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Old 3rd June 2003, 07:42 AM   #1
Raka is offline Raka  Europe
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Default Coupling cap

Hi,

Yes, I surrendered and built a gainclone. The scheme is the Thorsten and Peter Daniel one. Standard parts, of course.
Actually, only one channel is finished, but late at night without change to put volume up.
I want to ask the following:
- The coupling cap I use is a 4.7uF that was in my trash bin asking for his big time. Brand? could be Faco? The question: Is there any problem if I fit a 6uF (Electrocube) or even higher? I also have 1uF wimas that can be paralleled. Suggestions?
- Sound is slightly better (if so) than my Denon AV1801, but if I connect my speaker with my TNT DIY cat5 suddendly all starts to PLO-PLO-PLO very loudly!! Is the gainclone allergic to cat5?

Hum is low enough but not inaudible, that doesn't worry me because the wiring isn't something to show and can be improved.
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Old 3rd June 2003, 08:20 AM   #2
mikelm is offline mikelm  England
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Default Re: Coupling cap

Quote:
Originally posted by Raka
Hi,


- The coupling cap I use is a 4.7uF that was in my trash bin asking for his big time. Brand? could be Faco? The question: Is there any problem if I fit a 6uF (Electrocube) or even higher? I also have 1uF wimas that can be paralleled. Suggestions?
- Sound is slightly better (if so) than my Denon AV1801, but if I connect my speaker with my TNT DIY cat5 suddendly all starts to PLO-PLO-PLO very loudly!! Is the gainclone allergic to cat5?

I think Cap size can be higher but this cap should be quality poly pro or similar - i'm not familiar with the brands that you mention.

Peter may have some thoughts on this but my feeling is that his version requires low capacitance leads.

cheers

mike
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Old 3rd June 2003, 12:46 PM   #3
Nuuk is offline Nuuk  United Kingdom
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Hi Raka, welcome to the club!

I have 47 ufd caps as my DC blockers and they work fine. I only used that high a value because they are Black Gate NX-Q's and I didn't have anything else near that sort of quality.

PLO-PLO-PLO? Was that Estonia's entry into the Eurovision Song Contest?

Seriously, it could be those speaker cables. You could try a 0.22 resistor (3W) on the output of your amp and see if you still get the problem.
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Old 3rd June 2003, 01:38 PM   #4
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You can use any cap value above 2u or so. The better cap quality, the better sound. I'm not using coupling cap at all, as my source is AC coupled.

I tried 0.22 ohm output resistor. First, it didn't improve the sound as some people claim (at least not in my system). I noticed slight resolution degradation and very slight addition of resistor's signature (Mills). I'm using two parallel runs of Audioguest cable (bi-wiring) and I never had any problem with regard to that. Also a friend of mine tried Cat 5 cables on GC and it was fine.
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Old 3rd June 2003, 03:04 PM   #5
Raka is offline Raka  Europe
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Thanks for your reply,

I will try the Wimas (2x1uF) and the Electrocube 6uF, and maybe I bypass the cap, I only have to try. Tomorrow you will have my conclusions.
Another curious things happens when I switch off the amp. Suddendly it stops, but after two seconds is back!! Just for an instant, but scaries...
The star ground was made joining ALL wires at the star point, I will try to use the chip pin as ground and then to the star point.
Hum is low, but there is.
PLO,PLO is not a beautiful song, nor from Estonia BTW, I liked the Austrian the most.
Quiz:
How many of the Eurovision players were out of tune?
A: 95%
B: 96%
C: 97%
D: I only withstand the first one, so 100%
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Old 3rd June 2003, 03:39 PM   #6
Nuuk is offline Nuuk  United Kingdom
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Quote:
How many of the Eurovision players were out of tune?
None as bad as the British entry. I thought the voting was political until I saw the actual performance! Oh dear - better luck next year.
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Old 7th June 2003, 08:11 PM   #7
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Quote:
Originally posted by Raka
Another curious things happens when I switch off the amp. Suddendly it stops, but after two seconds is back!! Just for an instant, but scaries...
as i have 33,000uf per channel, my gainclone runs for 10+ seconds after i turn it off.
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Old 8th June 2003, 08:19 AM   #8
Prof is offline Prof  United Kingdom
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Default Scary Gainclone

Raka, My new Gainclone does exactly the same thing, two seconds after switch off it makes a bit of noise. Just the 1000ufs saying goodbye !

I also leave out the input coupling cap, of course I measured for DC on the output of my CD player first. In fact if you leave out the cap, I think it may be a good idea to have huge warning signs on your phono inputs and leads, just in case you decide to change your CD player or amplify another source. A bit of DC on the input may move your speaker cones a bit further than they were designed to !
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Old 9th June 2003, 06:25 AM   #9
Raka is offline Raka  Europe
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Mattcatt,

What about the sound with 33000uF per channel? I'm using the inverted of thorsten with just the 1kuF.

To continue the report, my clone is now with the impedance in the positive leg to ground and the output resistor (actually 0.25Ohm). Now the plo-plo is away and I can use the cat5 cable. Besides, I also tried a single pair of cat5 and sounded I think almost the same

Sound is the same with or without the mods, (that is: slightly better than my denon1801). If I can trust my ear, if not the same, better with the complete schematic from loesch.

shorting the cap (electrocube 10uF) I really don't notice the difference, so I suppose the cap is not doing bad.

I only have to finish the volume control. Nuuk, your page is really nice, I've been reading it since two years. I think I will try to source the components for the attenuator you suggest.

I hope to borrow a digital camera to show the creature, that now is not resting but playing Mozart violin concerto n2&4 in repeat mode.
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Old 9th June 2003, 09:58 AM   #10
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Quote:
Originally posted by Matttcattt


as i have 33,000uf per channel, my gainclone runs for 10+ seconds after i turn it off.


Man, you don't know how to make it small, do you?
Some drain resistors would cure that.

Raka, I use 1000uf too, and I don't have that problem.
Maby it's because I always bypass with 0.1uf caps.
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