A pair of 70's NOS single- ended 3W output transformers, 5.5K : 4 ohm, tube amp.

Description

*** One price for Two new old stock transformers. ***
During 70's the late period of vacuum tube, for tending to a smaller size, most radio manufacturing companies had adopted various miniature tubes to design the circuit. One of them was the 9- pinned noval power tube 6P1 (
6П1П
), whose characteristic was equal to the 7- pinned 6AQ5. In accordance with the original published datasheet, there are two typical operating conditions suggested. The one comes with the plate & screen voltages of 180V, bias -8.5V, plate current 29mA, screen current 3mA, load resistance 5.5K
Ω
, and the power output goes to 2W. Meanwhile, comparing with some similar kinds of tube stand the distortion above 10%, 6P1 or 6AQ5 outstandingly shows 8% only. What a fabulous design!
These OPTs were just made for 6P1 & 6AQ5 use. The impedance of the primary winding is 5500 ohm, and the second is 4 ohm. Though the B+ voltage was not very high as previously mentioned, but the producing process of winding was highly qualified. Each layer of well ranged enameled wire must be wrapped with Kraft, layer by layer. Then soaked in varnish thoroughly and roasted completely dry to strengthen the insolation and insure the longevity.
And via a modern tube fan's aspect to see, the impedance of 5K ohm approximately is welcomed by quite a few of small power tubes below 3W output. Without the coil frame, the size of the core is 3.9 cm (H)* 4.6 cm (W)* 2.1 cm (D), and weighs about 0.25 Kg totally. So
, the transformers could match miniature tubes ideally
, not only on size ratio, but also in characteristics.
Please refer to the attached photos of the practiced sample home- brewed by myself.
There is also a lighter by its side for size comparison.
The amplifier basically followed one classical circuit design consists of a twin- triode 6N2 (
6
Н
2
П
), as a
different pins arranged
12AX7, to drive the two channels' 6P1 independently.
After having a test listening, the tone of the OPT
performs soft and gently, quite
differs from the newly made. It may not have a distinguished linear frequency response from very low to extremely high as TANGO or TAMURA, but it does offer sufficient bass and treble by its size. This enjoyment indeed corresponds with the retro fashion said by senior pros. Personally, I am pleased so!
Well~ Actions speak louder than words. Give a try and you would taste the flavor what I have been......
@ NOTE @
DEPENDS ON THE GLOBAL SERIOUS EPIDEMIC SITUATION, MANY INTERNATIONAL TRANSPORTING WAYS ARE CLOSED. PLEASE REFER TO THE LAST PHOTO TO CONFIRM YOUR BIDS OR FEEL FREE TO CONTACT ME. THANK YOU VERY MUCH. GOD BLESS YOU.