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Old 30th May 2006, 12:01 PM   #11
frogert is offline frogert  United States
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Would the "soft start" option keep the fuse from blowing while that capacitor is charging up? I know that a soft-start switch is recommended for most tripath amps, but there are no specific instructions for one with the amp6. Do I need a "three position" rotary switch? What value resistor?

Alternately, how do I rig a switch so I can switch between the chips mute mode and normal mode? Would that do it?
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Old 30th May 2006, 07:46 PM   #12
Pano is offline Pano  United States
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The soft start on the AMP6 is the "sleep" function. If the sleep pin is tied to ground, the amp will wake up. From sleep to wake, there is only a very small noise.

The sleep pin is brought out to the connection row as is explained in the documentation. A simple switch will allow you use this function.

As for a soft start "a la Charlize", you would need to put a resistor in the path of the low voltage AC going to the board. It is the big 10000uF cap that causes the turn on surge. A resistor in series would allow the cap to charge more slowly. I don't think it would eliminate the turn on pop, but I have not tried it.

Jan of 41HZ says to use a 200ma fuse for testing. I can't get 200ma to work; it always blows when charging up the cap.
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Old 12th September 2006, 03:57 PM   #13
niiico is offline niiico  France
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Hi,

it has been a long time.

Since I still don't know if I'll use the AMP6 in an HC system or just in Hifi, I finally put the whole stuff in a paperboard box to test it in the Hifi part... Not very "safe" but sufficient to test it.

I still have my 2A fuse, but it seems to be ok (it becomes red in a flash when I turn on the amp, but it doesn't blow...).

I've added a stiffener cap (10000µF) and the speaker wires are made with 2 teflon 1mm diameter "silvered copper" wired together.
I use the same cable for the input, but I think I will use shielded cable in the final version.

Here are some pictures (you can click on them):

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

So how does it sound ? Fan-tas-tic ! I re-discovered my speakers : the basses are dry as I like and it is well more precise and defined than my Atoll AV500 (I use the AMP6 with my Atoll PR 5.1 pre-amp).
I'm sure the stiffener cap help a lot for the basses...


I have only one concern : when I turn on the amp, I hear a little "cloc" in the medium... Even with the mute.

Do you think it is possible to add some relays circuit somewhere to avoid this "cloc"?

Niiico
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Old 12th September 2006, 07:20 PM   #14
Pano is offline Pano  United States
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Salut Niico! Good to hear from you again.
Crazy box, dude - crazy. But, yeah, you should really like the way the amps sounds. The Amp 6 is great.

Next step is a better box, but you should also replace the input caps. Try some Solen 2uF for the inputs. If you have room, and can find them, try Sic-Safco paper in oil. Very nice! Bigger than the amp.

The Amp6 uses the sleep function, not mute. It causes a little more noise than mute. The "cloc" will not hurt anything, but if you don't like it, you can put relays on your speaker output cables.
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Old 12th September 2006, 08:55 PM   #15
niiico is offline niiico  France
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Quote:
Originally posted by panomaniac

Next step is a better box, but you should also replace the input caps. Try some Solen 2uF for the inputs. If you have room, and can find them, try Sic-Safco paper in oil. Very nice! Bigger than the amp.
I'm a little affraid about those BIG caps. I think it may be a EMI antenna because of the connexion wires. I'd like to do some tests, but I need some time and I don't have a lot of it... How are connected the input caps? Can we connect them somewhere else (not on the board) to limit the wires size?

About the box, I'm decided to built a 5.0 way amp, so I can know buy a "big" box. BTW, is it a problem to use only one half of the amp6?

Quote:

The Amp6 uses the sleep function, not mute. It causes a little more noise than mute. The "cloc" will not hurt anything, but if you don't like it, you can put relays on your speaker output cables.
How do you connect a relay on the speaker output wires? I'm not an electronician, so I have no idea about the way to do this...

Thank you for your help.
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Old 13th September 2006, 01:16 PM   #16
niiico is offline niiico  France
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About the input caps, do you speak about those:
http://www.solen.ca/caps/tin.htm


Niiico
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Old 13th September 2006, 01:23 PM   #17
niiico is offline niiico  France
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Or those ones:
http://www.solen.ca/caps/mkp.htm


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Old 13th September 2006, 01:57 PM   #18
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When Jan talks about a 200mA fuse for the Amp6, isn't it possible that he is referring to a fuse on the primary side of the transformer?

I have no idea if this calculation is correct, but:
200mA * 230V / 15V = 3.06A

200mA on primary side is roughly equal to 3A on the secondary side, yes?

Anecdotally, I seem to remember reading something about fuses being noisy, indicating that they should be on the as 'far away' from the circuit as possible, but I'd guess that this is only different with regard to on which side of the regulator the fuse lies. It's probably pretty hard to stuff a fuse after the regulator in an Amp6 anyway
(... but still, what happens to this hypothetical 'fuse noise' inside the toroid?)

Disclamer: Fuses being noisy could also very well be my imagination.

Mainly, I'm bringing up the primary / secondary side amperage rating issue for the fuse.

edit:
Niico, about the caps: Separate film and metal-foil caps are considered better than metalized film caps, AFAIK. Source:
http://tangentsoft.net/audio/input-cap.html - section RC Filter Weakness 3: Capacitor Distortions
The former page has film+foil caps, which I'd thus guesstimate to be superior. I don't have experience with these caps, though. A good rule of thumb is that if the capacitor is bigger and more expensive, it's "better"
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Old 13th September 2006, 02:02 PM   #19
niiico is offline niiico  France
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The 200mA fuse is only suggested for tests purposes.

But Jan admited it may blow even without input. He suggest 4 or 5A slow blow fuse for a normal usage.

I just put a 2A fuse because it's all I have today. I'll put a 4 or 5A fuse ASAP.
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Old 13th September 2006, 03:52 PM   #20
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What I mean:

Wall -> Fuse -> Toroid -> Amp6board

The fuse is therefore in untransformed 220V
In your amp it looks like it's so:

Wall -> Toroid -> Fuse -> Amp6board

Then the fuse is in the transformed 15V - tadaa!

I'm not sure that this is more or less correct, just that I believe that the fuse's value needs to be different. It should AFAIK be much smaller if the fuse is before the toroid.

Edit:
Wait, I thought some more about your answer and you probably understood me the first time The numbers from Jan seem to imply a secondary-side fuse. A 2A fuse like he suggests wouldn't make much sense in the 220V section :P Just thinking out loud
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