VALVE TYPES COMMONLY USED IN SELMER AMPLIFIERS

The KT88 VALVE

(Output Beam Tetrode)

 

 

PHOTOS COURTESY OF JOHN CHAMBERS, NOTTINGHAM, ENGLAND

THE VALVE AMP HOSPITAL (VINTAGE AMP REPAIRS)

 

 

A GEC KT88 - Batch Date 7307 (1973/July).

 

 

A modern day Russian Sovtek KT88.

 

 

JOHN'S VIEWS ON THE KT88:

The KT88! What a beast of a valve this is; it has always been one of my favourites! Designed and manufactured by our own great British company “The GEC/MO Valve Co”, she is one of the best. With a mere 550 volts on the anode (plate) and screen (grid 2), in the ultra-linear mode with fixed bias, this valve easily produces 100 watts from a pair!

 Like most valve manufacturers GEC did a few of their own circuits for the KT88. This included a massive 400 watt version  with no fewer than 5 pairs (10) of them!! 

(Link to the original circuit: http://www.webace.com.au/~electron/tubes/Circuits/GEC400w.gif

Selmer used them for just a short run in their 30 watt Twin Selectortone and Twin Thunderbirds. At only 30 watts they were used way below their potential. I would suspect that Selmer very soon changed back to EL34’s for further/future models because (a) EL34’s would do the same job quite easily at this power rating, and (b) KT88’s were always about 3-4 times the price of an EL34 even from day one! This wouldn’t have been too cost effective for Selmer to continue using them?

 As in most cases with valves nowadays, the Russians, Chinese & Yugoslavians are still manufacturing KT88’s. However the original GEC/MO ones are those most sort after (very rightly so) and are fetching unprecedented prices!! The originals are far superior.

 

 


 

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