SPDIF not good, how about AES/EBU?

[knoll]

I was reading somewhere that higher quality s/pdif cables have less jitter? Is there any truth to that?

Not unless you're using such a poor quality cable that you're actually getting bit errors. That's the same argument as a fancy HDMI versus a cheap one -- it's all digital, and you either get a perfect picture or bit errors, which are generally very noticeable.

This. Digital either works or not. That's it.

I used to think the same but now I'm not so sure anymore. I've increased my knowledge about digital connections after Cliff's statement about spdif quality. I must state here that I'm no spdif expert so the following may be correct or it may not.

"Digital either works or not". While that is true there still can be jitter issues, i.e. bit value changes too soon or too late.

Jitter is caused if the clock is not perfectly in sync, and no real world clock is ever perfectly in sync. In spdif the clock signal is embedded within the actual signal that is supposedly even worse. Receiver must extract the clock from the signal and that isn't easy to make accurate. Separate clock signal would be better. <wondering why axe doesn't have word clock output?>

SPDIF cable can also cause jittering. Well actually it's not the cable itself but outside RF (and position of the moon) affecting the signal. Now, it probably won't change the intended bit value from zero to one but it can change the point in time where transition from zero to one is happening (zero turns into one too soon or too late, not in sync). That is jitter right there in the cable. So shielding is important in spdif cable. I don't recommend buying any hyped best of all cables. I use diy spdif cable made from normal good quality tv-cable + rca connectors. Tv cables should have pretty good shielding and they are 75ohm, and cheap.

So far I haven't done any jitter measurements on my gear to get into more details.

 

[cloudsplitter]

OK...Got my Blue Jeans cables today. Replaced the cables going to my main studio monitors (Yamaha HS80M's) Old cables were Monster Pro-link Studio Pro cables(Not cheap, at least from a monetary point of view). The Blue Jeans cables were more accurate..cleaner sounding i.e it was easier to distinguish different elements of the mix....The stereo field was more pronounced..There seemed to be more "air" to the sound, which gave it a more pristine quality. I didn't think I would be able to hear much difference...I was way wrong....!! My Axe FX Ultra will be here Friday I'm guessing so I will be able to see how the S/PDIF cables size up. I did notice upon cutting away some of the coating off the Monsters they are using twisted copper wiring where Blue Jeans is solid core.

 

[Casper]

On Monster - maybe 6-7yrs ago, I figured I'd buy a 20' Monster guitar cable to see what all the hype was about. It was advertised with a lifetime warranty. Because I went thru about 1 cable every 6 months, I figured I'd get my money's worth.

Well, it hasn't failed yet and it takes the same abuse all my other cables took and they failed. In this particular case, I am satisfied even though I never had to use the warranty.

For all other cables, I make my own. I have spare guitar cables I've made and use sometimes. I am happy with cheap cables too, though I am a fan of quality plugs (Neutrik I like). If the Monster fails, it has the warranty, so I just get a new one right? It sounds fine.

 

[SparkyG]

Iv'e been using LavaCable for few years. Did a few tests agains George L's and Planet Waves, Lava sounded better to me.

Pre axe-FX I had a hugely complex pedal board all with Lava ELC cable, and using 4CM type set up with a Cornford head I was using a lot of cable. It's good stuff, and Mark , the owner was very helpful.

Never Tried Monster stuff. These Days Live I'm using a Line 6 Digi Wireless (and a small piece of Lavacable) - And I'm happy, in the studio, it's lavacable.



YMMV.

 

[grunge782]

Hi I read a thread yesterday where Cliff said that SPDIF is typically not as good as the normal audio out jacks. Does that also go for the AES/EBU jacks? I just realized that my MOTU sound interface supports AES/EBU as well.

Could you provide a link to that thread?

 

[cloudsplitter]

I just ordered a lava instrument cable...Blue Jeans doesn't make instrument cables. I did A/B my new Blue jeans mic cable against my Monster studio 1000 series..(thier top model) and the blue jeans blew it out of the water totally....way more depth and clarity. One thing I noticed about monster cables is they all sound incredibly dull and lifeless...that's not good. anyone want about $1000.00 worth of monster cables real cheap...??

 

[rsf1977]

blue jeans will do 1/4" jack cables just email them what you want i just got an order placed with them, they are top notch with helping customers out.

 

[cloudsplitter]

Hey Rsf, I emailed them two times and never got a response...! I did, however receive my cables in one day...!! I only live 30 minutes from their shop though. I will refit my studio with their cables but it is going to take some time.....

 

[rsf1977]

hey lava is great too, almost everything i have is from them. I think Blue Jeans is more geared toward Audio Engineers rather then giging musicians. they don't offer much for instrument uses. Lava is perfect for that kind of stuff.

 

[cloudsplitter]

hey lava is great too, almost everything i have is from them. I think Blue Jeans is more geared toward Audio Engineers rather then giging musicians. they don't offer much for instrument uses. Lava is perfect for that kind of stuff.

Yeh, I got the tip for Lava on here.....so, thought I would give them a shot...hopefully it will arrive friday with my Ultra.......that way I won't have to violate the purity of my Ultra with a monster cable...LOL

 

[Robboman]

I have a Monster guitar cord and it's the BEST cable ever! It came along with a used Martin acoustic/electric I bought from a rich beginner who gave up on learning the guitar. This smart gentleman paid only $120 for it. What a steal! It has these classy wooden inlays on the golden 1/4 plug ends. Beautiful Monster logo on the wooden inlay. The best part is the cable itself, it has little directional arrows labled 'signal flow'. Yes, they indicate which direction the signal flows inside. Does your cable do that? :mrgreen:

Since I got my signal flowing in the right direction my tone has never been better. The connector wood really enhances the tone. Best of all, now I always get jelaous, approving looks every time I whip out my Monster at a show. Everyone knows how much I rock now.

 

[grunge782]

Could someone please give me the link for the thread with Cliff talking about S/PDIF being "inferior" for recording? Or could somebody explain it to me? It doesn't make sense considering you don't deal with the A/D/A conversion...Arg... :evil: :evil: :evil: :evil:

 

[cloudsplitter]

Could someone please give me the link for the thread with Cliff talking about S/PDIF being "inferior" for recording? Or could somebody explain it to me? It doesn't make sense considering you don't deal with the A/D/A conversion...Arg... :evil: :evil: :evil: :evil:

Here you go Grunge ...!!
viewtopic.php?f=11&t=12800&p=122365&hilit=s%2Fpdif#p122365

 

[onemoreguitar]

If that's the thread yall've been talkin about then he isn't saying that spdif is bad. He is saying that spdif is only as good as the convertor that your plugging in, which is common knowledge to anyone who's worked with digital audio in the past couple decades. It wasn't a big epiphany. He was talking to someone that was plugging the spdif outs into a cheap desk with rubbish convertors and thus limiting the quality of his final sound to the low quality of the cheap convertors in his desk. If you're plugging your AFX into a high end D/A, then your digital sound will be just fine. That being said, the D/A in the AFX is already top notch so why bother unless have an uber HQ D/A. Not many people have that. The chances are, IME, if you have D/A convertors of equal quality to the AFX's, your analogue inputs will still be better again. D/A conversion is a common place to cut corners. For the most part, it's quite rare to have high quality digital conversion and low quality analogue.

All IME, YMMV and all that stuff....

 

[knoll]

Below are few connection options. To focus on spdif connections and D/A conversion let's assume that analog and firewire connections are of good quality.

A) axe ---<analog> --- audio interface w/crappy D/A ---<analog>--- monitors
B) axe ---<digital/spdif>--- audio interface w/crappy D/A ---<analog>--- monitors
C) axe ---<analog>--- audio interface w/crappy D/A ---<digital/firewire>--- daw
D) axe ---<digital/spdif>--- audio interface w/crappy D/A ---<digital/firewire>--- daw

- A is good. Axe handles the D/A conversion and rest of the chain is analog
- B sucks because of crappy audio interface D/A conversion
- C is good as long as audio interface has good A/D conversion
- D could be good? Depending on how good the spdif connection is, i.e. how accurately can the audio interface reconstruct the signal. That's what we are discussing here, right?

1) axe ---<analog> --- audio interface w/über highend D/A ---<analog>--- monitors
2) axe ---<digital/spdif>--- audio interface w/über highend D/A ---<analog>--- monitors
3) axe ---<analog>--- audio interface w/über highend D/A ---<digital/firewire>--- daw
4) axe ---<digital/spdif>--- audio interface w/über highend D/A ---<digital/firewire>--- daw

- 1 is good. Axe handles the D/A conversion and rest of the chain is analog
- 2 could be good? The D/A conversion would be top notch for sure but how about the spdif connection from axe to the audio interface, i.e. how accurately can the audio interface reconstruct the signal. That's what we are discussing here, right?
- 3 is good as long as audio interface has good A/D conversion
- 4 could be good? Depending on how good the spdif connection is, i.e. how accurately can the audio interface reconstruct the signal. That's what we are discussing here, right?

 

[aftec]

4) axe ---<digital/spdif>--- audio interface w/über highend D/A ---<digital/firewire>--- daw

- 4 could be good? Depending on how good the spdif connection is, i.e. how accurately can the audio interface reconstruct the signal. That's what we are discussing here, right?

In theory if you use 48Khz/24bit (what the Axe supports native ) on your DAW the SPDIF and Firewire is just a phisycal layer for data transport. There is no DAC or SRC involved in this situation.
The digital signal gets from the AXE to your DAW unchanged. Of course when you play back you will utilize your DAC, but that's a different story.

 

[grunge782]

Could someone please give me the link for the thread with Cliff talking about S/PDIF being "inferior" for recording? Or could somebody explain it to me? It doesn't make sense considering you don't deal with the A/D/A conversion...Arg... :evil: :evil: :evil: :evil:

Here you go Grunge ...!!
viewtopic.php?f=11&t=12800&p=122365&hilit=s%2Fpdif#p122365

404 not found

 

[grunge782]

4) axe ---<digital/spdif>--- audio interface w/über highend D/A ---<digital/firewire>--- daw

- 4 could be good? Depending on how good the spdif connection is, i.e. how accurately can the audio interface reconstruct the signal. That's what we are discussing here, right?

In theory if you use 48Khz/24bit (what the Axe supports native ) on your DAW the SPDIF and Firewire is just a phisycal layer for data transport. There is no DAC or SRC involved in this situation.
The digital signal gets from the AXE to your DAW unchanged. Of course when you play back you will utilize your DAC, but that's a different story.

This is what I was thinking, if you used even a cheap interface with SPDIF and firewire your DAW would still receive a "pure" signal with no conversion right?

 

[onemoreguitar]

The other part of Cliff's post is talking about the ability of the chip to decode the clock that's embedded in the signal.

Staying digital would be desired in a synchronous system. However, in the OP's configuration the system isn't synchronous. The mixer is running at one sample rate and the SPDIF in must be matched to that rate. Even if the rate is the same (i.e. the mixer is 48 kHz) it's not synchronous and therefore requires sample rate conversion (SRC). In this case the SRC would, for example, be 48.001 kHz to 47.999 kHz. The point being the clocks aren't locked.

and also

Sample rate and bit depth have nothing to do with the quality of SRC conversion. Even the lousy chips will do 192 kHz at 24 bits. Furthermore, it says nothing about the quality of the clock recovery and attendant jitter. The reason SPDIF is a lousy format is because you have to recover the clock from the data stream. SPDIF uses Manchester encoding to "embed" the clock in the data. The amount of phase noise in the embedded clock is large due to a 180 degree binary distribution. The receiver PLL locks on to the clock but it's constantly getting yanked back and forth by the phase distribution. The PLL bandwidth has to be large enough to deal with the frequency stability but this is at odds with the desire for low clock jitter.

The Axe-Fx doesn't use any SRC. That's why the output is locked to 48 kHz.

It all comes down to the quality of unit you're plugging in to. If you have to ask whether the chips in the piece of gear you're using are high quality enough to run digital with low jitter, then they're probably not.

Just use analogue outs unless you absolutely have to, but there is no reason, based on sound quality, to use the digital outs. If the analogue sections of your gear are significantly degrading your signal, than the digital side will more than likely be even worse IME.

BTW, these issues aren't particular to the AFX. Lots of people have have been on a digital signal chain trip for a while now. The thinking is that digital is just 1's and 0's and can't be affected like analogue. While that's correct, it only holds true if everything in the digital chain is synched. It's also assuming that the signal was accurately converted to those 1's and 0's in the first place, and that those 1's and 0's are accurately converted back to analogue audio at the other end of the chain. Same as analogue, there is no cheap route to quality and the final signal is only as good as the weakest link in the chain.

All above is IME, IMHO, YMMV and all the rest.

 

[aftec]

It all comes down to the quality of unit you're plugging in to. If you have to ask whether the chips in the piece of gear you're using are high quality enough to run digital with low jitter, then they're probably not.

Just use analogue outs unless you absolutely have to, but there is no reason, based on sound quality, to use the digital outs. If the analogue sections of your gear are significantly degrading your signal, than the digital side will more than likely be even worse IME.

BTW, these issues aren't particular to the AFX. Lots of people have have been on a digital signal chain trip for a while now. The thinking is that digital is just 1's and 0's and can't be affected like analogue. While that's correct, it only holds true if everything in the digital chain is synched. It's also assuming that the signal was accurately converted to those 1's and 0's in the first place, and that those 1's and 0's are accurately converted back to analogue audio at the other end of the chain. Same as analogue, there is no cheap route to quality and the final signal is only as good as the weakest link in the chain.

All above is IME, IMHO, YMMV and all the rest.

In a sync scenario like using 48/24 on the DAW, the SPDIF clock signal is not used for reconstructing audio data.