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help with op amp headphone amp hum and distortion
help with op amp headphone amp hum and distortion
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Old 4th March 2021, 03:41 AM   #71
gregas is offline gregas  Canada
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Join Date: Nov 2018
Location: Toronto
Hey Rick.
So I'm adding those 1/4w resistors to my order
Plus 4k7. Thanks.
https://www.mouser.ca/ProductDetail/652-3006P-1-103-LF/
How's this look for the trimpot?
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Old 4th March 2021, 03:58 AM   #72
Rick PA Stadel is offline Rick PA Stadel  United States
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Those are pretty standard, and pretty decent. Wouldn't mind if they would pick a tempco sign, and not just specify +/-200ppm. Or a little better cycles/life (only "200" means you can't, as a practical matter, just keep a handful of these in your prototyping parts box and expect them to be reliable when you pull one out -- check/measure every use!)

If you get 10k trimpots, you shouldn't need the 4k7's. (Unless I booted the arithmetic .. !)
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Old 4th March 2021, 04:20 AM   #73
gregas is offline gregas  Canada
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How about this for the perfboard?
https://www.mouser.ca/ProductDetail/...9HVnuJCg%3D%3D

Ok so no need for the 4k7 resistor
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Old 6th March 2021, 05:17 AM   #74
Rick PA Stadel is offline Rick PA Stadel  United States
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Yep, that looks just fine.

As long as you get 0,042" holes on 0,1" centers, and it's FR-4, you're getting pretty standard stuff.
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Old 7th March 2021, 02:35 AM   #75
gregas is offline gregas  Canada
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Rick,
I've been thinking. I have that leftover veroboard that i removed all those components off with the mosfets. I could probably cut that to size and just use it instead of the perfboard. I don't think saving a bit of space is a big issue here, is it? I could also mount it to some stand off spacers mounted to the mounting screws for the headphone amp veroboard.
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File Type: jpg headphone vero2.jpg (964.4 KB, 38 views)
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Old 7th March 2021, 07:01 PM   #76
Rick PA Stadel is offline Rick PA Stadel  United States
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Should be OK. But the ground lead from C1 on the bias circuit will need a short, direct (no service loop) connection, close to the pad between the bypass capacitors on the AD817 supply leads -- pins 4 and 7.

And if the bias circuit occupies somewhat less space, that's good thing.

Maybe don't worry about the mounting. Try to think of the little added circuit as a test assembly, instead of something permanent that needs to be properly secured.

Uhh .. one other thing I should probably mention: Sockets are not recommended for op-amps with bandwidth this high. Not sure what to suggest to change at this point in the project, though. Hopefully the rail bypass caps are close by.

Cheers
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Old 8th March 2021, 12:15 AM   #77
gregas is offline gregas  Canada
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Join Date: Nov 2018
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Hey Rick,
Thanks for the response.


I believe the sockets were used here's the ability to swap out chips.
Sounds like a major part of my problem is the chip that was chosen.


If the temp compens circuit works and I'm happy with the headphone amp, I would then find a way to mount it?
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Old 11th March 2021, 07:06 AM   #78
Rick PA Stadel is offline Rick PA Stadel  United States
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Join Date: Apr 2017
Location: greater Kansas City
Yup!

About the 'swap out chips' .. a lot of people have a lot of fun doing that. Trouble is, an op-amp is NOT an op-amp, is NOT an op-amp, etc ..

Not all flavors are directly interchangeable. Some of the times that someone complains about the exceedingly poor sound quality of an amp they subbed in, it's oscillating ultrasonically, or otherwise behaving poorly. And lacking an oscilloscope they have no idea(!), then they blame it on *fake* parts, or chalk it up to some other specious excuse.

Cheers
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