Grundig CD-4 decoder - new to this - help please
- Thread starter The Prof
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Doug G.
2K Club - QQ Super Nova
In a CD-4 system that is even close to working properly, the radar light should not be that difficult to light. Of course, it depends upon the demodulator and circuit design but with any demodulator I've worked with, the radar lighting is almost automatic and that just means the demodulator is seeing the 30kHz carriers. Passing a 30 kHz signal to the demodulator is something almost any cartridge can do, even 2 channel stereo cartridges. So, if you're having problems with the radar lighting, something is way off.
First of all, I would remove the brush from the XUV. I found tracking was being affected on mine with the brush so I never use it. Second, you have to be sure proper tracking force is actually being applied to the stylus. This is best done with an external gauge, at least until you are sure of the accuracy of your table markings. Anti-skating is critical with CD-4 because you MUST have reliable tracking on both groove walls.
Third, be absolutely sure you have very low capacitance cables in the turntable and between the turntable and demodulator. If the ultra sonic carrier signals get attenuated there, you won't have a chance with CD-4.
Most CD-4 demodulators are made so that, when switched to regular stereo mode, either manually or automatically, it outputs signals to both front and back outputs for double stereo.
Doug
First of all, I would remove the brush from the XUV. I found tracking was being affected on mine with the brush so I never use it. Second, you have to be sure proper tracking force is actually being applied to the stylus. This is best done with an external gauge, at least until you are sure of the accuracy of your table markings. Anti-skating is critical with CD-4 because you MUST have reliable tracking on both groove walls.
Third, be absolutely sure you have very low capacitance cables in the turntable and between the turntable and demodulator. If the ultra sonic carrier signals get attenuated there, you won't have a chance with CD-4.
Most CD-4 demodulators are made so that, when switched to regular stereo mode, either manually or automatically, it outputs signals to both front and back outputs for double stereo.
Doug
Be aware that the outputs of a CD-4 demodulator are line level, not cartridge output level. It is it's own preamp so you will need to feed it to an auxillary input on the amplifier, or a tuner input will work also. Do not use the phono inputs for a demodulator. You will overdrive the phono preamp. So, cartridge straight to the demod, demod to the aux inputs. I agree with Doug G. If the "radar" light flickers, you're getting a very poor signal to the demod, if the demod is OK. By the way, unless you really know what you are doing, I would not recommend that you mess with any of the trim pots inside the box. You're talking serious test equipment setups for this. I don't know what kind of turntable you have, the standard quality turntable has a weight on the back of the tonearm, beyond the fulcrum point. you adjust the weight until the arm is in balance, and then zero the scale on the weight, and turn the weight to dial in the desired weight. The brush is not a good idea, but if you must use it, it removes about a gram of weight when it settles down, so you must dial in an extra gram to account for it. That is, if it's hinged to the stylus. Antiskate should be adjusted for the desired weight. If you can't get a good signal, ditch the brush. if you still can't, ditch the cart. Be aware that the Astatic stylus might not be as high of quality than the original Pickering part. Of course, if you get an Audio Technica AT440MLa, you pretty much eliminate the possibility of the cart being the problem. Some of the quad era "quad" stylii were pretty bad. I understand that genuine Pickering was OK, but I wouldn't trust Astatic, unless they got it from Pickering and repackaged it. I doubt that because they made stylii for everything from grammophones to high quality carts. But I doubt their standards met OEM specs on quad gear. Good Luck!
They are on the rear side of the demodulator, marked "Uebersprechen links / rechts" (front/rear separation adjust for left chn. / right chn.), löwer right side. Can be accessed with a small screwdriver. Hard to see since the potentiometers are inside the housing, and the holes are protected with rubber rings.
Tp: Set "Blend" to "Aus" (Off).
-Kristian
Tp: Set "Blend" to "Aus" (Off).
-Kristian
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