Aleph3 biasing question

victor · 20th August 2001, 08:36 AM

Hello.
I just built the Aleph3,the problem is that i have the half
of the bias current(1A total)at the three output Fet's.
How can i increase the bias current?

Koy · 20th August 2001, 10:31 AM

Bias can be adjusted by resistor -R113-( 47k originally). The higher value the higher current - at about 68k it should run on about 2,7A. I use in this position the trimpot.

victor · 20th August 2001, 12:17 PM

Koy.
How many fet u using per rail and what type?
Thank's.

Koy · 20th August 2001, 12:54 PM

I have Volksamp modification build - ie 3 MOSfet per rail, IRFP 244.

yasalam · 25th March 2002, 07:13 AM

I have four matched IRFP240s and planing to build SOZ but after considering the cost I have changed my mind to Aleph 3. Since the Aleph 3 using 8 output devices, is it possible to use 4 output devices? It seems I must change the source resistor, but with how much resistant value?

Thank you for any response.

Yamin

BrianGT · 28th March 2002, 02:44 PM

I would assume that you could make the Aleph 3 with half as many output devices. If you look at Mark's Aleph 4 at:

Mark's Aleph 4

He used half as many output devices as the design called for, due to a mistake in the service manual, and it works great for him.

I am not sure exactly what values that you would want to use for resistors, but I would imagine that you would use half the resistance.

--
Brian
gte619j@prism.gatech.edu

yasalam · 28th March 2002, 04:46 PM

Thanks Brian.
By the way, Mr. NP have answered my question. He said the value is 0.22 ohm, same as you suggested.

Regards,
Yamin

25th March 2002, 07:13 AM	#5
yasalam diyAudio Member Join Date: Mar 2002 Location: Indonesia	Aleph 3 with 4 output devices I have four matched IRFP240s and planing to build SOZ but after considering the cost I have changed my mind to Aleph 3. Since the Aleph 3 using 8 output devices, is it possible to use 4 output devices? It seems I must change the source resistor, but with how much resistant value? Thank you for any response. Yamin

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20th August 2001, 08:36 AM	#1
victor diyAudio Member Join Date: Jul 2001	Hello. I just built the Aleph3,the problem is that i have the half of the bias current(1A total)at the three output Fet's. How can i increase the bias current?

20th August 2001, 10:31 AM	#2
Koy diyAudio Member Join Date: Jan 2001 Location: Zlin	Bias can be adjusted by resistor -R113-( 47k originally). The higher value the higher current - at about 68k it should run on about 2,7A. I use in this position the trimpot.

20th August 2001, 12:17 PM	#3
victor diyAudio Member Join Date: Jul 2001	Koy. How many fet u using per rail and what type? Thank's.

20th August 2001, 12:54 PM	#4
Koy diyAudio Member Join Date: Jan 2001 Location: Zlin	I have Volksamp modification build - ie 3 MOSfet per rail, IRFP 244.

28th March 2002, 02:44 PM	#6
BrianGT diyAudio Moderator Emeritus Join Date: Jan 2002 Location: near Atlanta, GA	I would assume that you could make the Aleph 3 with half as many output devices. If you look at Mark's Aleph 4 at: Mark's Aleph 4 He used half as many output devices as the design called for, due to a mistake in the service manual, and it works great for him. I am not sure exactly what values that you would want to use for resistors, but I would imagine that you would use half the resistance. -- Brian gte619j@prism.gatech.edu

28th March 2002, 04:46 PM	#7
yasalam diyAudio Member Join Date: Mar 2002 Location: Indonesia	Thanks Brian. By the way, Mr. NP have answered my question. He said the value is 0.22 ohm, same as you suggested. Regards, Yamin