radioactive
tube gear fanatic
what are they dave?
After ten years of looking, I may finally have the amp...
- Thread starter sheltie dave
- Start date
sheltie dave
Addicted Member
That is the Harman Kardon 700 series 725 preamp, 715 tuner, and twin 775 mono amps. They came out just when H/K was totally flush with cash from a half decade of success with the twin powered receivers, and these were the lower level of le plus ultra Citation XX and XXI amp and preamp, the peak efforts of H/K's second resurgence, with the tubed Citation I thru V being their first peak in 1959 to 1964.
They totally jumped the shark after this, though.
They totally jumped the shark after this, though.
SoCal Sam
Lunatic Member
The crazy part is this is the second set of monoblocs I had to pick up in the last two days. Here is the other matching set, and they are just about as rare, although far less valued. I wanted a pair of these since they came out in 1980, so this was a thirty five year wait. The specs are insane...
Power : 1x 130W (RMS / 8 Ohm / 20Hz...20Khz / 0,03% THD)
Power bandwidth : 8Hz...100Khz (65W output / 0,03% THD)
THD : 0,006% (1Khz ; rated output)
IMD : < 0,02% at rated output
Frequency response : 1Hz...300Khz (+0 / -3dB)
Damping factor : > 100
Slew rate : 150V / us (8 Ohm, rated output)
Square-wave rise time : 1,2µs (20Khz ; 8 Ohm ; rated output)
Square-wave tilt : < 2% at 20Hz
Total TIM distortion : < 0,007% at rated output
Total Interface IM distortion : < 0,007%
Power supply crosstalk : 0 [?]
S/N ratio : 123dB (IHF-A)
Input impedance : 1,2V for rated output
Input sensitivity : 24kOhm
Dimensions : 38,5 x 7,25 x 32cm
Weight : 10,1kg.
The hits keep coming. I've auditioned that set in my home with Yamaha NS-1000M's and seen them on the o'scope passing near perfect square waves 20-20kHz. In a blind test, these amps would compare favorably with much, much more expensive stuff.
I guess now we'll have to set up one of those 412s with a Fairchild mono arm and cart... 
On that note, the number of 412s that have popped out of the woodwork in Missouri the past few years is nothing short of insane.
On that note, the number of 412s that have popped out of the woodwork in Missouri the past few years is nothing short of insane.
sheltie dave
Addicted Member
Here are a few glamour shots...
sheltie dave
Addicted Member
radioactive
tube gear fanatic
they actually look pretty good.i know its early but for rectifier tubes i suggest philips miniwatt dario gz32 i use them in all my amps that call for 5v4 including my 260's
sheltie dave
Addicted Member
Chris, are the transformers/transformer covers potted and totally stuck together, or would I be able to remove the transformer covers to lightly sand and respray them in khaki? Getting rid of the surface rust and missing paint would get them well down the road to respectable again.
radioactive
tube gear fanatic
hi dave,they are potted but if you look there are screws around the transformers.i never had any need to see if the covers came off if you removed the screws so i cant advise if theyre removable or not.
sheltie dave
Addicted Member
Well, I found a friend who had a couple 6AB4s, so I am off to see what these beasts sound like. I'm hoping for a simple demo, and then a down for refurb period.
radioactive
tube gear fanatic
wow didnt notice they were even missing.just watch those output tubes .i sure wish i had the biasing setup for you but i dont.the 260 setup is a bit diffferent and involves a 1/4 jack hooked to a volt meter.goodluck with the auditon.
oh i got your email yesterday and phone call and will call you tommorow.i dug out my external hardrive so the sams should be on it if not tom bavis has it already scanned.unfortunatlely unlike the 260 sams the biasing setup is not included.
oh i got your email yesterday and phone call and will call you tommorow.i dug out my external hardrive so the sams should be on it if not tom bavis has it already scanned.unfortunatlely unlike the 260 sams the biasing setup is not included.
sheltie dave
Addicted Member
Chris, these have the 1/4" test jack and the bias current, grid balance, and current balance pots. Mike will be able to figure out the set points. Check out the very first photo and let me know if your 260s are the same. You have el34 output tubes, don't you?
radioactive
tube gear fanatic
hi dave,the 260's only have the bias and balance pots with the 1/4 inch jack iirc the balance you hooke d up a speaker to it and adjusted for miminal hum.its all in the owners manual available in the ak database.im sure mike will be able to figure it out though without the manual though.
radioactive
tube gear fanatic
nope dave im still using 6l6gc .i intend though one day to do the factory revision to el34 but i need to find one more pr of nos gec kt 77 output tubes.
sheltie dave
Addicted Member
Here is the heart of the Fairchild collection, although the 412-4ED will be a stereo turntable, while the 440 probably will be the mono table. The other 275(which had the gray interior and the extra black paper PF cap) has a hum issue in the power section, so I only brought this one home. It benched out at 62 watts at 0.3 % distortion, with used tubes in it. I'll play it for a minimal time, go at the transformer covers in situ with Krylon khacki spray and light wet sanding, and see about feathering in the Krylon Gray on the chassis.
I checked, and the Dynaco PAS stereo adaptor can mate with and do duty as the ganged volume control for the 240 not pictured and the 245 that is pictured. The 245 is totally spot on, the 275 works but needs a gentle refurb, and the 412-4ED needs a plinth and new belts. The plinth will need some thinking, as it needs to be pretty special. I think Scott, Chris, and I are about the only ones that can come close to this setup, though there may be a few Fairchild lurkers around as well.
I checked, and the Dynaco PAS stereo adaptor can mate with and do duty as the ganged volume control for the 240 not pictured and the 245 that is pictured. The 245 is totally spot on, the 275 works but needs a gentle refurb, and the 412-4ED needs a plinth and new belts. The plinth will need some thinking, as it needs to be pretty special. I think Scott, Chris, and I are about the only ones that can come close to this setup, though there may be a few Fairchild lurkers around as well.
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Dave, you are quite the lucky man. Fairchild gear is much too rare for me to go after, given the amounts of Allen, McIntosh and Fisher tube gear around me.
Can't believe you also got those HK's. When I got my first real audiophile setup in the early 80's, those mono amps were at the top of my wish list (my wife worked for HK's ad agency and got 50% off!). Unfortunately I ended up spending way too much on KEF speakers and a gorgeous MC turntable setup. That meant I had to drop to HK's then-flagship 680i receiver so I could afford the HK's CD401 Dolby Pro cassette deck. I've been looking off and on for your new HK setup since. Guess its time to see if any more are coming in from the wild.
Can't believe you also got those HK's. When I got my first real audiophile setup in the early 80's, those mono amps were at the top of my wish list (my wife worked for HK's ad agency and got 50% off!). Unfortunately I ended up spending way too much on KEF speakers and a gorgeous MC turntable setup. That meant I had to drop to HK's then-flagship 680i receiver so I could afford the HK's CD401 Dolby Pro cassette deck. I've been looking off and on for your new HK setup since. Guess its time to see if any more are coming in from the wild.
Wow. True dedication here.
Now you're going to have to find the ultra rarest of the rare, an NOS can of genuine Fairchild vacuum and a box of Fairchild beige electrons to put in there. Don't bother with the green electrons, the beige ones are the shiznit. These are even more rare than the Replacement Western Electric Magnetic Field.
Seriously though, congrats, I'll look forward to hearing this gear one of these days.
Now you're going to have to find the ultra rarest of the rare, an NOS can of genuine Fairchild vacuum and a box of Fairchild beige electrons to put in there. Don't bother with the green electrons, the beige ones are the shiznit. These are even more rare than the Replacement Western Electric Magnetic Field.
Seriously though, congrats, I'll look forward to hearing this gear one of these days.
