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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 17th Mar 2012, 10:42 pm   #1
david winter
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Default About to finish my Magnetophon HTS: tube question

Hi,

I'm about to finish restoring the amplifier of my AEG Magnetophon HTS.
It took me several hours (for nothing) to find why the sound was horrible, and in the meantime I (for once ) broke one of the two EL11 output tubes.
I read that an EL84 can directly replace it, so I salvaged the base and soldered a noval socket to try.
It plays well but the sound saturates quickly (before reaching 50% of the volume).
I still need to check one of the EF12 preamplifiers which tested quite low (1mA instead of 3mA) and eventually swap it with one of the recording section as I won't use right now.

The question is, how true is that the EL84 can directly replace the EL11 ?
It seems that RFT even made adaptors to use an EL84 on a EL11 socket.


Thanks,

David
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Old 19th Mar 2012, 1:11 pm   #2
Herald1360
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Default Re: About to finish my Magnetophon HTS: tube question

The EL11 and EL84 characteristics are similar- both data sheets are available here: http://www.tubedata.org/

I would think that a single valve class A would substitute OK, but if the setup is push-pull I'd substitute both for the sake of balance.
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Old 29th Mar 2012, 8:56 pm   #3
david winter
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Default Re: About to finish my Magnetophon HTS: tube question

Thanks for that. I wasn't sure but they don't have the same grid voltage so I used the third EL11 in the recording circuit to match the output stage. Sound is so much better now... Still significant saturation after half of the volume but nothing serious. The bass saturate more than the rest, and without schematic it will take too much time to trace and trouble-shoot. Unless any one has a clue ?
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Old 25th Apr 2012, 7:05 am   #4
mrmagnetophon
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Default Re: About to finish my Magnetophon HTS: tube question

Hello David. I think I have the schematic and have sent you a copy.

Chris
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