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Old 20th April 2012, 01:35 PM   #1141
Junie is offline Junie  Philippines
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it's just a normal 10uf/100V polarized caps korean made(SAMWHA) connected back to back.
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Old 20th April 2012, 02:27 PM   #1142
a.wayne is offline a.wayne  United States
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Maybe I'm missing something , why is the input caps needed if you don't have any DC on the inputs ....
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Old 20th April 2012, 02:35 PM   #1143
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Originally Posted by a.wayne View Post
... you don't have any DC on the inputs ....
Are you sure?

It's to remove that uncertainty, DC is baaaad....
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Old 20th April 2012, 02:36 PM   #1144
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Junie, what pole is facing outwards, pos or neg?
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Old 20th April 2012, 03:08 PM   #1145
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It's interresting to check the input caps and resistors...

If I understand correctly, the components circled in RED serves as a high-pass, which in this case gives a f0 of 3Hz, and the ones in BLUE act as a low-pass in this case giving a f0 of... 3.29Mhz? Ain't that low pass rather high?

For that low-pass, can we change the value of the capacitor to something like 6.8nF, or increase the resistor value to 6.8K, or a a modification to both (resistor let's say 4.7K and cap to 330pF)? This would give a f0 of ~106-102Khz, which would be more suitable for that application.

Martin.
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Old 20th April 2012, 04:11 PM   #1146
a.wayne is offline a.wayne  United States
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Originally Posted by canonnica View Post
Are you sure?

It's to remove that uncertainty, DC is baaaad....
Yes, but you would have to have really bad source to have DC and it won't be as bad as listening to that input. Cap...
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Old 20th April 2012, 04:13 PM   #1147
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by canonnica View Post
It's interresting to check the input caps and resistors...

If I understand correctly, the components circled in RED serves as a high-pass, which in this case gives a f0 of 3Hz, and the ones in BLUE act as a low-pass in this case giving a f0 of... 3.29Mhz? Ain't that low pass rather high?

For that low-pass, can we change the value of the capacitor to something like 6.8nF, or increase the resistor value to 6.8K, or a a modification to both (resistor let's say 4.7K and cap to 330pF)? This would give a f0 of ~106-102Khz, which would be more suitable for that application.

Martin.

You may want to remove the output inductor if you are going for more bandwidth and speed ...
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Old 20th April 2012, 04:26 PM   #1148
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Gonna go with less in fact... 3290KHz vs 106KHz.
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Old 20th April 2012, 04:43 PM   #1149
Junie is offline Junie  Philippines
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Originally Posted by canonnica View Post
Junie, what pole is facing outwards, pos or neg?

Mart I did open my amp again
Negative connected to each other.
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Old 20th April 2012, 04:48 PM   #1150
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by canonnica View Post
Ain't that low pass rather high?
As I said, Carlos never designed any of the DX range of amplifiers to what amplifier designers would refer to as "normal" methods. He guessed and listened on whatever speakers he had to hand.

But he is not alone in this guessing and listening. There are other that do it. Eventually one stumbles upon a guess that works. Then the next stage is after a few amplifiers have been tweaked one recognises a pattern and starts to adopt that as an "empirical" design method.

Look at how many times, over the past 6 or 7 years, that the DX range has been modified and each version has been guaranteed by the designer to be the best sounding amplifier ever.

I would suggest you try a range of filter time constants to find the highest RC that lets you hear all the treble you need to hear. That range of RC time constants is likely to be from 330ns to 1.5us, but don't exclude the possibility that your preference lies outside that suggested range.

220r + 220pF gives RC ~= 48ns. I seriously doubt that was the highest RC that did not cut the treble.

Once you have found the low pass filter that works for you and your equipment it is likely that RC will suit all your power amplifiers. It may be worth then reviewing any other you have to see how big you can make your RC and still get all the treble you could ever want.
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Last edited by AndrewT; 20th April 2012 at 05:01 PM.
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