Finished my snubberized BrianGT LM4780s

Russ White · 27th February 2005, 11:55 PM

Brian was kind enough to send me a hybrid LM4780 kit with the snubberized PS. Well, I spent today with the help of my wife doing blind listening tests against the plain vanilla LM4780 kit, and folks it was not at all hard to tell the difference.

The snubberized version ALWAYS plays with far more authority. There is a very noticable improvement to the beefiness and luscious goodness of the midrange and bass, while the top end seems excellent on both versions.

The snubberized version plays louder, and it just does not run out of steam as quickly as the standard version.

The improvement is vast. I am hoping this will be the impetus for Brian to create a LM4780 rev2 board specifically for the snubberized PS. I for one would buy a couple more.

One note, when I first got the snubberized amp working, the right channel was running quite hot. I double checked all my soldering, it was fine. I desoldered the LM4780 and replaced it with a new one, problem solved, seems I got a bad IC. Other than that it was smooth sailing. I referred to Brians snubberized Lm3875 pics to help me with the cap placement on the amps.

I have already dismantled the original 4780 boards for conversion to snubberized versions, there is no way I would go back. Here are some pics of the new amps in their new home.

Thanks Brian, I am a happy puppy.

D_GR8_1 · 28th February 2005, 12:00 AM

Hey Russ,

did you get the PCB layout of the design?

If not, can you take close-up pics of the boards & post them.

Russ White · 28th February 2005, 12:05 AM

The layout is the same as the the regular LM4780 except that you omit the 1000uf cap and ad the two smaller caps just like these pictured:

Just make sure you get the polarity right for the poly cap.

D_GR8_1 · 28th February 2005, 12:54 AM

you are showing me the LM3875.

What I'm interested in finding out is the positions of Rm, & the Zobel network on the PCB.

Russ White · 28th February 2005, 01:30 AM

RM is on the bottom of the PCB, no easy way for me to get a shot of that right now. Not much to a zobel. When I get a chance I will send closeups.

Russ White · 28th February 2005, 01:35 AM

FWIW You can see the zobel cap and resistor on the corners of the amp PCBs on the pics I posted. Its the red resistor and the blue cap on the side of the PCB closest to the heatsink.

27th February 2005, 11:55 PM	#1
Russ White diyAudio Member Join Date: Jan 2005 Location: Nashville, TN, USA	Finished my snubberized BrianGT LM4780s Brian was kind enough to send me a hybrid LM4780 kit with the snubberized PS. Well, I spent today with the help of my wife doing blind listening tests against the plain vanilla LM4780 kit, and folks it was not at all hard to tell the difference. The snubberized version ALWAYS plays with far more authority. There is a very noticable improvement to the beefiness and luscious goodness of the midrange and bass, while the top end seems excellent on both versions. The snubberized version plays louder, and it just does not run out of steam as quickly as the standard version. The improvement is vast. I am hoping this will be the impetus for Brian to create a LM4780 rev2 board specifically for the snubberized PS. I for one would buy a couple more. One note, when I first got the snubberized amp working, the right channel was running quite hot. I double checked all my soldering, it was fine. I desoldered the LM4780 and replaced it with a new one, problem solved, seems I got a bad IC. Other than that it was smooth sailing. I referred to Brians snubberized Lm3875 pics to help me with the cap placement on the amps. I have already dismantled the original 4780 boards for conversion to snubberized versions, there is no way I would go back. Here are some pics of the new amps in their new home. Thanks Brian, I am a happy puppy.

28th February 2005, 12:00 AM	#2
D_GR8_1 diyAudio Member Join Date: Aug 2004 Location: Sydney	Hey Russ, did you get the PCB layout of the design? If not, can you take close-up pics of the boards & post them. __________________ An expert is someone who knows more and more about less and less, until eventually he knows everything about nothing.

28th February 2005, 12:54 AM	#4
D_GR8_1 diyAudio Member Join Date: Aug 2004 Location: Sydney	you are showing me the LM3875. What I'm interested in finding out is the positions of Rm, & the Zobel network on the PCB. __________________ An expert is someone who knows more and more about less and less, until eventually he knows everything about nothing.

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28th February 2005, 12:05 AM	#3
Russ White diyAudio Member Join Date: Jan 2005 Location: Nashville, TN, USA	The layout is the same as the the regular LM4780 except that you omit the 1000uf cap and ad the two smaller caps just like these pictured: Just make sure you get the polarity right for the poly cap.

28th February 2005, 01:30 AM	#5
Russ White diyAudio Member Join Date: Jan 2005 Location: Nashville, TN, USA	RM is on the bottom of the PCB, no easy way for me to get a shot of that right now. Not much to a zobel. When I get a chance I will send closeups.

28th February 2005, 01:35 AM	#6
Russ White diyAudio Member Join Date: Jan 2005 Location: Nashville, TN, USA	FWIW You can see the zobel cap and resistor on the corners of the amp PCBs on the pics I posted. Its the red resistor and the blue cap on the side of the PCB closest to the heatsink.

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