Connecting balanced to unbalanced - CA Dacmagic to amp

[patricia1066]

I would like some advice on whether I can improve the sound of the Dacmagic without an expensive mod. I am unsure whether DAC was the right forum, but as its a question of interconnects please move if there is a better section.

I use Classic Squeezebox, Vortexbox in a Revo Aspire; currently the CA Dacmagic is connected with shielded RCA cable to the Talk Electronic amp. The improvement I first experienced in hearing the dacmagic has faded, and I want to cheaply upgrade if possible.

 

I read on avforums that changing the op amps to dual bursons (£90 UK) can help, and this was challenged on the basis that it assumed that one used unbalanced connections. The sound degradation produced by the stock op amp does not apply to balanced connections. Is this true?

 

If you need to use an unbalanced connection as I do, can I benefit by using an XLR/RCA cable?

Avforum members gave a link re considerations of how to build such a cable.

http://www.rane.com/note151.html

 

Any thoughts?

 

[Oystein]

You describe 2 different solutions which are not related to each other.

 

I use the Burson too in my cd-player with great sonic result.

If the DAC has Op-Amps and has balanced outputs then changing the IC Op-Amps to the Burson will not change the connectivity at the outputs. I would guess the Op-Amps are used as parallel twins in differential mode.

Both RCA and XLR should still be working fine when changing the Op-Amps.

There are however some technical issues with the Bursons ... they draw more current than an IC (10 mA went up to 50 mA each) and if you have SMD size IC's instead of full size DIL-8 I wouldn't even consider it.

 

The XLR plugs/cables do not improve the sound by itself.

The only benefit using balanced is the immunity to EMI/RFI distortion on longer cables. Mainly used in studios but hardly worth in a hifi set with max. 1 meter cables.

 

Hopefully this answers your questions ...

 

[patricia1066]

It sounded too good to be true, and it was!

Thanks for that. I suspect that I can get improvements by moving the furniture and speakers, before modding the dac.

 

[4est]

If it were me, I'd try a M2Tech HiFace for about the same investment ($150 USD). It is transferable and salable as well, which a mod is not. FWIW, IME changing from unbalanced to balanced does not net much unless you have issues already (hum, long runs ect.).

 

[patricia1066]

No long runs, just hoping for better sound with a different cable.

 

Is the Hiface intended to connect USB from Revo to the squeezebox?

 

I checked the M2Tech website which says that a linux driver will soon be available. Or is the ALSA driver update suitable? Of course the squeezebox is the limiting factor here as it cannot cope with music above 24/48

 

Update - is anyone else running the Hiface/squeezebox/dacmagic combo?

 

If dacmagic and Hiface was substituted for a cheap dac such as HRT music streamer £139, would this cope better or worse with streaming flac lossless from Vortexbox (fedora 11)?

 

Thanks

 

[4est]

The hiFace is an async USB to spdif reclocker that has really helped some of my DACs. I do not know about the linux though. From what I have heard, it will probably get you farther than a mod. The transmission of the signal is really key, and the hiface has taken a few up a healthy notch. For the money, it is really nice kit!

 

The HRT has an async version too IIRC. It is pricier.

 

[patricia1066]

This comment in Feb 2010, and no update on manufacturer's site, seems to confirm no driver for linux has been provided.

http://www.computeraudiophile.com/content/Are-you-waiting-Linux-driver-m2tech-hiface-device

 

So unless I drop linux in favour of Windows I wont be trying the Hiface.

Thanks for the advice anyway

 

[Audio_ELF]

I may sound defeatist here, but I'm not sure how much improvement you're going to get without some serious changes. As I understand, your player is currently a Squeezebox Classic, this is connected via Ethernet (or WiFi) to an Acer Aspire Revo running Vortexbox Linux distribution. The Squeezebox is connected (via Co-ax or Optical?) to the DAC Magic.

 

You could consider trying a Squeezebox Touch in place of the Squeezebox Classic - there have been reports that there may be a performance / sound quality increase in the newer device. If you use optical, maybe worth trying co-ax cable and vice versa. Another option would be to connect the DACMagic direct to your Revo - IIRC this has an optical output and then run MPD on the Revo to output via optical (or USB).

 

If you haven't already, there have been reports of performance improvements using third-party (linear) PSU with the DAC Magic rather than the supplied adapter, and the same goes for the Squeezebox though most say the improvements here are only applicable if using the analogue output. I'm always skeptical of the improvement vs. the cost of modding DACs, whatever the improvement, a modded piece of equipment is worth far less (often becomes worthless) than the original so if you're happy to loose any second hand value in your DAC then give it a go, otherwise be wary.

 

Beyond all that, I would think you need to be looking at am improved DAC, either direct to your computer or SPDIF from your Squeezebox.

 

Eloise

 

[patricia1066]

The Squeezebox is going to remain, as we have not one but two PCs configured as servers; its simpler for me and my husband to manage our music this way. Or more complicated technically, but simpler on a human level! If any component of the system was to go it would be the dacmagic.

I like the SB3. Great screen and responsive remote; if I could get the file handling improvements of the Touch without the changed form factor I would upgrade. From what I read, the dac in the touch isnt far removed in quality from the Touch so unless I drop the dacmagic no reason to buy it based on the dac.

I have been moving the speakers about and have heard a difference. I also put plugs into the back of the speakers - not sure about this yet.

I use toslink cable between Revo > SB and coax SB3 > Dacmagic.

 

 

[Audio_ELF]

Patricia... you said I use toslink cable between Revo > SB and coax SB3 > Dacmagic.

 

That doesn't make sense as a setup. There should be only Network connection between the Revo and the Squeezebox - either Cat5 crossover or via a hub / switch / router or wireless. Then there should be a single digital (SPDIF) cable - either TOSLink or Co-ax - between the SB and the DACMagic.

 

You could run a TOSLink from the Revo to your DACMagic but that would bypass the Squeezebox so no point in that.

 

Eloise

 

[patricia1066]

You are right Eloise, it is Revo > router > SB3.

 

 

[hytechrednek]

Patricia,

The Single Ended RCA Jacks are not as good sounding as the balanced output. Greatly improved my sound by using an XLR to RCA Adapter.

 

http://www.diyaudio.com/forums/digital-line-level/142184-opening-new-dacmagic.html

 

1) The unit cooks with 12V AC. There is over +/-30V going into the 7815/7915 regs for the output stage. Using a 9V AC unit this comes down to 20V. Sound did not suffer but the unit ran much cooler. (This is in London where my mains is around 250V most of the time - if yours is on the low side you may not have the same headroom, YMMV, etc.) My original PSU melted anyway!

 

2) The output coupling caps (100uf electros with WIMA mkp bypasses) are blocking virtually nothing. I measured all 6 outputs (L, L+, L-,R, R+, R-) and the highest was just under 3mV. I bypassed each pair of caps with wire. The improvement in sound was substantial.

 

3) Each phase of the balanced signal is generated from a pair of DAC outputs. There are two DACs in mono mode, so each DAC is producing a pair of identical balanced outputs, each pair fed into a differential amp (N5532).

L+, L- => L+

L-, L+ => L-

R+, R- => R+

R-, R+ => R-

These are fed to the XLR sockets, and also summed and buffered in the OP275 to produce the unbalanced signals.

Now do we really need to combine them for our unbalanced output? No, just take the L+ and R+ from the XLR sockets and you bypass the OP275 stage. Sounds MUCH better this way. Hook it up both ways and A/B it if you like. Sure you might lose a few dB of S/N or something but you're still getting the benefit of L/R isolation. Looking around the net I see that others have stumbled across this fact too. I made my own adaptors as I didn't want the negative phases shorted to ground like they are in some shop-bought XLR->RCA adaptors (intended for balanced amp inputs).

 

Do 2) and 3) and it's a much better sounding unit, and it was already great.

 

Not being able to resist the temptation to tweak further, mine's currently in pieces with a Zapfilter2 hooked up to it. I had one lying around anyway, though I'd have to re-box the unit to make it permanent, and I'm not sure so far that the improvement is worth the effort.

 

By the way, I think those TI NE5532 are a lot better than the old ones were.