Bridged 4780 for 4ohms load? - Page 2

AndrewT · 10th December 2006, 04:37 PM

Hi J,
what voltage are you running your chip from?

I assumed that you could achieve about 24Vpk from +-30Vdc.

jaste · 10th December 2006, 05:08 PM

I got a transformer with dual 30 volts secondaries, after rectifying that should be around 40 volts right? That may be a bit to much for the 4780 chip so then I regulate it down to whatever but atleast 34 volts since the lm338 requires atleast 6 volts regulation (i think). So maybe 30-34 volt supply to the chips. And again lm338 max output 5 amps, and I want to run one chip in paralell config per channel and there will be two channels, so two chips to drive. I hope you understand, cause i lost myself somewhere...

Restracto · 23rd May 2010, 03:55 AM

Why parallel and not bridged?

pacificblue · 23rd May 2010, 06:20 AM

Quote:

Originally Posted by jaste

4 ohm load

AndrewT · 24th May 2010, 07:29 PM

A 4ohm load is going to demand a lot more current than an 8ohm load.
A 5A limit from the regulator is not, in my opinion, going to deliver the goods.

jeronimo2003 · 25th May 2010, 08:46 PM

Also a 2x40 VDc supply is a bit to much for a 4 Ohm load. I suggest looking for a transformer with a 2x22 Vac secundairy. Given the very good PSRR of the Overture chips, I do not see the need of a regulated supply.

GAH · 26th May 2010, 04:10 AM

I've bridged a LM3875 chip amps (Audiosector kits - Dual Mono) running 6 ohm (nominal) speakers without any sonic or heat problems. Admittedly, listening levels are always kept at low to medium levels and the chips are well heat sinked.

AndrewT · 26th May 2010, 12:22 PM

Quote:

Originally Posted by GAH

I've bridged a LM3875 chip amps (Audiosector kits - Dual Mono) running 6 ohm

and the smoothing cap voltage is?

GAH · 26th May 2010, 04:46 PM

I'm using two 300va transformers with 22v secondaries. This feeds the chip amps with 31 volts DC.

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10th December 2006, 04:37 PM	#11
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi J, what voltage are you running your chip from? I assumed that you could achieve about 24Vpk from +-30Vdc.

10th December 2006, 05:08 PM	#12
jaste diyAudio Member Join Date: Dec 2005 Location: Stockholm	I got a transformer with dual 30 volts secondaries, after rectifying that should be around 40 volts right? That may be a bit to much for the 4780 chip so then I regulate it down to whatever but atleast 34 volts since the lm338 requires atleast 6 volts regulation (i think). So maybe 30-34 volt supply to the chips. And again lm338 max output 5 amps, and I want to run one chip in paralell config per channel and there will be two channels, so two chips to drive. I hope you understand, cause i lost myself somewhere...

23rd May 2010, 03:55 AM	#13
Restracto diyAudio Member Join Date: May 2010	Why parallel and not bridged?

24th May 2010, 07:29 PM	#15
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	A 4ohm load is going to demand a lot more current than an 8ohm load. A 5A limit from the regulator is not, in my opinion, going to deliver the goods.

25th May 2010, 08:46 PM	#16
jeronimo2003 diyAudio Member Join Date: May 2010	Also a 2x40 VDc supply is a bit to much for a 4 Ohm load. I suggest looking for a transformer with a 2x22 Vac secundairy. Given the very good PSRR of the Overture chips, I do not see the need of a regulated supply.

26th May 2010, 04:10 AM	#17
GAH diyAudio Member Join Date: Apr 2009	I've bridged a LM3875 chip amps (Audiosector kits - Dual Mono) running 6 ohm (nominal) speakers without any sonic or heat problems. Admittedly, listening levels are always kept at low to medium levels and the chips are well heat sinked.

26th May 2010, 04:46 PM	#19
GAH diyAudio Member Join Date: Apr 2009	I'm using two 300va transformers with 22v secondaries. This feeds the chip amps with 31 volts DC.