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Class D Switching Power Amplifiers and Power D/A conversion

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Old 17th August 2005, 04:14 PM   #1251
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Maybe i wrote the post in Russian too much, and noone can't understand it, but i'm sure that NTC+HeaterPTC for class D is really elegant three pin solution.
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Old 17th August 2005, 06:22 PM   #1252
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Default A question of starting

Hey guys,
How about something simple that will work? Use Chris's 20 ohm PTC but bypass it with a set of relay contacts. Have the relay driven from the rail voltage and set a resistance value in series with the coil so it don't close till say 80-90% of the rail voltage is present. This won’t require a heavy duty relay as when the contacts close most of the inrush is done. Seems this will solve the problem nicely.
Roger
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Old 17th August 2005, 07:35 PM   #1253
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Hi,

Yup that's the easy way, no point to using a thermistor though, simple power resistor would do.

Ivan I did have trouble understanding that I admit it.

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Chris
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Old 17th August 2005, 08:48 PM   #1254
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I keep reading about bleeders - however, the modules, when "off", still draw a bit power from the caps.

My 22.000uF's are at very low voltage after about 2 minutes. Isn't this enough?

It's a moot point for me actually, as i'm changing to the Hypex PS, which seems to have lots of resistors parallel over the rails, must be bleeders
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Old 17th August 2005, 11:53 PM   #1255
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I think the idea of using the positive temp co thermistor to heat the negative temp co one is interesting. I guess both are wired in parallel. Just how well it would turn out functionally is something to observe.
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Old 18th August 2005, 08:22 AM   #1256
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Quote:
Originally posted by subwo1
I think the idea of using the positive temp co thermistor to heat the negative temp co one is interesting. I guess both are wired in parallel. Just how well it would turn out functionally is something to observe.
It is necessary to wait for cooling NTC, before next turning on. 3-10 min i guess.
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Old 18th August 2005, 08:26 AM   #1257
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Now that I understand, t hank you!
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Old 18th August 2005, 02:18 PM   #1258
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I was talking about building my amp for pure stereo with volume control and a second line in straight to the amps for surround duties before...

In another thread I found this gem:

http://digitalanaloguediy.com/attenuator.html

Or this one:

http://www.hificollective.co.uk/comp...tiometers.html

Does this look like a nice solution for volume control? Also, what type is best for CD-player (cinch)->volume->UcD400AD? 10K type?

Is the quality identical?

Thanks,
Yves
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Old 18th August 2005, 02:33 PM   #1259
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Yves, not sure if thats a good idea or not as I am not qualified to say, however I am thinkning of doing something similar but using my S&B TX102 transformers as a volume control and housing them in the same box as the power amps.

What I dont know is if that would cause some sort of grounding hum type issues.

So far all the above exists as several boxes of parts !
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Old 18th August 2005, 03:05 PM   #1260
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Also see DACT and Goldpoint. Both do the same elma switches plus resistor things.

I have an 8 way DACT remote which is getting wired up in the next few days using an IR remote control gadget from Bent audio to help change volume without moving my fat **** for the couch...

Ed
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