germanium Preamp?

[vsmusic]

Hello,
Tell me "vsmusic", how to set-up the variable resistor R15, in the Victoria pramplifier ?
In the 70s, some auto-radios from Philips were manufactured in France, at Dreux.
I did an internship with them at that time.

Hello. It is necessary to adjust R15 so that at points E and F were the voltage shown in the diagram

 

[vsmusic]

Made another germanium Phono preamp . Transistors GT-308V, P-416B, and MP-16B ( all transistors of the USSR ) . I will start testing this Board tomorrow .

 

[adason]

I know this is an old thread, but I thought we could keep it going.
Friend of mine gave me vintage portable reel to reel player, beyond repair. I salvaged germanium transistors out of the board. 2SB170 and 2SB172.
Any simple schematics for buffer or line level preamp?
I see some already, but if someone has personal experience, even better.

 

[vsmusic]

JBL SG-520 ....

 

[adason]

thanks vsmusic, that looks impressive
i will start easy, with single stage
here is what i built on test board
its single stage preamp, with 2sb170
it performs admirably, distortion is 0.071%, intermodulation 0.112%
yes, I have some power supply hum, you can see 60 and 120Hz residual, i will work on that
i will be building buffer next, likely first stage from the schematics you posted, thanks

 

[vsmusic]

Eight years ago, a guy from Japan decided to make a preamp for himself . He used the 520 scheme . Unfortunately, the link to his project no longer works . He made only the Phono and the linear part . Without a tone control . He used the original transistors , as in the diagram of the JBL ......I made for myself only a phonopreamp from this scheme - my board is shown in the photo in message 202 . Work perfectly .

 

[adason]

I may try this...

 

[vsmusic]

General Electric 1964 . Preamp .

 

[vsmusic]

RCA 1966 / Preamp / ...If you don't need a tone control, just use the first two stages . And apply feedback via resistor R14..

 

[adason]

That GE schematics gave me an idea how to do a buffer with volume to minimize noise...

 

[vsmusic]

This is wrong . The level controller must be separated by a capacitor . If there is a DC-voltage on the level controller, it will make noise during adjustments ...There must be a capacitor in front of the level controller

 

[adason]

I agree, its a bad idea. But that is exactly how rca did it.

 

[adason]

I just did that buffer, with no volume control. It works fine, sounds good, little lower distortion that preamp. It measures ~0.066% distortion with RightMark Audio Analyzer (using crappy old laptop).

I think I will make one more buffer. Then I will use preamp (with volume control on the input, I already did that) first, then split the signal into high path (150Hz up) and low path (150Hz and lower) using just PLLC, and add those two buffers on the output. It should work as buffered passive line level crossover. Will see how it sounds.

 

[xiaoping]

JBL-SG520

oh,my god.....

Hi everyone, I want to copy JBL-SG520, just need its audio amplifier circuit, JBL SG520 has many unnecessary circuits, such as tone control, filter and tone oscillation circuit for gain adjustment, so I cut it off completely. Is this circuit diagram correct? I searched the network but couldn't find the 25uf capacitor in the picture.
Thanks for reply

 

[OldDIY]

Use the standard values of 20 μF. It works

 

[vsmusic]

Hi everyone, I want to copy JBL-SG520, just need its audio amplifier circuit, JBL SG520 has many unnecessary circuits, such as tone control, filter and tone oscillation circuit for gain adjustment, so I cut it off completely. Is this circuit diagram correct? I searched the network but couldn't find the 25uf capacitor in the picture. View attachment 903225
Thanks for reply

Yes - this circuit diagram correct .

 

[egellings]

1N34's are diodes. How do you get a transistor with those?

 

[xiaoping]

Yes - this circuit diagram correct .

The original circuit diagram is 25mf

 

[OldDIY]

Use the standard values of 20 μF
Mikrofarad

 

[OldDIY]

Use 20+5 parallel