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CD-4 using a Harman Kardon 900+ ?

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tcdriver

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I have a Harman Kardon 900+ circa 1974. I am having trouble getting the CD-4 decoder to work. The CD-4 section in this unit uses four IC's and about 34 discrete transistors. The CD-4 light illuminates when playing a CD-4 record but the sound is very distorted. I would like to know if anyone in the group has successfully been able to play CD-4 records through their Harman Kardon 900+?

The components I am using with the Harman Kardon 900+ are a JVC QL-5 (low capacitance arm and cables) and an AT14Sa cartridge.

Any help would be appreciated.

Sincerely yours,

tcdriver

 

JonUrban

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This may be a stupid question, but have you calibrated the modulator with a CD-4 test disc?

:-jon
 
T

tcdriver

Guest
I have used the CD-4 separation adjustments on the back of the receiver in conjunction with a CD-4 test record. I have not carried out a full calibration using the extensive procedure in the service manual as I do not have all the test equipment required. If I knew that with proper adjustment the decoder really worked, I would then try to get the test equipment to do the full calibration. I was hoping that someone who has experience with these units could give me a clue as to whether it is worth the effort. Thanks.

tcdriver

 

The Quadfather

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It sounds like you are working with a worn stylus. Getting CD-4 to work properly, and it will work properly, is a matter of getting a good signal to the demodulator. I had an AT14S I couldn't get working right for years, I finally replaced it with an Audio Technica Trackmaster 8. The improvement was wonderful. The trackmaster 8 is no lo9nger sold and has been replaced with the AT331LP. You also need to align the cartridge, and do the test record thing. If you pot down the separation adjustments you will hear only the separation signal. That is what you must get sounding right. When working properly, it will sound hollow, but not distorted.

The Quadfather
 
H

HDBRbuilder

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I have been a proud owner of a H/K 900+ since 1975...never any problems with the CD-4 demodulator in it...I also have a couple of H/K 800+ receivers I recently grabbed off of eBay for a song...no problem with their demodulators either...it must be in your cartridge or turntable, as mentioned above. Long live the H/K 900+!!!
 
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tcdriver

Guest
Thank you all for your informative replies to my inquiry. The information that HDBRbuilder provided was what I was really looking for. I will have another go at the turntable set up. Thanks again.

Sincerely yours,

tcdriver
 

The Quadfather

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When you get to the point where you are adjusting the carrier level, and the distortion is almost gone, make small increments of adjustment. and listen for awhile between them. It pays to take your time.

The Quadfather
 
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