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Is there a 'Gainclone' Of the tube world?

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#21
Mullard Three Valve Stereophonic Amplifier

Mullard Three Valve Stereophonic Amplifier

I came across this today whilst looking for something else.
Its from the Mullard "Tube Circuits for Audio Amplifiers" book circa 1959.

The 'three valves' are actually two valves plus the EZ80 rectifier.

Unfortunately my scanner is bust, so I can't post a schematic, but will try to sort one out.

Each side uses one ECL82 triode-pentode; the triode being the voltage amp and the pentode being the output stage.
Output power is a massive 2 watts (don't use them all at once🙂

QUOTE" The amplifier, although not comparable in specification with high quality equipment, has been found to give most pleasing stereophonic results during listening tests in a normal sized living room"

The circuit is made up of conventional triode and pentode building blocks. Component count is five or six C's and half dozen R's. B+ is 220v, OPTX 5kOhm primary.

I have found this schematic by chance, I am not posting as a builder of this amp; so I don't know how good (or bad!!!!) it sounds.

And if I'm waffling a bit its coz its 1am in the UK and I'm tired!!!!!!!!!!
 
#22
The 6BM8 is another triode-pentode like the ECL82. If you want more power a two tube push pull amp can be made with two of one or other of these tubes. One triode in one envelope is used as the input voltage amp. The triode in the other envelope is the phase splitter and the two pentode stages are used in push-pull on the output. Such a circuit has made Antique Sound Labs a lot of happy customers and puts out about 8-10 watts.
 
#25
rcavictim said:
One triode in one envelope is used as the input voltage amp. The triode in the other envelope is the phase splitter and the two pentode stages are used in push-pull on the output.
Click to expand...

I've also given thoy to using something like this as a phase splitter followed by the 2 triodes in a differential stage with a CCS in the cathodes, driving the pentodes... a little juggling of the supplies for the diff stage and you could get away with no caps in signal path.

dave
 
#26
Re: Mullard Three Valve Stereophonic Amplifier

powertriode said:
Mullard Three Valve Stereophonic Amplifier
Click to expand...

I have been giving this some thought. (God help us!!!!)

First I think that a SE amp will be the nearest tube equiv to a gainclone (IMHO)
A gainclone uses one chip, the nearest to this in tubeland is one tube per side.
This amp should be so easy to knock up, for B+ you could use two line voltage TX's back to back, (OK OK, so we need a filament TX as well) [in the US, use two line voltage TX's back to back and a voltage doubler] and as ECL82's were used in tube radios, it should be easy to find a couple of scrap tube radios to nick the OPTX's from.
By using SS rectification, we dump the EZ80.
I will try and knock one up I think......
Somehow, I don't think the result will be anywhere remotely near what we call hi-fi🙂 🙂
 
#29
No need to go that far afield -- a 6BM8 SE discussion here....

http://www.diyaudio.com/forums/showthread.php?s=&threadid=14694&perpage=10&pagenumber=1

and pictures

http://www.diyaudio.com/forums/showthread.php?s=&threadid=15354&highlight=

Japanese in particular are sweet on this tube, and you can build quite a reasonable sounding amp with them.

The ECL82/6BM8 was designed for double duty as an audio tube & a TV tube. It was later replaced by 2 tubes, the EXL86 being targeted specifically at audio.

dave
 
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