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GERMANIUM Single ended Class A Headphone Amp.
GERMANIUM Single ended Class A Headphone Amp.
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Old 13th June 2018, 10:41 AM   #91
merlin el mago is offline merlin el mago
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Mooly what's the final schematic? I guess the load can be high impedance hp 300 ohms? What about the sound, isn't the same as silicon right? What are the better GE parts for the circuit?

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Old 13th June 2018, 11:26 AM   #92
Mooly is offline Mooly  United Kingdom
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GERMANIUM Single ended Class A Headphone Amp.
Circuit is as per post #1 and used the devices that I had available. There are many devices that would prove suitable but it would (as always with something like this) be a case of trying them out.

High impedance phones might be limited due to the relatively low output voltage available. Realistically you could only expect around 10mw into that kind of impedance.
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Old 13th June 2018, 02:56 PM   #93
Dibya is offline Dibya
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DSI Germany still make germanium transistor . NTE is still making .
Acidfuzz is secretely making their own germanium transistor.
Motorola is secretly making oc series transistor in China . Don't be excited they sounds **** in comparison to mullard ,valvo and Phillips.
BEL in India is still making AC and AF series transistor .
Mistry solved.
Last month I brought ac128 for my guitar pedals. After some time even they are claimed new old stock they seems like brand new. w. After that I tried to solve the mistry.
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Old 13th June 2018, 03:01 PM   #94
merlin el mago is offline merlin el mago
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Quote:
Originally Posted by Mooly View Post
Circuit is as per post #1 and used the devices that I had available. There are many devices that would prove suitable but it would (as always with something like this) be a case of trying them out.

High impedance phones might be limited due to the relatively low output voltage available. Realistically you could only expect around 10mw into that kind of impedance.
Thanks Mooly.
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Old 13th June 2018, 03:25 PM   #95
Dibya is offline Dibya
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Hi guys and gals if I want to replace AC125 with NTE alternative ? Which one should I choose.
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Old 18th June 2018, 08:21 AM   #96
Dibya is offline Dibya
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I am unable to find ACY121 . Where can I get it?
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Old 24th September 2018, 01:57 PM   #97
DIYBras is online now DIYBras  Brazil
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Quote:
Originally Posted by ColinF View Post
Hi Mooly,
Just discovered your exploration of germanium transistors in your headphone amp design.
I've been making small amps and especially headphone amps since I was a kid and was always surprised at the loss in sound quality when I used silicon transistors in place of germanium ones. For me Ge has a more interesting and full sound that has more in common with tubes than Si which generally tends towards sibilance. The frequency response between the two technologies in my headphone amp is very similar so perhaps its a harmonic distortion difference. I've not measured it that way. All I've done is listen to the different transistors and selected the ones I like best. My headphone amp is also class A and uses a hybrid Ge-Si output stage as the BD140 silicon output transistor seems to work better at higher current than the even older Ge output transistors. I suspect Ge is better at medium-level circuitry like line stages and headphone amps rather than high power in poweramps and low noise phono and microphone circuits. Although I did build a Ge MC stepup with paralleled MP38s that was a touch noisy but sounded characterful and satisfying.
You tried the AF379? Is a very low noise Ge for hi-end color TV from late 60's and 70's. The quoted noise for RF range is very low, lower than most Si signal transistors, so chances for noise being low in audio are great even without paralleling. I bet less noise than eg. the famous 2SC2574E. In top-end TVs this transistor was replaced only by dual gate MOSFETs in the 80's. Caution is needed against RF oscillations since is a good performer even at GHz range...
The MP38 "seems" to have rbb' in the 220R region judjing by the poor translation I made from a russian datasheet. I have some and for normal line level the noise is excellent, but I'm tempting to try RF ones like AF379 for gain stages for a complete Ge phono preamp, along with GT311 and 313 (RF "almost" complementary pair).
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Old 24th September 2018, 02:26 PM   #98
Jenyok is offline Jenyok  Russian Federation
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I have many different germanium transistors (Russian, USSR) and many pieces of each type, low, medium and high power.
Generally germanium transistors are pnp structure.
.
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Old 24th September 2018, 02:41 PM   #99
DIYBras is online now DIYBras  Brazil
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I have many different germanium transistors (Russian, USSR) and many pieces of each type, low, medium and high power.
Generally germanium transistors are pnp structure.
.
And most are easy to buy on eg. eBay, so with proper equivalent substitution is possible to build most Ge projects, including the Mooly version.
Some of these russian Ge like the 1T910 are very interesting.
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