I used last holidays to make prototype of Aleph-X.
So now it's ready and works!
What i did and what I have in result:
I use schematics xa1build.zip from rtirion posted in Alepx-X thread with some modifications:
1. Matched pairs of 0.2 ohm resistors
2. Matched pairs IRF9610 in 10 mV.
3. Matched pairs IRFP044 with less than 10mV each.
4. R8 is 10k resistor + trimmer 200k.
5. Current source is with TL431 and one bipolar transistor (like described in TL431 datasheet) with trimmer 200ohm to adjust current. (I have a lot of TL431)
6. 300VA transformer 2 X 14 V secondary (may be for halogen lamp), bridge with 2 X 22mF capacitors on each rail (total 4 capacitors).
Results:
1. 8 mV output offset which is stable in the time. This offset can be compensated ot 0.0 mV with 200k trimmer, but one side was set to 1.9 A and other to 2.5 A. I return to both equal currents and again
have 8 mV DC offset on output.
2. No power on pulse in speakers, power off also don't exists.
3. Pulsations on power rails were about 1V. On output were very little hum audible from less than about 0.5 meters in front of the speaker.
4. I put coils from old power supply filter (1 mH, 4A) with common iron core and ripple on the rails lowered to 0.3 V. When cross pins on one coil ripple drops to less than 100 mV peak to peak! In this configuration (TR-BRIDGE-C-L-C) with these coils (1mH) and capacitors (2 X 22mF) there was no audible hum on speakers (input was open)!
5. Rail voltage now (with C-L-C) is 14V.
6. With modified Aleph-P preamplifier sound is excellent! Power is enough and bass is very controlled!
This was only prototype of one channel.
Now I'm making some PCB layout and will post here
results when build 2 channels.
Here is the schematics of front end current source:
So now it's ready and works!
What i did and what I have in result:
I use schematics xa1build.zip from rtirion posted in Alepx-X thread with some modifications:
1. Matched pairs of 0.2 ohm resistors
2. Matched pairs IRF9610 in 10 mV.
3. Matched pairs IRFP044 with less than 10mV each.
4. R8 is 10k resistor + trimmer 200k.
5. Current source is with TL431 and one bipolar transistor (like described in TL431 datasheet) with trimmer 200ohm to adjust current. (I have a lot of TL431)
6. 300VA transformer 2 X 14 V secondary (may be for halogen lamp), bridge with 2 X 22mF capacitors on each rail (total 4 capacitors).
Results:
1. 8 mV output offset which is stable in the time. This offset can be compensated ot 0.0 mV with 200k trimmer, but one side was set to 1.9 A and other to 2.5 A. I return to both equal currents and again
have 8 mV DC offset on output.
2. No power on pulse in speakers, power off also don't exists.
3. Pulsations on power rails were about 1V. On output were very little hum audible from less than about 0.5 meters in front of the speaker.
4. I put coils from old power supply filter (1 mH, 4A) with common iron core and ripple on the rails lowered to 0.3 V. When cross pins on one coil ripple drops to less than 100 mV peak to peak! In this configuration (TR-BRIDGE-C-L-C) with these coils (1mH) and capacitors (2 X 22mF) there was no audible hum on speakers (input was open)!
5. Rail voltage now (with C-L-C) is 14V.
6. With modified Aleph-P preamplifier sound is excellent! Power is enough and bass is very controlled!
This was only prototype of one channel.
Now I'm making some PCB layout and will post here
results when build 2 channels.
Here is the schematics of front end current source:
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