Hi all,
Today I just tried to make Aleph3 30w class A. once I build the circuit, it is working at the first step trial without any error. But some things I don’t really understand about “R8” and “R115”. Though I used pot but I need to clear this. Pls any one can help me?
Now my amp heat is about to 44c. its looks nice temp.
Need suggestion pls.
Thanks for help.
Today I just tried to make Aleph3 30w class A. once I build the circuit, it is working at the first step trial without any error. But some things I don’t really understand about “R8” and “R115”. Though I used pot but I need to clear this. Pls any one can help me?
Now my amp heat is about to 44c. its looks nice temp.
Need suggestion pls.
Thanks for help.
space2000 said:
led - you probably reversed it ( most often mistake
)R8 -- you can try without it , for start ; report what DC offsets on outputs are , so we'll know do you need them ;
R115 - leave it as is for start (820E ) , and later - when you learn few things , you can measure AC gain of output CCS ( upper output mosfets ) , and you'll know what to do .
Re: space2000
Good question.
actually i am learning by making many types of amp as i can. it is my hobby. i just make my own and keep as well. my friend took two to listen. one i make for my uncle he is very happy. i never took any extra money for workmenship or anythings at all. they will return me when they can....only to my uncle, i gave him as a present.
thanks for asking...
ttan98 said:
Good question.
actually i am learning by making many types of amp as i can. it is my hobby. i just make my own and keep as well. my friend took two to listen. one i make for my uncle he is very happy. i never took any extra money for workmenship or anythings at all. they will return me when they can....only to my uncle, i gave him as a present.
thanks for asking...
Regarding the LED
The 100k of RD in the schematic looks very high to me. The value should be more in the 1k to 2k range.
A LED needs current to send out light. This current is usually defined as If (forward current) and can be looked after in the datasheet. This current is usually in the range of 20mA.
With simple math and knowing that there is a voltage grop of 4 Volts on the LED (for a blue LED, yes it is Pass Labs) or 2.5 Volts for green, you can calculate:
R = (V_supply - V_LED) / If
R = (26V - 4V) / 20mA = 1100 Ohms
If you change RD from 100k to 1.5k the LED should be transmitting light.
The 100k of RD in the schematic looks very high to me. The value should be more in the 1k to 2k range.
A LED needs current to send out light. This current is usually defined as If (forward current) and can be looked after in the datasheet. This current is usually in the range of 20mA.
With simple math and knowing that there is a voltage grop of 4 Volts on the LED (for a blue LED, yes it is Pass Labs) or 2.5 Volts for green, you can calculate:
R = (V_supply - V_LED) / If
R = (26V - 4V) / 20mA = 1100 Ohms
If you change RD from 100k to 1.5k the LED should be transmitting light.
skizz99 said:
hi,
thanks for help.....
i had posted into wrong place so now i am posting here.
at first i just tried with one pair of IRFP240. heat sink heat was only 44c round . when i added another two more pair mosfet. wow, heat was nearly 60c. sound quality was great, clean too. instruments sound was very nice and sweet. i was listing quite long time. anyway i know its need very big heat sink.
i want to know, which sound is btr, mosfet or valve class A amp?
thank you
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