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Old 1st April 2008, 12:06 AM   #21
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eugenio
eliot 100w guitar amp is fine though you have two choices one is buying the pcb or designing your own for you already have the pre amp from albert kreuzer i think its best you to build only an amp module nmos 200 is just one of your consideration,you have lots of design just search our forum if you dont want a quasi design you can use match pair output design such the improve dx amp so for me just build what ever design you choose then see the availability of the parts in your place,just build a verry nice and good p.s.u
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Old 1st April 2008, 05:00 AM   #22
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Default I'l go the Nmos200 way.

Thanks to all of you for helping me make a decision. I decided to go and build the Nmos200 using TO-220 devices as that is what I have available. But looking at Quasi's designs, the 10 Fet model looked tempting hehe, maybe on my next try.

Thanks to all of you!

Eugenio
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Old 1st April 2008, 12:50 PM   #23
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eugenio
good choice quasi claim that the design begin from siemens design and the saint of aksa second emotion that,quasi is good for guitar amp just like having a tube amp npn vs. npn tube and siemens we know a german engineering
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Old 1st April 2008, 01:55 PM   #24
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Thank you Engel for making me aware of this design, now I only need to look for a good PSU design, I'l go unregulated. Have you decided on your pre-amp design?
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Old 1st April 2008, 04:19 PM   #25
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Default i wonder

if mr Ras has anything to say about all this ....

we worked for a while together on a project and beyond that i thing he is really a very nice guy he was also very very helpfull all the time we worked together ....
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Old 1st April 2008, 04:23 PM   #26
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Default Re: i wonder

Quote:
Originally posted by sakis
if mr Ras has anything to say about all this ....

we worked for a while together on a project and beyond that i thing he is really a very nice guy he was also very very helpfull all the time we worked together ....
This why I didn't offend him. I don't know him.
I know kis designs and these amplifiers are bad designs in my opinion.
I can't belive his designs would performing well. Anyway he could be a nice man of course.
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Old 1st April 2008, 04:42 PM   #27
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I agree with Andy L Francis and peranders, this is not a good design. In particular,
the BD139 and BD140 are 80V transistors. Running the circuits on +/-55V, the transistors will see much more than this for signals close to full power, and will fail prematurely.

Fixed biasing with diodes is a lottery and can give under or over bias, depending on the particular batch of output devices. I expect the designer made one prototype, and that was OK, so he thought no more about it. Adjustable bias with a pot is a must for these output transistors.

To get anything like 300W you need more output device pairs. He claims 380W rms into 4 Ohms. Now a quick calculation shows that that means delivering peak voltages of +/- 55V, equal to his rail voltage without any drop across the transistors! These voltages require nearly 14A of current, but each transistor is only good for 8A maximum, taking them very close to saturation, and giving a vast voltage drop.

The designer may be a nice guy, but his circuit is simply incapable of delivering anything like the performance he claims, and will probably just blow the BD139/B140 up the first time a big signal arrives.
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Old 1st April 2008, 06:07 PM   #28
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Quote:
Originally posted by PigletsDad
I agree with Andy L Francis and peranders, this is not a good design. In particular,
the BD139 and BD140 are 80V transistors. Running the circuits on +/-55V, the transistors will see much more than this for signals close to full power, and will fail prematurely.

Fixed biasing with diodes is a lottery and can give under or over bias, depending on the particular batch of output devices. I expect the designer made one prototype, and that was OK, so he thought no more about it. Adjustable bias with a pot is a must for these output transistors.

To get anything like 300W you need more output device pairs. He claims 380W rms into 4 Ohms. Now a quick calculation shows that that means delivering peak voltages of +/- 55V, equal to his rail voltage without any drop across the transistors! These voltages require nearly 14A of current, but each transistor is only good for 8A maximum, taking them very close to saturation, and giving a vast voltage drop.

The designer may be a nice guy, but his circuit is simply incapable of delivering anything like the performance he claims, and will probably just blow the BD139/B140 up the first time a big signal arrives.
Thanks for the verification!
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Old 2nd April 2008, 07:45 AM   #29
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eugenio
my 2nd attemp is not succesful,i have two nmos 200 waiting for albert kreuzer bass pre amp,if only i can give you one in exchange of pre amp i'll give it to you,
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Old 2nd April 2008, 09:53 AM   #30
Netlist is offline Netlist  Belgium
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Gentleman,

Play the ball, not the man.
I've split off the offending and off topic posts.

/Hugo
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