Aleph4 Basic Questions

[sprintsun]

Hi everyone,
I am new here.

I am in the midst of building aleph 4 stereo amp, waiting for pcb boards to arrive.

1. Aleph 4 is biased at 3 amp. Is is ok to use ERSE Super Q USA 2.2mh 14AWG ESQ55 series((up to 20 Amps)) inductor as simple pi filter?

2. Can aleph circuit be biased to class ab? If so which resistors need to be changed?

I have very limited knowledge on electronics and replies are very much appreciated.

Thnak you.

[sprintsun]

Also I like to thank http://www.penguinlovers.net/audio/aleph5_proj.html for all the instructions and tips. For mosfet matching I like to thank Diyaudio and Finnis for clear instruction. Most important of all, I like to thank Mr Passlab for his generosity.

I hope I can successfully build this amp.

[Nelson Pass]

Originally posted by sprintsun
1. Aleph 4 is biased at 3 amp. Is is ok to use ERSE Super Q USA 2.2mh 14AWG ESQ55 series((up to 20 Amps)) inductor as simple pi filter?

2. Can aleph circuit be biased to class ab? If so which resistors need to be changed?

1) Yes, I imagine they will work just fine.

2) Not really. Theoretically possible, but the result is not pretty.

[sprintsun]

Thank you, Mr Nelson Pass.

[sprintsun]

I did some mosfet matching and realised the my digital meter only gives 3 digit below 4 volt. So I can match irfp9610 to last 3 digit, but with the 240s, I can only get last 2 digits.

So, if I add a resistor in series with the multimeter to bring the reading below 4 volt, will the matching be accurate?

BTW: I smoked my finger. I didn't know the resistor for 240s is too hot to touch.

Thanks.

[Nelson Pass]

Originally posted by sprintsun
I did some mosfet matching and realised the my digital meter only gives 3 digit below 4 volt. So I can match irfp9610 to last 3 digit, but with the 240s, I can only get last 2 digits.

So, if I add a resistor in series with the multimeter to bring the reading below 4 volt, will the matching be accurate?

No. The impedance of the multimeter is too high to cause a
voltage drop across an input resistor.

When you say 3 digits, do you mean that the voltmeter only
resolves .01V or .001V. .01V is enough to match 10 mV on Vgs
which is about as good as you can expect.

[sprintsun]

It is .001V below 4 volts. If above 4 volt it is .01 onwards. Trying to understand, .01v should be fine.

Thanks Mr Nelson Pass.

Highest Regards.
Nicolas

[sprintsun]

Anticipation turns into anxiety.

Smoke come out from one of the current source irfp240 device. When I first on it, everthing seeems fine. I measure the voltage across the 10k output resistor that is in series with the led and I see smoke. I think I measure the wrong resistor (misreading instruction), suppose to be the 1.5 ohm 5 watt resistor. Have I done something wrong?

I change the fuse and it still blows.

I test the mosfet where the smoke comes out and it's not toasted. The 1.5 ohm and the 221 ohm resistor is ok too.

What shall I do now? Please help me.

[Nelson Pass]

My teleporter has the same problem, so you'll have to give
me usable information for me to help you.

[sprintsun]

Mr Nelson Pass,
I wanted to cry and you made me laugh.

I have problem explaining in electonic english, so bear with me. After the smokey senerio, I found one irfp240 that is "connect" to Q3(ZTX240) is dead.

Actually, I use the mulitmeter to measure the voltage across the output resister(10K) the is in series with the led, immediately I see smoke. I don't know if that is the problem. I also discover the 1000va transfomer is overheat base on the plastic wrapping on the trasformer partially melted.

When I first switch on the amp(one channel) for one minute or two, no smoke. So, I proceed to measure voltage and "smoke".

Please tell me what to do ... Please ....