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

[loudorren]

Hello Quadfather,

For phase cancellation to work the two signals being algebraically differenced must be identical in amplitude and 180 degrees out of phase. For others, this means that when one signal goes positive the other must be a mirror image going negative. That is the problem. When the 30 KHz sub-channel is passed through a bandpass filter, the filter modifies the amplitude and phase just enough to make the algebraic differentiation unsuccessful. So, although an interesting idea, unfortunately, in this case it will not work.

Lou Dorren

 

[The Quadfather]

Hey Lou:
Yeah, I thought it was an interesting idea. But you're probably right. You're getting a lot of feedback here. You will have your pick of the best ideas. There are certainly some good ones. Will the new demod be rack mountable?

The Quadfather

 

[loudorren]

Hello Quadfather,

The final unit is going to be pretty small. I suppose you could mount it on a 19 inch rack shelf. My friend Mike (wa6ubw) suggested using Velcro mounting strips on the bottom so that the unit could be easily attached and removed. Not a bad idea!

Lou Dorren

 

[The Quadfather]

The Rohs requirements are European Union law, not U.S. so if the demod was not Rohs compliant, it would only affect the ability to sell in Europe. Not that I mean to dump on our european friends, but it would be better to make a better product. These demods will be in service for a very long time, far beyond the normal lifespan of a piece of electronic gear. Europeans would just have to import them from the U.S. I don't know what would be the situation with Canadians and Aussies. But where there's a will, there's a way.

The Quadfather

 

[The Quadfather]

Small will work. I'll just get a single RU rack shelf and put it on that. I haven't had much luck with Velcro, the glue keeps coming unstuck. It can share a shelf with my Laserdisc Dolby AC3 demodulator after I get all the sticky goo off of it.

The Quadfather

 

[wa6ubw]

,,,after I get all the sticky goo off of it.

there is a liquid cleaning product called "Goo Gone" which might be useful.

 

[callmez]

there is a liquid cleaning product called "Goo Gone" which might be useful.

Or good old fashioned acetone!

Mark Z

 

[Cai Campbell]

Or good old fashioned acetone!

Which disolves everything, including the silk-screened lettering, the case, and your kidneys!

Ronsonol lighter fluid is the way to go...

 

[Quadzilla]

.

 

[Philip Spinner]

ahh, Goo Gone. Used it to remove many stubborn seals on Silverline discs.

 

[The Quadfather]

Aw, come on, all you guys got to talk about is Goo Gone?

The Quadfather

 

[callmez]

Aw, come on, all you guys got to talk about is Goo Gone?

Pretty lame, eh? Things should pick up a bit when we all have our new demodulators...

Mark Z

 

[wa6ubw]

Aw, come on, all you guys got to talk about is Goo Gone?

you give me more credit than I deserve; I'm in over my head if I talk about anything more esoteric or technical than Goo Gone.

 

[kfbkfb]

CD-4 Front to Back channel separation
maximization without using a test record:

I've tried 2 methods:
1. Connect the outputs of the CD-4 demodulator
(LF to L, LB to R or RF to R, RB to L) to the
line level inputs of an amplifier, listen with
stereo headphones, try a variety of CD-4 albums
and adjust the separation controls for what
seems to result in the most separation.
2. I wired a headphone jack so I could listen to
L-R (in mono on stereo headphones).
Connect the CD-4 demodulator as in method 1 and
(using my specially wired headphone jack), try
to maximize the volume of the difference.

Any other ideas?

Kirk Bayne

 

[Quadro-Action]

For my opinion the best methode further on and in principle is to adjust the channel front-back separation with an adjustment record. Meanwhile I prefere those with LP's. who are running also with a speed of 33 , because without a few singles of 45 all CD-4 records are those of 33 speed. Strange will be, that there are also different results by different adjust singles. May be also the same with the adjustement records with 33 speed (have not tested since now), but I think, the adjustement with the same (LP) speed will be optimal. And those are sometimes available by ebay - like actual from Lou Dorren (Soundbird) ore Harman Kardon and Fisher. And adjustment by playing music can be only an gambling attempt with only approximate results.

Dietrich

 

[Wagonmaster_91]

Add me to the list of first round buyers!

 

[loudorren]

Hello CD-4 Aficionados,

Here is some update information on some requests that you have made for the new demodulator. I have moved the cartridge DC Bias switch and the Cartridge EQ (R.I.A.A.) switch to the front panel. Also to the front panel I have added a phono/line level switch for you digitize experimenters, and direct preamp output jacks on the back panel as well as left and right outputs for use with matrix "decoders". After evaluating all these requests I found that they could be done without affecting the performance of the original design.

Look for the third installment, coming soon!

Lou Dorren

 

[The Quadfather]

Hey Lou:
There is a demodulator made by Marantz that has automatic carrier level control. It is generally considered to be inferior to it's predecessor which is a repackaged JVC 4DD5 (the 4DD5 is a fine demodulator). The problem seems to be that sometimes the carrier level control just doesn't get it right. I would hope that you would provide a manual gain pot with a switch allowing the automatic control to be turned off. This would provide the best of both worlds.

By the way, I listened to my 4DD5 and my AT440MLa cartridge last night. For a cartridge that won't work, it was doing a pretty good job. I'm not saying that a full bandwidth cartridge couldn't do better, I'm just saying that for a cheap cart, it gets the job done. Plus, when the stylus wears out, I will be able to afford another without pinching pennies. Then maybe I can afford your new demodulator!

The Quadfather
Ugh, my Pioneer DV45A appears to be going kaput. I reckon that will be my excuse for getting an Oppo.

 

[loudorren]

Hello Godfather,
No carrier level control at all, manual or automatic. A useless circuit. Serves no purpose! Not needed! The new cartridge will be quite affordable with full CD-4 performance.

Lou Dorren

 

[aludra]

Hey Lou,

Thank you so much for your inclusion of extra features!!! I simply cant wait to get one!!
Will the phono cartridge input impedance be compatible with Legacy Quad CD-4 cartridges??
Also I am very interested why you think carrier level controls are an unneeded circuit(less is always more!) and how do you overcome ALL CD-4 records carrier drop as it approaches the inner grooves?? Does the separation remain the same no matter what the carrier level of the disk is???
Thank you again for providing us "digitizers" a way to take advantage of your new and advanced preamp circuits and re-inputting the signal back to the demodulator....I am drooling in anticipation....!!
Warmest Regards,
Mike