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EL37 amplifiers

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Refugee
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I have found the silly money link.
It is in this thread.
viewtopic.php?f=3&t=567&start=75

 
Posted : 03/06/2012 5:08 pm
Valvebloke
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Supply. Demand. No more to be said really ...

VB

AmpRegen http://www.ampregen.com

 
Posted : 03/06/2012 5:37 pm
Refugee
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Well the amps i have were a skip pull 30 years ago and they are pretty easy to restore.
The bit that had to go was the live banana sockets on top of the case that provided power to the projector that once was bolted to the top.

 
Posted : 03/06/2012 6:43 pm
raditechman
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I picked up on this thread thanks to a link from refugee on Homebrew amp.

Very interesting amplifiersIi have never come accross a Bell and Howell amplifier with EL37,s, they did make amps with 6L6 and 6V6.

You can download Bell and Howell manuals for most of their 16mm projectors here

http://www.film-tech.com/warehouse/index.php?category=2

Scroll down to the 16mm projector section. There are a lot of 16mm Bell and Howell model. I have not found an EL37 one so far.
There is one where the projector stood on top and was an arc lamp model.

http://www.film-tech.com/warehouse/manuals/BH140LM.pdf

I wonder if the EL37,s were fitted in the UK models.

John

 
Posted : 19/02/2016 4:58 pm
Refugee
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I did some more research more recently to my last post in this thread and have as a result discovered that they are British. There is a marking on the inside of the top and base covers with a date.
I searched for APV and they came up as casting foundry based in the UK and still trading as of a couple of years ago.
Paramount is as we all know an obvious customer but the set maker?
I have also done a bit of reverse engineering too.

 
Posted : 19/02/2016 5:35 pm
Synchrodyne
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The Armstrong A10 amplifier of 1954 used an EL37 pair for its ultra-linear push-pull output.

I imagine that this was designed just before the EL34 became available.

The A10 as Armstrong’s fist step into the high-fidelity components market, the start of its slow transition (lasting until the end of the 1960s) from a maker of radiogram chassis to a maker of hi-fi equipment.

The A10 was an early example of a British amplifier with a U-L (Blumlein-type) output, and being so, was probably doubly rare in also using the EL37.

It also marked a move by Armstrong from mostly Mazda to Mullard valve types, although like Murphy, it hung on to the 6C9 in some of its radio equipment for a few years. The A10 was all-Mullard, ECC82, EF86, 2 x EL37 and GZ32. The circuit was a bit unusual though. One half of the ECC82 was use as an input stage, outside of the main feedback loop. The amplifier proper consisted of the EF86 followed by the other half of the ECC82 as phase-splitter then the EL37 pair. The corresponding control unit used a single ECC83.

The A10 was replaced by the A10 Mk II circa 1957, the latter using an EL34 pair.

Cheers,

Steve

 
Posted : 19/02/2016 11:56 pm
Refugee
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The Armstrong is pretty close to the valve line up of mine.
Mine are triode wired but with the same single triode phase splitter as the Armstrong but using half an ECC33 the other half being a voltage amplifier. There is a pentode preamp using an EF37A bringing up the gain enough to support a moving coil microphone.
The tone controls on mine are not ideal with the bass boost control mounted in a feedback loop around the volume control so that all the controls need to be adjusted each time.
An external preamp is best here.

 
Posted : 20/02/2016 3:27 pm
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