500W amp

[Diode]

This amplifier has been posted on this forum but not much said about it. Does anyone know anything about it? Is it a good design or does it have problems? Does it need extra things? Deleted things? Any help would be appreciated as I'm considering building this amp.

Thanks in advance,

Chris

 

[JBL]

Wich 500 wat amps could you link use to a schematics.

 

[Diode]

Sorry, My bad.......

HTTP:// Hugobross.com/500W.htm

Chris

 

[JojoD818]

schematic

Diode,

Hi, I am also interested in a 500w amp, however, I can't open/see the schematic you are referring to.

Jojo

 

[hugobross]

hmmm, seems he has read a thread I came with a long time ago.

link to thread

link to schematic: http://hugobross.tripod.com/500W.htm

best regards,

HB.

 

[rickpt]

I built an amplifier based on that schematic for my brother bass guitar amplifier...
I simply did some mods mainly on the output stage and also changed the input stage transistors
Measures quite well and sound good too...

I’m using a +/- 90volts supply

Regards

 

[Diode]

Can you please be more spacific as to what changes you made? Do you have a drawing or can you post it? What is your bias current or do you measure bias voltage somewhere?

I'm looking at using 2SA1943 and 2SC5200 for the output devices.... Is this a good match for this amp?

Thanks,
Chris

 

[rickpt]

Hi Chris

I'm sorry but I don’t have a schematic
But here are the mods I made...

Changed the input transistors to:
Q1,Q2,Q3= 2SA970
Q4,Q5,Q7=2sc2240

I have put a 10mf electrolytic cap in parallel whit D1, D2 and one in parallel whit ZD1

also the output zobel network is very wired... so I removed the inductor, the resistor and the cap and I have put there a normal zobel consisting of a 10 ohm resistor and a 100nf cap and no inductor... if you remove the inductor, you will have to be sure that the amp is stable on reactive loads...

The output now is a triple follower with a single resistor on the emitters of the driver transistor...


Removed the bypass caps, even the electrolytic ones...

And that’s about it...

I’ve set the bias to about 100ma

I only see one problem with that type of power transistors; they are much faster than the regular ones so you may have problems with oscillation, so a scope is mandatory...

Regards

Ricardo

Ps: the 820pf at the input is quit big... put there a 100pf cap, but them again you will have to be sure that the amp will remain stable...

 

[jleaman]

what about anthony E-holtons av800's

 

[Diode]

Hey Ricardo,

Thanks so much for the detailed reply. In my line of work, details are very much appreciated.

Thank you,

Chris

 

[Diode]

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

 

[Samuel Jayaraj]

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.

 

[rickpt]

You’re welcome Chris

I’m also not a fan of mosfet's and I don’t 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 wouldn’t 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 don’t like subjective analysis...

Best regards

Ricardo

 

[mikek]

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

 

[rickpt]

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

 

[rickpt]

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

 

[mikek]

hi rickpt..

...check your e-mail....file attached...cheers.

 

[rickpt]

Email received

thanks mike

cheers

 

[JojoD818]

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

 

[Diode]

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