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Old 26th February 2012, 07:21 PM   #731
lhquam is offline lhquam  United States
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UKToecutter:

I have some concerns about noise in the multi-board F5 Turbo. The (potential) problem is the the output boards have a voltage gain of between 8 and 16 into a 4 ohm load. The Turbo kicks in, the gain gets even higher. The voltage gain is calculated as follows:

Vgain = Rload * N-fets * 1/(Rsource + 1/Gm)

where Rsource = .5 ohm, Gm approx 2S.

The problem is that any voltage difference between the power rails of the output boards and the input boards due to noise will be amplified by the output stage. The Burning Amp v2.0 doesn't have voltage gain, since the MOSFET outputs are voltage followers.

This means that extra care is required to avoid AC voltage drops. The power rail wiring must be done carefully. Capacitors C2 and C2 probably should be eliminated or on the output boards rather than the input board to eliminate ripple and noise currents running through the rail wiring to the input boards. I suggest something like the following sketch:
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Old 26th February 2012, 07:24 PM   #732
lhquam is offline lhquam  United States
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Quote:
Originally Posted by labjr View Post
How about use the dual rectifier and a transformer with a couple more volts?
Should be fine. You should only need about 1 volt extra.
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Old 26th February 2012, 08:26 PM   #733
6L6 is offline 6L6  United States
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Quote:
Originally Posted by MASantos View Post
Regarding using fans, would it be for extra ventilation for the inside of the enclosure or directly on the heatsinks?
That would be completely dependent on your heatsinks. If they are undersized, (or made for forced cooling) they will need a fan.
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Old 26th February 2012, 09:12 PM   #734
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[QUOTE=lhquam:
... have a voltage gain of between 8 and 16 into a 4 ohm load. The Turbo kicks in, the gain gets even higher.
:[/QUOTE]

As voltage gain increases when turbo kicks in due to appearent diminushing Rs isn't that producing some kind of expansion of the dynamic?

Last edited by bobodioulasso; 26th February 2012 at 09:15 PM.
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Old 26th February 2012, 09:33 PM   #735
lhquam is offline lhquam  United States
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Quote:
Originally Posted by bobodioulasso View Post
As voltage gain increases when turbo kicks in due to appearent diminushing Rs isn't that producing some kind of expansion of the dynamic?
No, the feedback loop takes care of that. With turbo "kicked-in" the open-loop gain increases, and hence the amount of negative feedback also increases.
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Old 26th February 2012, 09:43 PM   #736
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Old 26th February 2012, 11:34 PM   #737
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Quote:
Originally Posted by lhquam View Post
UKToecutter:

I have some concerns about noise in the multi-board F5 Turbo. The (potential) problem is the the output boards have a voltage gain of between 8 and 16 into a 4 ohm load. The Turbo kicks in, the gain gets even higher. The voltage gain is calculated as follows:

Vgain = Rload * N-fets * 1/(Rsource + 1/Gm)

where Rsource = .5 ohm, Gm approx 2S.

The problem is that any voltage difference between the power rails of the output boards and the input boards due to noise will be amplified by the output stage. The Burning Amp v2.0 doesn't have voltage gain, since the MOSFET outputs are voltage followers.

This means that extra care is required to avoid AC voltage drops. The power rail wiring must be done carefully. Capacitors C2 and C2 probably should be eliminated or on the output boards rather than the input board to eliminate ripple and noise currents running through the rail wiring to the input boards. I suggest something like the following sketch:
Yes,
I see your point, however, I would also imagine that any ripple would be a greater problem on the input stage.

It's not a big deal to add some cap positions on the ouput boards although it will mean running a ground connection that wasn't previously required.
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Old 26th February 2012, 11:50 PM   #738
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Hello UKToecutter

Would you please be so kind put me to the list for a stereo V3 set with one PS board.
I did tried but I couldn't do.

Greetings Gabor
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Old 27th February 2012, 12:31 AM   #739
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Join Date: Jan 2010
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Quote:
Originally Posted by lhquam View Post
UKToecutter:

I have some concerns about noise in the multi-board F5 Turbo. The (potential) problem is the the output boards have a voltage gain of between 8 and 16 into a 4 ohm load. The Turbo kicks in, the gain gets even higher. The voltage gain is calculated as follows:

Vgain = Rload * N-fets * 1/(Rsource + 1/Gm)

where Rsource = .5 ohm, Gm approx 2S.

The problem is that any voltage difference between the power rails of the output boards and the input boards due to noise will be amplified by the output stage. The Burning Amp v2.0 doesn't have voltage gain, since the MOSFET outputs are voltage followers.

This means that extra care is required to avoid AC voltage drops. The power rail wiring must be done carefully. Capacitors C2 and C2 probably should be eliminated or on the output boards rather than the input board to eliminate ripple and noise currents running through the rail wiring to the input boards. I suggest something like the following sketch:
Yes,
I see your point, however, I would also imagine that any ripple would be a greater problem on the input stage.

It's not a big deal to add some cap positions on the ouput boards although it will mean running a ground connection that wasn't previously required.
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Old 27th February 2012, 12:34 AM   #740
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Quote:
Originally Posted by gaborbela View Post
Hello UKToecutter

Would you please be so kind put me to the list for a stereo V3 set with one PS board.
I did tried but I couldn't do.

Greetings Gabor
Gabor

for a stereo V3 you'll need 2 input boards, 4 output boards and 2 PSU's
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