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Old 28th April 2016, 11:52 AM   #1
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Default Need help reading an amplifier schematic

Hi.I found this 2000w pmpo diagram that can deliver 1000w rms @2 ohms.There's a part in this diagram that I don't understand.There's a path names as bridge input.(left side of the image).Can I know what it is and what it does.Does it use to bridge the amp?Any help would be deeply appreciated Click the image to open in full size.
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Old 28th April 2016, 12:21 PM   #2
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Bridge input is an inverting input that can be used alongside an identical amplifier. If you input the same signal to Bridge input on one amplifier and S input on another, the outputs from the amplifiers will oppose and allow bridge mode. Giving four times the power.
The bridge schematic is not correct as 120k into 33R will not work.
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Last edited by JonSnell Electronic; 28th April 2016 at 12:22 PM. Reason: More info
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Old 28th April 2016, 12:34 PM   #3
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Thank you for your reply.So how to correct that error?If I don't wanna bridge the amp what part should i remove from the diagram?
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Old 28th April 2016, 12:49 PM   #4
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Nothing needed, just ignore the bridge input, R04 and C03.
The gain is also too high, R05 + R06 / R06 = 3,637.4! I would change R05 and R03 to 47k and R06 to 470R giving 101. Much more stable.
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Last edited by JonSnell Electronic; 28th April 2016 at 12:55 PM. Reason: Information addition
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Old 28th April 2016, 12:54 PM   #5
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Moved to Solid State forum.
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Old 28th April 2016, 01:19 PM   #6
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Thank you so much.Do you think this is a good amplifier.I tried so hard to find a good amplifier diagram and this is the one i found.Do you have any recommendations for me?Im looking for something that can deliver 1000w or more @4 ohms.
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Old 28th April 2016, 02:42 PM   #7
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A good amplifier ? Can't really answer that fairly, this type of design isn't my thing. If you need that much power (do you ?) then this design is a fairly standard approach.
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Old 28th April 2016, 07:07 PM   #8
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Actually I don't need this much power.But I would like to build this since I'm on a vacation these days.
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Old 28th April 2016, 08:02 PM   #9
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OK if its what you want.

Its one seriously big amplifier, 28 output devices for a stereo amp, heatsink that's suitable, PSU that's suitable.

Why are so many of the resistors paralleled with something much higher in value ? What that all about.
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Old 29th April 2016, 01:33 AM   #10
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Without wishing to hurt anyone's feelings about the design, it really looks like someone has copied an existing, very ambitious, design but substituting a limited range of old generic parts.
All those paralleled resistors to trim values suggests to me the designer is slavishly trimming E12 values to substitute for E24 in the first design or (unlikely) those are literally what he/she used to get best results in their prototype. Either way, this makes it a suspect design and the outcome for DIY rather doubtful.
Personally, I'd look elsewhere unless you have the time to sort through the components for better suited types and more sensible values - then check by proper simulation.
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