Well done, it seems, Lou!
Well done, it seems, Lou!
Hello to all the CD-4 Quadraphoners,
Thanks to all of you for your interest in the new CD-4 demodulator. Two items for your information. All new demodulators will ship with a new high performance CD-4 pickup cartridge. I see by comments that some of you have CD-4 cartridges and that is good. In order for me to guarantee the performance of the new demodulator, however, I have to ship a known quality system. This does not mean that your CD-4 cartridge will not function. In fact it should function very well. However, if it does not, you have a known cartridge that has been tested with the new demodulator. All cartridges will be 100% dynamically tested in CD-4 mode at all diameters to confirm performance.
Item number two is service kits for the new demodulator. I have not yet designed these. They will contain all critical semiconductors and a complete test and diagnostic procedure. You will need a basic knowledge in soldering and using a Volt, Ohm meter (VOM). If you don't have this knowledge the instructions should easily be understood by a local repair shop. The demodulator will come with a 1 year service warranty that covers parts and labor. After that time I will offer for a limited time a repair service who's rate is to be determined.
One more comment, the RIAA preamplifier will be the lowest noise, most accurate tracking system that is available, so get ready for great CD-4, Stereo LP and 45 RPM playback.
Last edited by loudorren; 08-11-2008 at 06:14 AM.
Will the cartridge be pre-mounted on a head shell or will that be a necessity to purchase? And if I need to purchase one, where is the best place?
One more... how much is an extra stylus?
Thanks again for all the hard work. I am really looking forward to this.
Regarding the 2008 CD-4 Demodulator
and the use of other phono cartridges:
1. What's the maximum allowable (dB)
frequency response variation in the
20kHz to 45kHz frequency range?
2. What's the minimum required (dB)
channel separation in the 20kHz to
45kHz frequency range?
Any plans to sell the 2008 CD-4
Demodulator RIAA preamplifier section
as a separate unit?
Last edited by kfbkfb; 08-11-2008 at 08:41 AM.
Hello CD-4 fans,
The cartridge will mount in a standard shell. If you need an extra shell, I recommend www.lpgear.com and click on "Headshells&Mounts". Spare stylus are $39.00 which is the ones price. If enough are ordered the price will go down.
The sub-channel frequency response from 18KHz to 45KHz must be +- 3dB but has to have a Gaussian phase response. Minimum separation at 50 KHz is 5dB, however over the sub-channel band 15 dB or more is preferable.
With regards to the preamplifier as a separate item I would say not at this time.
Hello Lou, it may be, that some nervous fans like to know at first the result of the test report from John Urban before they make an order for the demodulator. If those will ask me, I like to ask you already now: Is it possible to buy a demodulator also after the usual time for registration or by general later time (for excample if they have to pay actual their new car?) This may be also interesting for any unsured fans in the states. I self belong of course to those, who have make an order actual, as you may have already noticed.
As much as it pains me to say this, I can't wait to put my JVC CD4-50 away into the closet. Yes, I have this level of expectation and that much trust in Lou!
Gee, I wonder how how many CD-4 conversions we'll see after this thing is released?
And how many price lift-ups on cd-4 records on ebay?
Even if this demodulator does not perform better than the legacy demods, it will be made with modern parts that will not be obsolete any time soon. How long will the industry keep making those phase locked loop chips common to most designs? Though I will have reservations about retiring my well performing 4DD5, I will buy the new demod for this reason only. Any improvement in performance I get will be pure bonus.
Lou stated in a reply to me that the PLL chip is proprietary. This maymake it nigh impossible to get once supplies are exhausted.
What PLL chip are you using? the PDF image is a little fuzzy.
Malcom, it is a custom chip I had made for another project. It's number is XY4240.
Hell to all CD-4ers,
Quadfather and Malcom2010,
I am working up the service kit. It will be complete as soon as the pre-production prototype is fully operational and has been in Jon Urban's hands for verification. The kit will be complete and you will be able to purchase extra ones if needed. As it gets closer to production, I will post the service kit price and have any one who wants one indicate so.
Hmmm, Proprietary, not good. I reckon I better get some extra chips. Are there any other parts that will be proprietary? We need to know.
Hello CD-4 Quad People,
Don't let the proprietary scare you. The PLL chip costs $2.00 each. The other proprietary chips might be the programmed filters. They are off the shelf chips but I have to program them. Again the service kit price will be quite reasonable.
Regarding the CD-4 disc
main channel/base band/sum signal delay:
The sum signal on CD-4 discs is delayed
40x10^-6 seconds compared to the FM based
Does the 2008 CD-4 Demodulator with the
specified phono cartridge compensate for
Just spent my Saturday evening reading 22 pages of this thread.
Thank you for providing a new CD-4 demodulator.
All of my audio equipment is silver but I will order the demodulator although its colour is black
Regards from the Netherlands.
Hello to QQ people all,
Kirk, The answer is yes. All CD-4 demodulators, old and new must compensate for the 40 usec delay to get the best separation Front to Back for the Left and Right composite channels.
Clemens, Welcome aboard the thread. If you have not yet, you might download the 5 installment paper on the new CD-4 demodulator. You will find it at :
With regards to the color, like Henry Ford said about his model T automobile "You can have it in any color you wand as long as it is Black*,
Success with the development of the demodulator.
Regarding an all software CD-4 Demodulator:
(This has been mentioned from time to time
in this discussion forum)
An FM "radio" has been developed, it seems like
the FM demodulation code could be adapted to
work with the CD-4 FM based difference signals.
The only remaining CD-4 specific functions that
would need a software implementation are ANRS
decoding and the muting system.
I reckon at two bucks a pop, I can afford to stock some extra chips.
Software demodulation or decoding might be cool but they're not 1/100th as cool as honest-to-goodness electronical types.
Kirk, The basic GNU FM algorithm is not good enough for CD-4. It must be modified to demodulate FM-PM-SSBFM. This adds a significant amount of processing. It is possible to use only the FM demodulation algorithm alone, however the midrange and high frequency separation will suffer.
Sometimes you can do things better in analog than digital and sometimes visa versa. The best approach is to use the strengths of both to optimize the end result.
You say that additional amounts of processing are required to handle the different levels of modulation that are different for different frequencies, I assume for the purpose of this question: Do the legacy demodulators compensate for this, or was this one of the cost compromises? I know most of them use a basic PLL chip that was widely used for FM demodulation in hobbyist projects at the time, suggesting that this chip was very basic. There really doesn't appear to be much except the ANRS. Not being in on the design, it's hard to know the purpose of every resistor or capacitor. I know that I sometimes look at my own circuit designs and see a particular part and think that if I hadn't designed this thing myself, I wouldn't know what that particular part is intended to do. Some functions are subtile.
To support my statement "Sometimes you can do things better in analog than digital and sometimes visa versa. The best approach is to use the strengths of both to optimize the end result" here is a case where analog is better. The Phase Lock Loop has some very unique and interesting properties. First, by the use of properly designed loop filters it can accurately track an FM-PM-SSBFM signal.
This was part of my original patent for the CD-4 PLL demodulator. In this case one well designed Integrated Circuit can do better than lines and lines of DSP code and do it cheaper.
Just the opposite is true when it comes to filtering. The program, though quite complex for the filters yields much more accurate filters then does analog.
Both techniques are used in the new CD-4 demodulator!
A few questions related to the stylus.
Some people are using two turntables, one only for CD-4 records and the other one for stereo, SQ, QS etc. records. I assume this is to obtain maximum lifetime of the Shibata stylus. I am using only one turntable (Technics SL1300).
Can I use your new Shibata stylus for all records? Or is it better to use it for CD-4 only? What is your recommendation?
Have you carried out any tests using Shibata needles for stereo records? What was the outcome?
In post #395 you are writing “QSI record cleaner works differently by emulsifying dirt on the record surface and using the playback stylus as a scoop to actually remove the dirt."
This means the Shibata stylus will scoop and remove the dirt?
Would this not damage the stylus and/or reduce its lifetime?
Do you have any test record left over or are they all sold through Ebay? (I missed that)