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Old 15th December 2012, 02:30 PM   #11
naf is offline naf  Indonesia
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nice...i have all active parts

Last edited by naf; 15th December 2012 at 02:34 PM.
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Old 15th December 2012, 02:47 PM   #12
pergo is offline pergo  Italy
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no source resistors? Something like 0.1ohm
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Old 15th December 2012, 02:52 PM   #13
Bigun is online now Bigun  Canada
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Quote:
Originally Posted by Lazy Cat View Post
I said it is not something new, just SSA/TSSA derivative.
Well for those folks who like to simulate here's my contribution so far to the Lazy Cat VSSA, a file to play with....
Attached Images
File Type: jpg LazyCat VSSA FFT.jpg (115.9 KB, 3278 views)
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File Type: asc Bigun VSSA.asc (7.6 KB, 213 views)
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Last edited by Bigun; 15th December 2012 at 02:57 PM.
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Old 15th December 2012, 02:57 PM   #14
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Quote:
Originally Posted by pergo View Post
no source resistors? Something like 0.1ohm
For only one pair and for a thermal stability they're not necessary, laterals have drain current negative tempco so thermal runaway cannot happen. Source resistors as local feedback for distortion reduction you can add them of course, but it will be at best only few dB of THD reduction.
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Old 15th December 2012, 02:58 PM   #15
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Quote:
Originally Posted by naf View Post
nice...i have all active parts
What are you waiting for haha?
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Old 15th December 2012, 02:59 PM   #16
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Quote:
Originally Posted by Bigun View Post
Well for those folks who like to simulate here's my contribution so far to the Lazy Cat VSSA, a file to play with....
Nice, second harmonic almost -100dB down.
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Old 15th December 2012, 03:08 PM   #17
Bigun is online now Bigun  Canada
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Quote:
Originally Posted by Lazy Cat View Post
Nice, second harmonic almost -100dB down.
yes, it looks very nice !

The Simplified thread started off with something simple like this and then wandered off to something not at all simple. Let's keep this one simple

for temp stability the drain current through laterals must be above some threshold, I think it's 100mA, depending on which FET.
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Last edited by Bigun; 15th December 2012 at 03:10 PM.
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Old 15th December 2012, 03:16 PM   #18
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Quote:
Originally Posted by Bigun View Post
yes, it looks very nice !

The Simplified thread started off with something simple like this and then wandered off to something not at all simple. Let's keep this one simple

for temp stability the drain current through laterals must be above some threshold, I think it's 100mA, depending on which FET.
OK deal, I won't mess with more parts on this one (values optimization only) I promise hehe, although it can be rocketed to complex version in any time

Yes, normally Id should be 100 mA or more, sweetspotted too I suppose.
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Old 15th December 2012, 04:01 PM   #19
lineup is offline lineup  Sweden
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Quote:
Originally Posted by Lazy Cat View Post
VSSA - Very Simple Symmetrical Amplifier, something in between SSA and TSSA. Similar schematics posted a lot of times but not exactly the same.

With only six transistors you can get genuine current feedback, high bandwidth amplifier, capable of driving 4 ohm speakers. PCB can be very simple and small too.
I setup the circuit from your diagram.
The DC-offset is very small, 12 mV.

The first thing I noticed is that circuit needs some compensation to be stable.
This was fixed with one 22pF from base to collector of KSA1381 and likewise 22pF around KSC3503.

The THD distortion at 1 Watt is remarkably low for such a simple amplifier:
THD 0.0002% at 1 Watt RMS.

Very nice amplifier
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Old 15th December 2012, 04:26 PM   #20
dadod is offline dadod  Croatia
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Quote:
Originally Posted by Bigun View Post
Well for those folks who like to simulate here's my contribution so far to the Lazy Cat VSSA, a file to play with....
This what I've got with Bigun file.This is at quite low level, at higher level it is much worse.
dado
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File Type: jpg TSSA-THD20k.jpg (226.6 KB, 2896 views)
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