SuperOPA

Stee · 29th November 2008, 09:28 AM

this is just a project for 50W class A

Nrik · 29th November 2008, 10:54 AM

Nice topolgi.

Drivers and outputs are BJT's but shown as FETs.

You forgot the feedback.

1 ohm is a pretty high value for emitter resistors in a 50W class A amp. (Edit: and I see now they are in the collectors - is that the way to do it?)

Are the tempco of the 33ohm NTC suitable to fit the outputs BJTs PTC?

But Stee - keep on going.

Stee · 29th November 2008, 11:33 AM

see now

0R47 with 1,5A of final's Ice current

need a big silent fan on dissipator

feedback
RA and RB can have ratio of 1:15
RA = 560
RB = 8K2

nelsonvandal · 30th November 2008, 07:08 AM

Haven't you drawn the output transistors the wrong way. I guess they should be common collector, not common emitter, or am I missing something?

Stee · 30th November 2008, 08:08 AM

i have taked inspiration from Accurphase design

so in the original schematic
the output bipolar was in reversal mode

but my idea is use output resistor as negative feedback

Stee · 30th November 2008, 08:16 AM

directly from japan

Nrik · 30th November 2008, 09:12 AM

Are you copying the Jung buffer input of that circuit or are you coying the darlington commomemitter driverstage?

It looks more like a Sziklai, and in that case I am not sure you can put the drivers emitters on the opposite outputs collector.

If you simulated it or build it and it works, then I am just gonna say - super - tell us how it sounds.
Otherwise check the sziklai from other amps, and see how they do.

nelsonvandal · 30th November 2008, 12:34 PM

Quote:

Originally posted by Stee
directly from japan

Since the whole schematic can't be seen, we don't really know what happens outside this fragment. It's not a Sziklai.

Look at the direction of the transistors to the left in this schematic. I think this is how it should be.

Stee · 30th November 2008, 01:33 PM

it's a Stee's invention!
next WE I will try to build...

scott wurcer · 30th November 2008, 03:15 PM

Quote:

Originally posted by Stee
i have taked inspiration from Accurphase design
so in the original schematic
the output bipolar was in reversal mode

but my idea is use output resistor as negative feedback

This output is drawn as positive feedback, the more V across the .47 Ohm resistors the harder the output is driven. Magic smoke?

30th November 2008, 01:33 PM	#9
Stee diyAudio Member Join Date: Jul 2005 Location: milan	It's not a Sziklai it's a Stee's invention! next WE I will try to build... __________________ Please download my best audio idea http://www.esafono.it/ISY.zip

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29th November 2008, 10:54 AM	#2
Nrik diyAudio Member Join Date: Feb 2005 Location: Copenhagen	Nice topolgi. Drivers and outputs are BJT's but shown as FETs. You forgot the feedback. 1 ohm is a pretty high value for emitter resistors in a 50W class A amp. (Edit: and I see now they are in the collectors - is that the way to do it?) Are the tempco of the 33ohm NTC suitable to fit the outputs BJTs PTC? But Stee - keep on going.

30th November 2008, 07:08 AM	#4
nelsonvandal diyAudio Member Join Date: Nov 2006	Haven't you drawn the output transistors the wrong way. I guess they should be common collector, not common emitter, or am I missing something?

30th November 2008, 09:12 AM	#7
Nrik diyAudio Member Join Date: Feb 2005 Location: Copenhagen	Are you copying the Jung buffer input of that circuit or are you coying the darlington commomemitter driverstage? It looks more like a Sziklai, and in that case I am not sure you can put the drivers emitters on the opposite outputs collector. If you simulated it or build it and it works, then I am just gonna say - super - tell us how it sounds. Otherwise check the sziklai from other amps, and see how they do.