High Fidelity Tubes

6CA7/EL34 tubes with a single straight seam in the glass across the top are produced by Matsushita or Hitachi. You can find them with different labels like Philips, RCA or Mullard. These are all made in Japan under supervision of Philips back in the 60s-70s .

Some people would say “These are fake EL34 tubes”, but i think it all depents how you offer them on the market these days. These tubes are made by a 3th party manufacturer, under the license of Philips and maybe even with there own machines. So i would say, this tube is not Genuine, and just dont try to sell them like that!

Remember last time that you were tube rolling in the dark? Well this could be the result of it, the keyway completely broke off. Still I wonder how people manage to do this. Specially with a valuable tube like this RCA 5692 extra care should be taken.

Luckily it did not damage the tube itself and it still works, but next time be carefull when you install it. To prevent further damage and restore the original beauty of this tube, I will show you how to restore the keyway using this replacement.

With a needle file remove the last pieces of the original keyway.

Once the base is prepared put the new keyway correctly in place.

Optionally glue it to the base with Mastic Silicone Kit.

Unfortunately there are more tubes arround that have been hurt. Look at this Telefunken EL34 “Wing Plate”, the best ever made. Very rare, expensive but less wanted with a broken keyway

Remove the last part of the original keyway using a small cutter and needle file. Care must be taken because the material of the socket can be very brittle.

Once the base is prepared, we restore the keyway with this replacement.

More soon.

There, in two words, is the net result of all the engineering which TUNG-SOL has put into the 5881. This completely new tube is designed to operate in circuits for which the 6L6 is specified and is completely interchangeable wherever the 6L6 is now in use. Full utilization of the design and production techniques which have proved themselves over the past 15 years, has created this exceptionally reliable tube. The 5881 has tremendous overload capacity. It maintains high efficiency throughout its life and provides low cost operation through reduced maintenance. The 5881 is manufactured under laboratory conditions accompanied by most severe tests. It is rugged both mechanically and electrically.

A new beam power amplifier embodying all the important improvements in electron tube design…Absolute reliability!

Here are six major features which assure its premium performance:

1. Glass button stem permits compact construction with high resistance to mechanical shock.

2. Rugged micanol low-loss base provides full lifetime electrical insulation and minimizes base leakage.

3. Cathode materials of exceptional stability give more uniform emission with greater life expectancy. Cathode is not poisoned by inactivity during standby periods.

4. Maximum control of grid emission achieved by gold plating and carbonizing.

5. Zirconium anode coating is most active under overload conditions providing ample gettering action to prevent accumulation of gases.

6. Life tests are made under severe overload conditions to assure adequate safety factor.

Miniature R.F. Tube With Internal Shield. Developed specifically for use in FM-AM tuners and receivers as a grounded-grid or grounded-cathode r.f. amplifier, and as self-oscillating frequency or cascode amplifier, the new Amperex Type ECC85/6AQ8 is a high-mu high-transconductance twin triode with a number of unique qualities.

Through the use of an internal shield which seperates the triode sections, the ECC85/6AQ8 reduces oscillator radiation from the antenna of the receiver to an extent not possible with earlier twin triodes. Higher transconductance permits increased front-end gain and lower noise. Detailed data and applications engineering information are available from Special Purpose Tube Devision, Amperex Electronic Corporation, 230 Duffy Ave., Hicksville, N. Y.

Matched Pairs of Output Tubes. The Mullard EL34/6CA7 high-fidelity output tubes are now available in matched pairs. This is of especial importance to owners of high-fidelity amplifiers because matched output tubes will keep distortion to a minimum.

Undoubtedly the original manufacturer either used matched pairs, or went to the trouble of matching them himself. These tubes are a small sample of the extensive Mullard audio line of tubes. International Electronics Corp., 81 Spring St., New York 12, N. Y. (August 1961)