DACing Off

[veloaudio]

Okay, so I finally got all my digital pieces of gear hooked up and I've been comparing my DAC-2000 and DAP-777 for the past hour or so with the following setup:

Notes:

-The optical switch was to be able to take out the Digital Lens if desired however the Lens makes it easier to switch back and forth between DACs since all the digital outputs are always on. Therefore I've used the Lens for all my listening.

-The NAD will switch between inputs with virtually no delay so there is no need to stop the music when I'm listening.

-I'm making the assumption that Coax = AES/EBU. I've read that Coax > AES/EBU and vice versa. I don't have an opinion as using both is the only way I can setup everything up. I could switch the coax and AES to opposite DACs but I have not done that yet. I could also get a 1-2 coax adapter I guess?

- Both DACs have manufacturer claimed SE output voltages of Reimyo - 2.45 Vrms and Parasound 2.75 Vrms. The difference is 0.3 Vrms which is 0.85 Vpp. I would think I'd be able to hear a volume difference but I can't.

- The DAP-777 has an upgraded power supply. All equipment is plugged into my BPT BP-1

Now for my testing

I've been listening to a variety of familiar music. I've avoided HDCD material to keep that out of the comparison. I switch back and forth (using the NAD remote) so it is not a blind test and I can't tell a difference!

Anyone see something I'm missing?

[Dusty Chalk]

Now for my testing

I've been listening to a variety of familiar music. I've avoided HDCD material to keep that out of the comparison. I switch back and forth (using the NAD remote) so it is not a blind test and I can't tell a difference!

Anyone see something I'm missing?

Well, you could go double-blind, but wouldn't really surprise me if you couldn't tell the difference. Not you, personally, but...anyone.

Also, you could now try two weeks at a time, to test for the fatigue factor.

[The Monkey]

The truth is, it can be hard to tell differences between these damn things. Also, the specs on the output voltages can be misleading. However, I'd like to know more about the Toslink switch in there. What make/model?

[Grahame]

This one?

HDMI Cable, Home Theater Accessories, HDMI Products, Cables, Adapters, Video/Audio Switch, Networking, USB, Firewire, Printer Toner, and more! $6.34!

And just because balanced / xlr may be better for audio frequency signals, don't assume the same applies to RF digital signals.

Its nice to know someone else agrees with me about AES EBU, I always thought I was the lone voice in the wilderness.

Anyway I see two main reasons for the inferiority of AES/EBU.

1. XLRs are horrible RF connectors. In order to send a square wave fairly faithfully the interface must support a bandwidth many times higher than the frequency of the square wave. For the signals in question that is getting well up into the RF spectrum where the XLRs are terrible. The impedance varies radically with frequency which will cause all kinds of bizarre reflections. The choice of XLR was a very poor choice.

2. Output voltage. The S/PDIF electrical spec is 0.5V into 75ohms, but the AES/EBU is 3-5V into 110 ohms. Think about that for a second, what happens when you put 5volts across 110 ohms? You get almost 50mA of current flowing. This means the driver sitting in the source box has to be able to dump between 30-50ma into the cable. That causes huge current spikes in the power and ground pins of the driver chip which is going to cause big noise spikes in the power and ground planes of the board. If you are not extremely careful that is going to cause significant jitter in the output signal.

All modern high speed interfaces use less than 0.5V signal.

As far as I can tell the XLRs were chosen because studios had lots of microphone cables and wanted to use them. Because they are such lousy RF transmission lines they had to go with high voltages to make sure there was some signal left at the end.

John S.

Squeezebox : Community : Forums - View Single Post - Help: Best new device for audiophile with DAC?

[veloaudio]

This one?

HDMI Cable, Home Theater Accessories, HDMI Products, Cables, Adapters, Video/Audio Switch, Networking, USB, Firewire, Printer Toner, and more! $6.34!

And just because balanced / xlr may be better for audio frequency signals, don't assume the same applies to RF digital signals.

Its nice to know someone else agrees with me about AES EBU, I always thought I was the lone voice in the wilderness.

Anyway I see two main reasons for the inferiority of AES/EBU.

1. XLRs are horrible RF connectors. In order to send a square wave fairly faithfully the interface must support a bandwidth many times higher than the frequency of the square wave. For the signals in question that is getting well up into the RF spectrum where the XLRs are terrible. The impedance varies radically with frequency which will cause all kinds of bizarre reflections. The choice of XLR was a very poor choice.

2. Output voltage. The S/PDIF electrical spec is 0.5V into 75ohms, but the AES/EBU is 3-5V into 110 ohms. Think about that for a second, what happens when you put 5volts across 110 ohms? You get almost 50mA of current flowing. This means the driver sitting in the source box has to be able to dump between 30-50ma into the cable. That causes huge current spikes in the power and ground pins of the driver chip which is going to cause big noise spikes in the power and ground planes of the board. If you are not extremely careful that is going to cause significant jitter in the output signal.

All modern high speed interfaces use less than 0.5V signal.

As far as I can tell the XLRs were chosen because studios had lots of microphone cables and wanted to use them. Because they are such lousy RF transmission lines they had to go with high voltages to make sure there was some signal left at the end.

John S.

Squeezebox : Community : Forums - View Single Post - Help: Best new device for audiophile with DAC?

That's the switch.

That write-up on AES makes sense to me. I'll try swapping the coax and AES.

After the swap I'll do extended listening with each.

[Voltron]

It seems to me that you are doing lots of things that make the two sources more blurred and more alike than different. If you want to hear the two sources, then take out all the other crap and compare Mac > Reimyo > G-Lite and then Mac > Parasound > G-Lite. Use the same cables to the extent you can, definitely using the same Toslink and the same RCAs, and just do a straight-up comparison listening to one and then the other. If you really have to be able to switch back and forth, then use the Toslink splitter and plug the output of both DACs into the NAD and use the tape out. I think that will affect the comparison, but you can get the satisfaction of A > B switching.

I also may be hated for saying this, but the G-Lite is not the most resolving amplifier of all time to do comparisons on this level. If you can compare with a better amp with two inputs, then you can also remove some steps and some limitations.

[Pars]

I'd agree with Al, and with the John Swenson quote (I assume that was him as John S?). Get rid of the switch. Simplify and isolate the variables.

[Currawong]

The truth is, it can be hard to tell differences between these damn things. Also, the specs on the output voltages can be misleading. However, I'd like to know more about the Toslink switch in there. What make/model?

I got a bit of a shock a couple of days ago when I decided to compare the output of the Fun (with DIR9000/AD1852/HDAM) to the Ref 1. When I switched between them in the midst of a song, I could initially hear no difference. Knowing that both would have been voiced the same and that tonal differences are much easier to spot than detail and that they likely have similar output voltage and impedance might explain things. It could also be that the Fun has a great DAC or that the Ref 1 is really just not that great, or my hearing is or has gone to shit. I tried both with a Phoenix and HD-800s and a T1 with LNS, and switching to a CDP as a source and the result was the same, though after some time listening the differences started to become apparent. When I compared a DAC19MKIII w/PMD100 to the Ref 1 there was not a small difference, nor with the Ref 1 to Assemblage DAC 3.0, but that was distinctly a tonal difference at the very least. Maybe I need to pay more attention to the electrical properties of the output and input of gear I have or play with.

[The Monkey]

MOAR SKIPJACK!

Also, good stuff here: http://www.inday.com/

Edited February 17, 2010 by The Monkey

[dreamwhisper]

Okay, so I finally got all my digital pieces of gear hooked up and I've been comparing my DAC-2000 and DAP-777 for the past hour or so with the following setup:

Anyone see something I'm missing?

Were you using your JH13's or speakers?

For speakers I can't see just an inegrated amp etc doing the job. I use studio monitors in a treated room. (built specifically with no parallel walls, auralex foam everywhere)

But I'm sure your JH13's are up to the task... so try using them if you aren't already.

If you still can't notice a difference listen maybe try listening to new songs that you aren't familiar with. When I do this I find I am more willing to listen for longer before labeling and defining what I'm hearing.

I'm getting even more curious now to compare the Assemblage 2.6 and the Parasound 1100...

[veloaudio]

It seems to me that you are doing lots of things that make the two sources more blurred and more alike than different. If you want to hear the two sources, then take out all the other crap and compare Mac > Reimyo > G-Lite and then Mac > Parasound > G-Lite. Use the same cables to the extent you can, definitely using the same Toslink and the same RCAs, and just do a straight-up comparison listening to one and then the other. If you really have to be able to switch back and forth, then use the Toslink splitter and plug the output of both DACs into the NAD and use the tape out. I think that will affect the comparison, but you can get the satisfaction of A > B switching.

I also may be hated for saying this, but the G-Lite is not the most resolving amplifier of all time to do comparisons on this level. If you can compare with a better amp with two inputs, then you can also remove some steps and some limitations.

Excellent points. As far as an amp goes, the G-Lite is all of I've got. I'd love to try a different amp but I'm at the point now where I've had way too many boxes arriving at the house compared to leaving.

I'd agree with Al, and with the John Swenson quote (I assume that was him as John S?). Get rid of the switch. Simplify and isolate the variables.

I was hoping to be able to A/B quickly but that may be the problem. The suggestion to simplify and isolate sounds like the right approach. My main concern being my memory and being able to accurately compare.

Were you using your JH13's or speakers?

For speakers I can't see just an inegrated amp etc doing the job. I use studio monitors in a treated room. (built specifically with no parallel walls, auralex foam everywhere)

But I'm sure your JH13's are up to the task... so try using them if you aren't already.

If you still can't notice a difference listen maybe try listening to new songs that you aren't familiar with. When I do this I find I am more willing to listen for longer before labeling and defining what I'm hearing.

I'm getting even more curious now to compare the Assemblage 2.6 and the Parasound 1100...

The listening was late at night so I was only using my JH13s. Good suggestion on the music. I'll give that a shot.

[Dreadhead]

I was hoping to be able to A/B quickly but that may be the problem. The suggestion to simplify and isolate sounds like the right approach. My main concern being my memory and being able to accurately compare.

I disagree with Al and Pars. Keep the switch the longer you have between the two the less chance you have of remembering what they sound like. Another option (which may have been mentioned) is to use a splitter on the toslink and feed both DACs at the same time or use two digital outputs of the transport at the same time, volume match and get a passive swtich like a skipjack or one of these which is what I use:

Kramer | VS-4X 4x1 Balanced Stereo Audio Switcher (XLR) | VS-4X

I would not be suprised at all if you can't hear a difference. I can't between my DACs.

[veloaudio]

I disagree with Al and Pars. Keep the switch the longer you have between the two the less chance you have of remembering what they sound like. Another option (which may have been mentioned) is to use a splitter on the toslink and feed both DACs at the same time or use two digital outputs of the transport at the same time, volume match and get a passive swtich like a skipjack or one of these which is what I use:

Kramer | VS-4X 4x1 Balanced Stereo Audio Switcher (XLR) | VS-4X

I would not be suprised at all if you can't hear a difference. I can't between my DACs.

My planning for the setup was to minimize the switch time. Another added benfit of the Lens is that both DACs stay "locked" on to the signal the entire time. The optical switch, while nice, is not easily switched (by design I'm sure), so there would be a delay in switching the optical input and letting the DAC lock on. The NAD really surprised me with its switching capabilities. I expected the need to volume match but I have not been able to detect a volume difference.

A note about interconnects, both analog ICs are the same wire and connectors, although one pair is shorter than the other.

I've kept an open mind about the comparison. I'm not assuming one DAC would be betterthan the other. My only expectation was/is that I would be able to hear a difference. Maybe I never will.

[Dreadhead]

Sorry. I dd not read the whole thing carefully about the interconnection but it seems like you've got it right. I prefer passive switches just because they are inert but if it's going through the same nad circuits for both dacs then it should be much the same right?

As long as the two cable runs are about the same and not LONG there shouldn't be much difference. In very long runs the cable can make a difference.

A way to check the volume difference is to play a test tone CD and check the voltage with a multimeter or the volume with an SPL meter. The fact you can't hear a difference probably points to the match being pretty good.

[The Monkey]

I get it better now, too. The switches aren't really the issue because the NAD is acting as the switch, right? Reading comp fail by me.

HOWEVER, I would like to know a little bit more about how things are working in the Genesis. Is it possible that only one DAC is coming through?

[veloaudio]

I get it better now, too. The switches aren't really the issue because the NAD is acting as the switch, right? Reading comp fail by me.

HOWEVER, I would like to know a little bit more about how things are working in the Genesis. Is it possible that only one DAC is coming through?

The optical switch is not really needed in the current setup so it stays in one position. The Genesis is before the DACs. It buffers the digital data from the Macbook Pro and sends it out via digital outputs (Coax, AES/EBU, Glass) to the DACs.

[The Monkey]

Ok, so the outputs of the DACs are always hot and they go directly to the NAD for switching, right?

[veloaudio]

Ok, so the outputs of the DACs are always hot and they go directly to the NAD for switching, right?

Yes, the only switching is done by the NAD. So I'm able to switch instantly (well, close enough) between the two DACs. No stopping music or moving cables. I could replace the NAD with a switch box but I'd get the same result.

[Dusty Chalk]

I use studio monitors in a treated room. (built specifically with no parallel walls, auralex foam everywhere)

Jesus, pics plz? (Feel free to post in 'post pics of your rigs' or something.)

[Eric5676]

Jesus, pics plz? (Feel free to post in 'post pics of your rigs' or something.)

I'd like to see pics of his setup as well!

[Voltron]

Jesus, pics plz? (Feel free to post in 'post pics of your rigs' or something.)

Here's a quick drawing:

[dreamwhisper]

Jesus, pics plz? (Feel free to post in 'post pics of your rigs' or something.)

haha, I have been meaning to do it for a while,

I'll prbly have some up later tonight/tomorrow