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Old 21st December 2009, 02:47 PM   #31
AndrewT is offline AndrewT  Scotland
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Hi,
the 16r in the Vbe multiplier is in the wrong position for Self circuit.
The output to the upper driver base comes from the collector of the Vbe transistor.

Have you omitted a connection from the input current mirror?
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Old 21st December 2009, 02:54 PM   #32
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Default Will check this

Thanks,

regards,

Carlos
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Old 21st December 2009, 03:09 PM   #33
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CCS does not create instability. Too much open loop gain with both a current mirror and the darlington VAS is what does it. Use just a low gain BD or MJE340
for VAS with 68 - 100 pf CDOM , all will be good.
OS
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Old 21st December 2009, 03:17 PM   #34
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Default Yes, i found errors, and the VBE multiplier returned to the standard mode

It is working fine this way those last years, will not try the new circuit.

Team that is winning, we do not make changes or player's substitution!

here you have the new images..sorry by the quality, but i think we gonna have a better board design soon, this one is a previous one offered to my orkut friends that are daily chatting with me, so they can ask me things and i can inform them the last modifications made.

regards,

Carlos
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Old 21st December 2009, 03:27 PM   #35
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Default Thank you Ostry!

Your informations about CCS will be registered and used as soon as they will be needed once again.

regards,

Carlos
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Old 21st December 2009, 03:31 PM   #36
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The cap you put to the rail to stop oscillation is called "shunt compensation" , it
lowers open loop gain in the VAS , that is why oscillation stops. You are defeating the extra gain of the VAS by shorting it out to the rail.
OS
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Old 21st December 2009, 03:32 PM   #37
BV is offline BV  Slovakia
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100pF from base of VAS "beta enhancer" to ground seems to me not a good idea..Straight way for hf disturbancies and possible stability problems. Use bigger value instead 33pF Cdom..And resistor about 1Megaohm in parallel with this capacitor will lower VAS gain (lower OLG-better stability) but at the same time you gain much better VAS linearity and lower VAS output impedance..

Last edited by BV; 21st December 2009 at 03:44 PM.
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Old 21st December 2009, 03:46 PM   #38
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Default So, remove them into your own board...happy Dx Blame ES

construction for you. Your own personal board your problem.

My dear friend, the Dx builder, those are my problem.

the capacitor will stay.

regards,

Carlos
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Old 21st December 2009, 03:55 PM   #39
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Default A profissional pcboard layout will be provide by Taj along monthes

of January and february...for a while, if you want to assemble, create your own board or use the one i have provided to my Orkut friends (the ugly one).

Failure into board layout design, when made by me, is always an option.

Better do to yours.

The amplifier is a hell sensitive to oscilations, i have lost several transistors when first time powering and tweaking.... make changes under your own risk and do not came to complain to the Corporation if something was modified.

Reliability is guaranteed the way it is.

The design will not be changed, was tested, working fine, sounding fine.... i have only to continue the endurance test to 4 ohms till wednesday.... the unit is playing all time long, loaded to be unstable and speaker connected together the crazy load (in series with a small resistance)...only schematic errors, wrong values (typping error), lines missed into schematic, well, those things may be fixed.

The amplifier is not opened to suggestions how to make it better.... the one can make it better can do it by himself opening a dedicated thread for this purpose.

regards,

Carlos
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Last edited by destroyer X; 21st December 2009 at 03:58 PM.
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Old 21st December 2009, 04:02 PM   #40
PMA is offline PMA  Europe
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Carlos,

just curious - could you kindly show an oscilloscope measurement of 10kHz square response into 8ohm//100nF load?

Thanks,
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