Simple Symetrical Amplifier

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Lazy Cat

Lazy Cat

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Joined 2007
terranigma said:
I don't understand why people here struggling with this BIGBT thingie that much. Was SSA standing for "Simple" Symmetrical Amplifier?
Click to expand...

SSA at this moment is present in three versions:
- SSA L-MosFet, sch, two different PCB layouts (single ch, dual mono), integrated PWS
- SSA BIGBT Basic, sch, PCB (single ch), integrated PWS
- SSA BIGBT High Performance, sch, PCB (single ch), separate PWS

New versions are expected from some experienced thread followers, each one in different type of topology. :)

So at the end there will be the SSA menu from very simple versions ranging from 30-50W to more complex ones ranging from 50-200W (still to come). :rolleyes:

SSA in basic version is practically front-end + feeedback loop + buffer and if you would like to test it even better. :cool:

Why BIGBT? Many explanations in its favour were presented previously in this thread and one of the most important ones is just to test this kind of combo gain device ... it works and sounds perfectly. So invitation to built one of the SSA incarnation to your taste is here, also listening impresions shared with us would be of the great welcome, regards Andrej. ;)
 
terranigma

terranigma

Member
Joined 2007
Thank you Lazy Cat and Alex, i appreciate your work and kindness.

Regarding to Alex's latest PCB;

Is there an important reason for BIGBT to use 2sc5359/2sa1987? It seems only difference between popular and easy-to-find 2sc5200/2sa1943's is wattage. 5359/1987 are 180W, 5200/1943 are 150W.

2sc2240/2sa970's are easy to find and cheap devices, then OK for me.

Is there an important spec for use another device in place of 2sc1478/2sc3788? Datasheet says they are 200V 150mhz and video devices. It seems 180V 200mhz 2sa1930/2sc5171 audio drivers suit here also, am i right?

Thanks.
 
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smartx21

smartx21

Member
Joined 2010
Since Elektor's IGBT output amplifier from the 80's I've been expecting such a new approach to that technology. Yet not so simple (not so SSA=NSSSA!), this thread tells us that there is always something to be discovered, or to improve. Thank you all for the effort and invaluable teachings!
Regards,
Max.
 
AKSA

AKSA

Member
Joined 2001
aksaonline.com
Nico,

Is it possible you are considering the RC for the input of Lazy Cat's amp?

This would lead us into an important decision; voltage, or current feedback.

The joy of this design is the way in which the feedback is brought to the emitters of the input devices. Since input to an emitter can only be current (as voltage of the emitter is set by base potential) then the RC affords us a voltage, rather than a current input for the feedback.

I believe this would confer a sound to the amp much like any other voltage fb amp, and due to parasitics it would lack the speed of Lazy Cat's approach.

I say stick with injecting the feedback as a current into the emitter.... it preserves Andrej's original intent with this very good design.

Cheers,

Hugh
 
Lazy Cat

Lazy Cat

Member
Joined 2007
MiiB said:
lazy....

when scaling you also add CCs to the front end.. why is that...?? as well as other complexities,, is that really vital...??
I really like the simplicity of the first versions...and to me they scale beautifully without adding additional complexity....

Am I missing something...??
Click to expand...

I agree that the beauty of the basic version is the one to admire, of how much do you get from only a few parts. Don't you worry guys nobody took the simple version away it is still there, alive and kicking. :D

The thing is that when you go scaling up for more complex versions, each and every detail should act as it is intended to. Two current supply resistors from 15V DC are a simple solution in theory these should be current generators instead, to supply constant current to the feedback loop. I tested both versions and I have to say that with constant current source/sink SSA still remains as current feedback amplifier, no doubt, only that the bias supply current injected to input BJT is more FB drive current independent. I noticed the difference at clipping behavior as well as in quiescent conditions as even more stable, predictable. ;)
 
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Lazy Cat

Lazy Cat

Member
Joined 2007
A

AndrewT

R.I.P.
Joined 2004
AndrewT said:
Go to the post you want to link to.
Right click on the post's number (#xxx).
Confirm: "copy link location".
Go back to your post & paste this location into your post.
Click to expand...

Lazy Cat said:
Both of them takes me to the post #347. :rolleyes:

By my side it works perfectly, cause that is the post I wanted you to see. ;)
Click to expand...
whatever you are doing in creating the link only works when someone has the same set up as you.
Whereas the other method should take all Members to the correct post, no matter what set up they have chosen.

Could some Members try both links in post523 and give feedback on where they take you?
 
M

MiiB

Member
Joined 2005
raidho.dk
But you have already a zener and capacitors holding it at a fixed voltage,, so the Reisitors transforms the voltage into fixed currents...Think it should should be sufficient...?

The Thing is that I have found that CCS's may improve specs, but rarely the sound...Think Nico and Joarchim second that observation

But as your'e closer and have the thing running.. you may know a lot better than I do...:)
 
Lazy Cat

Lazy Cat

Member
Joined 2007
MiiB said:
But you have already a zener and capacitors holding it at a fixed voltage,, so the Reisitors transforms the voltage into fixed currents...Think it should should be sufficient...?
Click to expand...

Here you are wrong, observe the two potentials where this resistor is connected, one DC 15V is constant but the other is changing with the FB signal and it goes from 0,6V at idle to 0,6V+/-Vout/(Rf/Rs+1) in dynamic conditions. So the current through this resistor is far by being constant.

MiiB said:
The Thing is that I have found that CCS's may improve specs, but rarely the sound...Think Nico and Joarchim second that observation

But as your'e closer and have the thing running.. you may know a lot better than I do...:)
Click to expand...

CSS makes only more stable conditions but if that majorly influence the quality of the sound, well that is to be tested. :)
 
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Nico Ras

Nico Ras

Member
Joined 2005
AKSA said:
Nico,

Is it possible you are considering the RC for the input of Lazy Cat's amp?

This would lead us into an important decision; voltage, or current feedback.

The joy of this design is the way in which the feedback is brought to the emitters of the input devices. Since input to an emitter can only be current (as voltage of the emitter is set by base potential) then the RC affords us a voltage, rather than a current input for the feedback.

I believe this would confer a sound to the amp much like any other voltage fb amp, and due to parasitics it would lack the speed of Lazy Cat's approach.

I say stick with injecting the feedback as a current into the emitter.... it preserves Andrej's original intent with this very good design.

Cheers,

Hugh
Click to expand...

Hi Hugh, I was not thinking of changing anything. I have my amps made and am happy with them.

Nico
 
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