Create an amplifier with RCA 2N2148 Gem. Transister

edi907 · 2nd July 2009, 09:45 AM

How did you build up an amplifier with 2N2148 Gem. Transister?
What sound is it? Do you suggest to use this?

picowallspeaker · 2nd July 2009, 10:22 AM

I'll give you the amplifier , you give me the semis!
Just joking.I was wandering around 'cause i had an old Fisher Tx-100 integrated without TO-3's in the back , and I think they should work on this unit.
The birth of the discrete era is wonderful , seems the engineers brought knowledge from tubes and applied to semiconductors - well,it is - like interstage transformers with extra windings for FB , regulated current source for the power transistors-forgive me for my incompetence. Well , living in HK should be no problem finding any device .

edi907 · 2nd July 2009, 02:02 PM

Yes, it is easily to find any device in anywhere because the ebay born. I am very interested in the old solid device, such as V-FET (Sony 2SK60). So expensive is it in ebay, but I just have P-channel side (2SJ18). I have planned to build up CSPP amp which is designed from Japanese. The 2N2148 which is happened in a shop but I don't purchase today because I want to know more about it. Just know that it is a geminium device.

Bone · 2nd July 2009, 02:59 PM

Here's the ratings for the 2N2148

Ge PNP Power BJT
V(CEO) =40V
V(CBO) =60V
I(C) Abs. Max Collector Current=5.0A pk
Absolute Max. Power Diss. =12.5W
I(CBO) Max. =10mA @V(CBO) =60
V(CE)sat Max. =1.0V @ I(C) = 4.0A & I(B) = 400mA
h(FE) Min. Static Current Gain = 40
h(FE) Max. Current gain.=160 @ I(C) = 1.0A & V(CE) = 2.0V
f(T) Min. Transition Freq=2.0MHz @I(C) =1.0A & V(CE) =2.0
Package=TO-3

These were taken from an old book of transistor specs that I have in my workshop.

Tony.

edi907 · 2nd July 2009, 04:49 PM

Do you have any experience about this, something like a circuit using similar device and the sound is which behavior. I am a fresh DIY player, I never enjoy it before and truly feeling it in this moment.

picowallspeaker · 2nd July 2009, 10:25 PM

Old germanium transistors suffer from thermal drift , have a very narrow bandwith , moreover they're not in production from...mid seventies of the past century.
It's better not to fall in love with them.

mjf · 3rd July 2009, 10:13 PM

hello.
here is an old schematic (around 1968) with ge - transistors ad167 that are similar to yours............
i think these amps are good for the museum.............but if you like to experiment with them...........why not?
greetings................

2nd July 2009, 09:45 AM	#1
edi907 diyAudio Member Join Date: Apr 2009	Create an amplifier with RCA 2N2148 Gem. Transister How did you build up an amplifier with 2N2148 Gem. Transister? What sound is it? Do you suggest to use this?

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2nd July 2009, 10:22 AM	#2
picowallspeaker diyAudio Member Join Date: Apr 2007	I'll give you the amplifier , you give me the semis! Just joking.I was wandering around 'cause i had an old Fisher Tx-100 integrated without TO-3's in the back , and I think they should work on this unit. The birth of the discrete era is wonderful , seems the engineers brought knowledge from tubes and applied to semiconductors - well,it is - like interstage transformers with extra windings for FB , regulated current source for the power transistors-forgive me for my incompetence. Well , living in HK should be no problem finding any device .

2nd July 2009, 02:02 PM	#3
edi907 diyAudio Member Join Date: Apr 2009	Yes, it is easily to find any device in anywhere because the ebay born. I am very interested in the old solid device, such as V-FET (Sony 2SK60). So expensive is it in ebay, but I just have P-channel side (2SJ18). I have planned to build up CSPP amp which is designed from Japanese. The 2N2148 which is happened in a shop but I don't purchase today because I want to know more about it. Just know that it is a geminium device.

2nd July 2009, 02:59 PM	#4
Bone diyAudio Member Join Date: Jun 2004 Location: Dorset, UK	Here's the ratings for the 2N2148 Ge PNP Power BJT V(CEO) =40V V(CBO) =60V I(C) Abs. Max Collector Current=5.0A pk Absolute Max. Power Diss. =12.5W I(CBO) Max. =10mA @V(CBO) =60 V(CE)sat Max. =1.0V @ I(C) = 4.0A & I(B) = 400mA h(FE) Min. Static Current Gain = 40 h(FE) Max. Current gain.=160 @ I(C) = 1.0A & V(CE) = 2.0V f(T) Min. Transition Freq=2.0MHz @I(C) =1.0A & V(CE) =2.0 Package=TO-3 These were taken from an old book of transistor specs that I have in my workshop. Tony.

2nd July 2009, 04:49 PM	#5
edi907 diyAudio Member Join Date: Apr 2009	Do you have any experience about this, something like a circuit using similar device and the sound is which behavior. I am a fresh DIY player, I never enjoy it before and truly feeling it in this moment.

2nd July 2009, 10:25 PM	#6
picowallspeaker diyAudio Member Join Date: Apr 2007	Old germanium transistors suffer from thermal drift , have a very narrow bandwith , moreover they're not in production from...mid seventies of the past century. It's better not to fall in love with them.

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