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]

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