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Old 27th August 2010, 11:17 AM   #11
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Quote:
Originally Posted by tryonziess View Post
Could you post a schematic of this amplifier please. Looks like a very professional pcb you have made. Nice work.

Tad
a square and symmetric pcb doesnt solve the problems ..it is very well known that in audio applications square corners and parallel lines will not perform properly ...proximity is also an issue ...

other than that yeap !!! it looks in order very square and very symmetric of course this doesnt mean that will work properly

regards sakis
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Old 27th August 2010, 11:25 AM   #12
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DjLeco, this is the picture I referred to in the previous message (fig.4).

By the way, what PCB software you use for the assembly?
Attached Images
File Type: jpg protectie_amplif.JPG (139.6 KB, 657 views)
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Old 27th August 2010, 11:36 AM   #13
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by DjLeco View Post
Protection will activate,............killing the differential INPUT stage.
Quote:
The protection works flawless, the amplifier will have separate section for limiter and muting.
please explain why killing = flawless.
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Last edited by AndrewT; 27th August 2010 at 11:40 AM.
 
Old 27th August 2010, 12:00 PM   #14
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I think he means killing the bias in the input stage. Not the parts. Doing that wouldn't be very productive.

So have you built an amplifier that does 500W into 8 ohms and 900W into 4 ohms like you suggest is needed to be "good"? It requires "a little" more extra bulk than getting so close to doubling in a 100W / 8 ohm amplifier...
 
Old 27th August 2010, 12:16 PM   #15
DjLeco is offline DjLeco  Romania
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In my case will shot down the differential outputs before go further in schematic.

Hope this explains better:

Click the image to open in full size.

donpetru, the pcb wasn't made by me, it was made by a friend of mine on CNC machine.

megajocke, as I said, the 500 and 800 watts power are estimative, I will give a test today to observe maximum power on 8 ohms speaker and another 8 ohm speaker, added parallel(4 ohms), also without speaker(no load) trying to calculate the damping factor(aproximately) too.

Keep close, Romanian time is 3:21 AM, and till 17:10 is "sleeping time" for my neighbours...

Last edited by DjLeco; 27th August 2010 at 12:24 PM.
 
Old 27th August 2010, 12:25 PM   #16
AndrewT is offline AndrewT  Scotland
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Originally Posted by DjLeco View Post
as I said, the 500 and 800 watts power are estimative, I will give a test today to observe maximum power on 8 ohms speaker and another 8 ohm speaker, added parallel(4 ohms), also without speaker(no load) to try to calculate the damping factor(aproximately) too.
don't use a reactive load.
Use a truly resistive test load.

I use a large bank of 5W wirewounds to produce 100W and 200W loads of 8r0+-0.5%
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Old 27th August 2010, 12:30 PM   #17
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by DjLeco View Post
In my case will shot down the differential outputs before go further in schematic.

Hope this explains better:

Click the image to open in full size.
Hi, as a mental exercise and to understand the consequences of protection, take a moment in time when the output is at -30V with +-35Vsupply rails and connect the output to ground with a 1r0 resistor.
Hold this snapshot and put in all your voltages and currents and see what the protection transistor has done to load up the VAS. Does this condition damage the VAS? Will the active (triggered) protection transistor and/or the damaged VAS cause consequential damage to the input stage?
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Last edited by AndrewT; 27th August 2010 at 12:33 PM.
 
Old 27th August 2010, 12:31 PM   #18
DjLeco is offline DjLeco  Romania
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Quote:
Originally Posted by AndrewT View Post
don't use a reactive load.
Use a truly resistive test load.

I use a large bank of 5W wirewounds to produce 100W and 200W loads of 8r0+-0.5%
I will make into speakers and into dummy load too, I have 2 pieces of 4 ohms/500Watts power, with low thermal derate, and low inductance too.

That means you don't saw it, because you don't have watched movies in mine first post...

Quote:
Originally Posted by AndrewT View Post
Hi, as a mental exercise and to understand the consequences of protection, take a moment in time when the output is at -30V with +-35Vsupply rails and connect the output to ground with a 1r0 resistor.
Hold this snapshot and put in all your volates and currents and see what the protection transistor has done to load up the VAS. Does this condition damage the VAS?
Whai is VAS?.

In my movies, IF ALL OF YOU, will have PATIENCE to watch it all from start till end, you will see SHORTCIRCUITS, DIRECTLY TO OUTPUT,AND UNDER 2 OHMS LOADING TOO with suplimentar dummy loading,during tests...

Protection works flawless, but must watch movies and see...

Last edited by DjLeco; 27th August 2010 at 12:36 PM.
 
Old 27th August 2010, 12:44 PM   #19
AndrewT is offline AndrewT  Scotland
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Sorry, VAS = Voltage Amplifier Stage in a Lin topology three stage amplifier.
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Old 27th August 2010, 01:07 PM   #20
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I think it was better if implemented protection from Mackie 1400 input stage. But who knows, maybe the next version of the amplifier!

The VAS is the transadmittance stage. At this stage, a word to say on performance amplifier it is determined solely by the Miller capacitor (called C_dom). All the voltage gain is provided by the VAS stage, which makes for easy compensation. The local NFB (negative feedback) working on the VAS through C_dom has an extremely valuable linearising effect.

Any amplifier operates in two regions: the LF, where open-loop gain is substantially constant, and HF, above the dominant-pole breakpoint, where the gain is decreasing. This regions must be controlled carefully by choosing proper values of capacitors and value NFB diagram audio amplifier. In the HF region, things are distinctly more difficult as regards distortion.

Nice day everyone.
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Last edited by donpetru; 27th August 2010 at 01:14 PM.
 

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