From tremolu–(at)–ol.com Sun Jan 5 22:04:03 CST 1997
Article: 33285 of alt.guitar.amps
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From: tremolu–(at)–ol.com (Tremolux)
Newsgroups: alt.guitar.amps
Subject: Re: 5R4 vs. 5AR4/GZ34
Date: 6 Jan 1997 02:01:28 GMT
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>>>My ’68 Super Reverb came with a Sylvania 5R4 rectifier tube instead of
the
specified 5AR4/GZ34.

>>>What’s the difference between these tubes?

Quite a bit. The 5R4 is built somewhat like a 5U4, EXCEPT the 5R4 is
designed to operate at higher voltages and lower load currents. The 5R4
does NOT belong in a Super Reverb. You don’t need the higher voltage
capability, but you do need higher current capability.

The 5AR4 used indirectly heated cathodes and can deliver more current than
a 5R4, with significantly lower losses. The 5R4 was used in transmitters
mostly, for powering 6146, 807 and 1625 type transmitting tubes at 600 to
700 volts on the plates.

>>>Is it OK to use a 5R4 instead of the 5AR4? If so how will it affect the
sound/performance of the amp?

I would recommend against it, for the above listed reasons, you need a
higher current rectifier. With a 5R4 in the Super, you’ll have lots of
envelope sag and lose a bit of power.

Tremo.