Would you use a 4780 in a parallel or bridged configuration with 6 ohm speakers?

GregH2 · 14th February 2010, 03:17 AM

Title says it all. My transformer choice is +/-22v.

Interested to know your thoughts, as this seems to be an intermediate speaker impedance and it is difficult to know which way to go. I'm thinking parallel would be best...

Thanks,

Greg.

sangram · 14th February 2010, 05:33 AM

Single 4780 channel is not 3 ohm capable, hence parallel is the only way out.

GregH2 · 14th February 2010, 08:18 AM

Quote:

Originally Posted by sangram

Single 4780 channel is not 3 ohm capable, hence parallel is the only way out.

Hi Sangram,

Thanks for your reply, however I am confused. What does 3 ohms have to do with anything when my speakers are 6? Could you please explain?

Thanks,

Greg.

Nisbeth · 14th February 2010, 08:25 AM

If you bridge an amplifier, each amplifier channel will see half of the load impedance, meaning 3 ohms here.

/U.

GregH2 · 14th February 2010, 08:31 AM

Quote:

Originally Posted by Nisbeth

If you bridge an amplifier, each amplifier channel will see half of the load impedance, meaning 3 ohms here.

/U.

OK, fantastic thanks. Parallel operation it will be then.

Greg.

AndrewT · 02:08 PM

I would be tempted to say the two channels inside a 4780 are not 4ohm speaker capable, but that many use them into this more demanding load and find the results good enough.
6r0 could demand upto 5Apk. A parallel 4780 can output upto 14Apk to a load. A pair of 4780 channels fed from 22+22Vac should have sufficient current capability to drive a reactive 6ohm speaker load without triggering Spike or any other limiting if you can keep the chip cool. There is your problem.

kuldeepsingh · 16th February 2010, 12:33 PM

Still parallel operation is more viable solution for 6 ohm @ normal listening levels, provided u don't use speakers at full volume.

olblueyez · 13th May 2010, 12:01 PM

If I get the PD 4870 kit and wish to run parallel monoblocks all I need to do is add the extra parts to the pcb and get two tranies correct? And that will put me at about 100w per channel at 8 Ohm?

Peter Daniel · 13th May 2010, 12:36 PM

Parallel will still produce up 60W into 8ohm, to get more power you need to use 4 ohm speakers.

Two tranies are required for dual mono, more info on the kit here: Kit arrived

geraldfryjr · 13th May 2010, 01:49 PM

You must also keep in mind that an amplifier output voltage swing is determined by the power supply's RMS voltage minus 2.5v to 3.5v (see data sheet) because it can't swing compleatly to the rail and not the peak voltage as measured at the filter capacitor.
therefore with a 22v transformer it can only produce less than 80 watts into a 6 ohm load.
At least a 26v-0-26v transformer should be considered and a 28v-0-28v would be optimum to get a full undistorted 100watts into 6ohms.
I have seen this question time and time again and this has never been mentioned or discussed.
Yes,a higher power supply voltage means warmer chip temps,just use an adequate heatsink and you shouldn't have any problems. jer

14th February 2010, 03:17 AM	#1
GregH2 diyAudio Member Join Date: Oct 2009	Would you use a 4780 in a parallel or bridged configuration with 6 ohm speakers? Title says it all. My transformer choice is +/-22v. Interested to know your thoughts, as this seems to be an intermediate speaker impedance and it is difficult to know which way to go. I'm thinking parallel would be best... Thanks, Greg.

15th February 2010, 02:04 PM	#6
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	I would be tempted to say the two channels inside a 4780 are not 4ohm speaker capable, but that many use them into this more demanding load and find the results good enough. 6r0 could demand upto 5Apk. A parallel 4780 can output upto 14Apk to a load. A pair of 4780 channels fed from 22+22Vac should have sufficient current capability to drive a reactive 6ohm speaker load without triggering Spike or any other limiting if you can keep the chip cool. There is your problem. __________________ regards Andrew T. Last edited by AndrewT; 15th February 2010 at 02:08 PM.

16th February 2010, 12:33 PM	#7
kuldeepsingh diyAudio Member Join Date: Aug 2006 Location: Chennai, India	Still parallel operation is more viable solution for 6 ohm @ normal listening levels, provided u don't use speakers at full volume. __________________ . . .. ... ..... ........ ............. ..................... .................................. My Best LM3886 PCB layout

13th May 2010, 12:36 PM	#9
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	Parallel will still produce up 60W into 8ohm, to get more power you need to use 4 ohm speakers. Two tranies are required for dual mono, more info on the kit here: Kit arrived __________________ www.audiosector.com “Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC

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14th February 2010, 05:33 AM	#2
sangram diyAudio Member Join Date: Sep 2002 Location: India	Single 4780 channel is not 3 ohm capable, hence parallel is the only way out.

14th February 2010, 08:25 AM	#4
Nisbeth diyAudio Member Join Date: Jan 2001 Location: Denmark	If you bridge an amplifier, each amplifier channel will see half of the load impedance, meaning 3 ohms here. /U.

13th May 2010, 12:01 PM	#8
olblueyez Banned Join Date: Apr 2010	If I get the PD 4870 kit and wish to run parallel monoblocks all I need to do is add the extra parts to the pcb and get two tranies correct? And that will put me at about 100w per channel at 8 Ohm?

13th May 2010, 01:49 PM	#10
geraldfryjr diyAudio Member Join Date: Feb 2008 Location: Jackson,michigan	You must also keep in mind that an amplifier output voltage swing is determined by the power supply's RMS voltage minus 2.5v to 3.5v (see data sheet) because it can't swing compleatly to the rail and not the peak voltage as measured at the filter capacitor. therefore with a 22v transformer it can only produce less than 80 watts into a 6 ohm load. At least a 26v-0-26v transformer should be considered and a 28v-0-28v would be optimum to get a full undistorted 100watts into 6ohms. I have seen this question time and time again and this has never been mentioned or discussed. Yes,a higher power supply voltage means warmer chip temps,just use an adequate heatsink and you shouldn't have any problems. jer

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