Koss Tube Headphone Amp
Jan 10, 2004 at 3:51 PM Post #2 of 14
The Koss A-1220 Amplifier appears in the 1962 Lafayette Radio catalog.

"An amplifier especially designed for use with the (Koss) SP-3 Stereophones. Can be used directly or connected to a phonograph fitted with a stereo ceramic cartridge or to the outputs of the pre-amps of a stereo tape recorder or tuner. Equipped with two phono jacks, a gain control for each channel, and two headphone jacks. Attractively made and compact, this unit lends itself to a variety of uses. Uses three tubes plus rectifier (* tube types not specified). Transformer powered. Shipping weight, 4 lbs. Net. $34.95"

Note that in 1962, $34.95 would be the equivalent of approx. $200 today. The Koss SP-3 Stereophone was an early Koss model, with a rated impedance of 4 ohms, that had a retail price of $24.95. (Approx. $140 in current dollars.

* The amplifier shown in the eBay listing clearly has only one tube (12AU7 type) and no place for more to be installed. Perhaps this is a later variation or maybe the catalog description was based on preliminary specs provided by Koss in anticipation of producing the actual item.
 
Jan 10, 2004 at 5:11 PM Post #4 of 14
Quote:

Originally posted by mkmelt
"An amplifier especially designed for use with the (Koss) SP-3 Stereophones. Can be used directly or connected to a phonograph fitted with a stereo ceramic cartridge or to the outputs of the pre-amps of a stereo tape recorder or tuner.


So you can hook it up right to a turntable. I'm guessing that's the RIAA equalization filter on top of the power transformer. Or is that part of the power supply?

Love that vintage gear!
 
Jan 11, 2004 at 3:59 AM Post #5 of 14
Actually, I did some asking around on the vintage forum and the information I received is that ceramic-type phono cartridges have an inherent response curve that closely matches the correct RIAA playback curve, so no separate phono stage is required for either amplification or equalization. So it is correct to connect a vintage record player with a ceramic phono cartridge to a high level input and the overall balance of the playback response will be fine.

Ceramic cartridges have a very high output as compared with moving magnet type phono cartridges, about 0.5 volt. The downside is they track at relatively high tracking forces of 3 -7 grams so record wear occurs quicker and is more severe.
 
Jan 11, 2004 at 4:06 AM Post #6 of 14
By personal experience the ceramic cartridges output is similar to a regular tape deck or CD player....(but the sound really sucks)
 
Jan 11, 2004 at 5:50 AM Post #7 of 14
I saw your post and the responses on the Vintage Forum and also on Tech Square. Very helpful responses. There was thorough information on ceramic cartridges on the Sonotone site via the link that was provided. It also makes sense that the Lafayette catalog should have read "triode" instead of "three tubes" Great research on your part mkmelt.

That's a fine piece of history that I wouldn't mind having myself. Definitely worth refurbishing. Any Head-fiers bidding?

Edit: I was just thinking that maybe we should make this a group buy, restore the piece, and then make it the first donation to the Head-Fi Museum in Hockey Town.
 
Jan 11, 2004 at 3:37 PM Post #8 of 14
You guys have any idea what the price should end up being on an item like this? I dont mind saying that I have made a bid on it for around $85-90 and the reserve has not been met? Is it really worth THAT much?
 
Jan 11, 2004 at 4:32 PM Post #9 of 14
I don't think it is worth much more than the current bid price. But keep in mind that it is a collectible so the value is somewhat hard to establish with so few examples showing up for sale.

If the bid price rises to what a used MG Head OTL tub amplifier costs, then it is not worth buying except to a Koss collector.
 
Jan 15, 2004 at 9:22 PM Post #10 of 14
Note that "loserfarm's" bid of $222.50 did not meet the reserve
confused.gif


http://cgi.ebay.com/ws/eBayISAPI.dll...EBWA%3AIT&rd=1
 
Jan 15, 2004 at 11:09 PM Post #12 of 14
these guys are right down town from me. their shop is like a museum. there are ancient tube amps everywhere, classic receivers and tons of tubes. check out their other auctions from time to time.
 
Jan 15, 2004 at 11:09 PM Post #13 of 14
it's funny how vintage items like that sell for 4 times the price it ever costed in the first place.

i hope it sounds as good as they guy wrote in the auction.
 
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