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Old 27th September 2013, 02:16 AM   #2751
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Quote:
Originally Posted by jaagut View Post
Congrats! DC at your outputs are acceptable, I even have 50mV on mine and it's fine.

So, what did you do to solve your bias problem?

I parallel a 50k trimmer to the 4k7.
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Old 27th September 2013, 03:26 AM   #2752
jaagut is offline jaagut  Philippines
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Quote:
Originally Posted by albertli View Post
I parallel a 50k trimmer to the 4k7.
I see, so so you opted to adjust the emitter-base resistor, instead of the base-collector. trimmer should be set at maximum resistance value initially, and lower the value to increase the bias current. but be careful not to adjust the trimmer to zero.

setting trimmer in series with 1k or 1k5 resistor is much safer in practice but not so easy to do than setting it in parallel.
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Old 27th September 2013, 01:09 PM   #2753
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Quote:
Originally Posted by jaagut View Post
I see, so so you opted to adjust the emitter-base resistor, instead of the base-collector. trimmer should be set at maximum resistance value initially, and lower the value to increase the bias current. but be careful not to adjust the trimmer to zero.

setting trimmer in series with 1k or 1k5 resistor is much safer in practice but not so easy to do than setting it in parallel.
I thought the other way. It's safer to parallel with a fixed resistor in case the trimmer open.
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Old 29th September 2013, 10:38 AM   #2754
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Yesterday i etch a couple of board based on Borys layout...I am waiting some parts to populate them.

Marc
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Old 29th September 2013, 03:18 PM   #2755
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Default In quest of bass

Hi all,

I have been listening to my AX11 mk2 for two days with no less then 10 hours. As said by the other members and all claimed that this design produces really good bass, but I don't have this feeling with my build. This is to compare all amps that I have of which include 6c33c otl, 6c33c se, Moskido and 807pp. I don't know if I have done anything wrong. I build this with the pcb posted at #2201 with BC546b instead of 2N5551, all other parts are same on that pcb. Power supply is Mur860 to 10,000uf to 33ohm wrapped with 40 turn 1mm wire as coil to another 10,000uf so to make the total of 20,000uf on each of + and - 35v rail.
Regards

Albert
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Old 29th September 2013, 04:55 PM   #2756
cjkpkg is offline cjkpkg  United States
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Quote:
Originally Posted by albertli View Post
Hi all,

I have been listening to my AX11 mk2 for two days with no less then 10 hours. As said by the other members and all claimed that this design produces really good bass, but I don't have this feeling with my build. This is to compare all amps that I have of which include 6c33c otl, 6c33c se, Moskido and 807pp. I don't know if I have done anything wrong. I build this with the pcb posted at #2201 with BC546b instead of 2N5551, all other parts are same on that pcb. Power supply is Mur860 to 10,000uf to 33ohm wrapped with 40 turn 1mm wire as coil to another 10,000uf so to make the total of 20,000uf on each of + and - 35v rail.
Regards

Albert
For PSU is it 33 or 0.33? Hopefully 0.33...

I am using 3x0.47 in parallel between the caps. Mine are also 10,000 uF x2 per rail.

What are your emitter resistors? I am using Fukushima mpc
What type of cap are you using for the 10uF input cap? I am using nichicon UFG or UKW I forget....both are audio grade.
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Old 29th September 2013, 05:34 PM   #2757
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Originally Posted by cjkpkg View Post
For PSU is it 33 or 0.33? Hopefully 0.33...

I am using 3x0.47 in parallel between the caps. Mine are also 10,000 uF x2 per rail.

What are your emitter resistors? I am using Fukushima mpc
What type of cap are you using for the 10uF input cap? I am using nichicon UFG or UKW I forget....both are audio grade.
Hey Carl,
They are 33 ohm,but only 0.46 ohm after parallel with the 40 round coil. I copied from the smymsyn thread. If this is the devil I can replace them with wire.
The 10uf input caps are blackgate monsite.
Albert
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Old 29th September 2013, 05:53 PM   #2758
cjkpkg is offline cjkpkg  United States
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Quote:
Originally Posted by albertli View Post
Hey Carl,
They are 33 ohm,but only 0.46 ohm after parallel with the 40 round coil. I copied from the smymsyn thread. If this is the devil I can replace them with wire.
The 10uf input caps are blackgate monsite.
Albert
Ok good...I would crank the bias up as high as you feel comfortable and let it break in. Which outputs did you use?
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Old 29th September 2013, 06:26 PM   #2759
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Ok good...I would crank the bias up as high as you feel comfortable and let it break in. Which outputs did you use?
They are running at 60mv since day one n I only found 33c at heatsink after 4 hours. I will crank them up to 100mv after I regroup my psu by taking out the 33 ohm / coil with a wire. Or do you think it better to put a big resistor there ?.
Do you mean the output transistors? TO-3 MJ15003/4. All my speakers are 8 ohms.
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Old 2nd October 2013, 09:09 PM   #2760
wiljj78 is offline wiljj78  Philippines
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AX-16 2 pairs...DC offset is 2.4mV...
Sounds very good!!!
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