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Old 21st December 2004, 03:59 PM   #21
thanh is offline thanh  Viet Nam
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thank greirin!
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Old 22nd December 2004, 10:15 AM   #22
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Quote:
Originally posted by GEirin

Thank you for the explanation. What is your opinion the C5?
I don't know, if its value is below 1n then it is probably slowing down the amplifier to preserve from oscilations again..

Quote:
Originally posted by GEirin
Now, I think other new amplifier. A symmetrical amplifier with double bootstrap? humm.....
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mirror T1,T2,T3- two complementary dirrirential stages with double bootstrap....may be interesting, don't you think?
Yes, symetrical amplifier with double bootstrap may be very interesting
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Old 22nd December 2004, 08:48 PM   #23
GEirin is offline GEirin  Argentina
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HI Darkfenriz.

OK. Thank you for recommendation. I will think your idea.

Guillermo Eirín
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Old 22nd November 2007, 03:03 AM   #24
GEirin is offline GEirin  Argentina
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HI all.
I have decide to improve my amplifier (GE50W).
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Old 22nd November 2007, 03:11 AM   #25
GEirin is offline GEirin  Argentina
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Default GE50W amplifier

Here first schematic.

I improve my old amplifier. I look many similar amplifier.
Input stage: Yamaha RX795, Ax392 and other Yamaha.
Vas: Arcam A60.
Output stage: Arcam A60, Cyrus 1, Naim.
Other amplifier: DX standart, Leach.
What is your think about the attached schematic?

Thanks
Guillermo.
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Old 22nd November 2007, 04:26 AM   #26
AKSA is offline AKSA  Australia
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Try taking C5 from the collector of VAS to the fb node, not to ground.

You may then be able to drop the cap across the fb resistor.

Can't tell you values, you need to find them empirically.

I generally agree with MikeB, who is 1 smart guy.....

Hugh
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Old 22nd November 2007, 08:51 AM   #27
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Default Rail resistances or two supplies, one for the input (higher voltage) and higher

power to the output... this "sounds"...easy to check and works fine.

Good ideas you are having friends.

Even my Symassym worked better with big rail resistances...to separate (insulate, to turn independent, not affecting one to the other) input supply voltage and output supply voltage....that PSSR people use to worry about...good worries....make sense and sounds.

My supplies, i think they are normal cheap ones.... loose voltage when drained during peaks... the input senses that... audio is modulated ... separating, using double output transformers, or, the worst trick, the use of rail (or rails) resistances to reduce the input voltage (also big condensers to help stabilize) works nice.

Try it folks...do not believe.... it is easy to try...do it and listen.

To the worst method.... the resistance, the unit must drop 3 to 5 volts (minimum)...and then you will listen better quality music.... this is the main reason people do not like the method and do not even try.... they do not know what they are loosing in sonics because of that.

They think...this is bad..will loose voltage swing..so..will not even try and goes living into the ignorance...because have not tasted the cake and go telling tastes bad.

regards,

Carlos
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Old 22nd November 2007, 10:05 AM   #28
GEirin is offline GEirin  Argentina
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Hi Hugh.
Thank for you reply.
C5 is in feedback.
C6 is colector Vas. This cap not a ground, to the node FB. Ok.
Guillermo
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Old 22nd November 2007, 10:30 AM   #29
GEirin is offline GEirin  Argentina
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Hi hermano Destroyer.

Thank for you reply.
Yo tengo pensado como opción usar fuentes separadas.
One suply for Vas and output.
Other suply for input stage and preamplifier. (+15V -15V)

Guillermo.
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Old 22nd November 2007, 11:51 AM   #30
ppa is offline ppa  Italy
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Hi all,


I woud propose these changes to Gulliermo's amplifier, they are showed in the photo.

1. the RC group I have added to schematic reduce the global feedback ratio to around 26 dB. This feedback network is well knowed from stasis amplifiers , but in these amp the global NFB is reduced to zero. In the Gulliermo's amplifier isn't possible reduce to zero the global NFB because it hasn't the many pairs of power bjts in the out like the stasis amplifiers have (or had).
I this moment I forgotten that a similar network is been used in some (or several.......) Nakamichi amplifiers.
I have studied very much the Gulliermo's amplifier and I think this is a very strategic but simple mod.


2. the others change are:
tr7=tr8=mj15003 or mj15023
tr1=tr2=bc557b or bc556b
c2= 47uF 35V or 50V hight speed series bypassed with 22nF 50V cap
c3= 470uF 16V no polar electrolitic bypassed with 22nF 50V cap
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