now i test and adjust the offset on output terminal and it reads. 1.0 and my multimeter was set to 200mV. i think this is ok. any opinions?
i have a hard time in tweaking the bias (VR3), the values in my Meter continue to increase. i leave it about 600mV and now it reads 636mV. are there any problem or is this normal? the amp is almost 30mins powered on.
i have a hard time in tweaking the bias (VR3), the values in my Meter continue to increase. i leave it about 600mV and now it reads 636mV. are there any problem or is this normal? the amp is almost 30mins powered on.
Hum can be your supply filtering... or bad input coaxial cable
or because you are using MP3/4 player in the input.
There's no registered complains about hum in this amplifier...you are the first to report this.
Power on thump is normal in this amplifier.
Current drift from cold to normal operation and hot operation is normal too.
Differences of stand by current when you measure the positive rail compared to the negative rail is also normal...this amplifier sucks more current in the positive rail because of zener current you have in the positive rail
regards,
Carlos
or because you are using MP3/4 player in the input.
There's no registered complains about hum in this amplifier...you are the first to report this.
Power on thump is normal in this amplifier.
Current drift from cold to normal operation and hot operation is normal too.
Differences of stand by current when you measure the positive rail compared to the negative rail is also normal...this amplifier sucks more current in the positive rail because of zener current you have in the positive rail
regards,
Carlos
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, Trying to build these amp , but can i use the 
hi , there are somes photographs of the pcb alone, and the populated pcb,this amp work quite well i tested it with b&w speakers ..its great,no hum , no hiss,easy to adjust as long as you follows instructions on greg web site ,as someone previously said if i can do it everyone can do it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
It 's a NPN tranzito ,This is data sheet of its. H1061 pdf, H1061 description, H1061 datasheets, H1061 view ::: ALLDATASHEET :::
Yes, you can substitute by H1061
It is cousin of the 2SC1061..... a little bit more strong but seems that belong to the same family.... you can also use TIP41C and TIP42C to all amplifier positions...i did that at home...even the differential have used TIP42C.
Result was not that good because TIP41C/42C are low speed transistors...but worked fine too.... i little bit slow i think, treble use to be better when using BD139/140.... these ones are the best sounding devices (if we can say transistor sounds), as work very well with colector voltages up to 40 volts.
Depending your substitutions you may have different adjustment to the bias trimpot, also the off set trimpot...but this will be the worst case scenario.
Be happy, enjoy, publish pictures..if you did, then publish more.
The more modern versions are more efficient as result of better construction techniques, higher speed and higher dissipation
regards,
Carlos
It is cousin of the 2SC1061..... a little bit more strong but seems that belong to the same family.... you can also use TIP41C and TIP42C to all amplifier positions...i did that at home...even the differential have used TIP42C.
Result was not that good because TIP41C/42C are low speed transistors...but worked fine too.... i little bit slow i think, treble use to be better when using BD139/140.... these ones are the best sounding devices (if we can say transistor sounds), as work very well with colector voltages up to 40 volts.
Depending your substitutions you may have different adjustment to the bias trimpot, also the off set trimpot...but this will be the worst case scenario.
Be happy, enjoy, publish pictures..if you did, then publish more.
The more modern versions are more efficient as result of better construction techniques, higher speed and higher dissipation
regards,
Carlos
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here 's result of my test voltage ,I replaced BD139 by H1061 in the schematic original , I remove all tranzito and test, but all of them is good.
An externally hosted image should be here but it was not working when we last tested it.
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