Help with CD-4 Marantz

[Stiffgriff]

I have bought the CD-400B Demodulator and have it set up the with my Marantz 4270 and Marantz 6200 currently running with a AT-VM95ML cartridge. Thinking about purchasing a Shibata stylus to play my CD-4 records properly. Should I just buy the AT-VMN95SH stylus or the whole cart and headshell AT-VM96SH & ATHS6BK in order to finally achieve discrete CD-4 quad capability? Also wondering what would be easier to switch back and forth and will this actually be my final step in achieving full discrete quad? My CD-4 records play currently, however the radar button on the CD-400B does not light up on 4CH Mode and it sounds the same on the 4270 stereo mode as it does on the discrete mode. Thanks and sorry if this is covered somewhere else within the forum!

Side note: I have the SQA2-B hooked up under the 4270 and my SQ records sound great. Excited to hopefully get CD-4 discrete quad up and running because I read it’s quality is better than SQ.

 

[fredblue]

I have bought the CD-400B Demodulator and have it set up the with my Marantz 4270 and Marantz 6200 currently running with a AT-VM95ML cartridge. Thinking about purchasing a Shibata stylus to play my CD-4 records properly. Should I just buy the AT-VMN95SH stylus or the whole cart and headshell AT-VM96SH & ATHS6BK in order to finally achieve discrete CD-4 quad capability? Also wondering what would be easier to switch back and forth and will this actually be my final step in achieving full discrete quad? My CD-4 records play currently, however the radar button on the CD-400B does not light up on 4CH Mode and it sounds the same on the 4270 stereo mode as it does on the discrete mode. Thanks and sorry if this is covered somewhere else within the forum!

Side note: I have the SQA2-B hooked up under the 4270 and my SQ records sound great. Excited to hopefully get CD-4 discrete quad up and running because I read it’s quality is better than SQ.

the VM95ML should be ok, the Microline stylus may turn out to be more forgiving than the Shibata, particularly with records in less than ideal shape.

are you going from the 6200 directly out into the CD-400B?

i only ask as you mention you have SQ working fine, since the CD-400B has it's own phono preamp and needs an unattenuated signal, the CD-4 demodulator should come first in any daisy chaining. looping from the 6200 into the 4270 and back out into the CD-4 demodulator may cause issues.

 

[Stiffgriff]

I have it wired as follows.
6200+GROUND —> CD400B PHONO
CD400B DIRECT OUT—> 4270 PHONO
CD400B 4Ch FRONT OUT —> 4270 CD-4 FRONT
CD400B 4CH REAR OUT —> 4270 CD-4 REAR

CD-400B SETTINGS: PHONO, 4CH, DIRECT OUT “OFF”

4270 SETTINGS: CD-4/AUX, DISCRETE, MAIN. (all 4 speakers are wired into the “MAIN” inputs on the back)

 

[Stiffgriff]

Is it possible since the radar button does not come on at all, and there seems to be zero difference in playing records in the 4CH or 2CH mode, that maybe that button is broke? Or needs to be cleaned with Deoxit? Every type of record is playable in both modes on my CD-400 and seems to just play everything in double regular stereo and might just be stuck in 2CH mode regardless of botton position?

 

[Owen Smith]

I have to agree that changing the cartridge should be delayed until you manage to get something out of the existing setup. As Stiffgriff says it sounds like there is something wrong with your demodulator, since what you have should give working CD-4 with at least some records.

 

[Doug G.]

If you were getting correct CD-4 performance and the radar wasn't illuminating, it would certainly be possible that the radar LED or driving circuit could be the issue. However, since you are not getting any CD-4 performance, it is not likely that the radar LED or circuitry is the problem. It is only an indicator.

The CD400B is either not getting the signals from the TT/cartridge or the CD400B is, itself, defective. Either way, it is not switching into 4 channel mode.

Doug

 

[ArmyOfQuad]

If you are getting double stereo in 4 channel mode, and you're detecting no difference between 2 channel and 4 channel mode, and you aren't getting a radar LED, that certainly implies there's no carrier detection.

However, the thing I'm seeing missing from this discussion is calibrating the separation controls. If it's a broken LED and the carrier is being detected, then the adjustment of the separation controls should result in some sort of audible difference between the front and back. With it turned all the way down, I believe it plays back just the difference signal (which would sound same front and back, but different than 2 channel mode. Rather hollow sounding.), and as you turn it up it adds the sum signal so you can dial in the maximum separation. If you turn it up too much, there will be minimal separation, and would get you into a state where you might not notice the difference between front and back. Of course using a CD4 calibration record with test tones would be ideal for adjusting the setting, but a record with a high separation mix can get the job done too.

If you aren't getting any front/back difference with adjusting the separation controls, or you aren't hearing the difference signal with the separation turned all the way down in 4 channel mode, then the question is, why isn't a carrier being detected? Is it a bad demodulator, or no carrier present in the signal coming into the demodulator? One method I can think of to check would be to connect the output of my turntable to an input of a computer sound card, and make a 96kHz recording of a CD4 record, and zoom in on the wav file to see if a carrier is visually present in the recording.