900W H-class PA Amp with Limiter

Input GND missing! Amplifier can't work without connect input GND. I can't see wire jumper (red line on component layout) on botom side of pcb, somethimes I forget connect that wire.
Regards
Hi sir
Good evening i have completed h900
before 2years but now i have time to check it.i have problem my dc voltages are at without load is 66v dc and 115 v dc after load voltages becomes 37v dc and 77 v dc what the problem please solve me.thanking you.
 
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NJM2068 is better than NE5532 in every way!!!

To everyone- please quit using this horrid sounding 30 year old op amp. The 2068 is better in every way, quieter, lower distortion, less offset and drift, larger output current, lower input bias, faster, and most important of all it sounds FAR better than any 5532 ever thought about.

Well the voltage noise is given in some bizarre way (FLAT + JIS A) and the current noise isn't given at all in the NJM2068 datasheet. NE5532's are commonly measured around 0.0005% distortion and can hold that into a 600 ohm load. NE5532/4 current noise is very low for bipolar opamps, so its much better at higher impedances than many bipolars for noise.

And the NJM is definitely slower on paper, having half the unity bandwidth, 2/3rd the slew rate.

Do you have some real measurements to back up your assertions? To me it looks like the NJM2068 is very competent, but its not quite up to the performance of the NE5532/5534.

Anyway here's some useful measurements I found: http://www.ac-vogel.de/Download/Dow...act, no myths and THD measurement results.pdf
 
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hi apex,

i cannot set the bias of h700
iam attaching pics and the layout of the board. i can vary the voltage across
collector and emitter of bd140 (2n5401) from 1.23 to 1.51 volts but there is no voltage across emitter (0r33) resistors.also attaching the measurements pic.
votage used 60-0-60v dc and 15-0-15v


regards
ravs
 
hi apex,

i cannot set the bias of h700
iam attaching pics and the layout of the board. i can vary the voltage across
collector and emitter of bd140 (2n5401) from 1.23 to 1.51 volts but there is no voltage across emitter (0r33) resistors.also attaching the measurements pic.
votage used 60-0-60v dc and 15-0-15v


regards
ravs

Replace 1k5 resistor in series with 470R trimer with 1k...