Burn out - and finding the joy in Quad again

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ArmyOfQuad

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Well....I predicted that one. Ortofon MCA-76 head amp, $170. Damaged Ortofon MC-20 moving coil cartridge, $350. Cartridge retipping, $400.

Finding out the Ortofon setup is a distorted mess vs. the Signet cartridge you've been happy with all these years? AAAAAAAAAAAAAAAAAAAAAARRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRGGGGGGGGGGGGGGGGGGGGGGGGGGGGHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I've got a marantz cd-400 and jvc 4dd5, both modified, both operating equally. Love the Signet, distort on the MC-20. Can't be the demodulator.

I haven't received my 2nd bluejeans cable yet to connect the head amp to the demodulator, but I'm using an Acoustic Research cable at the moment there, and I've gotten many years of great performance from the demodulator without bluejeans cables - that ain't it.

Plain and simple - the Ortofon combo just can't output the same stability in the carrier as the Signet.

Perhaps there's a cartridge/demodulator synergy that hasn't been more widely explored. I think the few uses I've seen referenced using the Ortofon setup for CD-4 do not mention the 4dd5. Perhaps while the 4dd5 is a recommended and preferred demodulator among the crowd that are putting MM cartridges into it such as AT or Signets, it's not a great pairing for the Ortofon?

Or perhaps the MCA-76 isn't in top shape? Audibly, seems to be performing fine, and I actually do hear a difference when turning the filter for CD-4 on and off, which suggests it is going beyond the range needed for a stable carrier.

It's a real frustration - because what I hear has a great tone, but that CD4 distortion rings through. It could be so much better than the Signet, if only it would lock in better......

Now to spend hours tinkering with this to figure out what to do about it.........because who needs to spend their time enjoying their music collection, when they can spend hours trying to make half assed audio equipment work right?


Also - it isn't the retipping. Retipping was done by sound-smith - which also retipped the Signet cartridge.
 
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tonyE

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Is the issue frequency response?

As I recall.... for CD4 you need 35Khz bandwidth and it was solved with a Shibata stylus?
 

par4ken

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Well....I predicted that one. Ortofon MCA-76 head amp, $170. Damaged Ortofon MC-20 moving coil cartridge, $350. Cartridge retipping, $400.

Finding out the Ortofon setup is a distorted mess vs. the Signet cartridge you've been happy with all these years? AAAAAAAAAAAAAAAAAAAAAARRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRGGGGGGGGGGGGGGGGGGGGGGGGGGGGHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I've got a marantz cd-400 and jvc 4dd5, both modified, both operating equally. Love the Signet, distort on the MC-20. Can't be the demodulator.

Also - it isn't the retipping. Retipping was done by sound-smith - which also retipped the Signet cartridge.
Well....I predicted that one. Ortofon MCA-76 head amp, $170. Damaged Ortofon MC-20 moving coil cartridge, $350. Cartridge retipping, $400.

I've had similar issues. I have the Ortofon MCA-76 and have used it successfully with the Sony XLMC-3. I have two of them the first with the most hours on it produced sandpaper sound on the inner grooves, the other worked fine. I found an Ortofon XL SL-20 Q for about $300. I guess because it wasn't new I was getting sandpaper sound with it as well, on the inner grooves. During the process of mounting and dismounting the cartridge I broke off the stylus tip! So if the Ortofon didn't need retipping it does now!

I'm using the Marantz CD-400B. I tried switching the MCA-76 between CD-4 and Flat and didn't notice a difference. I'm also surprised that CD-4 filters the signal, I would of expected it to boost up the carrier instead!
 

ArmyOfQuad

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As I understand it - the CD4 button on the MCA-76 is a filter due to the frequency response of the cartridges of the time going beyond what is needed for CD4. The MC-20 specs say it reaches up to 60k. I think the filter is to prevent any interference from supersonic frequencies.

My earliest experiments with the MCA-76 were pairing it with an Ortofon Rondo Bronze cartridge - I'm sure this story is documented multiple places on this forum by now. Adjusting the carrier level resulted in a pure signal even from the full clockwise position - normally it's supposed to start with distortion, and get pure as you turn counterclockwise. So already, that was a hint that my level was a little hot. But, I found that outer grooves would demodulate ok, especially on Japanese import CD4 records (they demodulate easier because of the lower level they were cut at, less interference with the carrier signal). But inner grooves would distort. Even on the Japanese CD4 - just barely, but noticeable. But once Ortofon support explained that their modern cartridges had too high an output for their older head amps, I chalked it up to that.

Before I give up on this for now, I had to dig out the CD4-10 and play with that a little. Oddly enough, the Ortofon system plays nicer with the CD4-10 than it does with the CD-400, and the CD-10 is working much better with the Ortofon than it does with the Signet. So.....it seems there is cartridge/demodulator synergy that one has to experiment with. However - the Ortofon on the CD4-10 is still exhibiting the symptom of more noticeable sandpaper on inner grooves.

Perhaps the CD4-10 modifications to a CD4-10S would nudge things enough to get rid of the sandpaper. Or maybe the MCA-76 needs some fine tuning. Or maybe a combination of both. Or maybe these are more future projects that will turn out to be fruitless.

Ah well - time to get the Signet back on the turntable, turn my attention to some digital sources, and perhaps dig up some vintage computer parts to bang around a bit and perhaps fix into something - at least I can listen to tunes while banging my head against the vintage computer brick walls.
 

GOS

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I agree.... I mean, it's not like you're spending all of your time listening to Sonny and Cher and Peaches and Cream... I think playing some Cream on a vintage system is awesome... except Traffic is better in a modern, more accurate, system.

And Clapton's Unplugged requires a modern, high resolution High End system!

I suppose it could be worse... imagine trying to make sense out of Ozzie's lyrics.
And, to be fair......Sabbath's lyrics were predominantly written by Geezer. (y)
 

barfle

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Not only do I still have laser discs, I still have Motorola Teleplayer films!

I often refer to my (retired) electronic engineering skills as “developer of obsolete technologies.” I still enjoy working on analog circuitry (and some digital). When I worked at Altec-Lansing in the early ‘70s, I bought a model 724 tuner-preamp that I’m bringing back to life. The circuitry is comprehensible, but there’s a voltage reference diode in the FM tuner that seems to be unobtanium.
 

edisonbaggins

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It's so strange that a fellow surround lover is burning out on Quad while it has been increasingly the focus of my passion for quite some time now.
First Quad blu-rays, SACDs, and friends' dubs, now SQ, QS and IA sources.
And who knows what's next!
My music enjoyment would be vastly diminished where it not for good ol' Quad!
 

ummagumma

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I sympathize with the OP re: vintage audio woes!

I have a few things that need work, and I lack the time to work on them, atm. Parts shortages worldwide aren't helping. But I can't wait to dig in & replace the old parts, get them back to 100%

As far as CD4, wouldn't a linear tracking TT be the best playback option, to avoid inner groove/stylus angle issues?
 

jimfisheye

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Real physics dealing with mechanical and electro-magnetic systems. Not only chasing calibrations but following skewed imperfectly calibrated bits along the way to try to reveal the source. And you can't just write code and tell a computer to do it!

My timeline starts after people gave up on the analog systems (for surround). I went from a cassette deck to an ADAT deck. And then two. They were affordable! 16 track 2" machines were unobtainium for the likes of me. Suddenly I can record 16 tracks! And then a 3rd and 24. Then Protools TDM comes along and I can suddenly mix even though I can't afford a real mixing board and the rack full of outboard gear I need.

And of course consumer flac files don't require test records, measuring equipment, and an electro-magnetic-mechanical adventure to set up for!
 

ummagumma

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Well, I cheated a bit: instead of jumping off a cliff into the maelstrom that is vintage quad gear, I bought a Surroundmaster!

I feed it into a pair of stereo amps.

But all my old stereo gear needs upkeep! Not sure I'd want to tackle restoring an old quad decoder...

I wish I could decode CD4. I have a copy of Rick Wakeman's "journey to the centre of the earth" that I'll probably never get to listen to :(
 

ArmyOfQuad

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I sympathize with the OP re: vintage audio woes!

I have a few things that need work, and I lack the time to work on them, atm. Parts shortages worldwide aren't helping. But I can't wait to dig in & replace the old parts, get them back to 100%

As far as CD4, wouldn't a linear tracking TT be the best playback option, to avoid inner groove/stylus angle issues?

Linear tracking tables bring their own set of problems to the mix. I had one for a while - actually, I had one when I did my initial experiments with the first MCA-76 head amp I bought for it. So those initial experiments where the outer grooves were demodulating alright, but the inner grooves were distorting, were on a linear tracking table. And some of the notorious problematic CD4 records out there, Barry Manilow This One's For You and Godspell, have problems with the inner grooves on just about any equipment. And if one notices, the vast majority of CD4 records do not go all the way into the inner groove area that most records do (which is why it would be a mistake to use a Stevenson alignment for CD4 playback). CD4 and inner grooves don't get along.

I eventually decided to give up on linear tracking turntables. In quiet passages, the arm adjustments can be audible. And I think much has been written about why the concept is flawed and will result in a certain level of error across the record as the arm has to catch up to the record. Perhaps the more expensive models that use compressed air to float the arm as it moves across may avoid those issues - but I eventually decided that, there is an abundance of fine options for standard pivot arm playback, and plenty of audiophiles using many turntables with that design, perhaps it would be foolish to dismiss it. Linear tracking - started as another one of those magical things I heard about that solves many problems, but in practice and my experience just introduced more. No thanks, I'll stick with the pivot.

However....I got in an audio discussion with another fellow streamer, deadpull, and he's quite fond of his Yamaha PX3 linear tracking turntable. Apparently he hates anti-skate. I mentioned my linear tracking woes, and mentioned the Mitsubishi turntable, and he was like "you gave up on linear tracking over a crappy Mitsubishi turntable?" Which makes me curious about the Yamaha. Not curious enough to spend any money, though. I'm still happy with my decision to walk away from linear tracking and never look back.
 

MidiMagic

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Here are the problems I found when helping others set up CD-4:

- Loud snapping noises are from very tiny dust or powder contaminating the grooves.

- The CD-4 light turning on and off is from not using low enough capacitance cables or wrong vertical angle.

- The sandpaper effect over the entire disc is from not using low enough capacitance cables or wrong vertical angle.

- The sandpaper effect in the inner grooves can be tracking error or it can be a worn stylus tip or one not right for CD-4.

- The sandpaper effect coming and going is usually due to record wear on the carrier.

- Total failure of the demodulator is due to the customer fixing it with a sledgehammer. :D
 

MidiMagic

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Not only do I still have laser discs, I still have Motorola Teleplayer films!

I often refer to my (retired) electronic engineering skills as “developer of obsolete technologies.” I still enjoy working on analog circuitry (and some digital). When I worked at Altec-Lansing in the early ‘70s, I bought a model 724 tuner-preamp that I’m bringing back to life. The circuitry is comprehensible, but there’s a voltage reference diode in the FM tuner that seems to be unobtanium.
What voltage is the reference for and what is the reverse current rating?

Or is it really a varactor?
 

Soundfield

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What voltage is the reference for and what is the reverse current rating?
Or is it really a varactor?
I’ll have to look that up. I’m afraid it’s been back-burnered for a few years. The reference diode is used for the varicaps in the tuner.
Varactor and Varicap are two names for the same thing (variable capacitance diode). “Varicap” was a TRW Semiconductors trade name which quickly became the more commonly used term for such devices. Voltage reference diodes however are Zener diodes. If you can identify the existing part's reference voltage it should be easy to find an modern Zener with that value.
 
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tonyE

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I admire you guys who maintain vintage equipment. What you do allows vintage quads, that are available no where else, to be played back in great fidelity in my listening room, with no real effort on my part. I'm thankful.

I just picked up my rebuilt Marantz 4215 ( it has the SQA1 module the RC4 remote). I don't have (yet?) the Marantz CD4 demodulator. This one has a gorgeous walnut cabinet... but it looks tiny compared to...

...the Akai AS980 which was redone, picked up, about a month ago. That one has all the decoders built in. It just doesn't exude the luxo feel of the Marantz.

So now I got two beautiful units, but no way to play Quad unless I set up my old Sony EP9ES into quad mode and decode stuff through it via the AUX inputs.

Oh, the 4215 has the 'dimension' control which generates an ersatz surround field.
 
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