S/PDIF Truly Untouched?

SonicExplorer

Member
Messages
35
Hi,

I want to bounce something off the forum to see if I understand something correctly or not....

The scenario invlves a guitar sim (for example Fractal or Kemper, etc) into a DAW interface (for example a Fireface 400 /800 or similar) and using powered monitors (analog input)

So the chain looks likes this: Guitar --> SimUnit --> DAW Interface ---> Monitors

My understanding is that if I were to run analog out of the guitar sim into the DAW interface then what is recorded goes through an A/D converter, and what comes out the monitors/phones has gone through an D/A converter. The D/A converter therefore plays no role in the signal quality of what is recorded or later being mixed.

Having said all that, here's the question: If I instead run S/PDIF out of the guitar sim into the DAW interface, am I correct to assume the signal then bypasses A/D conversion and as such remains untouched? So what gets recorded is pristine without any alteration or coloration. Granted, what I hear via monitors while recording or during playback is still touched by D/A converter, but what is recorded is untouched. Am I correct in this understanding or does each DAW interface potentially impose coloration to some extent even via S/PDIF? Asked another way, if the guitar sim was clock master then a track recorded via S/PDIF should end up the same using a $100 soundcard or a $3000 sound card.

Thanks,

Sonic
 

cubistguitar

Member
Messages
6,217
Any digital connection like s/pdif skips the preamps and converters. You already hit pres and converters in the guitar amp sim. That is really your interface, the device with the s/pdif is more or less a pass-thru gateway to your computer. Often these guitar amp sims have all the needed components to completely replace the interface in question, maybe you don't need the interface with the digi connection. Could you monitor the DAW signal thru the stereo outs on the "Kemper" ?
 

Rex Anderson

Member
Messages
5,524
Every analog signal has to go through A/D to get recorded digitally and D/A to get converted back to analog to be monitored.

Quality of A/D and D/A is always a factor. You want to minimize the number of conversions.

Go out of your guitar sim via the S/PDIF into the DAW digital in. Come out of the DAW via it's D/A (analog out) and go to monitors, unless you have monitors with D/A built in.
 

SonicExplorer

Member
Messages
35
Thanks guys, you confirmed what I always believed, just wanted to double check. I'm getting frustrated because, after purchasing a rather costly guitar amp simulator, it is now becoming apparent my Fireface 400 has been coloring distorted amp tones - in a kind of harsh manner in the upper frequencies. So I just wanted some assurance that what is being recorded via S/PDIF is at least "pristine" even though it may not sound quite the same after being converted D/A on the way out. The tones sound wonderful via monitor headphones on the amp sim, but if I plug those same headphones in the Fireface it becomes cold/harsh and more scratchy in the upper registers. Keep in mind, I have ears like a bat when it comes to this stuff but I can still hear it. I thought when I bought the FF400 back many years it would do the job as an upgrade to my M-Audio/Delta setup, but now I'm having major second thoughts on that decision. Shame because that unit was NOT cheap. It's great functionally, but at the end of the day it's all about tone quality.

Ugh...well, at least I know it's not tracking that way, it only is an issue for what I'm hearing when monitoring. And of course mixing, but once everything is layered into a mix I suspect it won't be as much of an issue. I hope not anyway.
 
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cubistguitar

Member
Messages
6,217
Thanks guys, you confirmed what I always believed, just wanted to double check. I'm getting frustrated because, after purchasing a rather costly guitar amp simulator, it is now becoming apparent my Fireface 400 has been coloring distorted amp tones - in a kind of harsh manner in the upper frequencies. So I just wanted some assurance that what is being recorded via S/PDIF is at least "pristine" even though it may not sound quite the same after being converted D/A on the way out. The tones sound wonderful via monitor headphones on the amp sim, but if I plug those same headphones in the Fireface it becomes cold/harsh and more scratchy in the upper registers. Keep in mind, I have ears like a bat when it comes to this stuff but I can still hear it. I thought when I bought the FF400 back many years it would do the job as an upgrade to my M-Audio/Delta setup, but now I'm having major second thoughts on that decision. Shame because that unit was NOT cheap. It's great functionally, but at the end of the day it's all about tone quality.

Just a quick look at the web, suggests that a Fractal is a complete audio interface and you could skip the FF400 entirely. Kemper usb is just a program manager connection and a separate interface is required to send to common DAW setups. The best and most pertinent features of the FF400 are the firewire (kinda old school now), 8 total inputs, the 6 balanced outputs, and a good clock, with clock in(clock from another unit) and out(clock provided by FireFace). If you are not using all that feature set, maybe let it go into the closet and work with what sounds nice. Maybe one of the newer usb units would work for you too, I see several high end companies making smallish interfaces for home studios, like the Prism Lya series and the Lynx HiLo, maybe you would like one of those even better, they get good reviews for the outputs and functionality, you know the FF400 is 10 yr old tech now.
 

loudboy

Member
Messages
27,306
The tones sound wonderful via monitor headphones on the amp sim, but if I plug those same headphones in the Fireface it becomes cold/harsh and more scratchy in the upper registers.

The FF may also have a less than great headphone amp. How does it sound patched directly into your monitors?

To your original question, yes, the digital in will give you the best fidelity.
 

jdogric12

Member
Messages
2,582
Good to know! I have an old original version Fender Cyber Twin. I record using the S/PDIF output (into my Saffire Pro 40). It's a bit tricky to keep it at a low enough level to avoid digital clipping, but it sounds pretty darn good. Only drawback is I have to stay in the stone age with 16/44.1, but hey if it's good enough for CD's, right?
 

Motterpaul

Tone is in the Ears
Messages
13,921
I have an Avid ElevenRack guitar interface. It has guitar in and is primarily a guitar effects unit, but Protools also sees it as a separate interface (it also has a mic preamp input and s/pdif in/out as well as monitor in/out).
 

SonicExplorer

Member
Messages
35
The FF may also have a less than great headphone amp. How does it sound patched directly into your monitors?

That's what I'm wondering if maybe the headphone amp isn't the greatest. Actually tho...I *think* the way the FF400 handles that is it actually uses the last two analog channels out (7/8) to drive the headphones somehow with a stronger signal. I got the impression it's not a conventional headphone amp per-se.

I'm not sure how to answer about the sound on the monitors because its all relative. I only know the headphone outs on the FF400 are not the greatest because I am able to compare it directly to the headphone output on the guitar sim unit (in this case a Kemper). The quality of that is clearly above the FF400. BTW, am using rather nice monitor headphones, not some garbage.
 




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