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Old 9th June 2011, 05:04 PM   #71
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by wakibaki View Post
Attachment 225174

Attachment 225180

Attachment 225181



w

If you see anything else don't hesitate to point it out.
Wakibaki,

May I have your permission to post your PCB files on another forum?

I would acknowledge your authorship, of course.
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Old 9th June 2011, 05:13 PM   #72
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Getting populated:

http://dl.dropbox.com/u/5430178/proj...ting%20PCB.jpg


I am using the 2N3019, and BC546/556 (C). I used 1N5822 and BAT85 for the schottky's. The outputs will be MJ802. The drivers 2SB649.

Just have to find some of these capacitors.
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Old 14th June 2011, 05:41 PM   #73
Elvee is offline Elvee  Belgium
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Some news:

I have tested (in sim) the idea of replacing the zeners with a resistor.

The result is disappointing: the change in linearity is insignificant, and for the worst.
It looked like a good idea in theory, but it doesn't deliver, and if there is no improvement in sim it's probably not worth testing in reality.
In addition, it would probably upset the compensation and degrade the dynamic performances.
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Old 15th June 2011, 01:02 PM   #74
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Elvee, what about these transistors? I have no TO-3 heatsinks, and I feel that I probably couldn't make the best mounting for TO-3 on a regular heatsink. These transistors would make it that much easier: MJW21196

https://www.onsemi.com/pub/Collateral/MJW21195-D.PDF

fT=4MHz. Right on the line according to your guide. Would it work with C12=180+pF and C11 not installed? I will probably just have to try it...
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Old 15th June 2011, 07:44 PM   #75
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by odysseybmx414 View Post
Elvee, what about these transistors? I have no TO-3 heatsinks, and I feel that I probably couldn't make the best mounting for TO-3 on a regular heatsink. These transistors would make it that much easier: MJW21196

https://www.onsemi.com/pub/Collateral/MJW21195-D.PDF

fT=4MHz. Right on the line according to your guide. Would it work with C12=180+pF and C11 not installed? I will probably just have to try it...
It should be OK.

Of course, since this exact type of transistor has never been tested in any of the prototypes, and the layout is different, I cannot give a 100% guarantee.

Never take anything for granted.

To be on the safe side, I would recommend you first try with C11 installed, and when you're satisfied everything works as expected (which it should), you can begin to tweak, make comparisons with/without the cap, and decide for yourself what's the best option.

When you install C11 and it's not needed, there is an infinitesimal degradation of the transient performances, but it is really very very small: the oscilloscope screenshots and the measurement have been made with C11 in place, and it was not really needed, since 2N3055's were used.
You can see for yourself that it still very good, and implementing the capacitor buys you peace of mind.

Anyway, even if oscillations do break out, they should be of a small amplitude and very high frequency, and pose no threat to tweeters or the amplifier itself.

With the MJW21196's, you will have an incredibly robust amplifier, even without protection: their SOAR is quite impressive
During the tests, I had some "accidents", but never succeeded in blowing the OP transistors.
With the MJW's, it will be positively bullet-proof.
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Old 15th June 2011, 08:13 PM   #76
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Quote:
Originally Posted by Elvee View Post
It should be OK.

Of course, since this exact type of transistor has never been tested in any of the prototypes, and the layout is different, I cannot give a 100% guarantee.

Never take anything for granted.

To be on the safe side, I would recommend you first try with C11 installed, and when you're satisfied everything works as expected (which it should), you can begin to tweak, make comparisons with/without the cap, and decide for yourself what's the best option.

When you install C11 and it's not needed, there is an infinitesimal degradation of the transient performances, but it is really very very small: the oscilloscope screenshots and the measurement have been made with C11 in place, and it was not really needed, since 2N3055's were used.
You can see for yourself that it still very good, and implementing the capacitor buys you peace of mind.

Anyway, even if oscillations do break out, they should be of a small amplitude and very high frequency, and pose no threat to tweeters or the amplifier itself.

With the MJW21196's, you will have an incredibly robust amplifier, even without protection: their SOAR is quite impressive
During the tests, I had some "accidents", but never succeeded in blowing the OP transistors.
With the MJW's, it will be positively bullet-proof.
Good to hear! Should have them soon then (hopefully).
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Old 16th June 2011, 11:05 PM   #77
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What's the minimum input power?

I want to run two channels on a 160VA traffo, don't need lots of power.
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Old 16th June 2011, 11:09 PM   #78
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Originally Posted by raypalmer View Post
What's the minimum input power?

I want to run two channels on a 160VA traffo, don't need lots of power.
I also play to use a 160va trafo. I feel it will be sufficient.
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Old 16th June 2011, 11:15 PM   #79
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Originally Posted by odysseybmx414 View Post
I also play to use a 160va trafo. I feel it will be sufficient.
Are you going to regulate it down at all?
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Old 17th June 2011, 12:27 AM   #80
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Are you going to regulate it down at all?
I have some high current regulator pcbs I made a while ago. Just simple 317/337 + pass transistors. The trafo will put out about 36VDC before regulation to 25(+-). Speakers will be 8 ohms only as well. Amp will only see light/medium duty for mostly movies in the bedroom. They were used on LM3886 for over a year now. They are adjustable also. Now that I think about it the trafo may be 200VA. I know the 11 volt reg drop isn't optimal, but the pass transistors work out. I could always run a bit higher than the 25 I think.
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