CD-4 Disc Demodulator JVC 4DD-5 . Please help.

[RSilverman]

Best of luck.
I have bought 4 of those "new-in-box" JVCs.
Only one has worked properly.
I have since acquired 5 other used and working demodulators, 2 with semiconductor options.
I have 2 quad set-ups in different rooms with same Kenwood DD 550 turntables and SME type 3 tonearms.

Did you write back to the guy and tell him it didn't work? He told me he sold 300 of them and never had anyone report an issue. I'm leaving for home soon. Cross fingers this one is perfect. But if not, I have one that works OK except for that pesky weak channel.

 

[RSilverman]

Well I tested my third one of these - the second "new" one from Canada, and....

Drum roll...

It's the worst one yet! No sound at all from the right and the left at about 10% volume with a fuzzy, distorted tone. Guess I should be happy I have one that functions pretty well and move on with my life.

 

[jrlinks]

Sorry, but predictable in my experience with those.

One of my best buys for $45.00 was a rare used PANASONIC SE-405 (SC strain gauge capable)
which the seller said still worked...which turned out to be true
If the seller can not tell if it works, skip it.
That includes those who say it "lights up" and that's the extent of it working.
I bought one of those as well, no demod at all. Phono section did work.

 

[RSilverman]

He's sending me a third one for free. When it arrives, I'll (most likely) have three dead JVC units, but a ton of RCA cables, for the low-low price of 160 dollars.

 

[jrlinks]

Yes a bunch of cheap cable that are most likely not OFC (oxygen free copper) conductors either.

 

[quadjoe]

He's sending me a third one for free. When it arrives, I'll (most likely) have three dead JVC units, but a ton of RCA cables, for the low-low price of 160 dollars.

I guess I got lucky, the one I bought hasn't had any issues (yet.) I do suspect that I'll eventually have to have it re-capped. Hopefully, this next one will work just fine for you.

 

[Quadwreck]

Yes a bunch of cheap cable that are most likely not OFC (oxygen free copper) conductors either.

Those three units could be cobbled together into a working unit in the right hands.

 

[jrlinks]

The other issue is what to play.
Even if you don't yet have a working demod, you should be looking for any CD-4 you can find now.
ebay is a good pace to start.
Sealed LPs are the safest.
There are a finite number of discs out there.
When these are gone, there will be no more...ever.

 

[RSilverman]

My CD4 collection is always growing! I found a couple odballs recently: 20th centurty percussion ensemble music (awesome!), and a sealed version of Richard Harris reads from "The Prophet" with original music. I really dug that one.

Anyway, the more I live with this JVC 4DD-5 the more I tend to side with those who say it's not a great preamp. It not only eats the highs, but the lows, as well. I have some early mono pressings of Sinatra albums from the 50s and when playing through my receiver's phono stage there's tons of bass. it jumps right out at you. With the JVC, it's about half, at best. I might wind up getting a switcher box -- assuming that doesn't kill my CD4 -- and setting it up so I can switch from between the receiver's inputs and the JVC, and just use the JVC for CD4 and SQ playback.

 

[RSilverman]

So is it a stupid idea to get two female-to-female RCA "Y" cables so I can split the signal from my turntable and steer it to the JVC and to my receiver? I'd use low-cap cables I have the rest of the way.

So the left and richt RCA leads from my turntable would each get plugged into one of these splitters. Then I'd run RCA cables from the splitter to the JVC and phono-stage of my preamp.

I guess the issue is, where do I get low-cap y cables, and is this really needed??? Anyone have any thoughts? Am I wasting more money with this project?

I'm trying to create a way to just use the JVC for quad and my receiver phono stage for everything else.

 

[jrlinks]

Stupid..yes.
You would double the capacitive load and no longer have 100K Ohm resistive load.
You could use the direct out switch on the JVC to feed the cartridge to another preamp.
I hope you have deox'ed that switch?

 

[RSilverman]

Yeah. I feel like it's a stupid idea, too. Even though it says "direct" I'm convinced the JVC is still filtering out highs and lows before it reaches those terminals. Quadfather says "no," and someone else said it's going through the CD4 filtre before going to the directs. To my ears at least, they are not "direct" at all. Something is lost in translation using those, but I'll give another go. I haven't actually used the directs out to my receiver without running through a preamp first, since I have a weak right channel on my receiver's phono stage, but I'm at the point where I can live with it if the sound quality is overall bett

 

[jrlinks]

Quadfather is of course correct.
I just looked at the schematic.
It is just a switch no filters.
If it doesn't "sound" right you may need to use Deoxit

 

[RSilverman]

This is what Doug G. said about the JVC direct outs. I'm not sure what effect "input to the internal demodulator circuits..." means. I plan to mess with it some more when I get home tonight. Any excuse to avoid finishing my taxes.

Regarding the 4DD-5:....the direct output jacks are, indeed, connected directly to the cartridge outputs. However, there is still input to the internal demodulator circuits too so this may explain a difference in sound out of the direct output jacks compared to directly into a receiver due to loading differences.

 

[jrlinks]

From the service manual.
So, switches set on both front and rear.

 

[RSilverman]

As always I appreciate all the advice from the experts here. Using my receiver's phono stage by way of the direct outs on the JVC is the way to go. My bass is back! I still have the channel imbalance on the receiver, but it's nearly the same as the imbalance on the JVC, so if I keep the balance knob shifted to the right at all times, I'm good to go for all purposes. Though I won't be playing Nilsson Schmilsson in CD4. There was a sealed copy on eBay that just went for 135 bucks today. I'm not spending that kind of scratch on quadradiscs.

 

[RSilverman]

I did notice that you can keep the direct switch to "on" all the time and still get CD4. Don't know if this might fry something internally, so I suppose I'll turn it to "off" when playing quad, just to be safe.

 

[jrlinks]

Brain error
No message

 

[Doug G.]

Of course, the key in the Nilsson Schmilsson album going for 135 bucks is it was sealed. Sealed quadradiscs always go for much more than regular run-of-the-mill CD-4 records. That's because it is a guarantee that the carriers haven't been tracked by a lesser cartridge and should still be in pristine condition (assuming a good pressing!). My Schmilsson is fine and I didn't pay anything special for it.

It won't hurt anything to leave the direct output switch "on" all the time but I think I would turn it off while playing CD-4 discs too. Best not to have anything extra connected to the input for those occasions. BTW, this is to what I was referring when I was talking about the input still going to the internal demodulator anytime the unit is set to 4 channel.

EDIT: Oops, I forgot that the direct output jacks should be disconnected when the demodulator is set to 4 channels. Try and see if you can still play records through your receiver with the demod. set to 4 channel. You shouldn't get any signals. Just residual noise. In that case, you definitely don't have to turn the direct switch off while playing quadradiscs through your demodulator.

Doug

 

[Quad Linda]

My Nilsson Schmilsson was never sealed, although it was new when I got it! It was a promo from RCA.