2sc2705 e-k-b npn https://static.chipdip.ru/lib/310/DOC000310064.pdf
2sa970 e-k-b pnp https://static.chipdip.ru/lib/947/DOC005947869.pdf
2sa970 e-k-b pnp https://static.chipdip.ru/lib/947/DOC005947869.pdf
I could remove oscillations by shorting R1. R1 is in series with the input coupling capacitor (coupling capacitor is C1 on this board which is actually C4 in JLH's original schematic). I used some arbitrary (but low k) for R1 and apparently that is not required as per JLH! Before I can test it with speakers, I need to re-assemble the board that I was playing around with.
At 12V and 8 ohms, it is enough to set the current to 0.8-0.9 A. The power will be 1.5 watts.
Some used BD911.
MJE13007 can also be used at the output. For a driver, their characteristics are not quite suitable. But it will work)))
Some used BD911.
MJE13007 can also be used at the output. For a driver, their characteristics are not quite suitable. But it will work)))
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Hello! It is currently in an experimental phase.
I haven’t measured it yet, I roughly calculated 4W music peak power.
I put it together quickly based on the circuit diagram.
It sounds good and 1.5W RMS is enough for me. I'll replace the transistor in it, that's all it was at home. 🙂
I'm sending some pictures:
I haven’t measured it yet, I roughly calculated 4W music peak power.
I put it together quickly based on the circuit diagram.
It sounds good and 1.5W RMS is enough for me. I'll replace the transistor in it, that's all it was at home. 🙂
I'm sending some pictures:
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Suitable radiators, correct position (vertical). If you want and use a more powerful power supply and a higher voltage (up to 27 V), you can build an amplifier according to the author's specification.
The 24Vac can be used with these transformers. Can be used up to 2.5A.
Voltage regulator is not a problem. LM317T (or 7824 (?)) with PNP power transistor.
I'm interested in the thing.
I have 6pcs 100VA 230V/30Vac hypersil transformer. 30Vac is too much, I can to make lower voltages.
Voltage regulator is not a problem. LM317T (or 7824 (?)) with PNP power transistor.
I'm interested in the thing.
I have 6pcs 100VA 230V/30Vac hypersil transformer. 30Vac is too much, I can to make lower voltages.
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24V AC will give 32V DC (no load). The surplus can be used to operate a stabilizer or a capacitance multiplier. Or DC-DC converter.
Maybe unwind from the secondary to about 22Vac(100VA 30V hypersil).
I am thinking hard about bringing step-down SMPS into the system.
Result: negative. 3-7V drop analog regulator is more sympathetic.
IQ=1,3A is enough for 24V(dc) stable / 10W 8 Ohm?
I am thinking hard about bringing step-down SMPS into the system.
Result: negative. 3-7V drop analog regulator is more sympathetic.
IQ=1,3A is enough for 24V(dc) stable / 10W 8 Ohm?
Hi Hanair, Yes, I am use this scheme. See my test in video:
TESTE #3 - Amplificador CLASSE A - JLH 1969 (10W) 25,5V DC - YouTube
Oscillation issue is fixed, my board has an input resistor and I used some random value in the range of k ohms. It works fine with 100R or even shorted. All good now!
I replace the driver to 2SD882 and increase supply voltage(use lab PSU), current set to 1,3A(24Vdc):
https://www.st.com/resource/en/datasheet/2sd882.pdf
Great!
My objective: 24Vac to 24Vdc(stab.)... I'm on it.
Hi Sierratds and Hanair!
Good job!
I watched the video, now I know it's 1.2A enough. Thanks a lot! 😉
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I would not recommend the 2N3773 for audio. At least, not without testing ft.
Old RCA spec ft(min)=200kHz. Maybe about the same as an OC71!
Moto's 2N3773's were made with a different process and today's 2N3773's will be epi base of some description and MAY have a better ft (around 2MHz) - but I don't have a 1981 era device to test. But the spec should disqualify as it is still 200kHz.
In the JLH the frequency response is not best aided with NFB because there is no additional drive current (e.g. from a driver transistor) to push the base current up when the gain falls. Yes it will improve at low output levels but full power at high (audio) frequencies is likely to have higher distortion.
Old RCA spec ft(min)=200kHz. Maybe about the same as an OC71!
Moto's 2N3773's were made with a different process and today's 2N3773's will be epi base of some description and MAY have a better ft (around 2MHz) - but I don't have a 1981 era device to test. But the spec should disqualify as it is still 200kHz.
In the JLH the frequency response is not best aided with NFB because there is no additional drive current (e.g. from a driver transistor) to push the base current up when the gain falls. Yes it will improve at low output levels but full power at high (audio) frequencies is likely to have higher distortion.
Hi! Thanks for the reply!
Probably true. I'll buy 2SC5200s. (with 2SC2625 is better than 2N3773? - 2SC2625 is already at home)
Its sound is tolerable with 2N3773, I have not tested it at a volume higher than 2 Watts. (for other reasons)
I'm testing the 24V stabilizer now. PC-PSU heatsink is small for this (old S478 proc. cooler is better)
MJE13007 + MJE13009 darlington, BZX18V + 3xblue LED. 😉
(I know the 7824 + PNP construction is better ...)
Some pictures:
Probably true. I'll buy 2SC5200s. (with 2SC2625 is better than 2N3773? - 2SC2625 is already at home)
Its sound is tolerable with 2N3773, I have not tested it at a volume higher than 2 Watts. (for other reasons)
I'm testing the 24V stabilizer now. PC-PSU heatsink is small for this (old S478 proc. cooler is better)
MJE13007 + MJE13009 darlington, BZX18V + 3xblue LED. 😉
(I know the 7824 + PNP construction is better ...)
Some pictures:
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2N3773 are well suited for power supplies. 2SC2625 have low Hfe. Check yours at 12v at 1A (on heatsink).
You can use the capacitance multiplier circuit, but add a zener diode (previously suggested here).
You can use the capacitance multiplier circuit, but add a zener diode (previously suggested here).
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2N3773 are well suited for power supplies-
yes, for which they are very good. And all I have ever used them for!
yes, for which they are very good. And all I have ever used them for!
5200s in progress (waiting for shipping).
Until then; output transistors MJE 15028 (ONS)
https://www.onsemi.com/pdf/datasheet/mje15028-d.pdf
Temporarily I applied the stable 12V back. IQ = 0.9A.
Until then; output transistors MJE 15028 (ONS)
https://www.onsemi.com/pdf/datasheet/mje15028-d.pdf
Temporarily I applied the stable 12V back. IQ = 0.9A.
The 2SC2039's I received don't look quite as rosy as your plot. These are 0-20V sweeps, 1mA/div and 20mA/div. Hfe is over 400. Lots of looping at low Ib. Linear beta at a given Vce, but beta expands with Vce. If AC appears across CE, this will be a beta modulator.
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MJE 15028 (ONS) - You can use parallel connection with resistors from 0.1 ohm in the emitter.
