Power Pentode
The EL33, EL33A and EL33B were identical electrically, differing only in the presence or absence of
metallisation around the bottom of the bulb and the pin it was connected to.
THEY ARE NOT INTERCHANGEABLE
The EL33 / 6M6G / N147 is an audio amplifier power tube
and requires an Octal Socket.
The KT61 (KT-61) vacuum tube is
NOT
a direct replacement for an EL33. Don't let the sales
people Fool you! They just want to make money at your
expense.
Only the 6M6G or N147 is a direct replacement.
The EL33 needs a cathode resistor of 150 ohms at least,
while the KT61 needs a cathode resistor of only 90 ohms.
Without changing the cathode resistor the EL33 and the
KT61 may never be used to replacing each other.
As a makeshift one can use a KT61 to replace an EL33, but
the performance will decrease.
An EL33 should never be used as a direct replacement for
the KT61. Due to the wrong cathode resistor the EL33 will
be severely overloaded and will give only low performance.
Electrical Data:
Heater Voltage ........................ 6.3 V
Heater Current ....................... 1.25 A
Prefered Substitutes....... 6M6G, 6P25, CV1438,
CV1853, CV2938, KT61, N147