3W amps - options: SS which sounds as good as DHT’s

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jack
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#31 Re: 3W amps - options: SS which sounds as good as DHT’s

Post by jack »

vinylnvalves wrote: Tue Mar 06, 2018 6:10 am I think I may not have expressed to question well. The output stage in the DSP is an Opamp gain stage(in mine I am using OPA627’s), why do I need to add another Opamp stage before the current buffer output stage If I can live with 6V ? The DSP and power amps won’t be in the same box but are close, so was ignoring any cable length effects.
You don't need any gain from the driver stage but you will need U3 as it handles the global feedback from the drivers - the first two opamps and their surrounding resistors can be left out as they wouldn't be needed in your case unless you wanted a balanced input, in which case the R3 change I mentioned would be required.
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#32 Re: 3W amps - options: SS which sounds as good as DHT’s

Post by vinylnvalves »

Maybe I am being thick but I don’t see any feedback to u3 from the paralleled buffer.
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#33 Re: 3W amps - options: SS which sounds as good as DHT’s

Post by jack »

vinylnvalves wrote: Tue Mar 06, 2018 8:03 am Maybe I am being thick but I don’t see any feedback to u3 from the paralleled buffer.
Look at R8...
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#34 Re: 3W amps - options: SS which sounds as good as DHT’s

Post by vinylnvalves »

More blind than thick. Need to get this schematic with a white background so I can see it.
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#35 Re: 3W amps - options: SS which sounds as good as DHT’s

Post by jack »

vinylnvalves wrote: Tue Mar 06, 2018 8:22 am More blind than thick. Need to get this schematic with a white background so I can see it.
Not thick at all - all very sensible questions. It's interesting that if you look at the schematic in detail, the part he's used is the AD797 which is pin-compatible, so he changed it later to the LME part or basically he couldn't be bothered to create a new part.
Last edited by jack on Tue Mar 06, 2018 8:27 am, edited 1 time in total.
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#36 Re: 3W amps - options: SS which sounds as good as DHT’s

Post by vinylnvalves »

Answers my question about a deleting the input stage, need it for feedback.
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#37 Re: 3W amps - options: SS which sounds as good as DHT’s

Post by vinylnvalves »

I am not an IC aficionados so would not know if an AD797 is better than the LME49990. I had thought of using the Burson discrete ones as they cost about the same as the discontinued LME49990’s. They are limited to +/-15v. So would have had to drop the voltage to the input stage or reduce it across everything.
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