Initial Project: 300W Power Amp

[bharfhy]

I found this on Google. power amp 300W
I am very interested in riding. I already started the scheme in KiCad
As I am inexperienced in sound I'd like information from an expert on the quality of the project.
It is worthwhile to mount it or recommend me a better design?

[Iain McNeill]

This is definitely not a first time project. Learning on something that has such power capability is a recipe for electrocution or house fire.

I would recommend something much more simple. Check out Nelson Pass' designs in his forum here or at his website. Also, look at the "chip amp" designs which can sound just as good (not as loud) but are more forgiving for beginners.

[Aldotin]

That's the ETI-466 amplifier (designed by Barry Wilkinson).
This link may help:
ETI-466 Amplifier Technical Review

[GK]

I've still got all the original magazines featuring these projects. That ETI design wasn't noted for its reliability. The CFP-like output stage with voltage gain was prone to oscillation and smoke. Cloning the design today with modern versions/makes of the same power output devices may even be risky due to the fact that the fT's are likely to be higher than they were back then.

The 300W Playmaster of the same vintage was a much better and stable design:

Electronics Australia Playmaster 300, 300W Amplifier Module

[Aldotin]

Looks like a nice solid design from the 70's era!
For public address purposes it's OK, but as Hi-Fi/audiophile amplifier it's outdated now...

Anyway the Q14-Q16 driver pair seems to be underrated. I'd choose a stronger driver pair - for example the MJE15030/31 pair from Onsemi would do the job!

Originally Posted by GK

I've still got all the original magazines featuring these projects. That ETI design wasn't noted for its reliability. The CFP-like output stage with voltage gain was prone to oscillation and smoke. Cloning the design today with modern versions/makes of the same power output devices may even be risky due to the fact that the fT's are likely to be higher than they were back then.

The 300W Playmaster of the same vintage was a much better and stable design:

Electronics Australia Playmaster 300, 300W Amplifier Module

[wahab]

Originally Posted by Aldotin

Looks like a nice solid design from the 70's era!
For public address purposes it's OK, but as Hi-Fi/audiophile amplifier it's outdated now...

Anyway the Q14-Q16 driver pair seems to be underrated. I'd choose a stronger driver pair - for example the MJE15030/31 pair from Onsemi would do the job!

the only thing thing that is outated are the bjts
wich are quiete old and can be bested by more recents parts..
for the rest, the dual differential proposed in this thread has no
advantages, moreover, the compound output stage is less safe than the
classic one on the australian amp..

[Aldotin]

I referred to the "Playmaster", not the "ETI-466".
Playmaster's OP stage is EF and differential stage isn't dual.

Originally Posted by wahab

the only thing thing that is outated are the bjts
wich are quiete old and can be bested by more recents parts..
for the rest, the dual differential proposed in this thread has no
advantages, moreover, the compound output stage is less safe than the
classic one on the australian amp..

[andrewlebon]

Great amplifier for pa using 4 pairs 2n3773 still going strong built 12 years ago
will post pictures tomorrow can it be modified for higher output using newer
semis
thanking you
andrew lebon

[AndrewT]

that is a difficult first project.
Start with something much simpler and much lower voltage.

BTW, the 200W into 8r0 is probably right. If the 310W into 4r0 is also correct then it indicates that this is a bad design for a 4ohm speaker.
Don't use it on 4ohm or 4 to 8ohm speakers.
It might work with 6ohm speakers, but you should take the others advice and select a better DIY 200W design as your second or third project.

[Aldotin]

Originally Posted by AndrewT

BTW, the 200W into 8r0 is probably right. If the 310W into 4r0 is also correct then it indicates that this is a bad design for a 4ohm speaker.

Are you sure?
A 300W/4Ohm rated conventional PA amplifier usually gives ~200W on 8Ohm load.