Germanium Amplifier

For the three and more legged things
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Mike H
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#46

Post by Mike H »

I am beginning to understand why it used to take me so long working out actual usable transistor circuits that will remain stable and work reliably, compared to this valves are a doddle :D


 
 
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pre65
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#47

Post by pre65 »

So Mike, after all this thinking, calculating and "wallowing" in nostalgia about Germanium transistors ( :wink: ) do you think the final results will be worthwhile ? :lol:
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Mike H
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#48

Post by Mike H »

Haven't the faintest idea, but there's all this ranting going on on the web about how germaniums sound good.

Even to the extent of converting to germanium outputs on anything modern. How about that.

Mainly though it's the challenge :D

But is becoming a bit of a marathon must be said. Wasn't supposed to be this difficult or involved originally :lol:

 
 
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pre65
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#49

Post by pre65 »

So has anything in the way of germanium transistors been produced in recent times ?

Or is it just old stock being used up.
The only thing necessary for the triumph of evil is for good men to do nothing.

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Mike H
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#50

Post by Mike H »

Good question ~ prices may indicate NOS, RS have got a few (and they are few) so could be surviving old stock

http://uk.rs-online.com/web/search/sear ... &x=29&y=12

Cricklewood seem to have lots, but only if it's actually got a 'buy now'

http://www.cricklewoodelectronics.com/C ... rch&page=1


See them weird brass coloured 2N174 types? Tried some of those once. And blew them up :( Didn't cost £40 each though, more like 2 quid IIRC


Only thing is with these survivng old stock can't get exactly what you want, I expect the most popular ones have all been used up so you're kind of left with "the dregs"

 
 
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pre65
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#51

Post by pre65 »

I'll make some if you like. :wink:

Monday I have to build a Nuclear power station,

Tuesday I have to negotiate with the Taliban,

Wednesday is lunchtime concert,

Thursday is free. :lol:
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
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Mike H
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#52

Post by Mike H »

You'll be worn out!


 
 
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al newall
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#53

Post by al newall »

Phil.

Don't tell the Taliban about the nuclear power station. :shock:
Much to learn there is.
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Mike H
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#54

Post by Mike H »

Yes don't get it the wrong way round :lol:


 
 
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Mike H
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#55

Post by Mike H »

Found some CV7084 (military version OC35 power tranny) on eBay [Langrex shop], cheaper'n Cricklewoods so might have a go at making the output as germanium p-p. Have to be contrived as Darlingtons though as the transformer is very small (read as, base current can't exceed 1mA)

They also got CV8314 (OC76) only £2 each which will do for the pre-amps so will have some of them as well.


 
 
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Mike H
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#56

Post by Mike H »

Summink like this innit
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Transis-Tronics Pwr-amp-7C.gif
 
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Mike H
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#57

Post by Mike H »

So looks like will have two AC128 left over, so last night I quickly scribbled this sketch for a high impedance input buffer. (Well reasonably high impedance input.)

Remember the low impedance input problem with the tone control network, 'speshly as regards the HF end, 'cause of the capacitors in it? Would help greatly if could be driven from a low impedance source.

And voila....
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AC128 buffer1.gif
AC128 buffer1.gif (6.89 KiB) Viewed 3709 times
 
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Mike H
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#58

Post by Mike H »

Interestingly there's no signal loss here, not like wot you get with a FET or a cathode follower! (I was thinking of using a FET buffer earlier on)

Put 1 Volt in, you get 1 Volt out. No less.

Input impedance is 300 kilohms, not at all shabby so means I can use a 100k log pot for volume (found I've got two stereo gangs going spare doing nothing)

 
 
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Mike H
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#59

Post by Mike H »

Yep that works.
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Transistronics-Tone Control-4.gif
 
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Mike H
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#60

Post by Mike H »

And the output be remains flat when vol pot not at maximum (and tone controls in the middle):
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Transistronics-Tone Control-graph.gif
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"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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