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Old 31st December 2012, 05:30 PM   #231
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by gaborbela View Post
Do these capacitor will degrade or effect the sound in a negative way?
sounds like they have more positive effect than negative
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Old 1st January 2013, 07:45 PM   #232
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VSSA measurements, +/- 32 V rails
1.pic - 50 kHz square wave, 20,7 Vrms/8 ohm, 2,5 Arms
2.pic - the same as first only 0,22 uF parallel to 8 ohm load

Not bad for six transistors amplifier with no CCS.
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File Type: jpg VSSA_Square1.jpg (559.8 KB, 944 views)
File Type: jpg VSSA_Square2.jpg (500.3 KB, 863 views)
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Old 2nd January 2013, 06:38 AM   #233
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Quote:
Originally Posted by Lazy Cat View Post

P.S. Miller caps are 12 pF SMDs and VSSA is completely stable.
Hi LC, are you using classical NPO smd brand for miller cap?

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Old 2nd January 2013, 06:49 AM   #234
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RF quality SMD capacitors. Copper heatsink is in electrical connection to sources of ALF, so a little portion of capacitance coming from here is in addition to Miller cap too.

I'll try to replace injection resistors with CCS to see possible improvement in the next test.

Regards L.C.
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Old 2nd January 2013, 06:53 AM   #235
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Quote:
Originally Posted by Lazy Cat View Post
RF quality SMD capacitors. Copper heatsink is in electrical connection to sources of ALF, so a little portion of capacitance coming from here is in addition to Miller cap too.
Thanks, what do you mean by copper heatsink?

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Old 2nd January 2013, 07:11 AM   #236
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LC one more question : in his layout Alex swap the 1000uf 50v implicated in first stage power supply to 470uf 50V is that sufficient to your taste?

Marc
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Old 2nd January 2013, 06:58 PM   #237
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Not fully satisfied with data i found about small heatsink for VAS i decided ti swap to ones well known and that i have in stock. Miller caps has swap to RF SMD type the more close i could to Vas transistors legs.
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Old 2nd January 2013, 07:45 PM   #238
sonnya is online now sonnya  Denmark
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You could hack this amp.

Yet another amp - simple inverted with 10x gain, mosfet output stage

Use the output stage (M1, M2), the buffer which makes the mosfet switch fast (Q15,Q18 R4,C1,R21,R13,R14), use the VAS (Q7,Q6,Q5,C3,C4,Q8,Q9,Q10,R5 - R8)

Q5,Q8,Q15,Q18 can easily be DZT5401,DZT5551.

The general bias in this amp is very low. V4 can be a trim resistor with 47uF in parallel. Or as Lazycat TL431.

We are down to 4 - 8W per channel from +/-35VDC supply.

The use the frontend of the VSSA.

C3 and C4 is in reallife 47pF each.
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Old 2nd January 2013, 09:36 PM   #239
pergo is offline pergo  Italy
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two CRDs instead the 470ohm resistors (input pair's collector to rail), improve THD by 30%, mostly 2nd order.
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Old 3rd January 2013, 06:45 AM   #240
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Quote:
Originally Posted by sonnya View Post
You could hack this amp.
What do you mean? To combine two amps? Please elaborate Sonny.

At VSSA we are fixed to six transistors only, as promised.
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