harman/kardon "Twin Power" Receivers

eThink

eThink

Well-Known Member
Model Summary

Series 1 (1973-75)
Appearance: Analog Black Tuner Display / Silver Case
> h/k 630 (Power: 30w; Price: $350)
> h/k 930 (Power: 45w; Price: $475)

Series 2 (1976-78)
Appearance: Analog Black Tuner Display / Silver Case
> h/k 430 (Power: 25w; Price: $325)
> h/k 730 (Power: 40w; Price: $400)
> Citation Receiver (Power: 85w; Price $1200)

Series 3 (1979-80)
Appearance: Analog Silver Tuner Display / Silver Case
> h/k 560 (Power: 40w; Price: $400)
> h/k 670 (Power: 60w; Price: $550)

Series 4 (1981-83)
> Appearance: Digital Tuner Display / Silver Case
> h/k 680 (Power: 60w; Price: $650)
 
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h/k twin power! hk630 Receiver

Series 1: 1973-75
Price: $350

AM-FM stereo tuner-amplifier.
RMS power 30 watts per channel into 8 ohms(both channels driven) with 0.5% harmonic distortion at any frequency 20-20k Hz.
Overall frequency response 4-70k Hz +/-0.5dB(aux input), IHF power bandwidth 10-40k Hz.
Hum and noise -85dB(aux input).
IM distortion 0.15%.
FM sensitivity 1.9uV(IHF), S/N ratio 68dB.
Stereo separation 32dB@ 1k Hz with 0.7% harmonic distortion. IHF capture ratio 2.5dB.
Independent power supplies for each channel.
Defeatable interstation muting and loudness circuit.
High frequency filter.
Illuminated function indicators.
Connections for Dolby B(FM) processor.
External preamp-power amp junction.
Remote speaker outputs.
Front headphone jack.
Phones/main/remote/both speaker switches.


My first harman/kardon unit was the h/k 630 receiver in Feb 1973 (30 years ago).

This was h/k's first use of the "twin-power" design for a receivers and outside of the high-end Citation line.

This h/k was a nice unit, but it's 30 watts/RMS @ 8 ohms (conservative) rating was just adequate for use with the KLH 17 2-way acoustic speakers.


h/k Service Manual:

http://manuals.harman.com/hk/Service Manual/hk630 sm.pdf
 
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h/k Twin Power! hk930 Receiver

Series 1: 1973-75
Price: $475

AM-FM stereo tuner-amplifier.
RMS power 45 watts per channel into 8 ohms(both channels driven) with 0.5% harmonic distortion at any frequency 20-20k Hz.
Overall frequency response 4-70k Hz +/-0.5dB(aux input)
IHF power bandwidth 10-40k Hz.
Hum and noise -65dB(phono input), -80dB(aux input).
IM distortion 0.15%.
FM section has FET front-end.
FM sensitivity 1.8uV(IHF), S/N ratio 70dB.
Stereo separation 38dB@1k Hz, 30dB@10k Hz, with 0.6% harmonic distortion.
Alternate channel selectivity 50dB, IHF capture ratio 2dB. Defeatable interstation muting and loudness circuit.
Independent power supplies for each channel.
Remote speaker outputs.
Front panel headphones jack.
Illuminated function indicators.
High and low frequency filters.
FM noise cancel switch.
Phones/main/both speaker switches.


Tech HiFi let me exchange the h/k 630 for the h/k930 receiver. This h/k was a "keeper"; I still own the unit after 30 years and used it on a daily basis for over the 20 years.

This unit was the basis of my loyalty to the h/k brand.


Comments by Todd Krieger in Vintage Asylum on June 22, 2002 at 23:50:18:

"Strengths: Pre/amp like the H/K 560 except more-musical. But with much better bass drive than the 730. Maybe the most-musical '70's integrated receiver made. The tuner section is not only the best I've heard in an integrated receiver, but also the best amongst tuners period."

"Weaknesses: More solid-state character than a good 730, but only slightly so. (But unlike the 730, the two units I have sound almost identical.)"


A "modified" hk930 converted to tubes!:

http://www.dogstar.dantimax.dk/tubestuf/gallery3.htm


Nude pictures are in this thread:

http://www.audiokarma.org/forums/showthread.php?s=&threadid=990&perpage=15&pagenumber=1


harman/kardon service manual:

http://manuals.harman.com/hk/Service Manual/HK930 sm.pdf
 
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h/k Twin Power! 430 Receiver

Series 2: 1976-78
Price: $325

Stereo tuner-amplifier.
Power output 25 watts rms per channel into 8 ohms with 0.5% harmonic distortion, 20-20k Hz, both channels driven.
Frequency response 4-40k Hz, power bandwidth 10-40k Hz, IM distortion 0.12%, hum and noise -65dB.
AM/FM-stereo tuner with 1.9uV FM sensitivity, S/N ratio 77dB. Selectivity 50dB, capture ratio 1.7dB channel separation 39dB with 0.7% harmonic distortion(stereo).
Signal strength meter, defeatable interstation muting, loudness switch(contour), high and low frequency filters, tape monitor circuit.
Front-panel headphone jack.
Outputs and switches for two sets of stereo speakers.


A "nude picture" is in this thread:

http://www.audiokarma.org/forums/showthread.php?s=&threadid=990&perpage=15&pagenumber=1


harman/kardon Service Manual:

http://manuals.harman.com/hk/Service Manual/hk430 sm.pdf
 
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h/k Twin Power! 730 Receiver

Series 2 (1976-78)
Price: $400

Stereo tuner-amplifier.
Power output 40 watts rms per channel into 8 ohms with 0.2% harmonic distortion from 20-20k Hz, both channels driven. Frequency response 4-40K Hz, IM distortion 0.12%, hum and noise -65dB.
AM/FM stereo tuner with 2.0uV IHF FM sensitivity, S/N ratio 70dB, selectivity 80dB, capture ratio 2dB, harmonic distortion 0.3%(stereo), separation 40dB.
Quieting meter, defeatable interstaion muting, loudness switch, high and low frequency filters, two tape monitor circuits.
Front panel headphone jack.
Outputs and switches for two sets of stereo speakers.


Comments by Todd Krieger in Vintage Asylum on June 22, 2002 at 23:50:18:

"Strengths: A good one is 90 percent of a H/K 930. Musical, almost tube-like in character. Honest 45 WPC rating. Excellent tuner section."

"Weaknesses- Has severe sample variation. Bad ones sound "dry." A little "anemic" in the bass. Needs a benign speaker load."


A "nude picture" is in this thread:

http://www.audiokarma.org/forums/showthread.php?s=&threadid=990&perpage=15&pagenumber=1
 
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h/k Twin Power! 560 Receiver

Series 3 (1979-80)
Power: 40w
Price: $400

Comments by Todd Krieger in Vintage Asylum on June 22, 2002 at 23:50:18:

"Strengths: Similar to 670 except not quite as much power. (One lower in the same line.) More-musical and more-reliable than the 670. "

"Weaknesses: Solid-state character not as pronounced."

h/k Service Manual:

http://manuals.harman.com/hk/Service Manual/hk560 sm.pdf
 
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h/k Twin Power! 670 Receiver

Series 3 (1979-80)
Power: 60w
Price: $550

Comments by Todd Krieger in Vintage Asylum on June 22, 2002 at 23:50:18:

"Strengths: One of few 70's integrated receiver that actually puts out power into real-world speakers consistent with its rating. Neutral. Excellent bottom-end response. Excellent lateral staging."

"Weaknesses: Has an solid-state "grit," like later Onkyo except not as severe. Tended to sound "boring" and "amusical." (Sucked the life out of the music.) Had thermal tracking/bias problems. "


Comments by bigerik in the Vintage Asylum site on June 22, 2002 at 22:25:03:

"The 670, that replaced the 730 and was recipient of many of the upgrades that HK performed on the dismal sounding Citation 16 when upgrading it to 16A spec, (HK was at this point activly involved with Matti Otala and his lab in Finland.)

The 670 has the honour of being the only mass market receiver that was ever tested by the snobby The Absolute Sound, in 1980. WHile they seemed to be holding their noses throughout the entire test and certainly felt it below them to be testing a RECEIVER, they summed up by saying "All in all, at 70 watts a side (actually 60), and being a receiver, one really can't go wrong." Hows that for glowing praise!?

While listed as being a "Twin-Power" unit, the 670 "cheats" by running only one transformer to the others two, and just separating the rectifiers and filters into two parts, all else running off the single transformer."


h/k Service Manual:

http://manuals.harman.com/hk/Service Manual/hk670 sm.pdf
 
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h/k Twin Power! 680 Receiver

Series 4 (1981-83)
Power: 60w
Price: $650
 
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great history show and tell on the H/K's. I have the 930.
The solid aluminum knobs weigh almost as much a a cd player.....
...well maybe almost.
 
I have a Harmon Kardon HK870 amp, (which I just retired) and was curious if you had any thoughts on it. (I've done a few internet searches on it with zero results...). Kahuna
 
h/k 870 Power Amp

I personally did not care for the h/k 870 power amp because it did NOT use the dual power supply design that h/k used in mnay 1970s and 1980s receivers and power amps. Note the single power supply in the picture below.

I use (2) h/k 775 mono power amps with an h/k 825 preamp and an h/k 915 tuner.
 
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I've got it free from someone because it scratches on the right channel. Hitting hit solves the problem when it happens :D (Not a good idea)

People suspect the 2SC1775 transistors, but hitting it :boxing: solves the problem, I suspect a cold solder joint.

I just suscribed... Is it me or the smilies are completely stupid? :banana: :naughty: :cry: :lmao: :beer: :ntwrthy: :stupid:
 
I'm also using an hk 825 preamp in addition to an hk TU615 tuner. My present amp is a Carver M-4t. (I have a 2nd one shelved in the basement, and when/if future speakers require some additional power, I'll bridge 'em). ;)
 
Twin Power Harman Kardon

eThink,

Great research! My Harman Kardon 900+ is also "twin power". I imagine some of the other quadraphonic Harman Kardon receivers were also twin power.
 
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