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Old 2nd May 2013, 05:11 PM   #21
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by Tony View Post
classB (or is it calssB2 says JMFahey) is fine for PA duities, at high volume levels, you can not distinguish it from a classAB.....
You're right !!!
Why bias at all?

Imagine all the money saved not fitting those expensive parts
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Old 3rd May 2013, 10:28 AM   #22
FoMoCo is offline FoMoCo  United States
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Quote:
Originally Posted by JMFahey View Post
You're right !!!
Why bias at all?
Imagine all the money saved not fitting those expensive parts
One of my former employer made linear amplifiers to drive motors. Their output stage was very similar. It was straight class B.

As for using this for PA duty... Sure, why not? I was thinking that a subwoofer amp was the only place that the high distortion at low output would be masked, but PA is another application. But, I don't understand why one wouldn't just build a better amp. There are better designs that are no more complex.
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Old 3rd May 2013, 10:32 AM   #23
JMFahey is offline JMFahey  Argentina
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Yes, that's the point.
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Old 3rd May 2013, 03:46 PM   #24
rmyauck is offline rmyauck  Canada
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Are Sanken 2SA1216/2SC2922 good outputs? What's a good circuit as I have some?

Thanks!

Last edited by rmyauck; 3rd May 2013 at 04:06 PM.
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Old 3rd May 2013, 03:50 PM   #25
AndrewT is offline AndrewT  Scotland
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Many ClassAB amplifier projects on this Forum can use the Sanken devices.
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regards Andrew T.
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Old 3rd May 2013, 04:07 PM   #26
rmyauck is offline rmyauck  Canada
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Thanks Andrew!
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Old 3rd May 2013, 04:39 PM   #27
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Talking Who told 8ohm?

Quote:
Originally Posted by JMFahey View Post
That "Yiroshi" amplifier will never never never never provide 200W into 8 ohms.
Besides being horribly underbiased : 2 diodes + 10 ohms to forward bias 4 (four) BE junctions?
And unstable (no Zobel network) to the point of self destroying with any real world speaker load at the end of any real world speaker cable.
Maybe that's why those 470pF caps had to be added, but that's not the right place or value.
Did I mention no short protection?

Just because the link was provided, I checked other "Yiroshi" schematics at Scribd.
Ouch !!!
is clear that no zobel network is a matter that you add what I do not think it is the other world.

link1:

Amplificador Monofonico Modular de 200W + PCB

link 2:
Amplificador Monofonico Modular de 200W + PCB - Página 8
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Old 3rd May 2013, 08:57 PM   #28
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by SERGIODS View Post
Who told 8ohm?
The original poster did
Look what he wrote:

Quote:
Is 200W possible with simple topology ?
I was wondering what Possibilities are possible with this simple topology?
Maybe VAS not good enough?
Triple Output should not draw to much current
Load is 8R
There you have it, he specifically asked for a 200W/8r amplifier which is impossible with +/-50V rails.

Quote:
is clear that no zobel network is a matter that you add what I do not think it is the other world.
Pity you do not think it important, this does not speak well about your design.
Fact is that amplifiers which work properly with resistive load a few inches away burst in uncontrolled oscillation with real speakers some meters away.

Well, I must not blame you for the errors , which were noticed also by other Forum Members.

I read the Links you so kindly posted, and saw you claim there that you did not actually design these amplifiers but copied (with *very* slight modifications) the Colombian "Zener" amplifiers, posted in
CONSTRUYA SU VIDEOROCKOLA.COM > Toda la información acerca de como construir una video rockola, sus aspectos técnicos, legales y comerciales.

one example of which is:

Click the image to open in full size.

So *now* I know why you use output transistors in Class B , add 470pF to drivers, etc. ..... although they did use a Zobel network

Not surprising, they have actually built a few of them

And after a few times , they must have added it.

By the way, they use +/-75V rails, so the power they claim is *much* more credible.

EDIT: now that I look at that schematic again: +/-75V Rails into 4 ohms with only 4 output transistors?
Weeeellll, ..... maybe ....

Last edited by JMFahey; 3rd May 2013 at 09:03 PM.
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Old 6th May 2013, 03:40 AM   #29
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Quote:
Originally Posted by JMFahey View Post
The original poster did
Look what he wrote:


There you have it, he specifically asked for a 200W/8r amplifier which is impossible with +/-50V rails.


Pity you do not think it important, this does not speak well about your design.
Fact is that amplifiers which work properly with resistive load a few inches away burst in uncontrolled oscillation with real speakers some meters away.



Well, I must not blame you for the errors , which were noticed also by other Forum Members.

I read the Links you so kindly posted, and saw you claim there that you did not actually design these amplifiers but copied (with *very* slight modifications) the Colombian "Zener" amplifiers, posted in
CONSTRUYA SU VIDEOROCKOLA.COM > Toda la información acerca de como construir una video rockola, sus aspectos técnicos, legales y comerciales.

one example of which is:

Click the image to open in full size.

So *now* I know why you use output transistors in Class B , add 470pF to drivers, etc. ..... although they did use a Zobel network

Not surprising, they have actually built a few of them

And after a few times , they must have added it.

By the way, they use +/-75V rails, so the power they claim is *much* more credible.

EDIT: now that I look at that schematic again: +/-75V Rails into 4 ohms with only 4 output transistors?
Weeeellll, ..... maybe ....
1. - I did not wrote
2.-I said that is a matter that is added (zobel network)

Not in the sense that it is not indispensable.
* if it is not on the main pcb. (so that if you add if or if)


3.-I do not copy anything. that this was YIROSHI redesign.
As I shared only repeat that their work is excellent.
On the other hand YIROSHI is also Colombian countryman video creator build jukebox.
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