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Replacing silicon with germanium

Z

ZZwergel

Member
Would it be ok to replace the output transistors in an amplifier with germanium ones? If it is, would the emitter resistors need to be increased in order to compensate for the lower voltage drop? I would like to possibly re-transistor a Crown D-75 amplifier.

Thank you
Edit: Fix typo
 
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Most transistors on ebay are counterfeit. What exactly do you think is to be gained by going to germanium? Are the transistors (outputs, I assume) faulty in your amp?
 
ZZwergel said:
Would it be ok to replace the output transistors in an amplifier with germanium ones? If it is, would the emitter resistors need to be increased in order to compensate for the lower voltage drop? I would like to possibly re-transistor a Crown D-75 amplifier.

Thank you
Edit: Fix typo
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I would expect the question the other way around. Just curious, why would you want to do that, germanium having better sound than silicon? I think I've heard that, like tubes over transistors. I have heard some very nice sounding early germanium Heathkit amps.
 
It only just dawned on me that the Crown's output transistors are NPNs. So even if the base biasing problem was solved, you'd need to find Germanium NPN parts, in a TO-3 case, good for an absolute-desperation-minimum of 60V Vcb and Vce.

I'm thinking counterfeits won't be a problem, as such, because you can't counterfeit what never existed. Anybody know of parts that did exist with those characteristics?

I see someone pitching 2N6576 on the 'bay, but despite what the listing says I don't think that's a Germanium part. Maybe the TRW 1700C, if you could find more than one? Can't find enough data on that one to opine.

All else aside, welcome to AK, ZZwergel. Hope this hasn't been too off-putting.
 
ZZwergel said:
Would it be ok to replace the output transistors in an amplifier with germanium ones? If it is, would the emitter resistors need to be increased in order to compensate for the lower voltage drop? I would like to possibly re-transistor a Crown D-75 amplifier.

Thank you
Edit: Fix typo
Click to expand...
There is a reason Germanium went the way of the DoDo bird. - Leakage -. And leakage causes distortion. So why would you even do that to a Crown amplifier? Even if you found NOS Germanium, they would likely already be on their way out from aging. If anything, I would rather modify germanium circuits to retrofit silicon.
Of course you can experiment all you want. And sometimes it can be "fun". :biggrin:
 
chazix said:
It only just dawned on me that the Crown's output transistors are NPNs. So even if the base biasing problem was solved, you'd need to find Germanium NPN parts, in a TO-3 case, good for an absolute-desperation-minimum of 60V Vcb and Vce.

I'm thinking counterfeits won't be a problem, as such, because you can't counterfeit what never existed. Anybody know of parts that did exist with those characteristics?

I see someone pitching 2N6576 on the 'bay, but despite what the listing says I don't think that's a Germanium part. Maybe the TRW 1700C, if you could find more than one? Can't find enough data on that one to opine.

All else aside, welcome to AK, ZZwergel. Hope this hasn't been too off-putting.
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All they gotta do, is re-stamp a germanium number onto a silicon component. If @EastPoint has any Germanium on eBay, it is genuine. Ben is...
Affinity For Artifacts
and...
peace.love.and.music
 
The leakage distortion does have a something about it. I've got an old Sony reel to reel full of germanium transistors, and it adds a certain fuzzy warmth to the sound. That plus hiss of course, but new resistors helped a lot with that. In the tape loop I think its got 2 or 3 active per channel, and its enough that you can definitely tell when its switched in. I've never felt the need to leave it in the rig but I can see where an instrument amp might want that sort of tone. Germanium guitar pedals exist to do this.
 
gadget73 said:
The leakage distortion does have a something about it. I've got an old Sony reel to reel full of germanium transistors, and it adds a certain fuzzy warmth to the sound. That plus hiss of course, but new resistors helped a lot with that. In the tape loop I think its got 2 or 3 active per channel, and its enough that you can definitely tell when its switched in. I've never felt the need to leave it in the rig but I can see where an instrument amp might want that sort of tone. Germanium guitar pedals exist to do this.
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Instrument amps (and add-ons) produce the tone and sound of what the musician(s) want.
Stereo amps should faithfully re-produce that sound without changing it.
If the OP wants to modify the D-75 as an instrument amp, then by all means have at it. However it will no longer faithfully reproduce the tones and sounds, but add further modification(s) to the sound when replayed back.
 
my bigger concern would just be reliability. Crown stuff is pretty tough as-designed. If the goal is the sonics I'd try and get that without all the reliability problems of germanium power transistors, or the need to re-engineer the amplifier. Looping in a pedal or some other low-level device before the Crown might get that done.
 
ZZwergel said:
Would it be ok to replace the output transistors in an amplifier with germanium ones? If it is, would the emitter resistors need to be increased in order to compensate for the lower voltage drop? I would like to possibly re-transistor a Crown D-75 amplifier.

Thank you
Edit: Fix typo
Click to expand...
Nope. For starters, the germanium ones have a much lower B-E junction voltage and will not bias up properly in a position meant for a Si one.
 
Powertech said:
Why
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Only ZZwergel can answer that, of course, and I think he or she might have been chased off by the (perfectly appropriate) skeptical nature of the responses.

But that won't stop me from bloviating!

I'm guessing that the motivation was to get a sound like one would get from a Fuzz Face effects pedal. Is it unlikely that putting Ge outputs into the Crown would achieve that? Yes, I think it is unlikely. Would it make loads more sense to achieve it by inserting a fuzz pedal into the input to the Crown? Yes, for sure it would make more sense.

And yet... The Crown having a quasi-complementary output configuration makes it just barely conceivable to me that Ge outputs could affect the sound in a way that a musician's ear's could detect. If someone could identify suitable Ge outputs - that's a huge doubt - I'll bloviate further about how I think the base bias could be adjusted to suit. Hell, if someone can identify such output devices, I'll volunteer to do the conversion!
 
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