Lou Dorren: A new CD-4 Demodulator!!! [ARCHIVE]

[Quadro-Klaus]

Hi Lou, hi CD-4 fans,
are there any news about the new demodulator? After four years of anticipationt it would be nice to have to test a pre specimen in Germany. Thanks, Klaus

 

[scratch17]

Hi Lou:

I am very interested in your new decoder, and the new Grado cartridge.

I do have a question. Can the built in RIAA equalizer be bypassed, so that
only the demodulation circuitry is in the signal path?

While I am sure that you have a fine equalizer in the new unit, I'd like to
explore an alternative.

I am about to get a Mac Pro.
There is a program (Mac only) called Pure Vinyl that has a digital RIAA equalizer. Michael Fremer
(the analog guru at Stereophile magazine) says this digital equalizer compares favorably
with analog hardware RIAA equalizers costing in the thousands of dollars.

I plan to use it to archive my stereo LP's. I'd also like to use it to archive my CD-4s.

In order to do so, I need to extract the four demodulated tracks without
equalization. I'll bus those tracks into Logic 9 so they stay in sync. Then, I'll output
two tracks through two instances of Pure Vinyl for equalization, and loop the tracks
back into Logic.

Next I'll use Sonnox plug-ins to remove pops and clicks. Finally, I'll create
a DVD-Audio image in Wavelab.

Since I am going to have to digitize the files to clean them with the restoration
plug-ins anyway, I'd like to use Pure Vinyl's RIAA equalizer.

If I can't bypass the built-in analog equalizer,
I'll happily use it before sending the audio to Logic.
I'd just like to have the bypass option available.

Of course, I'd consider paying extra for this modification.

Thanks, Steven

 

[loudorren]

Hello quadraphiles,

Important progress update in 5 days.

scratch 17,

Hello Steve,

CD-4 depends on all of the EQs, (RIAA, FM-PM-FM, and ANRS) to be precision and to be matched as of delay and phase. The RIAA EQ that I use is passive and uses .1% value tolerance components. The same is said for the FM-PM-FM EQ of the sub-carrier system. The critical ANRS EQs are matched even tighter, to follow the exact expansion curves for accurate separation.

Don't get caught by "digital" intoxication! There are certain things that digital systems can do better than analog and certain things that analog does better than digital. The best systems are ones that use the strengths of both analog and digital ( the new CD-4 demodulator). If you use the new CD-4 demodulator to archive your 2 channel and mono LPs and 45s as well as CD-4s, then you don't need to waist your money on the digital RIAA.

During the design phase of this project, all the members of QQ where asked what features they would like on this demodulator. One feature that was requested and is implemented in the design is set of wide band non filtered pre-amplifier outputs for those who wanted to try external digital demodulation.

I hope this info is helpful,

Lou Dorren

 

[scratch17]

Thanks for the quick reply, Lou.

I do want to make sure I understand you correctly.

implemented in the design is set of wide band non filtered pre-amplifier outputs for those who wanted to try external digital demodulation

Am I correct in deducing that you are referring to a pair of stereo outputs that are pre-demodulation?

I do not want to do the demodulation digitally, just the RIAA equalization. If I am understanding your
statement correctly, I can't use the wide band outputs to feed the digital RIAA EQ because I would still
need to send the audio back to the demodulator for demodulation into four channels. The EQ would then be
applied twice!

As I said in my initial question, I'm sure your new demodulator will be excellent in all respects. I will
go ahead and use it for all functions. I know I'll love the results.

Steven

 

[scratch17]

Thanks for the quick reply, Lou.

I do want to make sure I understand you correctly.

implemented in the design is set of wide band non filtered pre-amplifier outputs for those who wanted to try external digital demodulation

Am I correct in deducing that you are referring to a pair of stereo outputs that are pre-demodulation?

I do not want to do the demodulation digitally, just the RIAA equalization. If I am understanding your statement correctly, I can't use the wide band outputs to feed the digital RIAA EQ because I would still need to send the audio back to the demodulator for demodulation into four channels. The EQ would then be applied twice!

As I said in my initial question, I'm sure your new demodulator will be excellent in all respects. I will go ahead and use it for all functions. I know I'll love the results.

Steven

 

[loudorren]

Hello All QQphiles,

Here is something that you all have been waiting for. Enclosed in this posting is a picture of the final new QQ CD-4 Demodulator. It is shown on my test bench were it is in final assemble and test. The complexity of the system requires that individual sections be loaded and then tested to verify full stable performance of that section. Some circuit modifications were implemented from the subsystem breadboards. The performance of these subsystems is even better then the breadboards and significantly better then the QSI5022.

Watching this thread has indicated to me that several of you have been concerned about the curve adherence to the RIAA, FM-PM-FM and ANRS EQs. The use of .1% components is yielding text book results. The phono pre-amplifier noise is a low 0.9 nV/SQR Hz. The QSI5022 was 7.5 nV/SQR Hz.

I will publish a picture of the completed unit that I will send to Jon. It will be in a commercial equipment case. The unit that will be manufactured for all of you will be in a custom made cabinet.


In order for this to all work requires that all of you who have indicated that you want one should confirm your commitment. I designed and committed all of the engineering on this project and all of you will handle the production costs. To reiterate, the QQ New demodulator including a Grado Prestige Gold pickup with Shibata stylus and a QSI record cleaning kit will cost $505.00. Additional Grado pickups will cost $150.00 and additional Styli will be $100.00.

We currently have 141 orders indicated with 63 confirmed. If you have not confirmed please do so and don't forget to list any extra pickups or styli that you want. If you are not sure that you have confirmed your order, contact wa6ubw by private message and he can verify your confirmation.

After Jon has tested and written his article I will post the payment procedure. Production will not start until all who have committed have remitted.

If between now and Jon's post anyone wants to get in on purchasing a new demodulator, go to the confirmation thread and make a posting.

QQ's, This project has taken about 3 years to complete and all who are participating are going to really enjoy the results!

Lou Dorren

 

[dlaloum]

Couple of questions... been reading through the threads and trying to understand what the end result is exactly...

Does the new "box" include straing gauge cartridge capability (there appears to have been lots of talk of strain gauge at various times)
What is the situation if using it as a straight stereo stage?
What facilities does it have for custom loading of cartridges (does it have switchable R & C loading? or Loading plugs?)
Is it available in 240V version?
Is there a summary somewhere of what it's features are/will be?

thanks

David

 

[wa6ubw]

Couple of questions... been reading through the threads...
Is it available in 240V version?
Is there a summary somewhere of what it's features are/will be?

thanks

it has a universal power supply with detachable power cable. NO wall-wart required!

it takes reading lots of posts to see the history of features which have been incorporated in the final design. Lou adopted a number of reader suggestions.

if you have specific questions like those above, just post them here.


Mike
pre-order list mangler

 

[jefe1]

Awesome picture, nice to see a prototype finally. Will the custom cabinet be metal or plastic, and have you settled on a labeling design?

 

[wa6ubw]

Will the custom cabinet be metal or plastic, and have you settled on a labeling design?

the cabinet will be black metal. sometime earlier in the thread Lou posted a layout of the panel with parts placement, but I have no idea of the post number. (news flash: see posts 441 and 446)


Mike
list keeper

 

[dlaloum]

Thank you for the reference, went back and read further.... so more questions (some the same)

1) Deleted
2) Deleted
3) Wideband output and input question: - is the wideband output pre or post RIAA, and therefore is the wideband input pre or post riaa.... (there was some discussion of this, but I did not see a clear answer)
4) Deleted
5) RIAA EQ - there has been talk about the accuracy required of the RIAA EQ to get good reproduction, but I don't believe seeing any actual measurements or specs of the end result... how accurate is the RIAA EQ? (within what +/- db in what frequency ranges?... a plot would be even nicer!)
6) MM input setting - when set to MM, does it impose an additional capacitive load?
7) MC input setting - any loading options? (nothing apparent on the external panels, but there might be something internal in the way of dip switches or jumpers hence the question)
8) Deleted

Thanks & bye for now

David

 

[proufo]

Thanks, Lou!

 

[loudorren]

Hello CD-4 Groovers,

David,

The demodulator has 2 Phono inputs. These handle Semiconductor, Moving Magnet, and Moving Coil pickups. A front panel switch allows you to select between them. There is also a wide band line input for those who want to experiment.

There are two sets of outputs from the phono preamp. Set one is wide band out (no RIAA, flat response). Set two is with RIAA EQ out.

Curve tracking is more critical than just the RIAA curve. In CD-4 there are 3 curves that must be accurate. They are the RIAA, the FM-PM-FM, and the ANRS compression. If any of these curves are only 1 dB accurate the best Front to Back separation for that side (Left or Right) will be 17.8 dB. This requires the use of ultra precision components to get high separation. The curve for RIAA is in one of the previous posts.

The answers to your other two questions are no and no.


Hope this info helps,

Lou Dorren

 

[dlaloum]

Thank you Lou

Much appreciated, and my order is in!

 

[voltcontrol]

(Hi all) I signed up here especially decause of interest for this great project.

A noobie question before I sign up in the pre order;

Is the supplied cart just as capable for great stereo reproduction (playing a stereo record I mean) or is a 'normal' stereo cart in combi with the 'LD CD4' (What will the name be? ) perferable?

Cheers,

Voltcontrol

 

[Disclord]

(Hi all) I signed up here especially decause of interest for this great project.

A noobie question before I sign up in the pre order;

Is the supplied cart just as capable for great stereo reproduction (playing a stereo record I mean) or is a 'normal' stereo cart in combi with the 'LD CD4' (What will the name be? ) perferable?

Cheers,

Voltcontrol

The line-contact stylus for CD-4 is better for stereo/matrix playback too since it has much higher contact area and greater tracking ability, reducing record wear.

 

[Disclord]

One feature that I wish Lou could have included on the new demodulator is an Axial-Tilt adjustment, like the Audionics Space & Image Composer (and some Audionics pre-amps) had. Even though Audionics claimed it was patented, it never was - Lynn Olson, inventor of the circuit, told me it wasn't even patentable - it was a simple in-phase and reverse-phase blending and it allowed the performance of each cartridge to be optimized for perfect phase accuracy, which greatly improved logic decoding and removed high-frequency sibilance spill into the rear channels on certain records. Although the same optimization can be done by using a mirror and shimming the cartridge for perfect azimuth, if the cartridge has any internal alignment issues with its magnets, physical alignment won't work - only electrical optimization, as the circuit does, is possible. And, it allowed tape recordings to be optimized for best decoding. Although CD-4 doesn't rely on phase-cues for decoding, I would think that anything that improved signal recovery from the surface of the LP would greatly improve CD-4 demodulation, right?

Here's an external unit that 'seems' to do the same thing: http://www.kabusa.com/canceler.htm#CTOP - I've thought of buying one to give it a shot. Does anyone have experience with this unit?

 

[Quadro-Action]

I think, it should be now enough with special wishes. What we nowreally need after years of waiting is a well working Demodulator with high quality in sound and best possible channel separation. Only the different modes for the connection of different working phono cartidges like MM and MC is a wellcome feature. No more and no less. Those, who likes to experient with their PC may do this with stereo equipment. Most of us needs "only" a satisfying CD-4 Surround-Sound.

Dietrich

 

[dlaloum]

Hi Folks,

I recently managed to get my hands on a Panasonic SE-405 / EPC451C combo...
I am finding that there are 2 problems with them
1) Chanels out of balance on the SE-405 (at least 2db out - both in normal MM mode and SG mode)
2) High Frequency rise of about 8db (don't know whether this is typical, I would have expected Frequency Response to be flatter?)

Now I have to make a decision on whether to try and get the SE-405 worked on (or whether to try my hand at DIY refurbishment...) or whether to wait for the Demodulator.

The unknown factor being - how long till the demodulator? If we are talking a month or two.... I'll just wait.
But if we are talking a likely 5months++ then I need to take a look at what can be done with the SE-405.... (or perhaps one of the other Project SG pre's around)

Any thoughts? - Anyone know what ETA for the demodulators might realistically be?

thanks

David

 

[erniegiro]

I'm going to cast this crazy crazy thought out there for Lou and others to comment on. Thinking of the physical packaging of the 21st Century demodulator, in order to save on the the actual case, switchgear, in/out jacks, etc, may it not be possible to retrofit the circuitry into an existing case, say from a JVC 4DD5, of which there are many out there, in various states of decrepitude that may be used to house the new unit? I myself have 2, one in working order, another in "donor" condition that could potentially house Lou's circuitry. So what say you all?