GC Powersupply questions/clipping issue

[Crash&Burn]

Hi all, I am new here and have hit the end of my limited electronics knowledge with my new 3875 GC I just built. I made my own PCB's based primarily on Monster's regulated GC.

I picked a nice little transformer at a surplus store here in town that measures 32-0-0-32 and almost matchs a Plitron 160VA single primary model. But I suspect now that it is not 160VA in fact I'd be suprised if it was 100VA given how badly it clips.

I have +/-30V DC from the power supply with LT1083's as the regulators, 10000uF on the PS and 1000uF FC caps on the amp itself. I always hear people say that clipping occurs in the treble but in my case it distinctly clicks with bass heavy sections (in the bass of course) at anything more than low volumes. How much current would I need at 30V into 8 ohms?

The only other suspect is that my Pinoneer DV-434 has 1.1mV DC offset, but I am using a 4.7uF input filter and 1.1mV isn't enough to offset my input signal so badly is it?

In fact now that I am writting this down my Yamaha amp shuts down at higher volumes with audio from my DV-434 too but the cable box doesn't cause this issue. I have tried adding 6.8uF in series with the output of the DVD player into the Yamaha and I can turn the volume up higher before it shuts down but still bass will cause it to shut down...

OK so the new question is what is wrong with my DVD player and how can I fix it? is it the DC and how do I fix this offset?

[breez]

Originally posted by Crash&Burn
I have +/-30V DC from the power supply with LT1083's as the regulators, 10000uF on the PS and 1000uF FC caps on the amp itself. I always hear people say that clipping occurs in the treble but in my case it distinctly clicks with bass heavy sections (in the bass of course) at anything more than low volumes. How much current would I need at 30V into 8 ohms?

The only other suspect is that my Pinoneer DV-434 has 1.1mV DC offset, but I am using a 4.7uF input filter and 1.1mV isn't enough to offset my input signal so badly is it?

I too would guess it is current limited. Hit a big bass note and the current drains the caps out and the supply can't fill the caps fast enough.

Let's calculate: 30Vpeak = ~21.2Vrms. Into 8 ohm it generates ~2.65A rms current.

1.1mV is negligible and the input cap will take care of it.

[Crash&Burn]

Minor update, I spoke to a Pioneer service center and they say the DC is a bad thing. I also screwed up the model # it a DV-443 (slim line, crap it seems).
Whats a good replacement as an audio source and DVD that doesn't need tweaking to sound reasonable?

[Crash&Burn]

And again one more thing, the negative regulator in the PS seems to be getting way warmer with minimal load than the positive side. Is this normal?

[scone]

Originally posted by Crash&Burn
And again one more thing, the negative regulator in the PS seems to be getting way warmer with minimal load than the positive side. Is this normal?

I observed the same thing while building my GC. It seems the chip draws more current from the negative rail than the positive one. It could also be caused by mismatched secondary voltages, if the unregulated voltage on the negative rail is quite a bit higher than on the positive rail. Have you measured the unregulated DC voltages on each rail?

[Crash&Burn]

Well it's all moot now, I blew it up Tried to use one of my 925VA transformers and the surge protection thermisters didn't work... so I ordered new parts form Digikey and will have to rebuild, at least this time I will use a Plitron 300VA 25-0-25 model, apparently 6A per secondary so clipping shouldn't be an issue again.

My unregulated DC was 45V per winding, does phase come into play if I am using 2 completely seperate regulator boards?