Film-Tech Forum ARCHIVE: DAC decoder(s) in DTS-6D

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Posted by Rob J. Buskop (Member # 3338) on 07-29-2016, 04:25 PM:

Can anybody give me some more insight and info on the following?The Apt-X100 chips on the audio card decode the APT-X100 codec as
delivered by the CD-ROM / player combo. Hereafter we have a PCM signal that needs DAC's to get it all back into analog language. Question: What DAC's (make and type) are used for this purpose and where are they located ( or how are they individually masked by DTS..) in relation to their function?

Posted by Mark Gulbrandsen (Member # 72) on 07-29-2016, 06:53 PM:

I always assumed the APT-X100 chips were the D to A chips... I have a plastic tube full of them here if you need any... Have had a few fail over the years and got some extras from DTS.

Mark

Posted by Rob J. Buskop (Member # 3338) on 07-30-2016, 09:37 AM:

Well, the APTX100 chips "translate" the 4-bit compressed data stream back to the original 16 bit size that was the original sound format before it was 4x compressed to be written on the disc. That is the major task of these large proprietry APT chips... Even if one goes through the patent, it is not entirely clear if the final D/A conversion is built into the chip or that a secondary D/A decoder would be needed. I agree that it's most probably done on the chip, but I'm not 100% sure.
Difficult to find on the net, at least for me. Still would like to know...

Posted by Mark Gulbrandsen (Member # 72) on 07-30-2016, 10:24 AM:

I do not remember there being any extra DAC chips on the 6 & 6D audio boards. Just the APT chips. I repaired a lot of the 6D boards because the DC converter module failed quite often in a bunch of them leaving the unit with no audio at all. There were a number of output opamps though and it was these opamps which the DC converter powers.

Also, the XD-10 DID have an entirely different scheme for this and it did have separate D to A chips. All that is located on the audio board that is above the PC motherboard. If you cn track down Karen Hultgrin (SP?) on Facebook she would know the answer to your question for sure. I also looked at the patent and it is very vague what happens in that big chip... Almost too vague for a patent....

Mark

Posted by Rob J. Buskop (Member # 3338) on 07-30-2016, 11:42 AM:

Thank you Mark for looking into this. Funny you should say that about the patent reproduction. Of course large sections are way above my digital elementary scholl, but indeed it sort of fails to tell you exactly what the last stage(s) do. Indeed a bit hazy there. Anyway, thanks for your interest! Hereunder related text part of patent summary..... (accent on "can then..")
Playback is accomplished by reading out the recorded signals from the storage medi¬ um, decoding the read out signals in a manner complementary to the encoding, demultiplexing the decoded signals in a manner complementary to the multiplexing, and decompressing the demultiplexed signals in a manner complementary to the compression. The decompressed signals can then be pro¬ cessed through a digital-to-analog converter (DAC) and sup¬ plied to audio speakers.

Posted by Gordon McLeod (Member # 33) on 07-30-2016, 02:26 PM:

The patent applies to the technology not necessarily the actual design of the chip
On the 6 and 6D the da to conversion happened in the APx chip
The 6 had balancing output transformers and the CD did not but used opamps to balance the output

Posted by Rob J. Buskop (Member # 3338) on 07-31-2016, 04:39 AM:

Gordon said "The patent applies to the technology not necessarily the actual design of the chip..."
Thanks Gordon, I think you're absolutely right there! That absolutely correct observation had'nt crossed my mind, but your observation is of course spot on! So we're still in the dark. Will try and find out anyway and will keep you posted.

Posted by Carsten Kurz (Member # 5396) on 07-31-2016, 07:53 AM:

There is a brochure on APTX100 on the net describing 'the' chip, and mentioning common serial digital audio interfacing to 16Bit D/A converters. Don't know, however, wether that brochure references the DTS-6 chipsets, or later revisions. The paper is dated 1999/2000.

Keep in mind, APTX is still current technology, it is one of the (better) codecs used for Bluetooth audio, wireless headsets, etc.

I have a DTS-6D sitting in my basement, I may go and have a look at the D536 myself...

Wasn't there a digital audio out option for the DTS-6D amd SV? The back-plate has a connector option for it. And I don't think they implemented it D->A-A->D wise...

- Carsten

Posted by Daniel Schulz (Member # 1881) on 07-31-2016, 09:03 AM:

quote: Carsten Kurz
Wasn't there a digital audio out option for the DTS-6D amd SV? The back-plate has a connector option for it. And I don't think they implemented it D->A-A->D wise...

My memory is not 100% on this, but I don't think there were digital out options on the 6D, 6DSV or 6AD. There *was* a digital out option on the XD10. A Datasat soundtrack played back on the XD10, digitally output to an AP20 using Dirac Live was in my opinion the pinnacle of sound-for-film.

As to the DAC chips on the old units, I'll see if I can find someone to confirm. Now I'm curious.

Posted by Carsten Kurz (Member # 5396) on 07-31-2016, 09:44 AM:

They are Crystal (now Cirrus Logic) CS4333. I just opened the DTS-6D in my basement and had a look.

http://floe.butterbrot.org/matrix/hacking/limp/docs/cs4330.pdf

See this picture of my D536-D with my added red box outlining the three stereo DACs:

https://www.dropbox.com/s/vmtmk5jk4n9ftex/DTS6D_DACs.jpg?dl=0

Daniel - this D536-revD card actually has an onboard D15 connector labeled 'Digital out'. I wouldn't know for sure wether this actually means digital audio? I read a lot of DTS manuals and TechTalk, but never saw this connector being mentioned.

The analog back end of the card is towards the front of the DTS-6D unit (front level trim pots for obvious reasons), so the rear analog out is on a ribbon-cable break out/slot connector board. But the digital out is on-board.

- Carsten

Posted by Gordon McLeod (Member # 33) on 07-31-2016, 12:14 PM:

The 6d did have a digital out but it was not AES it would interface to the CinemaAccoustics processor and the older USL USL processor which model I cant remember

Posted by Carsten Kurz (Member # 5396) on 07-31-2016, 12:17 PM:

Yes, it was probably not some of the standard multichannel digital interfaces, but some proprietary format with separate data/clock signals etc.

Most people refer to the DTS-6 vs. the DTS-6D as the two drive vs. three drive model - was the 'D' in 6D actually indicating this digital output? Appears obvious now, but never thought about it before...

Also never heard about CinemAcoustics CPs before, but, yes, there is something to be found:

http://mkpe.com/products/cinemacoustics/EE%20Note%20002%20DTS%20Modification.pdf

- Carsten

Posted by Sam D. Chavez (Member # 1841) on 07-31-2016, 08:20 PM:

This company was a division of Peavey for all intents and purposes. Did not work out.

Posted by Brad Miller (Member # 2) on 07-31-2016, 10:53 PM:

I'll just leave this here.

Cinemark policy trailer

Posted by Pete Naples (Member # 761) on 08-01-2016, 04:25 PM:

I still have two of those on my patch, working!

Well, mostly. It really is time they retired.

The DTS 6SV did give some sort of oddball digital signal, just as Gordon described.

Posted by Gordon McLeod (Member # 33) on 08-02-2016, 10:17 AM:

USL DSP60 was the other processor that it interfaced to

Posted by Mark Gulbrandsen (Member # 72) on 08-02-2016, 01:13 PM:

A couple of famous industry guys took Megaplex Theaters for a big ride and installed all Peavey crap when they opened Jordon Commons around 2000. ALL of it had since been replaced with real actual Cinema Gear by about 2006 or 2007.

The USL DSP-60 wasn't that awful as long as you had the last firmware updates installed in them. I had two in use for about 5 years in Ketchum and they never even so much as blipped.

Mark

Posted by Marco Giustini (Member # 4544) on 08-04-2016, 02:40 AM:

So Rob, may we know why you asked for the DAC's in the DTS player? What's your project?