Regarding the comment in an earlier post that silpads have lower thermal resistance than mica and silicon grease, be very careful here - it is true that a few of them do, however in most cases they don't, and don't get close to the 0.1 degree C you can sometimes achieve with a thin mica washer (split carefully with a razor blade) and thermal grease. IMO less grease is better, just make sure that the device and heat sink are truly co-planar. (flat 
)
Good silpads cost a lot more money than the grease and mica washers.
The best solution is a non-conductive anodyze and no pads, just grease. (AKA the bose solution..LOL)
Heard a hybrid HK receiver in my teens (million years ago mid 1970's) with tubes and germanium output transistors, transformer phase splitter. Sounded quite good, not high end though by today's standards.
Those were the days when labels like "All Silicon Transistors" meant something..
)Good silpads cost a lot more money than the grease and mica washers.
The best solution is a non-conductive anodyze and no pads, just grease. (AKA the bose solution..LOL)
Heard a hybrid HK receiver in my teens (million years ago mid 1970's) with tubes and germanium output transistors, transformer phase splitter. Sounded quite good, not high end though by today's standards.
Those were the days when labels like "All Silicon Transistors" meant something..
I was out Choky, searching for stomach operation......hey!...i did not!!!
I was in my Capital.....Republic Capital, called Brasília, and my brother is a Doctor there...he told me the real thing, how many people had problems as result of the operation and i give up,. because of that, very fast.
I prefered to start a special destroyer "diet"..... i learned how to drink beer ( not more hot than 3 degrèes centigrades), and how to produce a barbecue with less salt!...now i am 26 pounds less heavy!...without any cut in my bely and much more happy to give up from the operation.
Kevinkr......ahahahahaha!...million years ago!!!, that's funny...zillion years old is my age too, i have born in 1951 and i turn a children again this last year, learning to drink beer and prepared to watch the world football games...ahahahaha!...will be funny see all those big guys running behing a single ball.
regards,
Carlos
I was in my Capital.....Republic Capital, called Brasília, and my brother is a Doctor there...he told me the real thing, how many people had problems as result of the operation and i give up,. because of that, very fast.
I prefered to start a special destroyer "diet"..... i learned how to drink beer ( not more hot than 3 degrèes centigrades), and how to produce a barbecue with less salt!...now i am 26 pounds less heavy!...without any cut in my bely and much more happy to give up from the operation.
Kevinkr......ahahahahaha!...million years ago!!!, that's funny...zillion years old is my age too, i have born in 1951 and i turn a children again this last year, learning to drink beer and prepared to watch the world football games...ahahahaha!...will be funny see all those big guys running behing a single ball.
regards,
Carlos
I have a dozen or so amplifiers that are all germanium powered
Leak stereo 30 /Truvox Tsa100/ Bryan 900 seies How do they sound ? answer quite good !! However these designs were first generation and I believe that using modern concepts germanium would sound ok .
However they were only ever low powererd and I don,t believe they could have ever improved much .
please prove me wrong
regards Trev
Leak stereo 30 /Truvox Tsa100/ Bryan 900 seies How do they sound ? answer quite good !! However these designs were first generation and I believe that using modern concepts germanium would sound ok .
However they were only ever low powererd and I don,t believe they could have ever improved much .
please prove me wrong
regards Trev
john curl said:
In had the chance to find some 2N1304, as JC recommend.
I made Rudolf Broertjes' I/V converted using silicium transistors for current sources and germanium transistor as active I/V component. I must say that JC is right.
"Germanium sound good" and I think that the secret is on the thermal dissipation (not thermal characteristic or beta dependency) of germanium.
Regards, Tibi
Some nice info about Germanium transistors:
http://semiconductormuseum.com/Museum_Index.htm
and Germanium audio amps:
http://semiconductormuseum.com/Transistors/GE/OralHistories/Jones/Jones_Page3.htm
The General Electric 2N508/2N508A was great low noise audio germanim under the 1960´s
Here in Europe we was the Siemens TF65 a great low noise type, together with AC107, AC160, OC603.
AC151, OC44 was typical general purpose audio transistors.
(I think 2N526/527 was also a general purpose in USA)
--Bo
http://semiconductormuseum.com/Museum_Index.htm
and Germanium audio amps:
http://semiconductormuseum.com/Transistors/GE/OralHistories/Jones/Jones_Page3.htm
The General Electric 2N508/2N508A was great low noise audio germanim under the 1960´s
Here in Europe we was the Siemens TF65 a great low noise type, together with AC107, AC160, OC603.
AC151, OC44 was typical general purpose audio transistors.
(I think 2N526/527 was also a general purpose in USA)
--Bo
As was posted earlier, Germanium output stages can be designed with minimal crossover distortion because of the lower Vbe drop (0.3 V). However, they are more susceptible to thermal runaway, so careful bias stabilization and thermal compensation is required for the Vbe multiplier. A popular output stage of the 60s/70s employed an AC187 NPN driver with an AD149 TO-3 power device in a Sziklai pair for the upper half, along with an AC188 PNP driver and an AD149 in a conventional darlington, for the lower half.
They sounded reasonable, but had audible shot noise, especially as they aged or overheated. Destruction and replacement of both the driver and power transistors was a fairly routine occurrence - frankly, the Si 2N3055 was huge step forward - utterly bulletproof and maintenance free.
Regarding preamps, there's no particular advantage to germaniums unless you want to run them open-loop, in single-ended class-A. That will give you vintage 60s/70s transistor radio sound, but no hi-fi. Most of the popular portable radios of that era used a push-pull output stage with two iron-core transformers - one on the input side which was driven by a single-ended open-loop class-A AC125/AC128, which would in turn alternately drive the bases of another pair of single-ended open-loop AC128s (or AC188s) in push-pull, which would in turn drive the output transformer, the secondary of which would directly drive the speakers. This arrangement accomplished impedance matching and biasing at one stroke.
DC biasing was accomplished with a single resistor connected to the centre tapping of each of the transformers - A high value resistor for the input transformer, and an optional lower value for the output. The DC betas of the transistors were part of the design process - you needed matched pairs for the output stage.
IMHO, part of the allure of the 'germanium sound' actually derived from the B-H saturating curves of the iron-core transformers that were employed. As a consequence of relatively sigmoid, smooth B-H curve (as opposed to the more rectangular curves seen on saturating ferrites), an abundance of valve-type even harmonics were bound to be generated, which might be perceived as pleasing to the ear, especially for vocals.
Without the iron transformer-coupled stages, I doubt that much benefit could be derived from germanium small-signal stages. I see no reason why the same scheme cannot be employed with silicon transistors also - indeed, many portable radios from the 70s used the same push-pull arrangement with iron-core transformers, but with bc147 or similar NPN silicon transistors, and had the similar wide-open mids usually associated with 'germanium sound'.
They sounded reasonable, but had audible shot noise, especially as they aged or overheated. Destruction and replacement of both the driver and power transistors was a fairly routine occurrence - frankly, the Si 2N3055 was huge step forward - utterly bulletproof and maintenance free.
Regarding preamps, there's no particular advantage to germaniums unless you want to run them open-loop, in single-ended class-A. That will give you vintage 60s/70s transistor radio sound, but no hi-fi. Most of the popular portable radios of that era used a push-pull output stage with two iron-core transformers - one on the input side which was driven by a single-ended open-loop class-A AC125/AC128, which would in turn alternately drive the bases of another pair of single-ended open-loop AC128s (or AC188s) in push-pull, which would in turn drive the output transformer, the secondary of which would directly drive the speakers. This arrangement accomplished impedance matching and biasing at one stroke.
DC biasing was accomplished with a single resistor connected to the centre tapping of each of the transformers - A high value resistor for the input transformer, and an optional lower value for the output. The DC betas of the transistors were part of the design process - you needed matched pairs for the output stage.
IMHO, part of the allure of the 'germanium sound' actually derived from the B-H saturating curves of the iron-core transformers that were employed. As a consequence of relatively sigmoid, smooth B-H curve (as opposed to the more rectangular curves seen on saturating ferrites), an abundance of valve-type even harmonics were bound to be generated, which might be perceived as pleasing to the ear, especially for vocals.
Without the iron transformer-coupled stages, I doubt that much benefit could be derived from germanium small-signal stages. I see no reason why the same scheme cannot be employed with silicon transistors also - indeed, many portable radios from the 70s used the same push-pull arrangement with iron-core transformers, but with bc147 or similar NPN silicon transistors, and had the similar wide-open mids usually associated with 'germanium sound'.
I don't think the 0.3 vs 0.65 Vbe drop is the reason for sound differences between si and ge (both 0.3 and 0.65 V have to be compensated in the circuit) but the germanium itself. Btw when i studied electronics (long time ago ) the first thing i thought of when i heard of the low Vbe of germanium, use it as an allmost ideal single ended amplifier!
) the first thing i thought of when i heard of the low Vbe of germanium, use it as an allmost ideal single ended amplifier!
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