Just received my Pioneer QD-240 CD-4 Demodulator....

[Q-Eight]

... and I'm curious to know if it works. Now, I've recently reported that I got decent CD-4 using a Panasonic SE-405C Demodulator, Pioneer PL-530 Turntable and an AudioTechnica CN5625AL stylus and cartridge.

Now, Turntable and Cartridge are the same, but change the Panasonic Unit to the Pioneer. No CD-4 light, not even a whimper. The pilot light does come on and I get front only stereo in 2CH mode, and dual stereo in 4CH Auto mode.

Is it a dud or is my stylus/cartridge combo not passing enough carrier signal to the demod? Just strikes me as odd that I could get decent CD-4 with the Panasonic unit.


Thanks,
Darrin.

 

[proufo]

Is it a dud or is my stylus/cartridge combo not passing enough carrier signal to the demod? Just strikes me as odd that I could get decent CD-4 with the Panasonic unit.

Have you calibrated for carrier level already?

There could be though something wrong with your unit though.

BTW, while working on the simplification of my 4DD-5, I discovered that one of the pots for carrier level provides one tenth of the resistance compared with the other, 50K vs 5K. It either has a malfunction or they used the wrong pot at the factory.

I'm separating the pots, so I can make individual adjustments for each channels, same as the big boys.

 

[Q-Eight]

The QD-240 has carrier level and seperation adjustments right on the front. I can fiddle with them all I want and nothing happens. No CD-4 light

 

[Quadzilla]

The QD-240 has carrier level and seperation adjustments right on the front. I can fiddle with them all I want and nothing happens. No CD-4 light

I think that I have a QD-240 kicking around in my closet of doom. I will hook it up and see if it does anything weird. I don't use magnetic cartridges though, so it may not be the same thing. Let me check it out. Mike.

 

[Q-Eight]

Cool, thanks! I have a feeling since my cartridge is a simple stereo cart, the QD-240 isn't picking up a carrier signal. It just seems odd to me that the Panasonic unit picked it up and worked OK.

 

[Quadzilla]

Cool, thanks! I have a feeling since my cartridge is a simple stereo cart, the QD-240 isn't picking up a carrier signal. It just seems odd to me that the Panasonic unit picked it up and worked OK.

That does seem a bit odd, but it might be something as minute as the internal wiring of each demodulator. If you are using a stereo cartridge, you are likely so close to the edge as far as working or not, that the slighest thing to tip you the wrong way. In any case, I just hooked mine up and the "CD-4" light in the top half of the little window lit up as soon as the stylus hit the grooves. Cool unit though, there is a separation meter in the bottom half of the window that only lights up when you push in one of the separation knobs. I really like having the 2-ch phono bypass on the front though. Having it on the back of my Marantz CD-400B is a pain in the butt. Anyway, sorry I couldn't get you any farther. Good luck, Mike.

 

[Q-Eight]

Well thanks for the tip on pushing in the Seperation knobs to get the meter to light up!! I did not know about that one. Maybe my CD-4 light is burnt out or maybe the cartridge/stylus I'm using just isn't up to par for using the QD-240. No big deal, it gave marginal CD-4 playback with the Panasonic unit. Could it be the Panasonic is just more sensetive than the Pioneer? Maybe I'll borrow my friends Marantz CD-400 and if it too does not light the CD-4 light, then I'll know for sure it's my cartridge. Thanks much.

One other question: When setting the knob to Direct (2 Ch output) it does not pass thru the amplifier. Is that the way it's supposed to work?

 

[Marcsten]

I hope this is not the case, but it may well be your demod. My experience with many different demods, although none with your particular unit, is that even if you have a cart that doesn't have a wide enough response to work well with cd4, nearly any good cart will at least light the light. As I say, hope I am wwrong. If it is the demod, probably not worth fixing - try again.
Marc

 

[Quadzilla]

One other question: When setting the knob to Direct (2 Ch output) it does not pass thru the amplifier. Is that the way it's supposed to work?[/QUOTE]

On my Marantz, and I am sure that the Pioneer is the same, the 2-ch phono direct passes an unmodified (read low output) magnetic phono signal to the phono outputs. Connect a cable between these on the back of the demod and a phono (preamp) input and then you can use a matrix decoder to decode SQ and QS LPs. Mine is connected to the phono input on a Bryston 0.5B preamp, and the tape output feeds my QSD-2 and Tate decoders to decode matrix albums. This is why I like the front panel switch knob on the Pioneer, rather than the one on the back of the Marantz. I hope I didn't confuse things. Mike.

 

[Q-Eight]

I hope this is not the case, but it may well be your demod. My experience with many different demods, although none with your particular unit, is that even if you have a cart that doesn't have a wide enough response to work well with cd4, nearly any good cart will at least light the light. As I say, hope I am wwrong. If it is the demod, probably not worth fixing - try again.
Marc

I hope you're wrong, Marc. I spent $58 bucks on this baby, and everything looks good inside.... but I fear what you say is true. My cartridge worked quite well with my Panasonic unit, but won't even light up the Pioneer. *sigh*

 

[sspsandy]

Before you give up on the unit, if you are serious about CD-4 it pays to get a shibata or line contact stylus type cartridge, it is the single thing that will give the CD-4 playback the most bang for the buck. The Quadradisc had a deeper groove with a second high frequency carrier track cut into it higher up on the groove wall. Only the CD-4 stylus is shaped and designed to play the whole area and pick up that secondary rack properly, standard needles are wider, rated for lower frequencies, and only play a narrower area of the groove. Another key thing is to have a turntable that tracks the groove accurately, or has a headshell and arm that can be adjusted. Finally, and I haven't done this yet, low impedence interconnects, the turntable has to be modified with RCA style female jacks replacing the cables, and even low impedence wiring from the cartridge to the jacks, supposedly improve the sound immensely. @:

 

[ress4278]

"I'm separating the pots, so I can make individual adjustments for each channels, same as the big boys."

Proufo,Is this a mod that you've already completed? Any improvement in sonics and/or operation of the unit? Lance

 

[proufo]

"I'm separating the pots, so I can make individual adjustments for each channels, same as the big boys."

Proufo,Is this a mod that you've already completed? Any improvement in sonics and/or operation of the unit? Lance

Still in the early stages and going forward slowwwly.

Wiil post a parts list soon.

 

[proufo]

This is the parts list for both my SQ-W and 4DD-5 R&R (rebuilding and refreshing).

Components for SQ-W

Qty ID Spec

2 R3,R4 1 KOhm 1%
2 R3,R4 Pot 5 Kohm Stereo
6 RCA Fem Chasis
4 R29, R30, R31, R32 470 Ohm 1%
4 Vol Pots Dummies 10 KOhm 1%
8 C11--C18 4.7 uF/25V
6 C1, C2, C4, C5, C6--C9 1 uF/50V
2 C3, C10 47 uF/10V
2 R109, R110 2.2 KOhm 1%
2 R111, R112 1 KOhm 1%
2 R111, R112 Pot 5 KOhm Stereo


Components for 4DD-5

QtyID Section Spec

2 C101, C102 Phono 1 2.2 uF/25 V Tantalum
2 C103, C104 Phono 1 47 uF/25 V
2 C107, C108 Phono 1 100 uF/6.3 V
2 C115, C166 Phono 1 10 uF/25 V

2 C117, C118 Phono 2 0.22 uF/25 V (LLC)
2 C121, C122 Phono 2 33 uF/6 V
2 C123, C124 Phono 2 3.3 uF/25 V

8 R135--R142 Matrix 10 KOhm 1%
4 C127, C129
C128, C130 Matrix 4.7 uF/25 V
2 C131, C132 Matrix 1 uF/50V


2 C325, C326 ANRS 0.22 uF/16 V (LLC)
2 C311, C312 ANRS 0.68 uF/16 V (LLC)
2 C329, C330 ANRS 33 uF/6.3 V
1 C343 ANRS 10 uF/10 V
4 C301, C302,
C341, C342 ANRS 4.7 uF/25 V
2 VR301, VR302
VR303, VR304 ANRS Pot 20 KOhm Stereo

2 C136, C137 Power Supply 470 uF/50 V
2 C133, C135 Power Supply 100 uF/50 V
1 C134 Power Supply 220 uF/35 V

2 C1, C2 Phono Input 0.01 Ceramic
6 Phono Input/
Line output RCA Fem Chasis

2 C301, C302 PM/FM Eq. 4.7 uF/25V