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Quadchuck

Well-known Member
Joined
Jun 14, 2005
Messages
173
Location
Quadsylvania
I have a second Zero 100 and 1 or 2 years back I got a Heathkit AD1507 cd-4 decoder on ebay that someone sold very cheap.
I was surprised that there were no other bidders.
As you know it uses that cd-4 chip, I tried to make my own decoder years back with ECG chip but their schematic had flaws
and it worked only so so.
This decoder works good, but appears someone made it but never finished mounting or using.
Now with AT14 cart, heath decoder and zero100 I did something I always wanted to do and it works fairly well.
I combined them , see pix



T 0917171937.jpg0917171931.jpg
 
I have a second Zero 100 and 1 or 2 years back I got a Heathkit AD1507 cd-4 decoder on ebay that someone sold very cheap.
I was surprised that there were no other bidders.
As you know it uses that cd-4 chip, I tried to make my own decoder years back with ECG chip but their schematic had flaws
and it worked only so so.
This decoder works good, but appears someone made it but never finished mounting or using.
Now with AT14 cart, heath decoder and zero100 I did something I always wanted to do and it works fairly well.
I combined them , see pix



TView attachment 30692View attachment 30691

Wow, sweet looking turntable! (y)
 
I once had a Zero 100 turntable, but with a silver aluminum base, it was very cool looking but it wouldn't track warped records at all. I also had a similar demodulator, to that shown,a kit (designed by Lou Dorran) from SWTP, could only get so so results. In hindsight it was probably too much cable capacitance, although the Grado cartridge that I was using was supposed to be non-critical in CD-4 application, meaning that cable capacitance didn't matter much.
 
In 'theory' the Zero 100 would be a great choice for CD-4 playback, but the tonearm linkage had to be loose so that it wouldn't impede the motion of the tonearm. Loose linkage chatters, causing continuous and unpredictable micro-mistracking ... a huge problem when it comes to Shibata styli and subcarrier groove tracking ... and it causes the sound to be muddy and unfocused. Shibata styli MUST be held firmly in the centre of the record groove for proper CD-4 tracking.

Linear tracking tonearms 'should' be the best choice, but very few quality models were available and most had their own issues. Servo-controlled models were constantly correcting, so they NEVER tracked tangentally (a similar micro-mistracking problem). A properly-performing CD-4 system requires a lot of thought and a lot of research. Most complaints about CD-4 performance start with trying to cobble something together because it was available.

I don't post this to cast shade on the OP. It looks like a cool project. I just know that a lot of noobies look here for advice on CD-4 systems.
 
The Zero has it's flaws,especially the great part of the detachable cart mount which is also problematic with age.

This AT14 works good but I think the AT15 is a tad better.

The new old stock JVC came with cables that measured 50 pf for their 30" or so length.
In this unit I used some cables that looked like low end cables blister packed I got decades ago
however they also measured 50pf too.

The heathkit tends to be brighter than other decoders. I compared schematics of heathkit to the ECG
catalog. The ECG was designed with a completely different parts in the preamp stage, I think due to the fact
it had a switchable input of mag/semi cart capatibility. One reason my attempt the ECG failed was I didn't have
BPF filters aside from ECG schematic error. I have seen other cd-4 units that use BPF in all 3 stages some only 2 or 1.
That has always interested me how designers got around BPF filters.

The most problematic decoder I had was the one in that Technics turntable with built in decoder.
Next was my Pioneer qx646 and 949 fair to good a little to noisy
Harmon kardon 800+ decoder decoded good but too many problems in the board.
Panasonic se405 ok but touchy
My new JVC 5dd seem pretty good though not bright.
Heathkit good , a little bright.
Technics (fancy stand alone ) uses the same chip as heathkit and ECG but incredible more complicated circuitry,
unfortunately my unit works but has problem.

I got 2 new old stock JVC on ebay, 1 for less than a hundred the other, over a hundred. They both work the same,
would recommend unit and they come with low cap cables
 
I once had a Zero 100 turntable, but with a silver aluminum base, it was very cool looking but it wouldn't track warped records at all. I also had a similar demodulator, to that shown,a kit (designed by Lou Dorran) from SWTP, could only get so so results. In hindsight it was probably too much cable capacitance, although the Grado cartridge that I was using was supposed to be non-critical in CD-4 application, meaning that cable capacitance didn't matter much.

I've had 3 zero's each had a different base but no metal.
 
I don't mean to cast aspersions on or offend anybody either but to be assured of successful CD-4, you have to follow the rules which means using equipment meant for CD-4 (OK, I disobey my own advice by sometimes using an AT440MLa) and low capacitance cables (less than 100pF but the lower the better) until you get to the demodulator.

I have always done this and have never had any real problems. I tend to believe a good pivoted tonearm will be better than most supposed linear tracking arms for the reasons Quadzilla gives.

BTW, I believe the Heathkit decoder is the equivalent of the Technics SH-400, an especially good decoder for the semi-conductor (strain gauge) cartridges.

Doug
 
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