peranders said:
I have lower noise with the OPA637 than the AD797 on my MM phono pre.
Also, the OPA637 sounds much better, but that's another story.
It's not that you notice when listening to the music, you won't.
It's just that I'm very picky and always test with the volume to the max and the ear on the speaker.
hi guys,
This is my first post to this great forum. I make world's smallest headphone amps (SuperMacro etc).
For the reason of Carlos' V+ to V- bypassing, you can find it in TI (BB)'s datasheets, such as OPA690:
"In addition to the usual power-supply decoupling capacitors to
ground, a 0.1 µF capacitor is included between the two power-
supply pins. In practical PC board layouts, this optional-added
capacitor will typically improve the 2nd-harmonic distortion
performance by 3dB to 6dB."
3dB to 6dB - that's a huge difference!
I found this trick by my own and used it in my headphone amps, then I was very excited to find that Carlos and TI also discovered this!
www.fixup.net
This is my first post to this great forum. I make world's smallest headphone amps (SuperMacro etc).
For the reason of Carlos' V+ to V- bypassing, you can find it in TI (BB)'s datasheets, such as OPA690:
"In addition to the usual power-supply decoupling capacitors to
ground, a 0.1 µF capacitor is included between the two power-
supply pins. In practical PC board layouts, this optional-added
capacitor will typically improve the 2nd-harmonic distortion
performance by 3dB to 6dB."
3dB to 6dB - that's a huge difference!
I found this trick by my own and used it in my headphone amps, then I was very excited to find that Carlos and TI also discovered this!
www.fixup.net
How much difference if we talk dB's? Is there any practical difference, I mean when you _not_ are have the volume at full throttle?carlosfm said:I have lower noise with the OPA637 than the AD797 on my MM phono pre.
Also, the OPA637 sounds much better, but that's another story.
It's not that you notice when listening to the music, you won't.
It's just that I'm very picky and always test with the volume to the max and the ear on the speaker.
as with everything in audio it is science vs art.
scientifically, the ceramic will probably be the best bet, ceramics have better high frequency properties (the whole reason a single cap isn't good enough in the first place).
artistically, some argure that the film-cap will allow for better sound.
scientifically, the ceramic will probably be the best bet, ceramics have better high frequency properties (the whole reason a single cap isn't good enough in the first place).
artistically, some argure that the film-cap will allow for better sound.
In this case:
* The cap is not in the signal path, no need to use a film one
* It works at frequency far above audio, ceramic is better for high freq.
* It acts as short-circuit, ceramic's non-linearty has no chance to show up (low freq. is short-circuited by a large electrolytic or tantanium cap).
Therefore, ceramic.
* The cap is not in the signal path, no need to use a film one
* It works at frequency far above audio, ceramic is better for high freq.
* It acts as short-circuit, ceramic's non-linearty has no chance to show up (low freq. is short-circuited by a large electrolytic or tantanium cap).
Therefore, ceramic.
DC Dave said:
This page at Anolog Devices has some interesting information related to cap types.
http://www.analog.com/library/analogDialogue/Anniversary/21.html
The high inductance characteristics of polypropylene caps are interesting.
I thought there was a more detailed paper following the same flow as this page on the AD sight but I cannot find it at this point.
moving_electron said:
In the link there is a comparison chart at the bottom. I am curious about the comment in the monolythic ceramic (multilayer) "disadvantages" box.
Does "poor stabilty" refer to stability of the capacitance value with tempature change? Or do they mean that the capacitance value is prone to shift over time?
CarlosFM. I think you have mentioned that you didn't notice any difference between Polypropylene or ceramic for cap bypassing at the pins (V+ to ground, V- to ground) but that you prefered Polypropylene for the V+ to V-.
Is the poly preference for V+ to V- poly just a personal preference for what you had on hand or did you really hear difference vs. mono (multilayer) ceramic?
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