CD-4 - The thin line between success and failure, but still in the fight!

[jupp369]

Here's a couple of attached files (CD-4 Quad pre-needle drop) of the hum for folks to check out. I boosted them about +20dbs already.

Pany SE-405 & Marantz CD-400B

The vocals are actually much more buried into this than I remember; but I do believe they are there (I'm not on any prescriptions for my mental state AFAIK )

Let me know if I'm hearing things please?

Hear and see a very sharp hum. Not the normal Hum of 50/60Hz (100/120Hz).
Constant, not radio. Not your amp's.
Looks like something as Thyristor / Triac, used in power regulation as for lamp dimmer, pump / motor engine control, Refrigerator , and (still thinking) ..

100ms / 12 = 0,00833, 1 / 0,00833 = 120Hz
so you have a 60Hz system?

but it's only with the CD-4 cartridge? did you check the contacts in the tone-arm, are they clean and moving?

 

[Sonik Wiz]

Well @J. PUPSTER it's been a while. Just wanted to bump this cuz I'm still interested in how things are going. Shaping up?

 

[J. PUPSTER]

Well @J. PUPSTER it's been a while. Just wanted to bump this cuz I'm still interested in how things are going. Shaping up?

not yet thanks

I did get some of those ferrite bead/clamps in and tried them on gear that didn't have them already, but didn't seem to help.

I'm still thinking maybe some kind of ground loop issue; but would it only affect the Demod's and nothing else?

Still hearing voices in the hum background, tried to isolate where it's coming from again (routers, lights, phones, dsl, etc.) but it has not revealed itself as of yet.

 

[edisonbaggins]

You've got everything powered through line conditioners?

 

[J. PUPSTER]

You've got everything powered through line conditioners?

not yet, but will give that a try shortly; something tells me that isn't going to work either, but worth a try I guess

 

[edisonbaggins]

In this case, I would love to be a buzz kill!!!

 

[quadsearcher]

I thought it got worked out with rewiring from tone arm leads to RCAs? Then putting the ground lead back on the demod?
Must've been someone else with CD-4 hum issues, or it was a dream....
Anyway, if the voices are radio (most likely) then that means something is acting like a diode when it should not. Typically that would be a poor connection with an air gap or crystallized flux. Like a cold solder joint where arm wires meet rca cables on a terminal strip. Maybe swap the short interconnects between the cart and headshell if this has those.
If another cart had essentially zero noise, but everything else was the same, I hate to say it, but that points to the cartridge itself.
Or things can change when changing headshells. Tiny drops of DeOxit on head shell/arm connections might help. on the ring that tightens the shell to the arm, that's a ground connection too.

 

[user 19847]

You can get the noise you are describing when you have a piece of equipment close to your phono cartridge. It could be your phono cartridge is acting like an antenna. Try removing or unplugging the audio component nearest your phono cartridge and see if that removes your hum and radio noise.

 

[MidiMagic]

A ground loop can also do this. I saw (heard) it happen with an electric keyboard in a small combo. There were two paths to ground from the keyboard, one through the power supply and the other through signal cable and the mixer. We heard CB radio.

Feeding the audio signal through a direct box and opening the ground isolation switch fixed it.

Look for two paths to ground in the turntable or wiring to the demodulator. And where you have two cables from one to the other, use twinned cables to make the two ground into one big one.

 

[proufo]

I haven't followed this but I read here that moving the cables inside the demodulator can eliminate/cause noise. Not sure if the noise was hum or a higher-frequency sound.

 

[J. PUPSTER]

Thanks everyone for their input and recommendations, it is very much appreciated

I guess I need to go back to the basic question for my system as it is now. Would using the same cart., I use AT15s; and wiring both power and RCAs (good quality Blue Jean LC-1's) create a hum with the only difference being using a CD-4 demodulator. As everything else in the line does not have a hum issue AFAIK. Also, the only other gear (ROTEL TT Preamp. & Surround Master v2) that're close by the TT are things I unplug during CD-4 testing.

I've decided to give an outlet Power Conditioner a try. If nothing else, it should be a step up from the surge protector I'm currently using (see main question number 1 above for that also.)

 

[user 19847]

Have you tried taking the CD-4 Demodulator completely out of the system and see if you still have the noise issue?

 

[J. PUPSTER]

Have you tried taking the CD-4 Demodulator completely out of the system and see if you still have the noise issue?

Yes, that's what I was referring to above.

I guess I need to go back to the basic question for my system as it is now. Would using the same cart., I use AT15s; and wiring both power and RCAs (good quality Blue Jean LC-1's) create a hum with the only difference being using a CD-4 demodulator. As everything else in the line does not have a hum issue AFAIK. Also, the only other gear (ROTEL TT Preamp. & Surround Master v2) that're close by the TT are things I unplug during CD-4 testing.

 

[user 19847]

Does any of your equipment have a ground pin on the AC plug? If so I suggest you get some ground lift adapters you can get at any hardware store and lift all the AC ground pins. These can be giving you your ground loop problem as your equipment is grounded via the interconnecting cables. You can try lifting all AC grounds except the one on your Rotel Preamp. Also did you verify your ground wire from the turntable to the demodulator is making good continuity?

 

[J. PUPSTER]

I am now self observing as Schrödinger’s Hamster (why should the cat get all the abuse.) I’m neither dead or alive; but with all this long term radiation exposure, I’m definitely a neutered Zombie Hamster!

 

[ndiamone]

I want to make it abundantly clear, that I have had some success with CD-4 (quadradisc.) But recently much more failure, primarily due to two things:

1- sandpaper effect &
2- issues with old 70's era gear (hum)

When CD-4 works well, the results can be amazingly great. Very discrete mixes brought to life. But let's not fool ourselves, CD-4 is a DEAD format for all practical purposes. I'm not aware of a single bit of hardware that supports/functions with it since the 70's (I'm sure others will correct me if I'm wrong here!)
Heck, even in the whole of this very niche QQ surround/Quad forum of supposedly over 10,000 members; I wouldn't be surprised if there're only a few dozen actively listening directly to CD-4 albums.

So when it comes to support for hardware, a grand search must be undertaken for places like qrxrestore etc. that still have the knowledge and abilities to do the job right.

Long before I started working towards a CD-4 system of my own, I was a non-member lurker here taking in the knowledge the forum offered. And once I took the plunge and got into the forum, I found friends with similar interests to help me along and further my education. To date, I believe I've pretty much read most of what's offered here for CD-4 information. But that doesn't necessarily translate to a golden ticket of success. The struggle must be endured to get there.

It took me till my 3rd try at a turntable before I found one I liked and fit the bill. It's a Technics SL1200MK7. Then I had to find the right carts. I started with an AT440MLb and that did a decent job, but I felt a little more separation could be had, so I changed over to an older AT15S (Shibata) which I've been happy with, especially for CD-4. I still have a new AT VM740ML (MicroLine) to give a try; however that's one area I don't relish, is changing out carts and having to adjust/realign each time.

I've actively been buying CD-4 albums (primarily through sellers on discogs) in NM or better condition which is another added expense. Of course that's all part of the cost of the hobby, I don't really mind that, the hunt is an enjoyable aspect for me. I had a nice little stack built up and cleaned ready to go and Demodulate/Convert to digital also; when I discovered my QRX-8001 had a couple of new issues. First the Left Rear channel is cutting in and out, but I could still rip/convert the LP. Then I discovered it also developed some nasty hums (both a lower level and some higher toned hums.) Well the Sansui had already been gone over a couple years ago by qrxrestore along with the Holy Grail alignment; I can tell you, along with the initial cost of the Sansui and the qrxrestore work (along with shipping costs for the beast) it ain't cheap folks! OK, so I'm not ready to send this back again to qrxrestore for more work. I can afford it just fine, I just hate all the tearing down of my system, packing up and shipping out, etc. etc.

So I decided to look for a stand alone Demodulator while I sit on the Sansui issue some more and chew on it. I found a nice Marantz CD-400B that was listed on eBay as a NOS, and it looked every bit of a new in box type unit. So I bid on it and got it for a measly $198 with shipping. Not bad, but I knew full well that even though it looked new in box, who knows what it's really been through and also that for a nearly 50 year piece of gear that doesn't count for much. But for that money, and feeling somewhat wanting of something right away I bit on it. Well it turns out it works pretty well except it too has a mild low level hum. I thought at first, after doing some research, and hearing some vocalization in the hum perhaps I have a ground loop issue. But, after doing some other testing on my setup of:

A: Recording a regular LP through a MOTU UltraLite mk4 with just my Technics SL1200MK7 and Rotel preamp, no hum!
B: Recording a QS LP through a MOTU UltraLite mk4 with my Technics SL1200MK7 and through my Surround Master v2 for Quad, and again no hum!

All that I've talked about here on the open forum is only a tiny tip of the ice-berg as to conversations I've had with very experienced and knowledgeable folks in private messages about my CD-4/Quad issues. They all have been very valuable friends and supportive in trying their best to help me out. I feel I am sooo very close to have it all working as it should, only if the old gear would hold up. But that's the rub right!

We're now working with the idea that the hum is possibly caused (the Marantz Demod.) by either a dry joint or a failing electrolytic capacitor. None of that means much to me, as I don't have experience in working on electronics, and have no interest in learning at my advanced age. So now where does that leave me? I guess I find someone that can work on such things, kindly offer to have a go at fixing my limping Marantz; or I find another old 70's piece of Quad gear to throw money at

From my perspective CD-4 can be a beautiful lady waiting to be aurally caressed, or as more often, it appears to me at least, a cold hearted soul crushing *****!
Yes I'm still in the fight, but my time is running short if I'm going to fully realize this dream.

Here's a sample of the Marantz hum (the Marantz was turned on at about 27 sec. into this one min. mp3 sample) and boosted about 30 dbs so you can hear the hum better.

Believe it or not there is still two working CD-4 MODULATORS. One is at Toshiba in Japan and the other one is at a heretofore-unnamed 80 year old retired CD-4 engineer's house in America's Southeast.

However, considerably better modulators and demodulators can be constructed with modern digital components.

The missing link is not only the vinyl itself, but the mastering. I keep hearing about guys who are trying to update the 1979 ortofon cutterhead prototypes that, while never having been used for CD-4 were having terrific results in 3/4 speed mastering (i.e 33 for 45).

Since the Apollo fire and more and more people going to DMM anyway, that technology is really going to be the only way for analog reproduction CD-4 to live in the modern world.

Between the enhanced top end of DMM in the first place, the severe reduction of bass contour effect at 3/4 speed mastering vs half-speed mastering and the e.g. grainless dye virgin vinyl etc and the ability to cut as deep on a DMM as on a lacquer (90-100 vs the normal DMM 50 or 60) is like I said going to be the only way forward.

Whoever wants to rescue the CD-4 modulator out of the American Southeast or EMI Toshiba Japan, revamp it and send it to Abbey Road or Gay-Zed Mastering in Prague or wherever will probably be blown out of the water with their CD-4 33-for-45 cutting on a revamped `79 Ortofon head.

See posts about it on Lathe Trolls record cutting forums.

 

[DuncanS]

I am now self observing as Schrödinger’s Hamster (why should the cat get all the abuse.) I’m neither dead or alive; but with all this long term radiation exposure, I’m definitely a neutered Zombie Hamster!

Thats a definite case of quantum entanglement!

 

[MidiMagic]

Does any of your equipment have a ground pin on the AC plug? If so I suggest you get some ground lift adapters you can get at any hardware store and lift all the AC ground pins. These can be giving you your ground loop problem as your equipment is grounded via the interconnecting cables. You can try lifting all AC grounds except the one on your Rotel Preamp. Also did you verify your ground wire from the turntable to the demodulator is making good continuity?

DO NOT lift the ground at the power cord. It is often illegal in local building codes.

Use ground-loop eliminators in the signal lines.

 

[J. PUPSTER]

I'm fairly ignorant about electrical & ground loop type issues. I'm going to wait until I get that new line conditioner in early next week and then try a few other things mentioned here.

One of my main problems is that I'm using an old and heavy office credenza for my Quad set-up and it's definitely not ideal. All the major unhooking and moving gear and furniture; just to get to the back of that credenza to plug stuff in (2 different surge protectors right now) is going to be a massive PITA and take some time as I'm no youngster any longer. I recall our good man Kal Rubinson recently had a large metal rack shelving he was giving away which would have been perfect for my situation, but on the other side of the country for pick up only.

So until that's all sorted out, I'm going to side step the CD-4 stuff for now and go back to some CD and LP matrix conversions with the SMv2 to keep my party going. Of course in the meantime, I'll still be engaged here and hope others will continue to offer up any past or present issues with their CD-4 adventures to keep this discussion alive.

SIGNED -
Radioactive, but still in the fight!

 

[Quad Linda]

While researching something else, I ran across this article on CD-4 setup. Thanks to Kirk Bayne who originally posted this link to Radio Electronics magazine article. It originally appeared in their October 1973 QUADRAPHONIC issue. CD-4 setup article begins on Page 33. https://worldradiohistory.com/Archive-Radio-Electronics/70s/1973/Radio-Electronics-1973-10.pdf

There is also a list of matrix Quad LP's rated ONLY by Quad mix quality.
from Radio Electronics:
Page 43: (matrix) Quad records: The scoring runs from one to four stars. One star is the lowest and four stars are highest on our scoring system. Note well that we are only evaluating the records from the standpoint of 4 -channel technical effectiveness. The ratings shown here have nothing to do with performance or artistic

Through college, high school and beyond, I subscribed to RE, Audio (1st look at Lirpa VDRS*), Stereo Review, High Fidelity, Popular Electronics & Down Beat. 1973 was my first year in the audio business, so I sold and used much of the gear discussed in that issue.

BTW: In the late 70's, one of our service techs built a Lirpa VDRS. Wish I had a pic. We featured the real McCoy in our phono cartridge case! Looked suspiciously like an Audio Technica AT 88e w/wheels and a flag w/pole. Never could get the damn thing to work! LOL!!

* VDRS = Vehicular Disc Reproduction System.