Germanium audio preamplifier

Mooly's circuit referred above can suit this. It's an easy to modify universal circuit, often used for video amplifiers. I'll run a silicon mod if Mooly approves.
But, as Mark Tillotson points justly, things will be different making a direct comparision rather wacky.
 
I've overlooked one small but very important issue: there is one npn (2SD77) in Mooly's circuit, but no npn on rediceman's list...
Sorry, but a no go for now unless rediceman can purchase 2 proper npn germanium bjt's.
 
Here is a quick sim of a silicon version delivering approx 20mW into 33 ohms. A couple of biasing resistors have been altered.
 

Attachments

  • H1.jpg
    H1.jpg
    446.8 KB · Views: 267
  • H2.jpg
    H2.jpg
    451.8 KB · Views: 254
  • H3.jpg
    H3.jpg
    378.3 KB · Views: 242
  • Headphone Amp.asc
    Headphone Amp.asc
    4.4 KB · Views: 73
Yes do please, so the Siklai is more controlled.
The spike on ~1.5 kHz is a bit surprising.
The rest is devine up to 200-300 kHz.
You may be proud of it (considering a hardware copy @home).

Do you approve #41 if rediceman finds ge-npn's?
 
I've overlooked one small but very important issue: there is one npn (2SD77) in Mooly's circuit, but no npn on rediceman's list...
Sorry, but a no go for now unless rediceman can purchase 2 proper npn germanium bjt's.


Hello MarsBravo,
I found 2sd77 equivalent transistors. 🙂
Ac127, Ac176,Ac187,2sd30


Thank you for your interest
Best regards.
 

Attachments

  • Germanyum_tr.jpg
    Germanyum_tr.jpg
    834.6 KB · Views: 184
Yes do please, so the Siklai is more controlled.
The spike on ~1.5 kHz is a bit surprising.
The rest is devine up to 200-300 kHz.
You may be proud of it (considering a hardware copy @home).

Do you approve #41 if rediceman finds ge-npn's?

Absolutely I approve as long as it's realised that you will have to alter the circuit to suit your exact needs. Remember this was designed to drive a low impedance load.

Here is a higher resolution sim and also a sim running into 600 ohms rather than 33 ohms and with a higher supply voltage. This one is delivering 1v rms into 600 ohm with a -15 volt rail.
 

Attachments

  • Untitled.png
    Untitled.png
    134.8 KB · Views: 275
  • Untitled2.png
    Untitled2.png
    146.3 KB · Views: 255
Ok, I'll suit it to -12Vdc supply and adjustable bias (5-50mA).
I omit the inputbuffer and volume (the input res may be replaced by a pot if preferred)
Just straigtforward as is with the given GE bjt's.
Considering a SI-variation for a two-channel left-right switchable box.