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Old 4th December 2006, 12:08 PM   #21
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I should pay a little more attention to what I am drawing...
Forget the above, this is how it works.
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Old 4th December 2006, 12:12 PM   #22
lineup is offline lineup  Sweden
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Quote:
Originally posted by HBarske
Simplicity is not an issue. Far better than 317/337 alone.
Yes, I buy that, HBarske.

Looks better than only LM317, LM337,
but still very simple and easy to build.
For anyone.


You know my tutor, Nelson Pass,
whenever he uses a voltage regulator for his amplifiers,
he prefers shunt before series regulation.
( LM317/337 are series regulators, while TL431 is a shunt diode )

And so do I.
This is why I love the many possibilities by using TL431
and sometimes in comb with bypass transistors
if need more current/power output.


A good temp stable little device with 3 pins in TO92 ( or in SO8 )
that can give you adjustable voltage of 2.5 - 36 Volt.
Isn't this fantastic!


lineup
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Old 4th December 2006, 01:41 PM   #23
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Just a quick shot to see how this might turn out.
We have:
- two channels
- board size: 109 x 63 mm
- seperate regs as shown above for each channel
- added pass transistors to the tl431 for more dissipation

This is how it looks right now:
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Old 4th December 2006, 04:37 PM   #24
karvid is offline karvid  Sweden
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Quote:
Originally posted by lineup


Yes, I buy that, HBarske.

Looks better than only LM317, LM337,
but still very simple and easy to build.
For anyone.


You know my tutor, Nelson Pass,
whenever he uses a voltage regulator for his amplifiers,
he prefers shunt before series regulation.
( LM317/337 are series regulators, while TL431 is a shunt diode )

And so do I.
This is why I love the many possibilities by using TL431
and sometimes in comb with bypass transistors
if need more current/power output.


A good temp stable little device with 3 pins in TO92 ( or in SO8 )
that can give you adjustable voltage of 2.5 - 36 Volt.
Isn't this fantastic!


lineup
Very interesting! Is it any good compared to a good serie regulatator or is there an shunt regulator that is easy to build with better performance? Many times the size is an issue when replacing old LM78XX in exicitning cuircuit! Meaning they must fit into exicting player...


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Old 4th December 2006, 04:52 PM   #25
lineup is offline lineup  Sweden
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Quote:
Originally posted by karvid

Very interesting! Is it any good compared to a good serie regulatator or is there an shunt regulator that is easy to build with better performance? Many times the size is an issue when replacing old LM78XX in exicitning cuircuit! Meaning they must fit into exicting player...
The one thing you should know
is that using shunt, like TL431
as the only regulation, like in HBarske circuit,
.. is that it, like using normal zener diodes,
is NOT suitable when you need very much current
and the drawn current can variate a lot.

But in this case, the RIAA, it works in Class A
at only like 6 mA per channel.

And as most know, a true Class A draws same amount of current
whatever power or voltage output.
It is 100% constant current taken via and from the regulator.

This makes a true shunt, like TL431 be perfect for regulate this BC550C phono amplifier.


For higher currents and in normal Class AB amplifiers or in chip Op-Amp amps
where current consumption variates depending of how much power output
TL431 is best used with a bypass transistor, to amplify currents.

lineup
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Old 4th December 2006, 05:13 PM   #26
lineup is offline lineup  Sweden
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Default RIAA phono riaa preamplifier MM BC550C BC560C Version 2

Quote:
Originally posted by HBarske
Just a quick shot to see how this might turn out.
We have:
- two channels
- board size: 109 x 63 mm
- seperate regs as shown above for each channel
- added pass transistors to the tl431 for more dissipation

This is how it looks right now:
Great layout!
As far as I can see.
It is not the most simple circuit to design a PCB for.
With all them transistors .....

Now, this was Version 1, from my first post.

If you could update to my Version 2.
In this post:
http://www.diyaudio.com/forums/showt...54#post1072254

... and as you see from my comments,
has been a new feature with two 1N4148 diodes
and one small Multi Turn trim potentiometer
for offset adjustment.

And if you read my comments further R17 has been removed.
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Old 4th December 2006, 05:25 PM   #27
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Okay, I will add those modifications.

Some PSU dimensioning thoughts:

The amplifier is normally rum at +/- 15 Volts, IIRC.
Let's assume the output stage is run at, as you said, 5 mA. So I think we won't have more than 10 mA overall current consumption.

Let's further assume we drive that thing from 2 x 18 V transformer secondaries, then we would have perhaps 22 V unregulated DC voltage.

Let's say we set the CCS to 30 mA, that's three times the maximum load current, certainly enough headroom. The LM 317 drops 1,25 V on the setting resistor, so we need 41,6 R - let's say 39 R, easier to get. This gives us a constant current of 32 mA and a dissipation of 40 mW, no problem for a small resistor.

Under worst case condition (output shorted, likely to happen at turn on) the LM317 dissipates 22 V x 32 mA = 0,7 W. A bit too much for a TO92 device, that's why I went for the TO220 type.

Worst case condidition for the shunt reg is an unloaded output, because it has to dissipate all the energy from the CCS. So maximum energy to get rid of is everything the CCS can deliver, somewhat less than the 0,7 W from above (less due to the voltage losses on the CCS). Also a bit hard for a TO92 device, that's why I added the power transistor to the TL431.

Transformer has to deliver 2 x 18 V @ 32 mA, what sums up to a little more than 1 VA, 2 or 3 VA with some safety margin. More is not useful due to the constant current consumption of the circuit.

Might result in decent and dirt cheap solution.
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Old 4th December 2006, 06:02 PM   #28
lineup is offline lineup  Sweden
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Quote:
Originally posted by HBarske
Okay, I will add those modifications.

Some PSU dimensioning thoughts:

The amplifier is normally rum at +/- 15 Volts, IIRC.
Let's assume the output stage is run at, as you said, 5 mA. So I think we won't have more than 10 mA overall current consumption.

Let's further assume we drive that thing from 2 x 18 V transformer secondaries, then we would have perhaps 22 V unregulated DC voltage.

Let's say we set the CCS to 30 mA, that's three times the maximum load current, certainly enough headroom. The LM 317 drops 1,25 V on the setting resistor, so we need 41,6 R - let's say 39 R, easier to get. This gives us a constant current of 32 mA and a dissipation of 40 mW, no problem for a small resistor.

Under worst case condition (output shorted, likely to happen at turn on) the LM317 dissipates 22 V x 32 mA = 0,7 W. A bit too much for a TO92 device, that's why I went for the TO220 type.

Worst case condidition for the shunt reg is an unloaded output, because it has to dissipate all the energy from the CCS. So maximum energy to get rid of is everything the CCS can deliver, somewhat less than the 0,7 W from above (less due to the voltage losses on the CCS). Also a bit hard for a TO92 device, that's why I added the power transistor to the TL431.

Transformer has to deliver 2 x 18 V @ 32 mA, what sums up to a little more than 1 VA, 2 or 3 VA with some safety margin. More is not useful due to the constant current consumption of the circuit.

Might result in decent and dirt cheap solution.

Yes, we use TO220 LM317T,
they are easier to find, also, than LM317L.

About transformer.
Earlier I told, we need only like 0.100A trafo,
to supply BOTH left and right channel.

But when consumption now will be 2x32 mA ( two LM317 and two LM337, for stereo )
I will recommend a transformer with 0.200 A, minimum.

2x18VAC and 0.2A gives transformer rating should be >= 7.2 VA.
One 10 VA, 2x18 would be easy to find and be perfect here, in my opinion.
Does not matter if is small toroid trafo or a normal small square one.
----------------

This transformer would not drop much from 1.4 x 18 volt.
Will deliver like +- 25 VDC unregulated.
Depending of transformer brand this may actually be ~24-27 VDC.
----------------


You say:
Worst case condition for the TL431 shunt diode is an unloaded output,
because it has to dissipate all the energy from the CCS.


True, but this only if using regulator WITHOUT any amplifier connected to supply.
But 5-6 mA less is nothing, giving still 26-27 mA in TL431.


OK, people do things we we do not expect.
This is why software debugging is so important, having normal people as test users.
They can try to enter whatever into a <FORM>.
Things that the designer is not 'stupid enough' to try.


So, we will design to make supply survive worst case, without load connected.

Very good working, HBarske!
Thanks very much.

lineup
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Old 4th December 2006, 06:24 PM   #29
AndrewT is offline AndrewT  Scotland
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Hi Lineup,
Quote:
And as most know, a true Class A draws same amount of current whatever power or voltage output. It is 100% constant current taken via and from the regulator
totally wrong.

There are a number of ClassA topologies.
All push pull and all but one of the single-ended modulate the supply rail currents.

The one exception that truly draws constant current is utilised very rarely.

Please do not repeat this tripe again. Some folk might think it's true.
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Old 4th December 2006, 06:40 PM   #30
lineup is offline lineup  Sweden
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Thumbs down reply to critics of one detail in one post - slightly off topic here

Quote:
Originally posted by AndrewT
Hi Lineup, totally wrong.

There are a number of Class A topologies.
All push pull and all but one of the single-ended modulate the supply rail currents.

The one exception that truly draws constant current is utilised very rarely.

Please do not repeat this tripe again. Some folk might think it's true.

I repeat whatever I like, for your information.
I have seen more stupid postings than this
even from you, AndrewT.

What the supply see when feeding a true Class A,
is a constant load.
Even if it is, like you say, modulated by eventual output.
Capacitor stores energy within amplifier and after the supply
this reduces some of the modulation seen from power supply.


Still this fact remain valid, although modulated by AndrewT, very correctly, thanks:

The average current drawn from any circuit called Class A, in the very sense of this expression,
is CONSTANT CURRENT.

If it ain't a very constant loading for Power supply - it ain't Class A.
Simply.


And this was what I wanted to tell about.
If you read me right.



No regards, this time
to this slightly off topic post with a slightly unpleasant tone

sincerely december 2006
Lineup Audio Lab
smart but simple amplifier solutions

------------------------------------------
If you like to contribute here, in my topic, AndrewT
you are very welcome as anyone else
if you can add something useful for us
which remains to see .......
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