD - if you have them, grab them, run them through software HDCD decoder and save as in 24 bit resolution. No dither needed there since most of the time, HDCD will show 17 bit resolution, going to 20 bit during peaks. When stored losslessly, there will be no difference in file size between 20 bit or 24 bit, but 20 bit is rather obscure format and may not be handled properly by some players.

Shame MDAC cannot apply HDCD filters for itself ;-)

PS: Why not just do the HDCD->24bit conversion on the fly when playing HDCD from a PC? I think there is no need to convert the actual files...

 

[Bazz]

Hi everybody,

This is my first post to this forum. Coming from a Musical Fidelity M1-DAC, i have recently changed this DAC to the audiolab M-DAC.
I m really satisfied with this device. The sound is great for me. i am waiting eagerly for the new M-PAX estension to improve SQ one step beyond. I use it with an classic QUAD 909 power amp.

Nevertherless, i meet the same situation as JTC (and probably Arthur) : the gain of the M-DAC is to high for the QUAD, since i listen to music with a level of -50 dB the most of the time.

I think that some good attenuators could help me to improve the SQ. That's why i've ordered two pairs of Harrison Labs attenuators (-6dB and -12dB). I will try the both and keep the one which best fit with my system.

Do you think my approach is a good approach ? What attenuator do you recommend for this situation ?

Thanks folks for your answers.

I feed my MDAC also directly into the Quad 909 and had the same problem with too much gain. Now there's 2 Rothwell attenuators at the Quad end (-10 dB) and my normal listening level is now -23 - -18 dB. No perceptible loss in SQ.

 

[Plutox]

...M-DAC...QUAD 909...gain of the M-DAC is too high for the QUAD

The right answer here is to deploy the balanced inputs of your Quad, fed from the balanced outputs of the M-DAC - and this will achieve what you need unless your speakers are extraordinarily sensitive.

You will have to get a non-standard lead made up to do this, but it's very cheap.

 

[Bazz]

Quad 909 has no balanced inputs, at least mine hasn't. It's no use to adapt a balanced plug to the Quadlink input, as the circuitry of that input is crappy and will lead to a loss in SQ.

 

[Plutox]

Quad 909 has no balanced inputs, at least mine hasn't.

Oh yes it does. Have you ever thought about what the DB-15 connector on the panel does? The so-called Quadlink is a perfectly standard balanced input. The circuitry is, in fact, very similar to that of the unbalanced input so if that's OK, so is the balanced. I'm not saying it can't be improved upon but there's nothing fundamentally wrong there.

The greater problem with the Quadlink system (for fashion-concious audiophiles at any rate) is that the supplied Quadlink cables are unshielded computer cables. I suspect that this is why they have never been made available in lengths above 1m. But there's nothing fundamentally wrong with the audio interfaces.

Don't believe every audiophile myth you encounter...

 

[EIffel]

Shame MDAC cannot apply HDCD filters for itself ;-)

PS: Why not just do the HDCD->24bit conversion on the fly when playing HDCD from a PC? I think there is no need to convert the actual files...

Yes, this will work with the right playback software (say Foobar 2000). This should also work with Windows Media Player / Media Center, although in this case it will not be bit perfect with Vista/Win7/Win8.

In my case, I converted the files to 24bit flacs so that my streamer (SBT) also gives me the benefit of HDCD

 

[Plutox]

HDCD is still patented, the rights having been bought by Microsoft.

Furthermore, the patent doesn't describe the algorithm sufficiently well to make it possible to emulate perfect HDCD behaviour* even if you were willing to buy a license. The patent is deficient in this respect as it is supposed to provide complete knowledge in exchange for the protection it provides.

* as provided if you bought the licensed chips back in the day

 

[Bazz]

Oh yes it does. Have you ever thought about what the DB-15 connector on the panel does? The so-called Quadlink is a perfectly standard balanced input. The circuitry is, in fact, very similar to that of the unbalanced input so if that's OK, so is the balanced. I'm not saying it can't be improved upon but there's nothing fundamentally wrong there.

The greater problem with the Quadlink system (for fashion-concious audiophiles at any rate) is that the supplied Quadlink cables are unshielded computer cables. I suspect that this is why they have never been made available in lengths above 1m. But there's nothing fundamentally wrong with the audio interfaces.

Don't believe every audiophile myth you encounter...

I know the Quadlink input contains a balanced input. But I've been told that, when upgrading the 909, the circuit just behind the Quadlink door should better be eliminated.

 

[Plutox]

Do you believe everything you've been told?

 

[Bazz]

Not normally, no. But this is from several sources, so I tend to take it for truth. Apart from that, I don't see or hear anything wrong in just using proper attenuators as opposed of trying to find a set of quadlink plugs, a wiring diagram and someone who can properly make the thing.

 

[Richard Kimber]

The greater problem with the Quadlink system (for fashion-concious audiophiles at any rate) is that the supplied Quadlink cables are unshielded computer cables. I suspect that this is why they have never been made available in lengths above 1m. But there's nothing fundamentally wrong with the audio interfaces.

I assume you don't buy the 'unshielded' argument. Is there an implication here that they can't actually be improved upon? I remember seing various criticisms of the Quadlink cables in the past but I've never seen a recommended improvement.

Having been convinced that pure silver analogue interconnects from the MDAC to the pre-amp sounds better on my system than copper ones, I have often wondered whether there was any future in looking to replace the Quadlink cables.

- Richard.

 

[Sober]

Yes, this will work with the right playback software (say Foobar 2000). This should also work with Windows Media Player / Media Center, although in this case it will not be bit perfect with Vista/Win7/Win8.

It will not be bit-perfect in case of foobar also. How can a [16 bit -> apply hdcd filters -> 24 bit operation] be bit perfect?

It's just a question of which software does better job in the conversion and dithering algorithms. I would expect the foobar, but on the other hand the HDCD may be implemented better in M$.

 

[Plutox]

Is there an implication here that they can't actually be improved upon?

OK - I'm about to talk about the link between the pre and power amp - known by Quad as "AMPBUS". They call the input side cabling "QUADLINK", the latter needing more pins. AFAIK, Quad sell identical cables for the two and herein may lie some of the oddities.

Frankly, I don't know what would happen if the type of cable supplied was extended to 10m or more. What I do know is that the supplied cables are far thicker and more rigid than they need be. As I said, it's unscreened computer cable and all 15 pins are wired - totally unnecessary for connecting pre to power amp. You actually need 7 connections - 4 for balanced audio, an earth and 2 to manage the switching (putting power amp into standby along with pre-amp). Serge made the appropriate lead for me out of some 8 core screened stuff which had an OD of about 8mm and was very flexible.

If you didn't want the standby switching, you could make an adapter to drive the Quad 909 from a pair of standard XLR leads.

I remember seing various criticisms of the Quadlink cables in the past but I've never seen a recommended improvement

I don't know why Quad have never offered alternatives here. They sell a tiny lead that's only useful if you stack Quad units on top of each other and a 1m lead for pre to power. The two are electrically identical. You could come up with all kinds of conspiratorial reasons to explain why Quad never offered, at the very least, a longer pre to power lead. My feeling is that it's the generally accepted belief in the business that manufacturers don't compete in after market cabling, an area in which dealers can make a decent buck.

 

[JohnW]

I know the Quadlink input contains a balanced input. But I've been told that, when upgrading the 909, the circuit just behind the Quadlink door should better be eliminated.

I must say that the very first thing the few of us at IAG who used the Quad 909 for serious listening was to remove the Quadlink board.

I didn't not spend much time trying to understand why it sounded bad - but the first suspect would be the nasty electrolytic coupling capacitors in the direct signal path...

Sadly, I don't seem to have the details of the input board any longer...

John

 

[Plutox]

...trying to find a set of quadlink plugs, a wiring diagram and someone who can properly make the thing.

Ask sergeauckland nicely!

 

[Plutox]

the first suspect would be the nasty electrolytic coupling capacitors in the direct signal path...

John, from my diagram, neither the balanced nor unbalanced inputs have any electrolytic caps. in the signal path of the input section... certainly not until long after the balanced and unbalanced input sections have combined to become one common path.

 

[JohnW]

John, from my diagram, neither the balanced nor unbalanced inputs have any electrolytic caps. in the signal path of the input section... certainly not until long after the balanced and unbalanced input sections have combined to become one common path.

Do you have the 909 Quadlink input board? - while in China there where various version of input board.... one would hope that only the capacitor on the Base of the input transistor was need.

While I was at IAG there where various issues with turn-on thump (or some such) that engineers where trying to resolve...

 

[Plutox]

... while in China there where various version of input board....

I can well believe that - I do know that I have used my 909's balanced input fed from the balanced output of the MDAC with 10m of cable and it sounds fine!

It does give a small thump on turn-on, nothing too scary though. Perhaps my 909 pre-dates the 'fiddling' to cure this.