No global Feedback Amp - Opinions

Havenwood · 24th October 2009, 03:59 PM

Hi, I take the idea from:
the Headphone amplifier

and I change the circuit a little, Vbe Multiplier, and put power output transistor (TIP3055/2955 ).

I built the amplifier in protoboard, and sound incredible good! better than SiliconChip 20W.

I accept ideas and sugestions to modify or upgrade the circuit.
The original circuit (Pioneer) use all cascode stage, what do you think about this?

Juanma
PS: my english is bad

lineup · 16th April 2011, 09:05 PM

It has got a sort of diamond input.
Haven't seen this solution before.

Bigun · 16th April 2011, 09:30 PM

Yeah, and some kind of CFP part of it too? And onother CFP in the output, for the drivers, provides plenty of drive for the output devices - at least on my TGM3 I found it a noticeable improvement over regular two stage EF.

lineup · 16th April 2011, 09:36 PM

CFP or Sziklai is also one favourite of mine.
It has lower distortion than 2T darlington. I have run test with SPICE.

I am now trying to do some No global feedback designs of power amplifier
So far I am experimenting.

Bigun · 11:36 PM

Lineup, did you ever see this one before:

http://www.angelfire.com/electronic/...less-Tube.html

my plan for no feedback includes at least one vacuum tube for voltage amplifier. I'm still exploring ideas, but they're a bit scattered e.g.

CELLINI-2 a hybrid
Integrating tube into F4 ?
Modified Wavebourn Tower II ?

would love to see your ideas.

lineup · 06:33 AM

Tube idea is good. They are good voltage amplifier.
That angelfire circuit uses feedback. Both local and global.

I have not come far. When I find some good way I will show it.
I only have tried with resistors to set local gain in stages.

Bigun · 17th April 2011, 04:45 PM

You're right, that's strange though as I remember a version of that Angelfire amp without gnf

ontoaba · 18th April 2011, 02:42 AM

Quote:

Originally Posted by Havenwood

Hi, I take the idea from:
the Headphone amplifier

I built the amplifier in protoboard, and sound incredible good! better than SiliconChip 20W.

Offcourse it souds good.

Make the output stages work in near classA and readjust R26 and R27, may be up to kilo ohm

lineup · 28th June 2011, 01:21 PM

It is not easy to create a global feedback free power amplifier with low THD.
It often involve using heavy use of local feedback and degeneration emitter resistors.
Sziklai, or CFP complementary feedback pair, means 100% local feedback.
So use of Sziklai is one way.l
Use of high supply voltage, Class A output and lots of resistance is another.

Bigun · 28th June 2011, 01:47 PM

Or don't worry about THD, only how it sounds.

16th April 2011, 09:05 PM	#2
lineup diyAudio Member Join Date: Dec 2005 Location: the north	It has got a sort of diamond input. Haven't seen this solution before. __________________ lineup

16th April 2011, 09:30 PM	#3
Bigun diyAudio Member Join Date: Jan 2009 Location: K-W Ontario Blog Entries: 2	Yeah, and some kind of CFP part of it too? And onother CFP in the output, for the drivers, provides plenty of drive for the output devices - at least on my TGM3 I found it a noticeable improvement over regular two stage EF. __________________ "The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.

16th April 2011, 09:36 PM	#4
lineup diyAudio Member Join Date: Dec 2005 Location: the north	CFP or Sziklai is also one favourite of mine. It has lower distortion than 2T darlington. I have run test with SPICE. I am now trying to do some No global feedback designs of power amplifier So far I am experimenting. __________________ lineup

16th April 2011, 11:31 PM	#5
Bigun diyAudio Member Join Date: Jan 2009 Location: K-W Ontario Blog Entries: 2	Lineup, did you ever see this one before: http://www.angelfire.com/electronic/...less-Tube.html my plan for no feedback includes at least one vacuum tube for voltage amplifier. I'm still exploring ideas, but they're a bit scattered e.g. CELLINI-2 a hybrid Integrating tube into F4 ? Modified Wavebourn Tower II ? would love to see your ideas. __________________ "The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig. Last edited by Bigun; 16th April 2011 at 11:36 PM.

17th April 2011, 06:21 AM	#6
lineup diyAudio Member Join Date: Dec 2005 Location: the north	Tube idea is good. They are good voltage amplifier. That angelfire circuit uses feedback. Both local and global. I have not come far. When I find some good way I will show it. I only have tried with resistors to set local gain in stages. __________________ lineup Last edited by lineup; 17th April 2011 at 06:33 AM.


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17th April 2011, 04:45 PM	#7
Bigun diyAudio Member Join Date: Jan 2009 Location: K-W Ontario Blog Entries: 2	You're right, that's strange though as I remember a version of that Angelfire amp without gnf __________________ "The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.

28th June 2011, 01:21 PM	#9
lineup diyAudio Member Join Date: Dec 2005 Location: the north	It is not easy to create a global feedback free power amplifier with low THD. It often involve using heavy use of local feedback and degeneration emitter resistors. Sziklai, or CFP complementary feedback pair, means 100% local feedback. So use of Sziklai is one way.l Use of high supply voltage, Class A output and lots of resistance is another. __________________ lineup

28th June 2011, 01:47 PM	#10
Bigun diyAudio Member Join Date: Jan 2009 Location: K-W Ontario Blog Entries: 2	Or don't worry about THD, only how it sounds. __________________ "The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.

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