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Old 18th February 2004, 10:37 PM   #11
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the emitter resistor for the VAS stage (121ohm) is pretty big, considering that JC2 has a 20ohm or so resistor there.
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Old 18th February 2004, 10:50 PM   #12
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Quote:
Originally posted by millwood
the emitter resistor for the VAS stage (121ohm) is pretty big, considering that JC2 has a 20ohm or so resistor there.

And the current in the VAS is 8,3 ma...
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Old 18th February 2004, 11:15 PM   #13
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Default The unbiased vue...

The unbiased electolitc capacitor in the emmiters of the LTP...is a strange feature...

Any comments??
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Old 19th February 2004, 01:25 AM   #14
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Default Re: The unbiased vue...

Quote:
Originally posted by Tube_Dude
The unbiased electolitc capacitor in the emmiters of the LTP...is a strange feature...

Any comments??

I think it is to reduce degeneration for a/c signals without causing excessive d/c offset. with the cap, the two 200r resistors are essentially tied together, thus no more emitter degeneration.

for a/c signal, the cap is open, thus each leg has a 200r resistor.
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Old 19th February 2004, 01:28 AM   #15
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Quote:
Originally posted by Tube_Dude



And the current in the VAS is 8,3 ma...

if this circuitry behaves like our simulation, the vas is likely running in the 1ma range.

maybe someone will have a service manual for the amp.
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Old 19th February 2004, 07:38 AM   #16
UrSv is offline UrSv  Sweden
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Quote:
Originally posted by K-amps
Based on the schematic. looks like 3 pairs of outputs. If it runs 100watts class-A into 8 ohms, i'd say the bias is as follows:

Total bias 2.5 amp per rail.
Bias per device 0.84 (x3 devices for each cycle of push pull) .
voltage across each emmitter resistor = 416.6mv.

This amp will dissipate 235 watts per channel at idle.

All this is based on the 100 watt class-A spec and the values on the schematic.

Chocoholic and Millwood, did I make you proud?

K-Amps
With regards to the 3 pairs of outputs I think it could easily be 4 pairs as the schematic clearly says x4 for the output transistors.
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Old 19th February 2004, 10:53 AM   #17
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Quote:
Originally posted by millwood



if this circuitry behaves like our simulation, the vas is likely running in the 1ma range.

maybe someone will have a service manual for the amp.
Not needed the service manual...if the simulation gives you 1mA...your simulation is flawed...

The current un the VAS is +-8,3 mA...

PS : How a 1 mA current can drive a follower that is not even a triple follower but only a double!???
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Old 19th February 2004, 11:50 AM   #18
MikeW is offline MikeW  United States
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Question sound

Has anyone built this amp?
How many output devices? Now I see the X4
How much bias? 2.5 amps per rail
How does it sound?
Is it worth doing a board for it?

Can it be scaled down so to +/- 40 volt rails?

Is anyone interested in boards if they are made?
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Old 19th February 2004, 11:59 AM   #19
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Default Re: Re: The unbiased vue...

Quote:
Originally posted by millwood



I think it is to reduce degeneration for a/c signals without causing excessive d/c offset. with the cap, the two 200r resistors are essentially tied together, thus no more emitter degeneration.
Yes!

Quote:
for a/c signal, the cap is open, thus each leg has a 200r resistor.
No..i think that what you mean is....for DC !!!
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Old 19th February 2004, 12:41 PM   #20
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Quote:
Originally posted by Tube_Dude


Not needed the service manual...if the simulation gives you 1mA...your simulation is flawed...

The current un the VAS is +-8,3 mA...
I thought it was settled on that other thread that for such a topology, you cannot calculate VAS and LTP current. Assuming that the current in the LTP legs is evenly split is falwed.

hopefully, the time and effort there were not wasted.
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