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Denon UDA-100 service/instruction manuals needed - plus my quad experiences so far

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thestig

New member
Joined
Jul 9, 2009
Messages
3
Hi all!

Long-time 'lurker', first-time poster. I've been fascinated by quad ever since I was a kid, but it was really the comparatively-recent advent of multi-channel home cinema (and DVD-A/SACD) that has truly sparked my interest in the subject. My AVR, like many others, has analogue inputs to which quad sources can be attached - rearrange the speakers into the traditional quad configuration, and enjoy! I had an old Sony SQA2020 that was sitting in a shed for years, having been given to me by a friend who was moving house. This needs restoring, and then I'll be able to play some of my old vinyl records encoded in the format (my old DSotM is the SQ release) and some of the CDs that preserve the matrix encoding. I might also experiment with some of the Audition decoding scripts that have been discussed here. Another acquisition was a JVC 1202 Q8 player, which I recapped, cleaned and demagnetised - the drive belt also needed replacement. The reason I finally got round to dealing with this was the chance discovery of a shrinkwrapped Q8 copy of Donald Byrd's iconic Black Byrd album (to the best of my knowledge, only currently available on 2-channel CD). I have to say that Q8 sucks in terms of sound quality; it's 'compressed' and hissy although the channel separation of this discrete format can be good if the vertical head alignment screw is adjusted properly. My sample had lots of 'clicks', which I attribute to static building up on the tape's slippery back-coating and discharging on the playback head. In the end, I disassembled the cartridge, and transferred the reel to a better-quality Scotch-brand 'blank' shell (which had sprung pressure-pads). The result was much better, and I was able to transfer the four audio channels to a PC equipped with a professional soundcard and use audio editing software to reduce the noise and restore a bit of high-end 'sparkle'. I'm pleased with the result, even on a high-grade home cinema system. I guess that for tape the Q4 format was the one to go for - but these reels are very rare in the UK (they're certainly less common than the 4-channel decks, notably the Teac 3440, needed to play them on). Some of the Q4-to-DVD-A conversions I've heard are superb.

But my next project is discrete vinyl. I have a few CD-4 albums, and a Philips cartridge (GP412) with '4-CH' (Shibata) stylus that I've had for many years (in the mid-80s, a local electronics broker had acquired Philips' entire stock of cartridges and stylii and was selling them on very cheaply - wish I'd bought more of that stuff now!). Apparently, Philips was hedging all its bets on the CD format it had developed in conjunction with Sony; CD players were however prohibitively-expensive to a teenager back then. The final part of the jigsaw is a Denon UDA-100 UD-4 'disc demodulator', which was acquired cheaply at a recent audiojumble. Although its main goal was to decode rarer-than-hen's-teeth UD4 discs, this box will also deal with CD-4 recordings (it does SQ/QS matrix too, albeit in basic non-logic form and so I'm not bothered about those - computer-based decoding will be far superior). I haven't tried it yet, and before powering it up I'll replace the electrolytics in the power supply. But does anyone have any instructions (how to set the separation controls without a test disc) or servicing information on this unit? There's nothing of any real use on the Internet! A schematic would allow me to investigate the possibility of modifying the circuitry for better performance (after all, it was not optimised for CD-4). One of the members of this forum produced an excellent guide to modifying a JVC CD-4 demodulator - but I don't have one of those, and CD-4 demodulators don't exactly crop up regularly on eBay UK (and being on a tight budget, I'm not paying large amounts of money to ship items from the US!). Here's an example of my thinking: To avoid paying more license fees to rival format developer JVC than was necessary, might Denon have 'skipped' on the ANRS noise-reduction circuitry that CD-4 uses for the rear channels - and instead used a simple 'top-cut' filter? ANRS does much the same job as Dolby B, and I have (ironically!) a high-grade JVC Dolby B/C noise reduction unit that was sold for use with reel-to-reel decks. If any such filters in the rear-channel paths are disconnected, the rear channel outputs could be passed through the Dolby unit thereby correctly-reversing the encoding process.

Congratulations if you've made it this far. But can you help with manuals?

Stig
 

The Quadfather

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Stig:
First of all, the ANRS system is not exactly like Dolby B. However, it is somewhat similar in how it works. To get a true ANRS decoding, you will need an ANRS decoder. But hanging it on to the rear channels, either Dolby B or a true ANRS unit, won't do the trick. You see, in CD-4, the subcarrier channels are processed in ANRS. These are not rear channels. Take the left channel of a record, it contains a mixture of the main audio which is left front mixed with left rear. It is not processed except for RIAA. I expect your UD-4 demodulator has this. In the same signal in the inaudible range is a phase modulated carrier that carries a mixture of the left front and left rear channels also. The difference between the two, is that in the carrier signal, the rear channel is inverted. This makes it a difference signal and it sounds hollow by itself. During recording, this signal is ANRS encoded before applying it to the carrier. In the demodulator, it is fed to the ANRS decoder before being fed to the remix matrix. (do not confuse this with phase shifting matrixes in matrix type systems.) The remix matrix does not phase shift but it does do two things. It recovers the front channel by mixing it straight. It recovers the rear channel by mixing it inverted. In both cases, the undesired channel is cancelled out. If the ANRS is not done before remix, the proportions won't be right and good separation will be difficult to impossible to achieve. Both the main audio and the carrier audio are present in both the front and the rear channels. Since ANRS is part of the CD-4 system, it must be present for the system to carry a CD-4 logo. I have written several detailed explanations about how the CD-4 systems work on this board. An archive search will find them. The writings will help you understand, I hope. Although I am an engineer, I have tried to write it so that a non engineer could understand. A CD-4 logoed demodulator such as the JVC 4DD5 will not have an ANRS logo on the panel. But if it is a true CD-4 demodulator, it's understood.

In Europe, I understand that CD-4 is hard to find, both the records and the demods. However, they are fairly easy to get in the U.S. I would think that you could find a demodulator on Ebay. After all, I have bought records from OZ on Ebay, Germany and England too. It is not difficult to get linear contact cartridges that will do a good job with CD-4. I use an Audio Technica AT440MLa. It's not even spec'd out for CD-4 but it works great. (it's microline stylus is an improvement on the original Shibata design). I do not have a manual for a Denon Demod, and UD-4 is practically non existant in the U.S. It is possible that Denon skipped the ANRS decoder, if that is so, then there would be no CD-4 logo on it, and maybe sly wording in the manual about whether it would actually play a CD-4 record. This is similar to the way some manufacturers referred to QS as RM or "Regular Matrix". Note, Sansui allowed this, but you couldn't use a QS logo. I would suggest you find a 4DD5, and consider your Denon a museum piece. Unless of course, you have a stack of UD-4 records. (it would be a small one). Happy Listening, and welcome to the forum!
The Quadfather
 

Clemens

Member
Joined
Aug 26, 2006
Messages
37
Location
Netherlands
Stig,
I have a copy of the manual and the wiring diagram of the Denon UDA-100.
If you sent me a PM with your email adress, I wll send manual and diagram to you.
Regards,
Clemens
 

thestig

New member
Joined
Jul 9, 2009
Messages
3
Many thanks for your detailed responses and offers of help - they are greatly appreciated. CD-4 is a remarkable achievement, considering the limits of late 1960s/early 1970s technology - it's amazing that it works with any degree of reliability at all! I certainly hadn't realised how involved the encoding/decoding process was - and so thanks for taking the time to share your obvious knowledge with us, Quadfather!

Funnily enough, after replacing its power supply capacitors and hooking it up into my system, the UDA-100 worked first time with a CD-4 record (turntable is a Technics SL1200 with Philips GP412 cartridge and 4-ch stylus, amplification is an Onkyo 905 AVR with multichannel line inputs, speakers are an old Rogers 5.1 set). No pops or 'hollowness' in CD-4 mode, and the unit's 'radar' lamp only lit up when the stylus was lowered - indicating that the CD-4 carrier is being recovered.

Even without adjustment of the 'separation' controls (and the front-panel 'mystery' push-button pushed in or out - that's where Clemens' generous offer of manuals will come in useful), the audio quality is better than expected with plenty of punch, clarity and a decent soundstage. Results with a QS record via the UDA-100's simple matrix decoder also surpassed expectations, although my Sony SQD-2020 (the circuit board of which had an awful lot of dodgy through-hole connections that needed resoldering before reliable results could be obtained) gives a more defined separation.

S
 

thestig

New member
Joined
Jul 9, 2009
Messages
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...I meant to say 'readjustment' of the separation controls; the previous user had marked the positions that give the best results from his equipment, and so I stuck with those. Maybe he was using a turntable and cartridge that had very similar characteristics to mine? Once again, pure luck...
 

The Quadfather

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Since 2002/2003
Joined
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Messages
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Dixie
That is an interesting piece you have there. Perhaps I was a bit hasty when I suggested that you make a museum piece out of it. Note that if you turn down the separation controls all the way, if this one works like most, that hollow sound (normal) you will then hear is the subcarrier audio. How clean that audio is, determines how clean the overall performance of the CD-4 system. It is the subcarrier that gives trouble when the cartridge isn't right. Since it is mixed in with the main audio (by turning up the separation pots) Anything that's not right will appear in the output audio. The separation is best when the subcarrier audio level is exactly matched to the main audio level. I like to overshoot the main audio level just a little to enhance quality. True, this sacrifices a little separation, but can lose a little and it will still sound discrete. Happy Listenning!
The Quadfather
 

Clemens

Member
Joined
Aug 26, 2006
Messages
37
Location
Netherlands
Hi Kirk,
Thank you for alerting me about your request. I do not visit the forum regular.
No problem to send the Denon info to Richard. I will do this asap, just need to find where I stored the files.
 

Circular Vibes

1K Club - QQ Shooting Star
Since 2002/2003
Joined
Mar 12, 2003
Messages
1,573
Location
Ottawa, Ontario, Canada
Hi Kirk,
Thank you for alerting me about your request. I do not visit the forum regular.
No problem to send the Denon info to Richard. I will do this asap, just need to find where I stored the files.
Could you offer them to Www.quadraphonic.info so anyone can download them please? I have one of these coming and it will need reatoration. Thank you.
 
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