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Old 18th April 2013, 07:53 PM   #251
borys is offline borys  Poland
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Quote:
Originally Posted by ALAZ View Post
hi,LC can i use irfp240/9240 insted 2sk1058/2sj162?
I do not know if you can use it but I know that if you are going to use it you should add some bias compensation (additional transistor mountet on heatsing with outputs). Looks like pair irfp240/9140 suits better.
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Old 19th April 2013, 07:31 AM   #252
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That is the amp anyway.
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Old 19th April 2013, 08:43 AM   #253
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Originally Posted by borys View Post
That is the amp anyway.
nice borys!...how does it sounds?
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Old 19th April 2013, 05:36 PM   #254
borys is offline borys  Poland
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Originally Posted by boyet0173 View Post
nice borys!...how does it sounds?
First impression is nice, but I have listen only free air full range driver so can not say much about it. There is hearable noise when I put my ear to the speaker, from the distace is dead silent.
I have 20cm not shielded wires to the input and there is loud noise comming from speaker if I leave in not connected to gnd - so input has to be well shielded.
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Old 19th April 2013, 07:53 PM   #255
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Quote:
Originally Posted by borys View Post
First impression is nice, but I have listen only free air full range driver so can not say much about it. There is hearable noise when I put my ear to the speaker, from the distace is dead silent.
I have 20cm not shielded wires to the input and there is loud noise comming from speaker if I leave in not connected to gnd - so input has to be well shielded.
Input low pass filter essentials:

- 100 pF capacitor from bases to GND located as close as possible to input transistor pair
- signal serial resistor value at least 560 Ohm
- input interconnect cable can be unshielded, but in this case should be anti-parallel to speaker cable and located away from it, to avoid their coupling, otherwise one can get HF positive feedback and consequently amp's oscillation. This cannot happen with shielded input interconnect cable. Tested.

Also no sound of the VSSA can be evaluated before min 50 hours of burn-in period, since elcos in FB path changes the sound signature from hour to hour since it stabilizes to normal conditions. Also tested.
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Old 19th April 2013, 09:49 PM   #256
borys is offline borys  Poland
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Quote:
Originally Posted by Lazy Cat View Post
Input low pass filter essentials:

- 100 pF capacitor from bases to GND located as close as possible to input transistor pair
- signal serial resistor value at least 560 Ohm
- input interconnect cable can be unshielded, but in this case should be anti-parallel to speaker cable and located away from it, to avoid their coupling, otherwise one can get HF positive feedback and consequently amp's oscillation. This cannot happen with shielded input interconnect cable. Tested.

Also no sound of the VSSA can be evaluated before min 50 hours of burn-in period, since elcos in FB path changes the sound signature from hour to hour since it stabilizes to normal conditions. Also tested.
Thanks very much for advise!
Can you tell me can I leave vas bias as it is 25mA(after 30min stabilise) ?
In atatchment I have measurement. THX
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Old 19th April 2013, 10:01 PM   #257
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Hi,here is another PCB.I tried CCS circuit (jfet 2sk170 and two resistors) instead of one resistor.It can be easily inserted in pecebe as a module or P2P leg to leg,but i went another way,new SMD-melf based pcb.Ok it's messy as it's one sided.Had to use some laquie to be 99% sure it is safe.

Farnell forgot to include 22pf (compensation) capacitors in my order,so at first ,without them amp was oscillating - one amps both chanells had strange hum,another amp in the background had sound like CDP trying to play scratched CD but after i found some 10pf everything went fine.

Used j112 in CCS.
Also 1K feedback resistors instead of shaan's 2.2K-didnt measured active speakers setup yet,but the gain was changed i think this way...
The sound with shaans pcb and CCS was like heaven,now-i can't say so.All new capacitors needs time,so do i,i finished it only few hours ago..
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Last edited by daudio25; 19th April 2013 at 10:06 PM.
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Old 19th April 2013, 10:21 PM   #258
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Quote:
Originally Posted by borys View Post
Thanks very much for advise!
Can you tell me can I leave vas bias as it is 25mA(after 30min stabilise) ?
In atatchment I have measurement. THX
You're welcome.

VAS bias should be 12-15 mA, just in a middle of hFE/Ic curve where VAS BJTs are in the most linear region. Also 25 mA gives senseless too much heat to dissipate. Adjust both 15k resistors to set correct VAS bias and 0 mV output DC offset.
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Old 19th April 2013, 10:22 PM   #259
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Originally Posted by daudio25 View Post
The sound with shaans pcb and CCS was like heaven,now-i can't say so.All new capacitors needs time,so do i,i finished it only few hours ago..
Congratulations!

Happy listening.
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Old 20th April 2013, 05:29 AM   #260
anod is offline anod  Indonesia
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very nice tq shaan
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