AudioSector-chip amp kits, dacs, chassis - Page 50

Peter Daniel · 8th December 2005, 03:07 PM

It is R1 on the board (220R in premium kit). You can short it with a piece of wire and effectively remove it from a circuit. I'm not using those resistors in the Patek amps, and it works fine. You'll gain a bit more of clarity and if the amp does not oscillate you can leave it like that (may be depend on the rest of a system).

LBHajdu · 8th December 2005, 03:14 PM

Hello again Peter,
It’s unfortunate that the LM3875 sounds better, as it is less powerful then the LM4780. I take it that two LM4780 boards can be bridged and then balanced with the xlr to 2rca cable. That would be like 200W at 4ohms at about 27V (I didn’t calculate it’s just a ballpark guess). I don’t have any high efficiency speaker that’s why I ask.

Because the LM3875 sounds better would it be possible take your LM4780 Amplifier bridged Schematic and replace the amp with two LM3875s’s (I can draw it for you if you don’t understand what a mean). I know there are a lot of circuits out there to do this already however many of them seem like compromises. The extra benefit of this arrangement would be, if it works, better heat dissipation as all the chip dies are in separate packages. Of course it may be better to just use the LM4780 as you already have the boards ready to sell.

Leve,
Oh no it’s another power hungry amp builder.

Peter Daniel · 8th December 2005, 03:23 PM

Hi,

The difference between both chips is not really that big. I was using for at least 2 months LM4780 amp in stereo configuration then I switched to bridged setup (same chip) and I liked them both. It is a matter of deeper refinement and it is not always that obvious and greatly depends on the rest of the system. After few months of using LM4780 in bridged mode, I switched not to LM3875 in bridged mode and the difference is rather subtle.

Besides, two bridged LM3875 seem indeed more powerful. The bridging schematic for LM4780 aplies equally well to LM3875.

If you really need power, go with a bigger chip, you shouldn't be disappointed.

Peter Daniel · 8th December 2005, 03:34 PM

The buffer boards I described here: http://www.diyaudio.com/forums/showt...650#post748650 are already fabricated. As soon as I test them, they will be available (it will be at least 10 days before I receive them though).

sangram · 9th December 2005, 01:21 PM

Hi Peter

Is the site down for some reason?

How long do you think it would take from Canada till the kits get here?

I have a couple of 4780s lying around, I want a 4 way amp (bridge/parallel) so I was wondering if I could customise my order a bit or you are pretty fixed as far as kit order goes. I basically need 4 complete amps and I already have 2 chips, and I would love to get my hands on some good passives (Hint - Riken/Caddock/BG in exchange for two chips - I'm just being a miser here but I need to $ave)...

And why can't I access the site?

Geek · 9th December 2005, 01:49 PM

0648 PST - I see it OK here

sangram · 9th December 2005, 02:27 PM

Still can't see it....

Peter Daniel · 9th December 2005, 07:58 PM

Well, I made it: five channels Patek version

Peter Daniel · 9th December 2005, 08:00 PM

.

Peter Daniel · 9th December 2005, 08:02 PM

..

8th December 2005, 03:07 PM	#491
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	It is R1 on the board (220R in premium kit). You can short it with a piece of wire and effectively remove it from a circuit. I'm not using those resistors in the Patek amps, and it works fine. You'll gain a bit more of clarity and if the amp does not oscillate you can leave it like that (may be depend on the rest of a system). __________________ 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

8th December 2005, 03:23 PM	#493
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	Hi, The difference between both chips is not really that big. I was using for at least 2 months LM4780 amp in stereo configuration then I switched to bridged setup (same chip) and I liked them both. It is a matter of deeper refinement and it is not always that obvious and greatly depends on the rest of the system. After few months of using LM4780 in bridged mode, I switched not to LM3875 in bridged mode and the difference is rather subtle. Besides, two bridged LM3875 seem indeed more powerful. The bridging schematic for LM4780 aplies equally well to LM3875. If you really need power, go with a bigger chip, you shouldn't be disappointed. __________________ 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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8th December 2005, 03:14 PM	#492
LBHajdu diyAudio Member Join Date: Feb 2002	Hello again Peter, It’s unfortunate that the LM3875 sounds better, as it is less powerful then the LM4780. I take it that two LM4780 boards can be bridged and then balanced with the xlr to 2rca cable. That would be like 200W at 4ohms at about 27V (I didn’t calculate it’s just a ballpark guess). I don’t have any high efficiency speaker that’s why I ask. Because the LM3875 sounds better would it be possible take your LM4780 Amplifier bridged Schematic and replace the amp with two LM3875s’s (I can draw it for you if you don’t understand what a mean). I know there are a lot of circuits out there to do this already however many of them seem like compromises. The extra benefit of this arrangement would be, if it works, better heat dissipation as all the chip dies are in separate packages. Of course it may be better to just use the LM4780 as you already have the boards ready to sell. Leve, Oh no it’s another power hungry amp builder.

9th December 2005, 01:49 PM	#496
Geek diyAudio Member Join Date: Sep 2004	0648 PST - I see it OK here