Tips on getting my CD-4 system running

[Tpapp54321]

Hello! I’m still fairly new to the quad scene and despite lots of warnings to avoid CD-4 I decided that I would attempt it simply to experience all the forms of quadraphonic vinyl.

Starting with my equipment...
1. A Sansui QRX-7001: Planned to use the onboard demodulator
2. JVC VL-5: Seems to check the box for low capacitance wiring and even states it’s “CD-4 Ready”
3. Audio Technica LP 331 Cartridge: Got off eBay and was said to be new old stock, stylus looks good under a microscope.
4. Warner, Electra and Atlantic CD-4 Demonstration Quadradisc for adjustments

After acquiring the JVC and AT Cartridge this last week I decided to hook everything up. I adjusted the best I could to the Baerwald system and don’t seem to be getting noticeable distortion like I was after my first few attempts so I decided to move to the receiver and work on demodulator adjustments.
However, I don’t seem to be getting anywhere using the calibration knobs and by changing the carrier level. I’m getting the CD-4 light to shine after turning the carrier level knob clockwise past 10 degrees, but I don’t notice any separation from the fronts to the rears. The separation knobs just seem to change the volume but no separation occurs and the volume is the same between the fronts and rears. So that brings me to some questions...

-Does this seem like a receiver problem or is the demodulator most likely receiving a poor signal?
- Are there any adjustments I can try and do to my turntable or stylus that may help?
- Any tips, tricks or advice in general?

 

[Circular Vibes]

Are you using a CD4 set up record to calibrate? If not, get one and use the written directions supplied. The test signals are designed to help you and put the rear signal in the rear with the fronts removed when calibrated properly. Some of us can use a standard CD4 LP with known channel placement, but this comes from experience. I have an America track to tweak with as the rears are almost silent until a certain point. The 30 kHz signal should be set just after the point it comes on.

 

[The Quadfather]

I have written much about CD-4 and how to set it up. Check the archives. Search for: "Proper Adjustment of a CD-4 demodulator" This post discusses the technical aspects of how a CD-4 record is recorded, how the demodulator works, and how to set it up. The search will also bring up the follow up posts. Also, The first thing you need with CD-4 is a cartridge and stylus that can actually track the fine modulations of the subcarriers. This is essential for distortion free CD-4 performance. I don't know how good the one you have is, but the Audio Technica AT440MLb is still availlable, is a modern microline cart, and does a good job. I use the AT440MLa, it's predecessor, and it performs quite well. There were a lot of cartridges made in the quad era, that were rated for CD-4, but just didn't perform well. Plus, you have to track it a little heavy, about 1 3/4 grams. This does not harm the record. You used to be able to get an AT440MLb at around $150.00 . Last time I checked, the price had gone up considerably.

 

[The Quadfather]

By the way, I think you mean that you have the AT331LP cartridge. I used those for a while. I was buying old stock and since I could get the cart with stylus for what a stylus cost, I would just buy a cartridge whenever the stylus wore out. I got about 6 months off of a stylus before it would no longer track a CD-4 record properly. When I couldn't get them anymore, I switched to the AT440MLa. The performance was better, and cleaner. Also, since then, I am only on my second stylus and the same cart. That was probably about 15 years ago. Still going strong. I still have a bunch of AT331LP carts that are great for stereo, but useless for CD-4. By the way, has anyone tried the Audio Technica VM540ML? It should be a good cart.

 

[Mark Anderson]

has anyone tried the Audio Technica VM540ML? It should be a good cart.

I purchased one with a new turntable and hope to get CD4 going by the end of the year. It has been great for stereo so far

 

[J. PUPSTER]

By the way, has anyone tried the Audio Technica VM540ML? It should be a good cart.

I'll be trying out a new TT soon with an Audio Technica VM740ML (with much to learn also.) Seems I still don't get all the upper Frequency Response requirements (in actual use) concerning CD-4.
*"Soon" - being relative?

 

[The Quadfather]

Keep in mind that the AT440MLa and AT440MLb do not show specs that indicate that it might be useful for CD-4. My guess is that they didn't want to guarantee CD-4 compatibility, so they short sold the specs. However, these carts do perform well.