TDM / RTAS Comparison
Old 14th April 2004
  #1
Gear nut
 

Thread Starter
TDM / RTAS Comparison

Hi everyone,
Just a quicky! Im interested to know how RTAS plugs compare against TDM in terms of quality. I used to use a Mix plus system at my old university and now id like to invest in PT LE for my home studio. Many of the plugs i used in TDM are also avaliable in RTAS, but im concerned that they wont sound as good running natively - Waves TDM sound notably different to Waves DX imo.

Any thoughts?
Old 14th April 2004
  #2
FX smörgåsbord user
 
Charles Dye's Avatar
 

On TDM systems you can convert plugs over to RTAS if you have the RTAS version installed. Whenever I've done it I've not noticed a sound difference.
Old 14th April 2004
  #3
Gear nut
 

Thread Starter
Really? Thats supprises me considering the cost difference between TDM and native versions. I use Waves DX with Cubase SX right now, but im seriously considering moving to PT LE. If the RTAS plugs are indeed of similar quality to their DSP powered brethren, then thats great.

Cheers!
Old 14th April 2004
  #4
Lives for gear
 
Jose Mrochek's Avatar
 

I'm assuming that the price difference comes in , at the A/D - D/A converters on TDM Hardware, and that it's expandable when linking I/O's together... Is that true Charles or are there more reasons ???
Old 14th April 2004
  #5
Lives for gear
 
Mike Jasper's Avatar
 

Quote:
On TDM systems you can convert plugs over to RTAS if you have the RTAS version installed. Whenever I've done it I've not noticed a sound difference.
I've heard that said by other Pro Tools users at the Digidesign forum. It's reassuring to us LE users.

Jasper
Old 15th April 2004
  #6
Gear nut
 

Thread Starter
Quote:
Originally posted by tee boy
Really? Thats supprises me considering the cost difference between TDM and native versions. I use Waves DX with Cubase SX right now, but im seriously considering moving to PT LE. If the RTAS plugs are indeed of similar quality to their DSP powered brethren, then thats great.

Cheers!
Indeed, thats a question i would very much like answering myself. PT HD is clearly aimed at professional studios and has a price tag to match, but what are the 'real' differences between HD and LE systems. I think i goes without saying that the digital coverters are in a different league, and I know that HD can work with higher track counts... but is that about it? Im sure that the higher end TDM plugs could easily be matched if not bettered with hardware, so the lack of TDM support wouldnt be that much of a loss.

The reason i ask is that Im currently planning some major studio purchases and Im considering two options - go PT HD and pretty much max out my budget, or go with LE and add some nice outboard (SSL 384, Apogee Rosetta 800, Avalon 737, Neve 1272, Lexicon PCM91). I already have a load of VST plugs that I could use including Waves Platinum, Sonalksis, PSP etc. Is there any reason at all for me to opt for a HD system?

PS Sorry, I meant to quote Jose, doh!
Old 15th April 2004
  #7
Gear addict
 
Will's Avatar
 

I have two PT LE platforms (MBox and 002 rack) but use Mix systems alot.

I'm not sure about the sound difference between LE and a full system, but the advantage of a full system (IMO) defeats alot of PT problems during a session.

For example the issue of the latency caused by using an LE setup whilst tracking (this causes loads of problems because you have to use a hardware mixer).

The benefits of HD (other than said comparisions between RTAS and TDM) is that you can easily work in one field, that being Pro Tools. Having worked with LE and an out board mixer I found that I couldn't consentrate on the music properly because I had to worry about headphone mixes, which converter to use blar blar that could have easily been solved using PT if there was no latency.

Going HD would solve these problems. Also, I have found that TDM systems are more stable than LE systems (esp firewire systems such as the 002) which is a big consideration when working. I recently tracked a classical session where my firewire system 'read/wrote wrongly', and the audio was gone. Not good. I have never experienced this on a full system.

I'd go HD and start saving for those bits of out boardthumbsup

Will.
Old 15th April 2004
  #8
Lives for gear
 
Berolzheimer's Avatar
 

TDM & RTAS do their math slightly differently; TDM does it's processing 48 bit linear, RTAS is 32 bit floating point. Which is better? I can't tell you. There are slight differences, I've found that sometimes after processing a file each way with the same settings that the resultant peak level is slightly different- by one or 2 tenths of a dB. I don't know that I've ever found a qualitative difference though.

Hey Bob O, care to wiegh in here? Something tells me you have an opinion RE 48 bit lin VS. 32bit float.
Old 15th April 2004
  #9
Motown legend
 
Bob Olhsson's Avatar
I did a pretty extensive comparison between a PT-24 TDM system at the studio and PT-le 5.0 at home. My conclusion was that PT-le was at least as good and in some cases better because many 32 and 64 bit float plug-ins can't be overloaded. The only "gotcha" besides the latency is that the mixer output isn't dithered however an L1 set to 24 bit solves the problem. Hopefully somebody will bring out a 24 bit dither plug-in to save the DSP and latency of using an L1.
Old 15th April 2004
  #10
Gear nut
 

Thread Starter
Right, so it seems that one of the major cons of LE is the latency issue. Im suprised this has not been addressed, expecially considering that Cubase SX offers both direct monitoring and plug in delay compensation! Is there anyway around this problem for LE users?
Old 15th April 2004
  #11
Gear maniac
 
hammer's Avatar
 

Quote:
Right, so it seems that one of the major cons of LE is the latency issue. Im suprised this has not been addressed, expecially considering that Cubase SX offers both direct monitoring and plug in delay compensation! Is there anyway around this problem for LE users?
Um, well I believe digi is addressing latency delay comp in tools 6.4 (due out in a few weeks if it's not out already)

As long as your running LE on a Hi end PC or g5 latency isn't such a huge deal till you start maxing out the system with plugs. You shouldn't have to worry about an outboard mixer with an LE system. The latency is low enough to do headphone mixes and external reverb sends.

Latency is always gonna be better on a TDM system, and it remains constant cause the plugs are running seperately to the CPU. You can have a MUMUNGOUS session running and not have to worry about disabling plugs and stuff to do that alll important kazoo overdub.

the big one tho is that LE is limited to 32 tracks. Which is a real PITA sometimes.

Why r u thinking about going tools? If you're doing the whole commercial facility and compatibility with everyone thing then go for it. If it's for your own private stuff then why not stick with cubase? If a native plug RTAS, VST Direct X AU whatevever has a TDM equivalent they will sound and work the same. TDM plugs really come into their own when there is a bonza plug that ONLY exists in the TDM environment. (massenberg, reverb one etc) U sound like you already have an awesome collection of plugs. Moving to protools won't make them sound any better.
Old 16th April 2004
  #12
Gear nut
 

Thread Starter
Hey, thanks everyone for the advice! Much appreciated.

The fact that Im considering PT came about purely by chance. I was browsing Ebay and noticed how cheap s/h Mix24 cards are going for. Ive been planning to expand my current DAW and it seemed a PT 24 card + interface would meet many of my requirements. Then I got to thinking, how much better (for me) is a TDM system compared to LE? Are the plugs better? What about the adc / dac's? etc etc

And this is how i wound up here asking you guys. Iv not made a decision as yet whether to move to PT (I have no problems with using SX), but Iv used the system for several projects and i do like it. Having the ability to move projects around various studios would be a HUGE advantage right now.

So, thanks again, I feel much more clued up now to the various PT options. What I'll probably do is try out some of the Powercore and UAD plugs and compare them to the better TDMs. If they prove to be as good then I'll probably stick with SX and save myself a few quid. If not, I'll have to see about getting a TDM rig. Doubt ill be going HD though, I reckon I could find plenty of better ways to batter 20k... (sorry, having a moment of gear lust )

Cheers!

PS Mixing in box is the future, deny it at thy peril!
Old 16th April 2004
  #13
Lives for gear
 
Berolzheimer's Avatar
 

Quote:
Originally posted by Bob Olhsson
I did a pretty extensive comparison between a PT-24 TDM system at the studio and PT-le 5.0 at home. My conclusion was that PT-le was at least as good and in some cases better because many 32 and 64 bit float plug-ins can't be overloaded. The only "gotcha" besides the latency is that the mixer output isn't dithered however an L1 set to 24 bit solves the problem. Hopefully somebody will bring out a 24 bit dither plug-in to save the DSP and latency of using an L1.
Hi Bob,
Waves does have the IDR plug, which is the same dither that's contained in L1. I think it can be set to 24 bits, though I could be wrong about that....
Old 16th April 2004
  #14
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Mike Jasper's Avatar
 

Berolzheimer writes:

Quote:
Waves does have the IDR plug, which is the same dither that's contained in L1. I think it can be set to 24 bits, though I could be wrong about that....
That's what I thought too. I also thought PowR Dither could handle it as well, but no. They both only go up to 20 bits.

Jasper
Old 16th April 2004
  #15
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Gerax's Avatar
 

Hi everybody

Could some of you please expand a bit on this "dither" on the master fader issue?

I always use to work at full 24 bits when mixing, then dither down to 16 when I'm finished (by use of Waves IDR or UV22HR), or leaving the files 24 if the project is going to a mastering house; I guess I'm missing something about internal resolution and the PT summing bus.

Thanx

L.G.
Old 16th April 2004
  #16
3 + infractions, forum membership suspended.
 

Quote:
Originally posted by Bob Olhsson
I did a pretty extensive comparison between a PT-24 TDM system at the studio and PT-le 5.0 at home. My conclusion was that PT-le was at least as good and in some cases better because many 32 and 64 bit float plug-ins can't be overloaded. The only "gotcha" besides the latency is that the mixer output isn't dithered however an L1 set to 24 bit solves the problem. Hopefully somebody will bring out a 24 bit dither plug-in to save the DSP and latency of using an L1.
Couldn't you just use the Crane Song dither CD or just sample the dither noise from the L1 and put it on it's own track?
Old 16th April 2004
  #17
Gear nut
 

Thread Starter
Some people feel that 24 bits is not sufficient a resolution to perform export / bounce to disk functions due to the large numbers created. Its a very technical issue that i only partly understand, so I wont go into it in any detail. However, it seems that dithering on the master bus might help reduce any ill effects produced by said number crunching. Eitherway, I chose to mix in 32bit floating point (on SX) and i dont feel i suffer any noticable degradation on mixdown. I think the real issue is that many engineers born and bread on analogue are missing the desirable colouration of their SSL's and Neve's. This is understandable, but at the same time I dont feel the lack of this colouration is in any way a limitation of digital systems. I was born and raised on digital, and this is where i work best and most comfortable.
Old 16th April 2004
  #18
Motown legend
 
Bob Olhsson's Avatar
The reason for dithering is eliminating distortion. When you don't dither, you always get the distortion. I dither everything I can because I've found that it delays the point at which the digital "crunchies" set in. Any argument that you can't hear the distortion is also an argument that you can't hear the dither. My experience has been that you sometimes can hear the distortion after a signal has been processed a number of times. I prefer not to take that risk.
Old 16th April 2004
  #19
Gear nut
 

Thread Starter
Bob,
The impression i had of dither was that it introduced a random number at the first bit, ie noize. This smooths out any perceived quantization and rids music of the digi-crunch. What i found interesting was that this noize is the most desirable option of removing distortion. I'd have thought that the real hardcore sonic purists, mastering engineers etc would have some really miss givings about 'adding' anything to a signal. I know that dithering algorithms are developed to be as transparent as possible, but so are many high end compression algorithms, and watermarks come to think of it. I wonder why it is that engineers shun things like data compression and watermarking which many consider invisible, yet have no problem using dither.

Kind of OT i know, but curious non the less.
Old 16th April 2004
  #20
Gear maniac
 

In the early years of digital the BBC refused to ad dither to their classical recordings because they couldn't justify adding "noise" to their recordings.

The term for the trailing off of bits (into silence) during fades, or very low level signals is often called "digital deafness". Dither does the trick of preventing audible digital deafness.
Old 16th April 2004
  #21
Motown legend
 
Bob Olhsson's Avatar
The best estimate I've heard is that it would take 10 dB of additional noise to cover up the distortion after the fact.

Dither PREVENTS distortion, it doesn't hide it. The idea of "optional dither" is no more legitimate from an engineering standpoint than optional analog tape bias or an optional wimpy power supply. It has never been optional in high-end digital hardware.

Yes, you can record a distorted signal without dither or bias but WHY?
Old 17th April 2004
  #22
djs
Gear nut
 

sorry if this is a redundent question or the like, but are you guys saying that you dither a 24 bit signal to 24 bits (instead of say 16 bits for a cd), efectivly adding dither noise, but not changing the bit depth? i've hear about this, but never understood why it was done. if that is indeed what you are talking about, it makes sence ...if not, what am i missing?
thanks,
dan
Old 18th April 2004
  #23
Gear maniac
 

If you are just running a small home setup then Pro Tools LE should be sufficient for you.

TDM is mainly for pro users working in studios or post. Native DAW's run out of steam in large sessions, and the latency issues are unacceptable for live studio work.

ADC in PT 6.4 addresses latency on playback but all native systems have live latency issues. ADC can't fix that short of having a time machine...

Also - ADC is only in the TDM version of Pro Tools, not the LE version as far as I know.

As for outboard gear, you can't easily compare it to TDM plug-ins. Some analog outboard gear has a unique sound. Likewise, you'll see the difference the minute you go to patch in your outboard gear for a track and realize you already used it. You can use a $500 plug-in on 50 tracks. You can only use an outboard box once, unless you have time to bounce everything to disk. OK, maybe you can use it more than once if it is a reverb on a bus send, but you get the idea.

The funny thing is that a lot of the digital outboard gear uses the same DSP chips that Pro Tools does. You are just paying for a piece of sheetmetal to wrap it in and some slightly different software.
Old 18th April 2004
  #24
Motown legend
 
Bob Olhsson's Avatar
Quote:
Originally posted by djs
are you guys saying that you dither a 24 bit signal to 24 bits (instead of say 16 bits for a cd), efectivly adding dither noise, but not changing the bit depth?
Almost any signal processing increases the bit depth beyond 24 bits and then needs to be dithered back down to the file or port depth.

All of this OUGHT to be done transparently but early DAWs didn't have enough horse-power so developers chose to advertise features that would only work if one left out dithering and accepted the added distortion. Hence all the "spin" suggesting dither is an option rather than the simple truth that leaving out dither is piss-poor digital signal processor design.
Old 18th April 2004
  #25
djs
Gear nut
 

thanks, bob. it's nice to get some background info to help put things in perspective. i'll try it out on my next mix. thanks again.

-dan
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