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Old 10th June 2009, 03:12 AM   #11
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All in all - a different sound was the end result.......BUT.........SOMETHING IS NOT RIGHT

Uh Oh......

.........on large dynamics such as percussion music, closely miked kettle drums, I noticed some distortion coming in to the equation. Replacing the bypassed bank with a couple of 20, 000 uf Nippon Chemicon vintage caps, the distortion went away so it seemed.


I always thought that the metal wrapper on an electrolytic is actually part of the unit and needs to be there for proper operation. Not to be confused with "nude" capacitors with the paper or plastic insulating wrapper removed. I still don't understand "nude" capacitors, what difference could it possibly make but I digress.

So putting back some "normal" caps made the nasties go away, I'm thinking you ruined a perfectly good set of caps. Try the same caps in there without removing anything and use the same bypass caps and listen to how it sounds. My curiosity is now fired up.
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Old 10th June 2009, 03:57 AM   #12
jwb is offline jwb  United States
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In my opinion you're high, or deaf, or both. Two feet of wire is going to have so much inductance as to render your bypass caps completely worthless. Try running it without the caps. It probably sounds the same.
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Old 10th June 2009, 05:28 AM   #13
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jrockhead,
all encapsulation materials, aluminum, plastic, beeswax, even the air have an electrical impact, causing distortion and coloration.
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Old 10th June 2009, 05:42 AM   #14
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http://sound.westhost.com/articles/capacitors.htm#6.0
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Old 10th June 2009, 07:58 AM   #15
Ziggy is offline Ziggy  Australia
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jwb.....thanks for the insult I can still hear to 16khz ,so I don;t think I'm deaf.
''High''............yeah.....................love to sniff that bees wax............mmmmmmmmmmmmmmmm.......beeeeeeeeeee eswaaaaaaaaaaaaax........

I have heard the difference AS I ADDED EACH CAP BANK, so the wire inductance thing is B.S.

Tonight I am going to listen to some well run in 1000uf 50v Black Gate STD caps : 2,000mf only per rail. The other caps were disconnected and the B.G's wired in this morning. So, they'll have a 12 hour re-form by the time I listen to the amp tonight.

Bearing in mind that the original caps had 2X 5600uf, the 2,000mf per rail had absolutely no hum or noise when I listened briefly after connection. I would presume this amp has very good power supply rejection at such low capacitance?

Maybe there will be little or no bass?........or perhaps high speed transients?........or both?...........will report back.
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Old 10th June 2009, 01:46 PM   #16
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Quote:
Originally posted by Lumba Ogir
jrockhead,
all encapsulation materials, aluminum, plastic, beeswax, even the air have an electrical impact, causing distortion and coloration.

Interesting statement, Lumba. Can you point me to any articles or sites to further read up on this? During my great capacitor info hunt a few years ago I read a lot of stuff about different cap materials and how that makes a difference but not encapsulation methods or materials. Thanx.
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Old 11th June 2009, 05:58 AM   #17
Ziggy is offline Ziggy  Australia
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O.K..........the Kenwood receiver truly has superb power supply rejection. The Black gates were as silent as first tried so you can go as little as 2,000mf per rail on this unit. But........bass seemed a bit flabby and I was only doing this as a quick test on P.S.R. and nothing else.

To my dismay, I realised that somewhere along the line, I had accidently switched the 8 ohm/4ohm switch at the back of the unit to 4 ohm ............bad news as this is why the capacitor bees wax block and all those bypasses and even the larger Nippons to some extent, suddenly sounded lousy.

Looking at the circuit and measuring the D.C voltage at the caps shows that when switched to 4 oihm, the amplifier uses the lower voltage taps of the power transformer - 17 volts A.C per rail difference The difference to the sound is now dramatically better at the 8 ohm setting - no distortion,great dynamics and transparency. Better than it should be for a modest amp like this, even though it has been modded.

Can anyone care to comment on why Kenwood do this, and what it's supposed to achieve with lower impedance speakers?
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Old 11th June 2009, 07:57 AM   #18
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jrockhead,
Quote:
During my great capacitor info hunt a few years ago I read a lot of stuff about different cap materials
Of course, the dielectric materials overwhelmingly determine the characteristics.
Quote:
Can you point me to any articles or sites to further read up on this?
Sorry, I cannot. However, in audio use, the often massive encapsulation is unfortunate.

Could we call this light encapsulation?
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Old 11th June 2009, 09:09 AM   #19
Stuey is offline Stuey  Australia
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Quote:
Originally posted by Ziggy
Looking at the circuit and measuring the D.C voltage at the caps shows that when switched to 4 oihm, the amplifier uses the lower voltage taps of the power transformer - 17 volts A.C per rail difference The difference to the sound is now dramatically better at the 8 ohm setting - no distortion,great dynamics and transparency. Better than it should be for a modest amp like this, even though it has been modded.

Can anyone care to comment on why Kenwood do this, and what it's supposed to achieve with lower impedance speakers?
I think it's because a 4 ohm speaker requires more current for a given output, so the voltage has to come down so the power through the output devices stays within their rating.
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Old 11th June 2009, 10:07 AM   #20
AndrewT is offline AndrewT  Scotland
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A power amp designed to drive an 8ohm load is completely different from a power amp designed for 4ohm loading.

To get the most sales from a compromise that is affordable, they have used a dual voltage PSU. This helps overcome the major difference between the designs, the heat dissipated in the output stage.


I suspect that the reason for it sounding better is that the voltage amp stage and the PSU are optimised for 8ohm loading and that the 8ohm setting clips the transients less often.
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