Marantz CD-400 stopped working

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n8nagel

Well-known Member
Joined
Oct 7, 2016
Messages
142
I got two sides out of it before it quit... I played both sides of a Stravinsky quadradisc and it worked flawlessly.

Then I went to play a regular LP just for enjoyment and I noticed I was getting significant output out of the rear channels. Now the "RADAR" light lights up whenever the turntable motor starts.

Are there any common problems with these things or is it time to take it to a tech (assuming that I can find one who won't laugh at me for having such a thing and trying to still use it?
 
I got two sides out of it before it quit... I played both sides of a Stravinsky quadradisc and it worked flawlessly.

Then I went to play a regular LP just for enjoyment and I noticed I was getting significant output out of the rear channels. Now the "RADAR" light lights up whenever the turntable motor starts.

Are there any common problems with these things or is it time to take it to a tech (assuming that I can find one who won't laugh at me for having such a thing and trying to still use it?
The radar light comes on even in 2ch mode? I have a jvc demodulator that cannot be left in 4ch mode with non-cd4s(radar light comes on, loud sound from rears). It is kind of annoying that the cd-4 demodulators have to be connected to the phono input as well as the 4ch input(it won't work as a regular 2ch preamp, only cd-4), I use the built-in demodulator on my receiver more often because of this inconvenience.
 
The radar light comes on even in 2ch mode? I have a jvc demodulator that cannot be left in 4ch mode with non-cd4s(radar light comes on, loud sound from rears). It is kind of annoying that the cd-4 demodulators have to be connected to the phono input as well as the 4ch input(it won't work as a regular 2ch preamp, only cd-4), I use the built-in demodulator on my receiver more often because of this inconvenience.

no, but in "auto" mode the radar light comes on as soon as the platter starts spinning (tonearm not even dropped), and yes, I get sound out of the rears. In "2CH" mode the light is out, but now you've got me wondering, I do not remember if it was still outputting sound to the rear channels or not. I want to say that it was.

I swear the one time I played a CD-4 disc, the radar light didn't come on until after the stylus passed the lead-in groove, and it went out at the end of each side. That was the one and only time it actually worked like I expected it to work. I also swear that I've used it as a 2 channel phono stage before and the radar light didn't come on no matter which position the switch was in.

I can't remember, was it the CD-400 or CD-400B that I was told was basically a JVC unit? Thing about this one is it is nice in that it also has an aux input so you don't lose an input when you use it (which is actually relevant to my interests; I've also got my Oppo hooked up to downmix digital sources to 4.0) where I was just looking on eBay this morning and the JVC units that I saw didn't have that aux.
 
the radar light comes on as soon as the platter starts spinning (tonearm not even dropped)
Strange, maybe aging components in the demodulator possibly causing ground-related issue, does it still play cd-4s ok?
I have the oddball JVC 4DD-10 which only has 2ch direct out/4ch out with auto carrier, it works fine for cd-4, but for non-cd4 I have to push the 2ch-button which uses 2ch direct out into the phono level input on the receiver, otherwise I get the horrible noise in 4ch mode. The built-in demodulator on my Kenwood 9940 never has this problem, it will even decode matrix records while in cd-4 mode(I tried it with an SQ test record). Do you use the 2ch direct to play non-cd4s?
 
I am going strictly from memory here as I haven't tried it in a while but I believe most demodulators output to all four channels in auto mode even if it switches to 2 channel mode. It's double stereo. I'll go down and try it with my SE 405 and report back.

Also, anything that radiates 30kHz, at a strong enough level into the demodulator, will light the radar. You might try relocating the demodulator.

Doug
 
I am going strictly from memory here as I haven't tried it in a while but I believe most demodulators output to all four channels in auto mode even if it switches to 2 channel mode. It's double stereo.
I was playing an SQ record(in SQ mode) but forgot to switch out of cd-4 source selector, didn't notice till the end of the side, the receiver blends the matrix decoder with the double stereo(possibly as an idiot-proof feature to prevent completely losing the 4 channel field). The seperation pots still work also, so its interesting to fiddle with them while in matrix mode, but yes, output is plain double stereo with non-cd4 in discrete mode.
 
I have confirmed my SE-405 outputs to all four channels in 2 channel mode, whether the demodulator switches out of four channel when the carriers aren't present or when the demodulator is manually put into 2 channel mode. Same with my SH-400.

I believe this was pretty standard practice with all stand-alone demodulators.

An SQ record played through a demodulator won't be decoded and will be the same as played through a regular two channel system. The two quad systems are entirely different.

Doug
 
To address the original query, there may be nothing wrong with the Marantz. Output from all four channels in two channel mode is most likely normal and the radar turning on anytime the turntable is on, indicates a 30kHz signal is entering the demodulator, whether through the air or the input cables. If the unit is enclosed in its original cabinet, through the air is unlikely but not impossible. Disconnect the inputs to the demodulator and see if the radar extinguishes.

Doug
 
An SQ record played through a demodulator won't be decoded and will be the same as played through a regular two channel system. The two quad systems are entirely different.
You are correct, it's just an anomaly on the 9940 that I always trip about. I still don't understand why the radar gets triggered so easily with non-cd4s on the JVC vs. never on the Kenwood, aged caps I guess.

Maybe try plugging in the power for the demodulator or tt in a different outlet, moving the demodulator as Doug said, switch out the cables, or(if you have one available) try it with a different turntable/cartridge.
 
The radar turning on more easily on one demodulator than another may just be a difference in threshold or sensitivity. Turning the carrier level controls, if present can even make a difference.

In fact, on the SE 405, the carrier level is adjusted by setting the demodulator to discrete, unplugging the input from one channel and turning the carrier level control until the radar just comes on and repeating for the other channel.

The SH 400 is really cool with the meter. Just turn up the carrier level until the meter pointer is in the right place on the meter. Sometimes, it's surprising how much difference there is in carrier levels from one record to another. This was all supposed to be fairly standard.

Doug
 
Glad you were quick with your investigations Doug. I was flipping through both a JVC 4DD-5 and a Marantz CD-400B user's manual earlier today reading about the "Direct Out" switch and was surprised to read that in "4 Ch Auto" both models will output double stereo from non-CD-4 discs. Kind of like the discrete world's way of synthesizing quad (very badly).

Also ghalteman, interesting observation about LED's activating the radar light. I was wondering if something with the turntable motor is generating a carrier signal? If the demodulator is disconnected from the turntable, will the radar still illuminate when the platter begins spinning?

The big question is, I guess, are you still getting demodulation regardless of the radar behavior, and is it the same sound quality as previously?
EDIT - I just re-read the original post and that half answers my question: sound is coming out of the rear channels, but it's louder, when playing a stereo LP.
furui_suterioo may have hit the nail on the head with his comment about the problems he experienced with stereo LPs through a demodulator. So,
is your demodulator still performing as you expect when you play a Quadradisc?
 
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I'm going to have to play more. I can tell you that the radar light doesn't light anymore with the TT plugged straight into the receiver's phono input. Beyond that I will have to rearrange some stuff and retest. I downloaded the CD-400 manual and didn't see the double stereo thing, but I just skimmed it. Also I need to find and clean my test disc and do the separation adjustments assuming I don't need a repair.
 
I'm going to have to play more. I can tell you that the radar light doesn't light anymore with the TT plugged straight into the receiver's phono input. Beyond that I will have to rearrange some stuff and retest. I downloaded the CD-400 manual and didn't see the double stereo thing, but I just skimmed it. Also I need to find and clean my test disc and do the separation adjustments assuming I don't need a repair.
Here is the answer:
20201227_000218.jpg

In my case according to this, all of my non-cd4 records "contain enough high frequency signals to render them unplayable in the 4 CH AUTO position". Not very convenient, I suppose now that recapping won't really improve the situation either, doesn't really matter since just have to push the 2ch button. I bought Blue Jeans LC1 cables to run from the 2ch-direct to the receiver phono in, just so that I could still use the receiver's built-in demodulator along with JVC demodulator, but even that setup still causes a slight performance decrease in the built-in demodulator vs. without the JVC. Demodulators swirling around my brain 🧠🧠
 
I'm assuming that's the owner's manual? Where did you find it? I only found the service manual on HFE and I think I need the owner's manual as well, as the service manual refers you to the owner's manual for carrier level adjustment (which the 400B doesn't have) or is it simple enough one of you could walk me through it?
 
It was always best to use the 4 CH Auto mode for CD-4 and switch to 2 Channel for stereo (prevents false triggering).

It was always best to use the direct output for stereo/matrix phono to bypass the demodulators 15KHZ low pass filter.

Outputting double stereo was necessary as the demodulators decoded FM difference signal adds and subtracts from the stereo signal, you wouldn't want the back channels disappearing with carrier dropouts!

I always prefer double stereo to regular stereo anyway, I was annoyed that receiver manufactures didn't always (or rarely) gave that output switching option.

Modern electronics and even LED lights emit electromagnetic interference, much more a problem today than in the seventies!
 
OK, correct me if I'm mistaken, but a little googling appears to reveal that the CD-400 (but not the similar looking CD-400B) is basically a JVC 4DD-5 with an added auxiliary input. That given, I was able to find an instruction manual for a 4DD-5 and also rummaging through my as yet uncleaned/unfiled records the Marantz CD-4 calibration disc. Will it be obvious what I'm listening for with the 30 kHz adjustment? I will hook it back up later and report back... (don't want to do it now as everyone else is asleep and if I run the disc through the ultrasonic now I might be bludgeoned...)

Also, it sounds like I need to hook a pair of RCAs from the direct out to my receiver's phono stage to listen to 2ch, SQ, or QS. Can I leave the "DIRECT OUT" switch engaged all the time then without any ill effect in the "4CH AUTO" mode? (I understand that that will disable sound output in the "2CH" front panel switch position) Do I add a ground wire from the CD-400 to the receiver? Am guessing no as I see no mention of it in the booklet, but that seems counterintuitive to me. It does confirm that I should have "double stereo" in 4CH AUTO. Not clear whether that is supposed to be also true in 2CH or not.

Why am I doing this again...? this whole mess makes playing a simple LP seem so complicated.

I apologize if all of this is really basic for some of you, but please understand that I wasn't even in grade school yet when CD-4 died, and my parents were music lovers but neither wealthy nor audiophiles so I was not exposed to this stuff back in the day and I have literally no knowledge base other than what I've read online here and elsewhere.

As to the comment about PREFERRING double stereo - I get it. I just want to make sure that everything is working correctly and that my system can reproduce the sound exactly as intended. Then if I want to adjust that sound, sure, let's do it. Maybe even listen to a stereo disc with QS or SQ engaged. Coincidentally, I've noticed a similar issue with Spotify playback from my PC. Since I got this quad setup hooked up I changed my PC playback from a dedicated 2 channel DAC to a HDMI connection to my Oppo BDP-105 which then downmixes multi-channel sources to 4.0 and inputs into the (coming back around to topic) aux input of the CD-400. What I've found is, while the speaker check in my Linux sound preferences does exactly what I expect it do (that is, FL and FR play through FL and FR, center plays through both FL and FR, SL and SBL play through RL, SR and SBR play through RR, LFE plays through all speakers) when I actually play music over the HDMI connection, it plays through all speakers. Again, the effect is not unpleasant, but I really would like to have control of the situation.

Then, of course, once I get this all working, then I get to pull my QRX-7001 out of storage and test that. Then, see if my KR-9940 has been fixed yet... (no it was seriously not intentional to collect this much quad stuff)
 
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OK, correct me if I'm mistaken, but a little googling appears to reveal that the CD-400 (but not the similar looking CD-400B) is basically a JVC 4DD-5 with an added auxiliary input. That given, I was able to find an instruction manual for a 4DD-5 and also rummaging through my as yet uncleaned/unfiled records the Marantz CD-4 calibration disc. Will it be obvious what I'm listening for with the 30 kHz adjustment? I will hook it back up later and report back... (don't want to do it now as everyone else is asleep and if I run the disc through the ultrasonic now I might be bludgeoned...)

Also, it sounds like I need to hook a pair of RCAs from the direct out to my receiver's phono stage to listen to 2ch, SQ, or QS. Can I leave the "DIRECT OUT" switch engaged all the time then without any ill effect in the "4CH AUTO" mode? (I understand that that will disable sound output in the "2CH" front panel switch position) Do I add a ground wire from the CD-400 to the receiver? Am guessing no as I see no mention of it in the booklet, but that seems counterintuitive to me. It does confirm that I should have "double stereo" in 4CH AUTO. Not clear whether that is supposed to be also true in 2CH or not.

Why am I doing this again...? this whole mess makes playing a simple LP seem so complicated.

I apologize if all of this is really basic for some of you, but please understand that I wasn't even in grade school yet when CD-4 died, and my parents were music lovers but neither wealthy nor audiophiles so I was not exposed to this stuff back in the day and I have literally no knowledge base other than what I've read online here and elsewhere.

As to the comment about PREFERRING double stereo - I get it. I just want to make sure that everything is working correctly and that my system can reproduce the sound exactly as intended. Then if I want to adjust that sound, sure, let's do it. Maybe even listen to a stereo disc with QS or SQ engaged. Coincidentally, I've noticed a similar issue with Spotify playback from my PC. Since I got this quad setup hooked up I changed my PC playback from a dedicated 2 channel DAC to a HDMI connection to my Oppo BDP-105 which then downmixes multi-channel sources to 4.0 and inputs into the (coming back around to topic) aux input of the CD-400. What I've found is, while the speaker check in my Linux sound preferences does exactly what I expect it do (that is, FL and FR play through FL and FR, center plays through both FL and FR, SL and SBL play through RL, SR and SBR play through RR, LFE plays through all speakers) when I actually play music over the HDMI connection, it plays through all speakers. Again, the effect is not unpleasant, but I really would like to have control of the situation.

Then, of course, once I get this all working, then I get to pull my QRX-7001 out of storage and test that. Then, see if my KR-9940 has been fixed yet... (no it was seriously not intentional to collect this much quad stuff)
With the direct out selected the input to the demodulator will be cut off altogether. I would add a ground wire as you describe, between the demodulator and the receiver. I would only remove it in the unlikely event that it causes more hum. You will have double stereo in both output modes.

Why are you doing it again? I'm sure I've asked myself that many times before as CD-4 is so finicky! I found that the CD-400B produced the best results for me, although some prefer the adjustable demodulators. I was getting decent results with the JVC 4DD-5 as well but the automatic carrier of the 400B seems to work much better. Usually you are told to adjust the carrier level until the test tone starts to sound distorted, then back it off. That doesn't seem like a very precise adjustment to me, and carrier levels can vary from disc to disc. The Grado cartridge says not to use the test record but to just turn the carrier all the way up and set the separation controls midway! You need to make sure you use low capacitance cables, set the cartridge overhang properly, adjust the anti skate (Grado instruction say to disable anti skating). Also any stylus wear will effect results. A stylus that sounds fine on stereo records may still not work properly on CD-4.

I hear you about the HDMI connection, I'm not a fan of that I prefer to use the analogue outputs. You can plug a USB hard drive directly to your Oppo, or steam from your PC via the LAN connection. I've found that DSD sources (played through my Oppo BDP-103) don't get mixed down, only PCM does.
 
Update:

I think I need a better calibration disc... I hooked everything back up, this time with the extra interconnect between the CD-400 DIRECT OUT to the 4270's phono input.

I first got frustrated because I could not get the radar light to light at all. I discovered that the DIRECT OUT switch has to be OFF even in 4CH AUTO mode to light the radar. Too much capacitance? Or is this normal operation? The DIRECT OUT should be very low capacitance as it's a 18" IC that I made myself from Mogami mini coax and Switchcraft connectors. Nevertheless, the thing doesn't work unless I turn that switch off, which is annoying as it is on the rear panel. (FWIW the ICs between the CD-400 output and the receiver are the same ones, although you'd think that wouldn't matter. Table is a Technics SL-1650 with stock permanently connected ICs. I did not connect ground from CD-400 to 4270 as I did not detect appreciable hum with 4270 in PHONO, CD-400 in DIRECT OUT and 2CH with nothing playing.)

First test: carrier level - sounded best in either full clockwise position or one click back. This sounds opposite of the procedure for adjusting the 4DD-5 but again I can't find a CD-400 owner's manual and the control is not labeled, maybe it works in the opposite direction of the 4DD-5?

Second test: "CD-4 adjust" - I did these blind and both controls ended up straight up in the 12 o'clock position so I'm assuming this is right. I never got the rear speakers completely quiet but I could tell a difference as I was adjusting.

Third test: channel identification - the chimes all sounded like garbage, with lots of crosstalk.

However, the Shostakovich disc still sounds pretty good. Maybe better than when I just threw everything together and played it.

I've been occasionally able to reproduce the behavior of the radar light I described above (coming on as soon as the TT motor starts) but it only happens after I've fiddled with all the switches and controls, so maybe this is something where I need to let all the capacitors reform etc. before worrying about it.

Somewhat more annoyingly, the 7" set down point for the SL-1650 is way off... if it's not one thing, it's another.

So, quadraphonic hive mind, what are your thoughts given the above? Do I need to find a better copy of the calibration disc before going too much farther? Does what I describe sound indicative of a cartridge alignment or VTA issue? Any other thoughts? Thanks for sticking with me.
 
With the direct out selected the input to the demodulator will be cut off altogether. I would add a ground wire as you describe, between the demodulator and the receiver. I would only remove it in the unlikely event that it causes more hum. You will have double stereo in both output modes.

Got it. So really, that switch should have been on the front panel, or maybe a 3rd position of the 4CH AUTO / 2CH switch. But no sense second guessing something designed back when I was maybe 2 years old. That also means that apparently I'm seeing more or less normal operation (see above, you and I were posting apparently at the exact same time.)

Why are you doing it again? I'm sure I've asked myself that many times before as CD-4 is so finicky! I found that the CD-400B produced the best results for me, although some prefer the adjustable demodulators. I was getting decent results with the JVC 4DD-5 as well but the automatic carrier of the 400B seems to work much better. Usually you are told to adjust the carrier level until the test tone starts to sound distorted, then back it off. That doesn't seem like a very precise adjustment to me, and carrier levels can vary from disc to disc. The Grado cartridge says not to use the test record but to just turn the carrier all the way up and set the separation controls midway! You need to make sure you use low capacitance cables, set the cartridge overhang properly, adjust the anti skate (Grado instruction say to disable anti skating). Also any stylus wear will effect results. A stylus that sounds fine on stereo records may still not work properly on CD-4.

I hear you about the HDMI connection, I'm not a fan of that I prefer to use the analogue outputs. You can plug a USB hard drive directly to your Oppo, or steam from your PC via the LAN connection. I've found that DSD sources (played through my Oppo BDP-103) don't get mixed down, only PCM does.

I could stream from LAN from PC to Oppo? not sure how to do that... will have to look into that later.

I was using an asynchronous USB DAC before, but that's only 2 channel, as is the similar connection to the Oppo. I was able to use Kodi to play back a 5.1 mix of King Crimson ITCOTCK that I had kicking around my HDD using a DisplayPort to HDMI adapter. It's a total kludge but it's working. I have a 5 port HDMI switch, inputs are Roku, Fire Stick, Chromecast, and PC (5th not populated yet) output goes to HDMI In-Back of Oppo, output of Oppo goes to TV. I can't get ARC working to save my life so TV sound is through optical input to Oppo. Oppo analog outputs go to the aux input of the CD-400. So basically I have duplicated the functionality of an AVR except I have more remotes than any sane person should have in his bedroom, and I still have to get out of bed to adjust the volume. Nothing like doing things the hard way eh what :)

then as I said before, once I'm comfortable with this setup, I'll swap it out for my Sansui QRX-9001 and the fun starts all over again, unless that just happens to work just as well right out of the box. I started with the Marantz however as it has pre-outs and the Sansui does not, I was thinking of integrating a sub and/or adding a power amp (I do have a spare HK770 kicking around, that's about the right power level to mate with the 4270 in bridged mode...) but that might just be stupid for a bedroom system...

Now, I was flipping trying to see if I could get the Steelers game in, and I find that when I am in "Discrete" mode on the receiver, I correctly get stereo or mono signals only out of the front speakers, but in "2CH" mode, I get "double stereo" again. Is this correct? I'm at a little bit of a disadvantage as I'd have to drag another computer out to get on HFE and DL the 4270 manual (long story.)

Edit: found it at vintageshifi and yes, double stereo is correct again. They sure like pushing you to listen in double stereo don't they?
 
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