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Old 8th September 2010, 01:53 AM   #1
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Default Bypass capacitor!

Hello! I have a question for the pro here. Right now I am using the NXV200 from Aussie Amplifiers, power supply is 45vdc x2, and 20,000uf (mundorf caps)per rail. The sound is wonderful, no complaints at all I am very happy like it is now. But I have read a lot about Bypassing the big caps with some 22uf Solen caps, would this "extra" improve something in the sound?. Please do not say "get some caps and see for yourself" answer. I just need to know if this "extra" will improve the sound or something else. Thanks for your suggestions and comments.
I have read that in other amps some people say it is a big improvement putting a bypass cap and some say it is just a waist of time and money.
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Old 8th September 2010, 02:55 AM   #2
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I wouldn't bother. If you had some radio frequencies floating around there, I would consider some small capacitors, nothing as large as 22 microfarads though.

If you want to get serious about this, make a capacitor tester that can measure impedance at the high end of the audio frequency range and see what your filter capacitors do. Or check their data sheet to see impedance curves. It they don't go up high past 10 kHz or so, all is well as it is.
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Old 8th September 2010, 09:09 AM   #3
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by pass caps always help ...... especially when you have such a big capacitance over there
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Old 8th September 2010, 09:16 AM   #4
djk is offline djk
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A lot of large computer grade capacitors have 'muddy' sounding bass.

A small bypass capacitor in the range of 22F~100F can make the bass sound much 'tighter'.

"Please do not say "get some caps and see for yourself" answer. "

Bad attitude.

"I just need to know if this "extra" will improve the sound or something else."

It will probably change the sound. If you like 'warm' (muddy) sounding bass, you probably won't like adding bypass caps. If you own a Lateral-FET amplifier you may not hear as big of a change as if your amplifier has BJT outputs.
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Old 8th September 2010, 09:20 AM   #5
Bonsai is offline Bonsai  Taiwan
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"If you own a Lateral-FET amplifier you may not hear as big of a change as if your amplifier has BJT outputs. "

Can you give us some e more detials as to why this is the case?
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Old 8th September 2010, 12:56 PM   #6
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Thanks for the comments. as you can see here, some people recommend them and some do not!. I will wait if more people have more comments in this matter.
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Old 8th September 2010, 02:24 PM   #7
Mooly is online now Mooly  United Kingdom
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I can't see them making the slightest difference at all tbh.

That's not to say PSU decoupling isn't important... it is... but it needs to be done correctly at a more local level on the pcb's, not as add ons but as part of the initial design concept.

Why not build a simple high pass filter, say a 0.047uf and 10k to ground directly across one of the main caps and scope the output directly across the 10k then add the extra cap and see if the noise alters. And if it did, which I doubt, then the amp should have it's own on board filtering to stop any audible problems, and should have a high enough PSRR anyway.

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Old 8th September 2010, 02:42 PM   #8
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Mooly View Post
............... not as add ons but as part of the initial design concept.

........... build a simple high pass filter, say a 0.047uf and 10k to ground directly across one of the main caps and scope the output directly across the 10k then add the extra cap and see if the noise alters. And if it did, which I doubt, then the amp should have it's own on board filtering to stop any audible problems, and should have a high enough PSRR anyway.

you must be capable of measuring the effects of modifying the PSU.
If you can't see the effects, you could be making the PSU and/or amplifier unstable without realising why it sounds different.
An unstable amp sounds quite different from the same amp that is compensated correctly.
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Old 9th September 2010, 01:25 AM   #9
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""If you own a Lateral-FET amplifier you may not hear as big of a change as if your amplifier has BJT outputs. "

Can you give us some e more detials as to why this is the case? "

My experience with Hitachi Lateral-FETs has been that they sound 'warmer' than BJT. I think this is because they have an Rds on over temperature of about 1R7, and as you hit them hard this increases.

"I will wait if more people have more comments in this matter. "

Bad attitude, again.

If you like 'warm' (muddy) bass, do nothing. If you like 'tight' bass, give them a try.
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Old 9th September 2010, 02:48 AM   #10
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Quote:
Originally Posted by djk View Post
""If you own a Lateral-FET amplifier you may not hear as big of a change as if your amplifier has BJT outputs. "

Can you give us some e more detials as to why this is the case? "

My experience with Hitachi Lateral-FETs has been that they sound 'warmer' than BJT. I think this is because they have an Rds on over temperature of about 1R7, and as you hit them hard this increases.

"I will wait if more people have more comments in this matter. "

Bad attitude, again.

If you like 'warm' (muddy) bass, do nothing. If you like 'tight' bass, give them a try.

Hey djk what is wrong with your "bad attitude" thing ?. I guess you are in your days!.... and That is attitude buddy!!!!
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