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Old 27th October 2009, 02:46 AM   #11
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Default Oldest Amplifier

I happened upon this new thread and I offer the following. The text below is from another DIYAUDIO thread about KT-88 amplifiers. I and another person decided to build the 60 watt 6550 amplfiers featured in a 1955 article in Radio-Electronics. I built the first one over the winter of 1958-1959 and the second one over the winter of 1959-1960. They are still running, daily. 1958 was the year of introducing stereo LPs to the market. It was natural that a second one had to be constructed. The pre-amps were single Heathkits (WA-P1, or something like that). All this hardware was installed in a rack cabinet. When I got married 5 years later, WAF set in and I had to get rid of the rack cabinet and got a Barzilay walnut console cabinet for all the equipment (new preamps, FM-AM tuner, tape recorder/playback, turntable, etc). The cabinet is still there but with upgrades through the years. But the 1959-1960 anmplifers are still pumping out power.

John

---------------------------------

I don't think you can go wrong with this one:
http://vacuumtubebrasil.profusehost....0operation.pdf

This was after Herbert Keroes and David Haller parted company, Hafler founding Dynaco and Keroes Acro Products. This amplifier uses the then-new 6550 and the Acro 330 OPT. Note that it has a vacuum tube rectifier.

I built two of these 50 years ago (!!!) and they are still very solid. I've variously used 6550s and KT-88s. Right now there are pairs of the Russian Gold Lion KT-88s in place. I used WWII surplus oil capacitors for the 500V KT-88 plates and electrolytics for the 6SN7 circuitry. Construction was with military-style terminal boards. I substituted the Dynaco 430 for the Acro 330 (The 430 was $30 then, the 330 was $40, big savings for a student at the time), The power transformers are surplused replacement transformers for the RCA 630 TV chassis. Surplused HV capacitors and power transformers were purchased at the original Radio Shack store in Boston (I'm estimating total cost for all to be $10 maximum)

Reliability through the years has been very good with minimal problems. Output tube replacement of course. Several years ago the electrolyics were replaced. Also, the inter-stage coupling capacitors were replaced (also stabilizing the output tube bias setting).

I'll never replace them.

John

Quote:
Originally Posted by toobnoob View Post
tsmith1315 suggested i start this thread in the kenwood kac-7020 thread.

so what is the oldest amp you have running, or plan on running?

i currently have sitting waiting to be tested is a kenwood kac-7020 which is from 86-87 time period.

what do you have?
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Old 27th October 2009, 02:59 AM   #12
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Join Date: Sep 2007
Default Oldest Amplifier

I'm sorry. I just submitted information about an old home audio amplifier. I did not note that this thread is for Car Audio. The best I can offer for this was the Blaupunkt Frankfurt radio I first had in a 1959 Porsche. It migrated to a 1962 Porsche where it stayed until the 1990s. I then installed a Pioneer AM/FM unit with cassette player. When I sold the car a few years ago the original Blaupunkt went along for use for originality in Concours competition. It was working then!!

The radio was all tube in the tuner section and with a separate chassis with transistors for the audio amplifer and the inverter (for the tube B+).

John

Quote:
Originally Posted by toobnoob View Post
tsmith1315 suggested i start this thread in the kenwood kac-7020 thread.

so what is the oldest amp you have running, or plan on running?

i currently have sitting waiting to be tested is a kenwood kac-7020 which is from 86-87 time period.

what do you have?
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Old 1st November 2009, 02:56 AM   #13
jol50 is offline jol50  United States
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Join Date: Nov 2007
I've used an alpine 3518 for a long time, I'd guess that to be an 80s amp and now I have two. They are alpine DIN only. Now have three blaupunkt BPA 260, I might run two on IB subs they were great for that. They are STK IC amps one of which I replaced having blown it running subs like 15+yr ago, just plain abusing it at 2 ohms 2x80rms. Have a harmon kardon ca260 and ca240 to try for fun, 260 not running yet. Not sure in year but they can't be that new. I have some boosters, one was the black clarion with the led on each side, 5 band, I recall those in the early 80s in people's cars. Pretty sure I have a beat up one without the led that works, I've not tried the larger one. Also have some other ancient things I've not checked yet. Do have a nice sparkomatic 7 band booster that worked when I last used it, maybe a kraco too.
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Old 1st November 2009, 03:06 AM   #14
dd63 is offline dd63  United States
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Join Date: Aug 2009
I have a Sanyo bi-amp from the late seventies, with individual woofer and tweeter amps and individual level controls on a wired remote. I think the woofer amp is good for about 15 watts/side and the tweeter amp for about 5 watts/side.
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