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Old 29th March 2007, 12:17 PM   #1
tadiam is offline tadiam  Argentina
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Default mosfet opinion?

Diy opinion of this mosfet amplifier......

http://www.pcpaudio.com/pcpfiles/pro.../Schematic.pdf
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Old 29th March 2007, 05:32 PM   #2
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looking quite good ;]
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Old 29th March 2007, 06:00 PM   #3
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Default Re: mosfet opinion?

Quote:
Originally posted by tadiam
Diy opinion of this mosfet amplifier......

Hi tadiam

If you connect R 17 (22K) to ground instead the negative rail , you get much more PSRR...
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Old 29th March 2007, 08:52 PM   #4
tadiam is offline tadiam  Argentina
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Default ok

thanks tube dude
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Old 29th March 2007, 08:56 PM   #5
tadiam is offline tadiam  Argentina
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when up all volume have an motor boating in tha bass and one fet are more hot (no modification original circuit)
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Old 29th March 2007, 09:16 PM   #6
CBS240 is offline CBS240  United States
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Do you think Q9 is saturating and causing the bias of Q5 to change? Maybe a base resistor on Q9 would help this.
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Old 29th March 2007, 09:30 PM   #7
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Is R17 even required?
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Old 29th March 2007, 09:37 PM   #8
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Quote:
Originally posted by davidallancole
Is R17 even required?

No!

Without R17 the distortion will be lower.

But some people think that lower open loop gain is better...

Another tip , use two 1N4148 diodes as voltage reference for the CCS of the LTP, a Zenner is a very noisy reference...
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Old 30th March 2007, 01:17 AM   #9
jaycee is offline jaycee  United Kingdom
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I'd say R17 is a silly idea...

Why bother with the diode in the VBE multiplier... the BD139 on the heatsink alone will be plenty. Also, don't wire the bias pot like that - an open circuit wiper will spell disaster.

I agree about the zener in the CCS, although I would use an LED (better temperature stability). 1K in the base of Q9 will also help prevent saturation in that transistor killing the CCS.
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Old 30th March 2007, 02:02 AM   #10
Ipanema is offline Ipanema  Malaysia
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For better thermal tracking and stability, you can replace BD139 with a Hexfet.
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