Tinkerers - JVC 4DD-5

Hello to all.

Has any of you adventurous quaddies modded a 4DD-5 as this?

1) Removing the crappy 2-ch out direct wiring and switch and also the selector switch in order to input the cartridge signal directly to the board, keeping just the input capacitors.

2) Adding the extra C136 capacitor to the power supply. Should be identical to C137 (470uF)

Thanks in advance and the best for all in 2004.

hi Pablo

the JVC 4DD-5 is not worth tinkering around. i don't think any CD-4 decoder is worth messing around unless it is the sansui Holly Grail (9001) thanks Gerardo

quadgdiaz said:

hi Pablo

the JVC 4DD-5 is not worth tinkering around. i don't think any CD-4 decoder is worth messing around unless it is the sansui Holly Grail (9001) thanks Gerardo

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Hello Gerardo.

In the old Yahoo forum, Greg Bogantz, who used to be profesionally involved with CD-4, claimed that the best consumer demodulator was the 4DD-5.

Maybe CD-4 demodulators as a class are not worthy of tinkering, given the limitations of the format. But for the cost of a few components and a couple of hours, it may be fun to tinker with a "standard" demod to see how far it can go.

Regards.

hi Pablo

i don't know who Greg Bogantz is or was ????? and i don't know what kind of research he did with CD-4 to make him think the JVC 4DD-5 is the greatest demodulator ?????? quadbob & i have done several CD-4 test with different demodulators and the most crappy one from all was the JVC 4DD-5. but what do i know !!!!!!!!!!!!! thanks Gerardo

quadgdiaz said:

hi Pablo

i don't know who Greg Bogantz is or was ????? and i don't know what kind of research he did with CD-4 to make him think the JVC 4DD-5 is the greatest demodulator ?????? quadbob & i have done several CD-4 test with different demodulators and the most crappy one from all was the JVC 4DD-5. but what do i know !!!!!!!!!!!!! thanks Gerardo

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Hello again, Gerardo.

I don't believe he knows you either

Any comments from Quadfather Ralph?

I'm no audio engineer, but I run a JVC 4DD5, and it blows all other surround formats away in terms of separation, fidelity, and overall quality of sound. Friends who hear it never cease to be astounded by the dynamic range of CD-4, the new high rez formats may be cleaner and sharper, but you can really crank the volume on a CD-4 disc, and it sounds sweet to your ears, no headache producing artifacts. Now, not having heard a Holy Grail demodulator, I'm sure I don't know what I'm missing. Maybe if I could get one as a separate unit. But the JVC is hardly lousy.

I agree with the comments about the JVC 4DD5. I have a Marantz 400B and I prefer the fidelity of the JVC. With a well recorded CD4 disc, the sound is every bit as engaging as a well recorded SQ disc thru my S&IC. One of the best qualities of the S&IC is the smoothness with which it decodes and the class A sound quality. The JVC operates smoothly, w/o harshness, & w/o calling attention to itself. If someone decides to mod a 4DD5, I'd like to know. The cost of the unit is so low, (I paid $14.00 for one of mine), the improvement could make it a very cost effective mod.

Any comments from Quadfather Ralph?[/QUOTE]

You had to drag me into this didn't you! Well, my 4DD5 performs just fine. It performs at a level where I cannot tell it's CD-4 if I am not within the quadrangle. Within the quadrangle I hear excellent separation. I would not remove the selector switch because I use the 4DD5 as a preamp when I'm not demodulating quadradiscs. While it will operate as a preamp just fine with most material in CD-4 mode, some stereo records cause the lock light to come on and you will get splatter when that happens as the PLL oscillator tries to lock to the extended range of sound on the record. Setting the selector switch in two channel mode stops this cold. Greg Gobantz did mastering work for RCA Quadradiscs as I recall, and is responsible for the schematic that most of you 4DD5 owners have obtained from me. He was the only one who had one, and I would have had to trace one out if he had not come up with it. I once had an opportunity to compare my 4DD5 to a Technics SH400, and the SH400 was not as clean. I have not heard the Marantz, so I cannot comment on it knowingly. I know one thing, My 4DD5 runs circles around the Claricon demod I bought in 1980. It was all I could find at the end of the quad era. The Claricon might have been a decent demod, for I believe someone else made their boards, but the power supply was weak, and they didn't include a carrier level pot, using a switch instead. This doomed it to crappy status.

The Quadfather

You had to drag me into this didn't you! ?

Click to expand...

What took you so long ;-)

Have you noticed that there's a space on the board for a second large capacitor? I will install it, but don't expect any before and after test from me.

Thanks in advance.

I have seen the place for the cap, but since I have experienced no hum problems with the 4DD5, I saw no need to install a capacitor there. I suppose it couldn't hurt anything to put one in. Probably they originally designed the power supply capacitance value to be split between two caps, but advances in size reductions allowed one to be used instead. One could always install a larger value cap in the power supply even without the "place", but you reach a point of diminishing return, where you get no more improvement in the sound, or lack of background noise.

The Quadfather

proufo said:

What took you so long ;-)

Have you noticed that there's a space on the board for a second large capacitor? I will install it, but don't expect any before and after test from me.

Thanks in advance.

Click to expand...

I would not remove the selector switch because I use the 4DD5 as a preamp when I'm not demodulating quadradiscs.

Click to expand...

You can clean the circuit a bit by removing the provision for the '2 ch direct out' output, and keep the functionality you already have.

BTW, my Sylvania DQ 3700 is just as good as the JVC 4DD5 ;-)

I will do the mods indicated in the first post and make a WWW page of it, with pictures.

Maybe someone else can do a How-to on the really important adjustments, such as ANRS alignment, muting coil alignment, PLL free running frequency alignment, and statick lock range control alignment. My guess is that most of our demods are sub-optimal after so many years.

Greg Bogantz posted this at the ye olde forum.

'As a designer of CD-4 recording and playback hardware, I can tell you
that virtually no demodulator even approaches the actual performance limits
specified for CD-4. Most of them are tremendously rolled off in the
demodulated carrier channels (and have inaccurate ANRS tracking) in an
attempt to reduce the system noise. I specifically developed modifications
to the JVC 4DD-5 which made it come very close to the system specs. I still
use mine tuned this way. It sounds dramatically more wide-band with much
better directionality at high frequencies, but it is noisier than the stock
units. When I would make test cuts in lacquers and compare the playback to
the master tape, it was very hard to tell which I was listening to - the
system design is actually very good. So I prefer to hear the additional
noise if it means better fidelity otherwise. Most people, however, don't
like the noisiness and prefer the detuned units that were universally sold
to the public by all the manufacturers. The Technics models are among the
most dull sounding of them all. Even if you manage to set up these consumer
demodulators to the factory specs, they are designed to be dull sounding.

It's a shame that no "audiophile" grade of CD-4 demodulator was ever
available to the public. The best demodulator ever commercially built was
the JVC X-7206 studio standard. It actually did what the system spec says
it should do. But it was sold only to recording and mastering studios, and
there probably aren't half a dozen of them in the USA. It's built in three
rack-mount chassis that take up about 20 inches of rack space. The next
best one was the JVC CD4-10s. This was a semi-professional model about the
size of an integrated amplifier. It's circuit was very similar to the
4DD-5, but special care was taken to make the demodulated carrier channels
have pretty accurate frequency response and to get the ANRS control voltage
filters correctly designed. These are almost as hard to find because they,
too, were sold only to recording professionals.'

And sadly:

'I was afraid that someone would ask for the 4DD-5 mod details. I am usually quite diligent about saving these kinds of data, but apparently I left my file on this work at the RCA Records lab when we closed the record plant in Indianapolis in 1988. I have looked for it and can't find it. However, I do have the original sketch-matic for the 4DD-5. AND I have the factory sketch for the CD4-10. And if I get motivated enough, I could reverse engineer my 4DD-5 and find out what the parts values changes are. However, setting the ANRS tracking is an equally important part of the final tweak. It seems to me that the procedure given in the 4DD-5 manual is not correct, but I can't remember what the proper way to do it is. But, again, I could probably figure it out by measuring what my 4DD-5 is now adjusted for. I just need to get motivated. But I've got too many antique phonographs and radios that are calling me to fix them (my current main hobby).'

Ok, I guess I better wade into this thread!

First off, a lot of things will "work" inspite of the published specifications for CD-4.

You can use a turntable that wasn't rated for CD-4 frequency response and that doesn't include either proper anti-skate adjustment for CD-4 nor low-capacitance tonearm wiring.

You can use "standard" interconnect cables that again are not "low-capacitance" as defined by the CD-4 specifications (and virtually every user's manual for a CD-4 demodulator or receiver)

You can use any cartridge you like........disregarding frequency response and/or its internal impedence.

And then, of course you can come right here and post about how great (or horrible) it performs!

In any discussion of this nature.....there are always subjective and objective observations. I usually do my best to define my comments so that you know a) the facts......and b) my own subjective analysis.
Anytime we start discussing whether A is better than B, or that C is a tremendous improvement you really have to start with my old favorite "What is your point of reference? (POR)". I've noted that even within this
thread some of you have at least made comment about what else you've heard and experienced. That is really good! But, one thing that "flavors" all these discussions is the rest of your setup.....as I noted at the beginning.......your TT, cables, cartridge......AND the demodulator under review!

Ok, here is my POR when it comes to CD-4. I have owned, modified, experimented with and/or listened to the following:

Demodulators: JVC 4DD5 (about 6 copies), JVC 4DD10, JVC CD4-1000 (Greg B. referred to it as the CD4-10 which is incorrect and could be confused with the 4DD10) and the JVC 5456X receiver (CD-4 built-in demod). The Technics SE-405 (about 4 copies), SE-405H, and SH-400 (3 copies). Lafayette CD-4, Marantz 400 (4 copies) and 400B (about 6 copies). Sansui QC-04 (4 copies) and of course the built-in demodulators in receivers by Sansui (QRX-7001/
8001/9001), Kenwood (9940), Pioneer (747, 949, and 949A) and the aforementioned JVC. And, probably a few others that I can't remember right now!

Cartridges: AT 12S, 14S, 15S, 20S. Empire (can't remember the model...but it was their "true" CD-4 cart) JVC 4MD-10, 4MD-20. Pickering UV-15 2000Q and 2400Q. Sansui SN-40. Shure M-24, V-15 III, IV, V. Stanton 780 4DQ. And, again probably a couple of others.............

TT: Teac (non CD-4 circa 1982), Kenwood 2050 (non CD-4 circa late '70s), Duals; CD-4 rated 1229Q, 2046, 2056 and a few others! And the designated CD-4 tables by Panasonic, JVC, and Sansui.

Many of these I "tested" by doing direct A/B or switching...calibrating, listening tests one after the other. I've used various combinations over fairly long periods of time (up to 8 years). Over the years I've often been asked and advised others on setting up for CD-4 playback.....and I've always tried to emphasis the basic requirements for CD-4 as the "starting point":

1) CD-4 capable turntable.....rated for CD-4 use and including low-cap wiring
2) Low-capacitance interconnect cables of the highest quality affordable
3) A "true" CD-4 cartridge capable of a full 20-45KHZ (minimum) frequency response.

Deviate from those 3 design requirements for CD-4 playback and as far as I'm concerned you've entered the "twilight zone"! It may work, it may not......it may sound good, it may not and you may or may not be actually hearing CD-4 as intended and designed!

I've often seen others here recommend one cartridge or another totally ignoring the 100K impedence requirement of ALL CD-4 demodulators....the Shure V-15's and Trackmaster come to mind. I've tested the
Shures.......I haven't tested the Trackmaster (no opportunity/desire). But, from technical publications and comments, I've seen it published that an impedence mis-match will cause a loss of High Frequency transmission and/or possible "ringing" between the cartridge and phono stage.

I do know that while I love my Shure V-15III for stereo/SQ/QS application.....I've never preferred it to most of the better "true" CD-4 cartridges when properly setup and adjusted with a good/new stylus.
I readily noticed high frequency distortion....not always really annoying.....but there nonetheless.

Ok, the above is my point of reference......and this thread is really dealing with the JVC 4DD5 rather than CD-4 in general. The 4DD5 has the honor of probably being the "first" commercially available CD-4 demodulator ....
...introduced around 1972 as CD-4 rolled out the gate towards the great
quadraphonic train-wreck.

Any claims that the JVC 4DD5 is the "best" demodulator....would have to presuppose that; No advancements were made to CD-4 demodulator design or production after 1972. And that gentlemen, is very easy to refute! JVC themselves brought out the 4DD10, and their last demodulator design
which can be found in the 5456X receiver uses the very same CD-4 ICs as the 1974 introduced Sansui QRX-7001. And, I'm not trying to denegrate JVC at all! They invented the format, and their CD4-1000 studio demodulator that I listened to at Nick P's house with its matched JVC cartridge
still is the best sounding CD-4 I've heard via long term memory.

In my research/modification/testing of the Sansui QRX-9001's demodulator I still had the memory of the CD4-1000 in mind as I listened. The "HG" Sansui demodulator is the closest to it I've heard! If I had to choose one or the other......I'd probably lean towards the JVC, but my astonishment when
I first heard the JVC probably plays a large part in that! Greg B's. comments I think accurately reflect his experiences at the time........remember he worked for RCA, and at the very beginning there wasn't much other than the 4DD5 to choose from. In my experience I would agree on his comments regarding the ANRS circuits and the Panasonic/Technics demodulators dullness, although I always preferred "dull" to overly sensitive and noisy (as he mentioned). I can say that part of the process in "creating" the HG Sansui is recalibrating the ANRS circuit to really open up the freq. response!

However, in comparing the "HG" Sansui vs. anything else.....its not even close! And, yes the 6 or so 4DD5s that I've used would rank well down the list. And, yes that is my own totally subjective opinion, with the only corroboration being the few others who have heard the "HG" Sansui. I've yet
to have any feedback from them that anything they've heard is better. (Feel free to chime in here guys!). And, I should note that when I tested the
4DD5.....it was with a "true" CD-4 cartridge, CD-4 capable TT, and low-cap
interconnects!

So, use what you want.....connected anyway you want. It's your ears and your enjoyment! But, I think you might really want to review the technical requirements before making strong recommendations to those that are just starting out trying to set up for one of the most technically challenging
audio formats ever brought to market!

So, use what you want.....connected anyway you want. It's your ears and your enjoyment! But, I think you might really want to review the technical requirements before making strong recommendations to those that are just starting out trying to set up for one of the most technically challenging audio formats ever brought to market!

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Hello QuadBob and thanks for your comments.

This thread was meant to bounce ideas about modding/calibrating a 4DD-5. It was crapped to turn into which one is the best demod, why there's nothing worthy but the HG, and a lesson on CD-4 basics.

Does anyone here have info on adjusting a 4DD-5 to factory specs?

Thanks in advance.

I have carried the 4DD-5 schematic in my subway rides.

The FM demodulating circuitry is a still a mistery, but beyond that it seems that there's just a pair of level pots, and the ANRS calibration pots.

Idea: swapping the board ANRS pots for panel mounted stereo pots and setting ANRS by ear, allowing for taste, individual record noise/signal balance, and spur of the moment adjustments.

The ANRS system is a double ended system. If the decoding doesn't track the encoding, the results are inaccurate. To assure that it does, it would require calibration. As far as I know, those procedures have been lost to history. My service manual doesn't have it, nor any of the ones I have distributed. Good luck!

The Quadfather

By the way, I've always recommended the Trackmaster 8 because it has worked for me, giving me CD-4 worth listening to for a very modest price. It is a good starter cart. If there are better carts, which I don't doubt, I don't have the financial resources to try them. I certainly don't have the bucks to blow on a cart that costs a couple hundred dollars that turns out to be worse.
Then what do I do with it after I put the Trackmaster back on the turntable? I have always recommended a CD-4 compatible turntable, cables, and a good demod such as the 4DD5. But having done that, if the cart isn't any good, the rest is meaningless. I know that the trackmaster works. So, what IS the holy graille cart?

The Quadfather

Idea: swapping the board ANRS pots for panel mounted stereo pots and setting ANRS by ear, allowing for taste, individual record noise/signal balance, and spur of the moment adjustments.[/QUOTE]

The Quadfather said:

So, what IS the holy graille cart?

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Hello Quadfather.

There's a Van DenHul Colibri, tracks lightly (1.35 gram) and can be special order with even less tracking force, has a wide tracking radius, and reaches 65 kHz. All for about 5 grand.

Ah, and you need a step-up transformer to use your demod.

http://www.vandenhul.com/phono/colibri.htm

Okay, this may be leaning a tad bit off-topic, but let's say i have a CD-4 turntable, with of course a CD-4 cartridge, and of course it works fine with any CD-4 discs i may have, but what if I played stuff encoded in QS, or SQ (of course running it through the proper decoder)? Would I want to use a different stylus or turntable altogether, or would it still work good with a turntable completely set up for CD-4 use? And another dumb question. I doubt this exists, but is there such thing as a CD-4 capable Micro Seiki turntable with a linear tracking arm? Just wondering..

I use my CD-4 stylus to play all my lps, it works fine. For matrix quad you don't need a special stylus. Linear turntables generally work well for CD-4, but avoid the cheap ones with the stubby plastic tonearms or the arm built into the cover.

With a linear turntable vs a CD-4 specific turntable, because linear turntables are much less likely to skate, would the fact that the linear turntable was designed for stereo and not CD-4, adversely affect the quality? My guess is that CD-4 turntables are just designed with a special anti-skate adjustment for use with CD-4 discs.