Hello Lou, thank you for the quick answer. So we have now a good information, that it is looking well for the Demodulator. But please don't be overworked - we need you.
Dietrich
Dietrich
Lou Dorren: A new CD-4 Demodulator!!! [ARCHIVE]
- Thread starter loudorren
- Start date
Help Support QuadraphonicQuad:
Regarding CD-4 Demodulator
Automatic Carrier Level System(s):
(Marantz and Lafayette demodulators)
https://www.quadraphonicquad.com/forums/showpost.php?p=8302&postcount=6
Are the Marantz and Lafayette automatic carrier
level system(s) similar to the system used in the
2008 CD-4 demodulator?
EDIT: Not adjustable might be a better description
than Automatic.
Kirk Bayne
Automatic Carrier Level System(s):
(Marantz and Lafayette demodulators)
https://www.quadraphonicquad.com/forums/showpost.php?p=8302&postcount=6
Are the Marantz and Lafayette automatic carrier
level system(s) similar to the system used in the
2008 CD-4 demodulator?
EDIT: Not adjustable might be a better description
than Automatic.
Kirk Bayne
Last edited:
I, for one, have positive experiences with automatic carrier level adjustment:
The automatic carrier level system in my Pioneer QX-749A works very well, whereas the manual adjustment of the carrier level in my three B&O Beogram 6000 causes hassles.
The automatic carrier level system in my Pioneer QX-749A works very well, whereas the manual adjustment of the carrier level in my three B&O Beogram 6000 causes hassles.
The Quadfather
1K Club - QQ Shooting Star
I have had excellent results with my 4DD5's manual carrier level adjustment. It's a hassle to get it right, but once you do, it stays set.
Lou's system is not an automatic carrier level. It is a limiter system. The carrier is over amplified, and the waveform is truncated on the top and bottom to make essentially a square wave. The square wave is then sent to the PLL at an optimum set level. Small level variations have no effect at all. Is that about right Lou? It's the same thing that is done in an FM radio and that makes a radio more resistant to static and signal level fluctuations.
In an automatic carrier level system, the unmodified waveform, a sine wave, is sent to the PLL circuit after it's level is controlled by a variable gain amplifier stage. A level detector is used to detect the level to control the amplifier. A workable system , but not as good.
The Quadfather
Lou's system is not an automatic carrier level. It is a limiter system. The carrier is over amplified, and the waveform is truncated on the top and bottom to make essentially a square wave. The square wave is then sent to the PLL at an optimum set level. Small level variations have no effect at all. Is that about right Lou? It's the same thing that is done in an FM radio and that makes a radio more resistant to static and signal level fluctuations.
In an automatic carrier level system, the unmodified waveform, a sine wave, is sent to the PLL circuit after it's level is controlled by a variable gain amplifier stage. A level detector is used to detect the level to control the amplifier. A workable system , but not as good.
The Quadfather
loudorren
Well-known Member
Hello Quadragobblins,
Happy CD-4 Holloween,
kfbkfb,Tonedoev, Quadfather,
Kirk, I have a better one, Not Needed. The key to an FM system is the complete removal of any incidental AM. The problem with all of the carrier level systems is that they do not remove the incidental AM. In fact the automatic systems create additional incidental AM by the hysteresis in the detector gain control.
I had a big argument with the Technics engineers about this for the SH-400. It added a lot of extra circuitry which did not improve the performance.
Quadfather's explanation is perfect. Armstrong found that the limiter made the FM receiver (in our case the CD-4 demodulator) completely impervious to the effects of incidental AM for FM radio and CD-4 demodulators.
No trick, a great treat is coming,
Lou Dorren
Happy CD-4 Holloween,
kfbkfb,Tonedoev, Quadfather,
Kirk, I have a better one, Not Needed. The key to an FM system is the complete removal of any incidental AM. The problem with all of the carrier level systems is that they do not remove the incidental AM. In fact the automatic systems create additional incidental AM by the hysteresis in the detector gain control.
I had a big argument with the Technics engineers about this for the SH-400. It added a lot of extra circuitry which did not improve the performance.
Quadfather's explanation is perfect. Armstrong found that the limiter made the FM receiver (in our case the CD-4 demodulator) completely impervious to the effects of incidental AM for FM radio and CD-4 demodulators.
No trick, a great treat is coming,
Lou Dorren
Hearing forward to it!!!!!!!!!!!
Regarding the (JVC) CD-4 FM-based Difference
Signals and 1970s JVC FM Tuner Technology:
JVC FM tuners sold in the early 1970s didn't have
FM sensitivity adjustments, why didn't JVC use their
FM tuner technology in the first generation CD-4
demodulators and avoid carrier level adjustments
altogether?
Kirk Bayne
Signals and 1970s JVC FM Tuner Technology:
JVC FM tuners sold in the early 1970s didn't have
FM sensitivity adjustments, why didn't JVC use their
FM tuner technology in the first generation CD-4
demodulators and avoid carrier level adjustments
altogether?
Kirk Bayne
loudorren
Well-known Member
Hello All New CD-4 QQ 2008 Signature Series CD-4 Demodulator People,
Time is getting close. This and next four posts will contain the 9 page final schematic of the new demodulator. This is the working circuit and the Urban evaluation is coming soon. Jon will be getting a preproduction unit that physically will not look exactly like the final production, but the inside will be the final production electronics. I have incorporated the features that you have requested and if any of you have questions please feel free to ask.
Each post will define the section of the schematic that comes with it.
Every body enjoy, and I will answer hanging questions in 10 posts from now.
This post contains the Left channel and Right channel Phono preamps.
Lou Dorren
Time is getting close. This and next four posts will contain the 9 page final schematic of the new demodulator. This is the working circuit and the Urban evaluation is coming soon. Jon will be getting a preproduction unit that physically will not look exactly like the final production, but the inside will be the final production electronics. I have incorporated the features that you have requested and if any of you have questions please feel free to ask.
Each post will define the section of the schematic that comes with it.
Every body enjoy, and I will answer hanging questions in 10 posts from now.
This post contains the Left channel and Right channel Phono preamps.
Lou Dorren
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Active Member
Heh Guys & Gals...
aren't you glad I went by Lou's house and woke him up? :howl
I thought he was in a Rip Van Winkle sleep cycle! :zzzzz
aren't you glad I went by Lou's house and woke him up? :howl
I thought he was in a Rip Van Winkle sleep cycle! :zzzzz
Thanks Lou. Now if I can just get my replicator fired up, I'll be all set. 
Seriously, I appreciate your work on this and with great anticipation, look forward to the day they roll out.
Thanks, - Ben
Seriously, I appreciate your work on this and with great anticipation, look forward to the day they roll out.
Thanks, - Ben
Now let's see what we've got here:
The ANRS looks like a NE570. In fact, a half used NE570 per channel. (BTW: This chip is still in production, whereas the Phase Locked Loop NE565 has been discontinued by most, if not all manufacturers.)
Then we have a chip at the mid-bottom with QD to QN which seems to be a 4060, an oscillator with 13 stage divider. (or something, I do not have the datasheet in my head right now...)
The chip connected to the F-B output op is a dual 4 to 1 analogue switch. Hopefully not from the 4000 series. Anyway, I would recomend to terminate all unused inputs, even from the second unused switch, to ground. Just to avoid unwanted noise during switching, and to avoid any unwanted oscillation / static voltage / whatever might happen at those "open" input pins, of the input stages.
Then we have all of those OPAs running with 40 Volt. Hmm... most OPAs I know have a maximum supply voltage range of 36 Volt (+/-18 Volt). I wonder what type those are.
I miss bypass capacitors on the supply lines of all ICs.
There are two voltage regulators, one 15 Volt, one 5 Volt. Both no input capacitance, nor output capacitance. Most of them require a load capacitance on their output, placed near the device. If not, the output tends to oscillate, especially the ones providing a fast regulation.
(Input capacitance might be provided from the +/-20 Volt regulation, but these were probably "far away" regarding Layout...)
My observation is just from a first look, without exploring datasheets... I might be wrong.
-Kristian
The output capacitors weren't polarized? Since there seems to be no capacitance inside the whole design (not even bypasses for the chips) I do recommend at least 47µF to 100µF as output capacitance. Even more so regarding the regulators for the ANRS.
-Kristian
Funny Filters! Custom made?
Can't say anything about the PLL, nor the Limiter. Any ideas from you cracks out there?
-Kristian
Interesting supply voltage generation. When time permits I have to redraw it for further exploration.
From what I can see here, the input channel selection is done with a switch on the front panel connected to ground. S0 and S1 of the analogue switch are fed with the information from the switch. But a logic high is done with the input pin open? Pull-Up resistors recommended here, especially when the analogue switch is CMOS. Even if the chip provides something like an internal pull-up, those are often in the 100k to 500k range, so a 10k resistor to Vdd makes it more stable against radio noise.
Is it really necessary to include a 5 Volt regulator just to provide a logic high on the enable pin?
Termination of all unused input pins of the analogue switch is missing.
-Kristian
