So I ran across a bunch of new NTE181 power transistors. I am a tube guy but would be interested in making an amplifier with these. Inter webs are not very helpful for schematics with these particular transistors.
Anyone know of a place or have a schematic to throw out? It would be high power preferably 100 watts or more.
Like I said I’m a tube guy and don’t know a whole lot about solid state so bear with me please.
Anyone know of a place or have a schematic to throw out? It would be high power preferably 100 watts or more.
Like I said I’m a tube guy and don’t know a whole lot about solid state so bear with me please.
They are in the ballpark of some fine old Motorola transistors like MJ802/4502 and those can take some real punishment even if they're pretty slow (Ft 2MHz) like most original Motorola T03 audio types. These would be best for class A audio operation or a musical instrument amplifier, I'd think.
However, here's a design with a good Hifi pedigree.
A Paul Kemble web page - Lecson AP3 MkII, schematic.
However, here's a design with a good Hifi pedigree.
A Paul Kemble web page - Lecson AP3 MkII, schematic.
According to the DS this is a 200W 30A 2MHz device which does sound like an MJ802. The PNP complement is NTE180. One issue I have with older devices like the MJ802 is that their safe operating area rating is really quite poor. Old bipolar devices are not at all like tubes which can operate at their max power at any voltage, but have to be de-rated at voltages above a safe operating area limit. The MJ802 derating starts at only 25V, so I'd recommend classic Class AB, not class A, and quasi-complementary if you don't have the PNP device. (New bipolars still have the same problem but allow higher voltages before derating has to be used). NTE DS does not show the second breakdown rating chart.
You should be able to run the amp at +/-45V rails which will deliver perhaps 100W peak if the PSU is relatively stable (40V peak into 8 ohms, peak sinewave 200W) with a single pair, but certainly a sustained output of 70W RMS.
Depending on how much of a challenge you want, a quasi-complementary design based on the Blameless architecture might be a useful starting point.
You should be able to run the amp at +/-45V rails which will deliver perhaps 100W peak if the PSU is relatively stable (40V peak into 8 ohms, peak sinewave 200W) with a single pair, but certainly a sustained output of 70W RMS.
Depending on how much of a challenge you want, a quasi-complementary design based on the Blameless architecture might be a useful starting point.
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There is an amplifier design, by RCA, that dates back to the 70s but is quite reliable. If you use your NTE transistors as output devices, it should perform well.
https://www.updatemydynaco.com/documents/70WattRCAAmplifierDesign.pdf
https://www.updatemydynaco.com/documents/70WattRCAAmplifierDesign.pdf
The schematic in #4 shows a quasi-complementary design since both output devices are the same NPN type. You may be able to beef that up to meet your power requirement.
If your aim is to use only your NTE181 transistors, you may be taking a hit to performance though, depending on your application.
The MJ802/4502 complements were known (ref. Douglas Self's trimodal amplifier writings) to be good complements for the time so it would seem appropriate to use the NTE182 complement too, despite the extra cost.
A locally produced kit amplifier (Digi 125) using just one pair of MJ802/4502 devices proved fully capable of 125W/4R so perhaps that meets your power criteria too. DIGI-125 Kit Amplifier Module
If your aim is to use only your NTE181 transistors, you may be taking a hit to performance though, depending on your application.
The MJ802/4502 complements were known (ref. Douglas Self's trimodal amplifier writings) to be good complements for the time so it would seem appropriate to use the NTE182 complement too, despite the extra cost.
A locally produced kit amplifier (Digi 125) using just one pair of MJ802/4502 devices proved fully capable of 125W/4R so perhaps that meets your power criteria too. DIGI-125 Kit Amplifier Module
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