741 op.amp works, tl 071 is oscillating?

[zoranaudio]

Originally posted by megajocke
You're welcome, and it's nice to hear you got it working!

42kg? Not a lightweight amp! But with that construction I bet it's sturdy enough to support it and you probably won't have to worry about transformer overheating with heavy use...

This transformer is over sized for this power 2 X 450 W @ 4 ohm, I have not over heating problem, even I have not PA speakers to test it, I did test only transformer with I think about 1 kw two parallel heaters for home heating each one 1kw but for 220 volts, and I have 2x50V =100Vac. on the secondary during all night 7 -8 hours non-stop and the transformer was about 5 deg C hotter than room temp. , perhaps max 35 deg C!!!,
I have automatic thermo switch for the fans adjusted on 54 deg C on the alu. heatsink cooling down to 45 deg C and than turn off.

[AndrewT]

of course you have speakers to test it.
Any 4ohm or 8ohm speaker can be used to listen to this amplifier.

It is hamfisted operators that don't listen to the effects of wrong settings on their gear that breaks speakers and amplifiers due to excessive outputs.

This is approximately 250W into 8r0. This is probably double the power needed to get most speakers to their maximum.
But, you only have to turn the volume down by an extra 3dB to 6dB to allow the speakers to survive.

If you want to "test" it you need a selection of dummy loads not speakers.

[zoranaudio]

Originally posted by AndrewT
of course you have speakers to test it.
Any 4ohm or 8ohm speaker can be used to listen to this amplifier.

It is hamfisted operators that don't listen to the effects of wrong settings on their gear that breaks speakers and amplifiers due to excessive outputs.

This is approximately 250W into 8r0. This is probably double the power needed to get most speakers to their maximum.
But, you only have to turn the volume down by an extra 3dB to 6dB to allow the speakers to survive.

If you want to "test" it you need a selection of dummy loads not speakers.

This is everyday in use non-stop, but on normal home hi-fi speakers, I measured with just resistive load 4,7 ohm ceramic tube about 3cm diameter x 20 cm , with 1KHz sine , and this resistor gets hot in just 3 seconds, I measured start to clip at this resistor at 38 Volts output measured with analog voltmeter and scope , old one 1 Ch.
What is the power? 38V ac(analog multimeter) point when starts soft clip on 4,7 ohm load.
I hope this is about the same as the specification shows 450 W at 4 ohm, and 280 W at 8 ohm.
I never measured in the bridge mode but i know that is very loud according to the volume pot( about twice loud ) than in normal mode.
Oh yes, I burned the fuses once when tested bridge mode on this 4,7 ohm resistor , but I should find 8 ohm load for bridge mode, I am not sure if this amp can work properly on 4 ohm and bridge mode?
Perhaps I should put higher value fuses, this original are 4 or 5 amperes Fast.