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Old 22nd January 2013, 08:25 AM   #3771
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thanks alot on your advice, lazy cat. I will 'take one step at a time'.
I'm more on TSSA since until now I haven't touched other transistor (only BJT), So maybe VSSA would be next if I had time, as you see I'm late in schedule for these things. Now I wish to complete this basic SSA for real before I move on or turn away.

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Originally Posted by Lazy Cat View Post
Hi Leong

Of course I remember you and I wish you'll successfully build something with SSA in its name.

Look when someone starts to play with the design involving some changes like PCB, some parts etc, it is absolutely necessary to have some gear on your desk like scope, PSU with soft start, serial rail resistors for safe work in initial phase of testing and calibrating, digital rms meters, signal generator.

Simply you have to "see" what is happening on the output and other parts of the circuit as well, to take apropriate measures to eliminate anomalies like oscillations etc.

In your case you definitely have a problem with HF oscillation, which raises the bias current level in certain stages and represent as hiss-noise heard from speakers when connected to the output.

So my advice is to go step by step and each step has to be cleared-understood before proceeding to next one.

Regards, Andrej

P.S. I suggest you to go for VSSA
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Old 22nd January 2013, 08:31 AM   #3772
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Originally Posted by pete_schumacher View Post
Here's what I got with 480W instantaneous peaks into 8 Ohm. This is a multi-tone IMD test. Excellent results!
Please try to simulate the same circuit but first change R10, R11 with high impedance CCS, lets say formed by j-fet.
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Old 22nd January 2013, 08:36 AM   #3773
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hehehe Pete removed his post in a split second, probably too good sch to be public, but still it is VSSA with more output pairs and +/-70 V rails.
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Old 22nd January 2013, 08:43 AM   #3774
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VSSA has the precious essence of all SSAs: it is unconditionally stable, has enormous damping, has the best CCS injecting spot to the input stage and it is simply scalable to higher power levels, highly recommended.
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Old 22nd January 2013, 08:55 AM   #3775
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Ok, sorry for deleting that last post. I'm tired and wasn't paying attention when I went to edit it.

But here the results using a current source in place of the resistors, same 4 tone IMD test. Still great results simulating what would be more like a music signal.
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File Type: gif PSSA Multitone result.gif (20.5 KB, 224 views)
File Type: gif PSSA.gif (20.9 KB, 224 views)
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Old 22nd January 2013, 09:02 AM   #3776
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So what are you waiting for hehe? Go for it

Thanks for a kind response, regards.
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Old 22nd January 2013, 09:08 AM   #3777
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Originally Posted by Lazy Cat View Post
VSSA has the precious essence of all SSAs: it is unconditionally stable, has enormous damping, has the best CCS injecting spot to the input stage and it is simply scalable to higher power levels, highly recommended.
By refering to the text above, it seems there are some correlation between symetrical amplifier here. Which schematic have that quality ?

As I know there is TSSA SSA and VSSA, is there any other ?(maybe I'm not aware), what is their difference in sonic or working principle.
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Old 22nd January 2013, 09:13 AM   #3778
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Originally Posted by guitar89 View Post
As I know there is TSSA SSA and VSSA, is there any other ?(maybe I'm not aware), what is their difference in sonic or working principle.
There's also CSA, most complex of them all, but that means nothing at the moment since it has not been tested for its sound yet.

Otherwise all of them shares the same input stage at least what concerns basic topology.
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Old 22nd January 2013, 09:21 AM   #3779
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There's also CSA, most complex of them all, but that means nothing at the moment since it has not been tested for its sound yet.

Otherwise all of them shares the same input stage at least what concerns basic topology.
Yeah, I forgot CSA which I seens before. They all uses current feedback, isn't it ?

Well, TSSA is obviously alot lesser of transistor in IPS, so what would be affecting significantly ? Didn't get the chance to ask this before ^^ What about VSSA ?
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Old 22nd January 2013, 09:29 AM   #3780
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Go through VSSA thread, it is not so long, there's explained everything, even squares responses plots.
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