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Old 15th March 2003, 04:38 PM   #11
Diode is offline Diode  United States
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Hey JasonL,

I really like Anthony's designs. I have had a real headache trying to find FET's and getting enough to match them is a real drag. The only company I have found that carries those FET's demands either a 100 piece minimum. Since I'm not independantly wealthy, I give up on FET's. I can't see much improvement using FET's. They are made as switches not for analog use. Using them in a different use produces heat. Fets are also known to be noisey. Maybe, for audio, they would be OK with proper filtering and rejection rate designs. I know that there are many designs out there and they work great. I've just had poor luck getting FET's or getting them at a reasonable price. For now, bipolars will do me fine. I am wanting to use TO-3P's as my heat sinks are flat and I have dealt with TO-3 packs and drilling for them for too many years. I want a change.

Thanks for the tip,

Chris
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Old 15th March 2003, 06:20 PM   #12
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rickpt, any specific reasons why you removed all decoupling caps? Did you leave Q24 and Q25 in place with all the associated short circuit protection components in place? And what output devices did you use? Does the amp sound really powerful being powered with +-90 volts? How is the sound quality?

Sorry for too many questions but I couldn't hold back my curiosity and I am sure many would like to know about these aspects too. Thanks in advance.
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Old 15th March 2003, 08:43 PM   #13
rickpt is offline rickpt  Portugal
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Youíre welcome Chris

Iím also not a fan of mosfet's and I donít think that driving them with high source impedance is a good design practice but so many designers do just that...

Parallel caps create resonances in the power supply.

I used the mj15003/4.

This amp is inside a Trace Elliot bass power amplifier so I only have one channel, this one replaces the old mosfet amplifier...

Yes, I did keep the protection circuitry because this amp is intended for P.A. , if it were meant to HI-FI I would remove that, but in that case I wouldnít build such a big power amp. 50\100 watts are enough for me and in my avatar, you can see my speakers...

About sound quality I have no remarks about it... I donít like subjective analysis...

Best regards

Ricardo
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Old 15th March 2003, 10:11 PM   #14
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Unhappy hugo boss amp

Sadly, the rudimentary and vastly inefficient short circuit protection will not allow loads of less than five ohms, (resistive), to be driven to the rated supply rails by this amp......

Moreover, the absence of voltage-sensing with this circuit means that an overly-reactive load would probably destroy the output devices anyway....

rickpt....send me e-mail, and i'll send you more info...cheers!
mike
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Old 15th March 2003, 10:35 PM   #15
rickpt is offline rickpt  Portugal
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I mike

I dont have a lot of experience with this type of protection circuits as i dont use them in my amplifiers so this information will be most welcome... time to learn know

Thanks in advance

Best regards

Ricardo
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Old 15th March 2003, 11:36 PM   #16
rickpt is offline rickpt  Portugal
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Hi mike

I already send you a mail...

an additional mod that I forget to mention to Chris... as you probably know zener are very noisy, so I did replace the zener ZD1 by two red led's in series... five 1N4148 in series would be even better

Best regards

Ricardo
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Old 15th March 2003, 11:54 PM   #17
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Smile hi rickpt..

...check your e-mail....file attached...cheers.
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Old 16th March 2003, 12:07 AM   #18
rickpt is offline rickpt  Portugal
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Email received

thanks mike

cheers
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Old 16th March 2003, 11:17 AM   #19
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Default mods?

rickpt,

did you modifiy the protection circuit of the hugo 500w amp? can you please post it?

i'm trying to choose between the 500w amp and the leach superamp for my project. however, i'm still trying to check if the devices used are available in my country.

best regards,

jojo
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Old 16th March 2003, 04:25 PM   #20
Diode is offline Diode  United States
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Hey again,

Thanks for the update on the Zener. I have heard the same thing. I have also heard the same or worse about LED's. If I do the 5X 1N4148's in series, do I need the droping resistor? How should I hook it up. Also, you refered to oscillation. This is probably my weakest area of knowledge. How can I prevent this from happening? Did you place the output transistors in the traditional manner..... all PNP's on one side with the bias transistor in the middle and the NPN's on the other side of that?
Thanks for the update.

Chris
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