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adding more caps to my headphone amp? upgrade transistor?
adding more caps to my headphone amp? upgrade transistor?
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Old 21st December 2017, 01:56 AM   #11
laserscrape is offline laserscrape
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Quote:
Originally Posted by phase View Post
I wouldn't recommend going without a .01 to .1uf to ground on each rail as well, but the smaller electrolytic part from rail to rail has helped when I had used the lme49720/4556. This was in addition to 47uf parts nearby.
sorry for my lack of knowledge but what exactly does it help with? are these measured or audible differences (or both)?
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Old 21st December 2017, 02:25 AM   #12
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Originally Posted by hpeter View Post
opamps have higher PSRR than tube circuits, but still can be affected by crap powersupply.
ideal psu-has zero impedance across whole frequency range.
this is not doable with just few wet capacitors.

wet caps are good maybe up to 1khz, foil caps are much better, stable params.

you "smoothened your power rails with 1000grit sandpaper", but you may try some more.
Click the image to open in full size.
yes I doubt they chose they large electrolytic caps for any reason other than cost reduction.

just by ear alone I can tell the amp performs imuch worse in the HF but it does sound good, could the current caps be contributing to the smooth/rich sound?
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Old 21st December 2017, 02:57 AM   #13
phase is offline phase  United States
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The improvements I noticed were subjective, however, following a basic bypassing scheme of 1/10 of the next larger part isn't anything new.
I would say that the midrange had become smoother, most noticably. Your results may vary, but if you can easily try it...
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Old 21st December 2017, 08:52 AM   #14
laserscrape is offline laserscrape
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Originally Posted by hpeter View Post
wet caps are good maybe up to 1khz, foil caps are much better, stable params.
So I just discovered that film caps barely exist above 100uf, over 1uf they are available but very expensive.

Is the capacitance a concern here? would 10uf of film caps per channel be enough to smooth above 1Khz?
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Old 21st December 2017, 06:52 PM   #15
phase is offline phase  United States
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Most film caps of that size are going to be too large, have inductance.
There are some smaller Wima MKS4 that are about the smallest film cap that I have seen for through hole mounting.
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Old 22nd December 2017, 06:33 AM   #16
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Originally Posted by phase View Post
Most film caps of that size are going to be too large, have inductance.
There are some smaller Wima MKS4 that are about the smallest film cap that I have seen for through hole mounting.
nice, these are available locally and arent too expensive.

So Ill add an 4.7uf rail to rail near the op amp and an additional 0.1uf on each rail. Would you suggest anymore? Ill still have lots of room on the PCB.

Im also wondering about the replacing the vintage 8000uf with 2 4700uf (buy another 4700uf and reinstall the 4700uf that I removed), would this be ok or would I be better with one?
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Old 22nd December 2017, 01:35 PM   #17
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Actually I think you were already pretty thorough with your first suggestions, Im just wondering what hpeter had in mind for optimal >1KHz smoothing.
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Old 22nd December 2017, 05:55 PM   #18
phase is offline phase  United States
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The higher fequency smoothing is accomplished with the tiny(.01 - .1uf) bypasses that are located as close as possible to the load.
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Old 23rd December 2017, 11:53 AM   #19
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Originally Posted by phase View Post
The higher fequency smoothing is accomplished with the tiny(.01 - .1uf) bypasses that are located as close as possible to the load.
I see, no need to buy anymore then. thanks for the help.

I also had another question that I was going to make a thread about but I suppose I may aswell ask here first.
I had already swapped the NE5532 for an LM4562 with good results but when I tried putting in an AD8066 there was some problems. There was a loud buzzing when the volume pot was at zero, also the pops you get when connecting headphones were extremely loud... is there any explanation for this? it seems to be working ok otherwise but these problems make it unusable
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Old 23rd December 2017, 12:16 PM   #20
cliffforrest is offline cliffforrest  United Kingdom
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adding more caps to my headphone amp? upgrade transistor?
You will need to do a bit of research on data-sheets and details of op-amps before blindly stuffing different parts in!

The AD8066 is a very fast amplifier specified for video NOT audio and has a maximum supply rating of 24V or +-12v.

It was almost certainly oscillating like crazy and might have blown up depending on the rail voltages in your circuit.
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