HARMAN KARDON HK670 AMPLIFIER RECEIVER 120V CANADIAN VERSION

My apologies for not-so-sharp photos, using a 2009 pocket camera here....

***Note: I also have a rare 100/120/220240V world voltage version (also nice and fully serviced) listed here for $1195, great for those wishing to enjoy classic H/K sound worldwide:

https://www.kijiji.ca/v-stereo-systems-home-theatre/ottawa/harman-kardon-hk-670-stereo-receiver-amplifier-rare-100v-240v/1713706209

****************************************************** A SUPERBLY ENGINEERED TOP OF THE LINE MODEL, 1979-1981

NICE, SERVICED, WORKS AND SOUNDS LIKE NEW See 10 pictures

Super clean in and out, smoke-free; All-original transistors including original premium heavy duty TO-3 power transistor pairs: (Hitachi 2SD675A + 2SB655A) x 2 matched pairs, same batch codes

In my view, this classic HK line (HK 340, 450, 560, 670) is at least as good as vintage Marantz or Sansui G series of the same age, possibly better; This means the likes of 2252B or 2265B or G-6000, which sell for $1000-$1500 in 2025, in standard 120V voltage versions; world voltage models always sell at a steep premium, because they were never sold in North America, to start with, the owner had to bring them from Europe or Asia.

The sound is big, sweet and the clarity is amazing; Besides, these 1979-1981 H/K look like a million bucks, photos do not really give them justice; Folks don't like selling them; very few on the market in nice condition.

Twin Powered DC Amplifier with Ultra-Low Negative Feedback; The very low amount of NFB contributes to outstanding musicality of this machine. This design is also characterized with high slew rate and wide power bandwidth. HK 670 was top of H/K line when released in 1979, and its 60 Watts per channel RMS sound like 100 Watts when compared to vintage Pioneer or Nakamichi. The HK 670 is made of HK 505 integrated amplifier with HK 500 tuner added, all in custom engineered enclosure. Earlier generation's HK models had better build (930, 730 models), but the sound quality was inferior, muddier/slower.

Please do not confuse HK 670 RECEIVER model with new millennium production HK 670 INTEGRATED AMPLIFIER; for some reason they are named the same, but are entirely different in design and sound quality.

3.5 hrs in-depth maintenance service ($280 at current repair shop prices) all done by me:

* Taken apart, preamp dissassembled; * Dusted off using industrial size air compressor; * Cleaned and detailed in and out; * All controls deoxed/lubed using pro grade D100/F5/G5 ($128/3 cans), move smoothly; * All potentiometers inside deoxed/lubed; * Then sealed for long lasting protection with Stabilant-22 (expensive, used by NASA and avionics industry; I was lucky to buy a whole non-diluted bottle directly from chemicals manufacturer in 2018); * Cold solder joints in power supply reflowed with fresh solder; * Lamps replaced with new matched 8V; * Fresh heat sink compound applied to power transistors; * Bias 33mV L/R and 0V DC offset adjustments all done, to factory specs (this alone takes 1 hr to do the right way, as values take time to stabilize after adjustment, adjust and wait, adjust and wait....); Those values are crucial and must be done; with bias settings too low the sound will be cold and lifeless/dull, too high and the amp can overheat and self-destruct; Those values drift greatly as decades go by, in any conventional amplifier. * MPX Stereo adjustment done, for best tuning; * Reassembled and tested at full power into dummy load for 2 hrs;

The amp works to specification, running not hot, not cold but lukewarm as it should; The sound quality is sublime, highly detailed and warm, exceptionally musical!

If the 670 that you own does not sound that way, it's either badly out of specs, needs repair, or has leaking/weak capacitors due to very high hours/abuse or extra long storage time without powering up at least once every 2 years.

NOTE: A complete restoration with all new (many dozens) premium grade genuine Japanese Nichicon/Panasonic electrolytic capacitors is available at $650 cost, done expertly; prepaid only; 3 months turnaround. This makes sense if you intend to keep this H/K for the next 40 years.

HK 670 is considered the second best sounding H/K receiver ever made, after The Citation Receiver (that one sells for $2500 used fully working in nice shape, if you can find it).

* Designed in USA by famous Matti Ottala (google him), Made in Japan, 1980 * MSRP: US$695 = CAD $900 in 1980 = CAD $3468 in 2025, per Bank of Canada inflation calculator; that's how much it would sell for if marketed brand new today;

* HK505 integrated amplifier + HK500 tuner in one chassis * Dual Mono, 2 Secondary Windings (single transformer for both channels, but everything down the chain from transformer is dual mono, completely separated channels) * Ultra-low negative feedback design * High Current Capability: HK units are designed with no current-limiting ICs in the signal path * Robust twin power supply: Double wattage into instantaneous transients when needed * Remarkable square wave response and spectral analysis at all frequencies * Excellent dynamic range * Compounded "T" circuit design * Power switch witrh dual LEDs * Patented (SMQ) Signal strength/Multipath/Quieting meter * Electronic speaker protection outside the feedback loop * Capacitors: TK Toshin Kogyo (used in many vintage H/K stereos, also Adcom, comparable to Nichicon Muse series) and Matsushita (for big filter caps) * Extra protection: 5 fuses (1 in-line, 4 in power amp)

* Speakers A, B, A+B, Off; can use 1 pair of 4 Ohm or 2 pairs of 8 Ohm speakers; this HK does NOT like difficult impedance below 6 Ohms (2 to 4 Ohms); you can still hook up those for use at lower volumes, just keep in mind parts (resistors/capacitors) are not rated for high output at 2 Ohm use; Can be DIY upgraded of course, with circuit mod. The best sound is always with one pair of 8 Ohm speakers, for dynamic headroom reasons. * Headphones jack * Tone Defeat * Loudness * Phono MM, Dolby FM, FM Stereo, FM Mono, AM, Aux1, Tape1/Aux2, Tape2/Aux3 * FM muting * Variable mute level (FM) * Bass, Treble * Balance, Volume * Stereo/Mono * Tape Copy 1,2 * Tape Monitor 1,2 * Subsonic filter * High Filter * 2 extra power outlets, 1 switched, 1 unswitched * 120V only, North American version; has blue CSA sticker (certified to Canadian safety standards)

* Rated Power Output RMS: 60 + 60 Watts (into 8 Ohms stereo), conservatively rated, same as old Marantz; it is LOUD * Rated Power Output DIN: 75 + 75 Watts (continuous into 8 Ohms) * Rear label: 400 Watts (rule of thumb: divide by 5 to get real world RMS power for any conventional (not class D garbage) amplifier) * Frequency response: 3 - 140,000 Hz * THD: 0.08% * IMD: 0.05% * Damping factor: 30 (like tube amps) * Rise Time: 2.5uS * Slew Rate: 65V/uSec * Input sensitivity: 2.2mV (MM), 130mV (line) * SNR: 90dB (MM), 102dB (line) * 47.6 x 15.9 x 36 cm * Net Weight: 12 KG

QUOTES (Google search):

"Probably one of the 3 best receivers they ever made."

"H/K amps were usually rather good. Back in the '70s they always sounded a good step above anything else. The 930 and 430 receivers are fabulous things. And of course the Citation kit was always well thought of and sounded good. However, probably the best sounding H/K amp of the '70s (which just about made it into 1980) was the HK505, designed by Matti Otala. The pre-amp section was probably the weakest part - the power amp section was superb - as good as anything at the time. It was fairly expensive at over £300 when new and only just starting to be rediscovered these days so s/h bargains still exist. There was a matching tuner too - the HK500 - which was similarly superb."

"The 60wpc is under-rated, the tuner section is great. This was H-K's top of the line in its' day and was the first (maybe the only) receiver reviewed by Stereophile. Very favorably reviewed, btw."

Reviewed Jul 31st, 2019 by Legend-Collector81 "Rare classic , beautiful sounding , lots of power , great bass , wide open soundstage. Very under rated in all aspects . My personal favorite vintage amplifier. Its what got me into vintage audio . Its definitely a great experience every time i listen to it. Oldschool HK magic !"

Reviewed May 29th, 2018 by Ricster63 "One can only marvel and the beauty and craftsmanship of this receiver. The sound quality is superb by anyone standard. The 60 watts per channel is a conservative rating. It easily drives 4 large speakers for long periods without losing the sound quality from overheating. I've owned mine since 1982 and it has never given me a lick of troubles in all those years. It's a classic for the ages."

Reviewed Jun 23rd, 2015 by nikoleouf " Harman Kardon top of the line model in '79-'81. Designed in NY and built in Japan. 60 watts RMS Big sound !!!!! I have it I love it........."

"In doing my "research" for this, I found this reply. Seems the 505 was held in high regards at HK. " In Reply to: Harmon Kardon 505 Integrated Amp posted by HKFanMan on May 17, 2001 at 12:20:23: I was the h/k rep for the Rocky Mountain States when that amp was current in the line. It and the h/k 670 receiver were the two most advanced pieces in the h/k inventory. Leon Kuby (one of the top audio gurus at h/k corporate) told me that the 670/505 were sonically superior to any of the Citation series, which were in the process of a makeover. That the 505 was superior to the Citation 19, is quite an achievement, considering that the 19 still is one great sounding amp. Sixty watts, high slew rate, wide power bandwidth, very low negative feedback (in the single digits as I remember). Great phone preamp also.""

LINKS: https://www.hifiengine.com/manual_library/harman-kardon/hk670-r.shtml

https://www.bigazspeakers.com/single-post/harman-kardon-hk670

https://pinkfishmedia.net/forum/threads/harman-kardon-amps-any-good.116964/

https://audiokarma.org/forums/index.php?threads/harman-kardon-670.220366/

https://audiokarma.org/forums/index.php?threads/harman-kardon-hk-670-am-fm-receiver.257789/

https://www.audioasylum.com/cgi/vt.mpl?f=vintage&m=185730

https://forum.polkaudio.com/discussion/135282/nice-classic-harmann-kardon-hk-670-60-watt-ch-am-fm-receiver-1979-serviced

*********************************************************************************** Local buyer much preferred (cash, pick up in Orleans);

I will ship in Canada if paid by Interac e-transfer, packed nicely with PP foam/styrofoam, insured and tracked. Shipping costs: $49 ON/QC; $62 to Alberta, $67 to BC. Pickup or shipping only, no deliveries.

Shipping outside of Canada is only possible if prepaid by Moneygram or Western Union or US cash by registered mail, nothing else. I shipped a few amps to the States like that before, no issues.

I've been collecting vintage stereos for a long time, so trades/trade-ins, old receiver, amplifier, CD player, speakers, EQ, tape deck, turntable in any condition will be considered.

SERIOUS BUYER ONLY - SEND CELL PHONE NUMBER WHEN READY TO BUY See my other ads - Thank you!