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Old 12th December 2010, 01:10 AM   #11
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Quote:
Originally Posted by AndrewT View Post
generally no.
Quote:

ClsA.png

Quote:

ClsA.2.png

From:

High Performance Audio Power Amplifiers
- Ben Duncan, A.M.I.O.A., A.M.A.E.S., M.C.C.S
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Old 12th December 2010, 01:36 AM   #12
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That first ref is wrong.

The second ref looks about right. I will re-read it.
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Old 12th December 2010, 01:37 AM   #13
AndrewT is offline AndrewT  Scotland
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The second ref is also wrong.

Ben Duncan is usually a very reliable source. I don't know why he could have made those mistakes.
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Old 12th December 2010, 01:46 AM   #14
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Quote:
Originally Posted by AndrewT View Post
The second ref is also wrong.

Ben Duncan is usually a very reliable source. I don't know why he could have made those mistakes.
Gee Andrew, I think I'm going to take HIS word for it. After all, he has all those letters after his name and you only have one after yours - 'T'

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Old 12th December 2010, 01:19 PM   #15
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Back to the topic:


Quote:
Originally Posted by brucegseidner View Post
This can only mean I don't understand how they work and need to be pointed to a schematic which has the transformer-bridge-regulator ahead of the capacitors and is set up to work correctly reducing the voltage to the capacitors from 35VDC to 24VDC.
You want something like this:

HCreg.png

2 or more pass transistors, depending on the load.
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Old 14th December 2010, 03:24 AM   #16
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NOW THAT IS HELPFUL.

There are application sheets that I have been finding that show this circuit, but they presume one can derive the values.

It seems that there is much less for the capacitor bank of the F5 amp to have to smooth and that other than some cost of components and time that there would be no downside to having regulated DC going into the capacitors which become more of a cistern/reserve of power than a filter for ripple.

Is there some performance penalty for an amp like the F5 using regulated DC ahead of the "filter"capacitor?

I have had friends who found ginormous isolation transformers that they used to branch off the household electrical system and were dedicated to powering the audio equipment. This was a bit overboard but while it might be lost on the ear, I can remember the mutual grins and high fives after muscling a refrigerator sized transformer into the basement of a mate. I really miss those ham fests that sported military and industrial surplus.

Thanks again.

Bruce
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Old 14th December 2010, 11:01 AM   #17
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by MJL21193 View Post
You want something like this:

Attachment 200576
looks simple and looks effective.
Compare this to Pass' Zener Follower regulated power supply.
The LM317 replaces the Zener. VERY similar but improved voltage with changing current demand.

MJL,
does the lm317 need to be the K version?
Could the T version with a 1.5A limit be sufficient?
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Old 14th December 2010, 02:40 PM   #18
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If this circuit only sees the demand coming from a largish, bank of filter capacitors, that is, it sits on the other side of the circuit, does this pose a problem for an amplifier like the F5?

I know that this has been a concern for other types of amplifier circuits.
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Old 14th December 2010, 03:02 PM   #19
AndrewT is offline AndrewT  Scotland
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the regulated power supply sees both the capacitor bank and the F5 as it's load.
The F5//Caps is a complex impedance and the regulator must be capable of supplying that complex demand.

I would be very tempted to look at some type of current limiter to prevent the caps being charged too quickly. Electrolytics do not survive high V/us very well.
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Old 14th December 2010, 04:48 PM   #20
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Quote:
Originally Posted by AndrewT View Post
MJL,
does the lm317 need to be the K version?
Could the T version with a 1.5A limit be sufficient?
In this scheme, the LM317 only provides base current - all of the 'heavy lifting' is done by the pass transistors.
To produce the schematic, I just grabbed an LM317 from the list - it isn't important in regards to current capacity which type it is.

Quote:
Originally Posted by brucegseidner View Post
If this circuit only sees the demand coming from a largish, bank of filter capacitors, that is, it sits on the other side of the circuit, does this pose a problem for an amplifier like the F5?

I know that this has been a concern for other types of amplifier circuits.
I think I would split the total capacitance, putting half before the reg and half after.
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