Group order of non-inverted LM4780 pc boards? Anyone interested? - diyAudio
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Old 11th May 2004, 03:17 AM   #1
BrianGT is offline BrianGT  United States
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Default Group order of non-inverted LM4780 pc boards? Anyone interested?

Well, with a prototype made with the board layout, I am considering organizing the order based on the current layout.

As for pricing, it looks like 1 pcb set would cost $20, and include:
- 2 power supply boards
- 2 amplifier boards
- 1 bridging board (DRV134)

This price would be for 4 oz copper (for the extra current handling), and the boards would be put together with scoring, as with my current LM4780 boards. (boards to either be red or black)

The amplifier pcb would be a single LM4780 chip hardwired in paralled configuration.

One pcb set would allow for these configurations:
- 2 channel amplifier (one amplifier pcb per channel) with a single or dual power supplies. (dual monoblock setup possible with one pcb set)
- bridged setup producing 150-200w for one channel

Remember that the LM4780 is hardwired in parallel mode, so one chip = 1 channel.

The non-bridged board should put out around 50-100w, depending on the power supply voltages and the load driven.

Kits will also be offered, and pricing will be announced soon. Pricing should be just a bit more than the current LM3875 group order.

I modified the Wiki for a new list to see the interest out there. If the interest is fairly substantial (100+ pcbs being the target to get the price), I will go through with the order, and offer kits. Please sign-up again here:
http://www.diyaudio.com/wiki/index.p...CB+Group+Order

Please indicate your initial interest. This will allow for me to determine the kit pricing, and the whether there is enough interest for me to put time into this.

Drop me an e-mail if you have any questions. PCB set pictures will be posted soon.

--
Brian
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Old 11th May 2004, 03:18 AM   #2
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I'm at the feeler stage for my paralleled version, so it appears we'll have both bases covered.

EDIT: Oh, didn't see yours was also a paralleled design. Wowsers, two designs to choose from at once. Hope there's a ton of interest for both.

oO
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Old 11th May 2004, 04:04 AM   #3
hams is offline hams  United States
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Default 150 watts

so to get teh 150w for a single channel, i need 1 complete pcb kit correct? so if i wanted six 150w channels, i'd need 6 kits?

what size toridal transformer is needed to power a single channel to 150w?

thanks,
kevin
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Old 11th May 2004, 07:35 AM   #4
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Brian, if you do go ahead with this, and are offering a component kit, is it likely you will be using the Mills MRB-5 power resistors at all? Just if you are I would also be interested in buying a bunch of these seperately, to use as output resistors for my Aleph-X (preferably 0.33 or 0.22 ohms).

Alternatively, if anyone knows where you can buy these off the shelf I would really appreciate it if you could let me know.
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Old 11th May 2004, 10:02 AM   #5
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I'm curious - looking forward to seeing the prototypes. Personally, I like red.

But is there an option to order just the LM4780 PCBs? For my application, I won't need the rectifier boards. I guess the answer to this might be "no", as I guess you get all 5 boards made on one piece of FR4...

BTW, hams, I'm not sure that you'd get 150W from one PCB. To get 150W into 8 ohms, you need an RMS voltage swing of 35V, which is 50V peak. The highest supply rails you can put into an LM4780 are +/-42V, and these will fall under load to perhaps around 35V (this is hard to predict, of course). Allowing for other losses, I reckon you'd get around 30V peak, or 21V RMS, which is 55W. The parallel configuration will reduce some of these losses, so you might get nearer to 65W - I reckon that 60W is a fair guess of the continuous RMS power output of one of these PCB's.

Bridging a pair of these boards will give you double the voltage swing, which is 4 times the power in theory. Unfortunately, losses will reduce this to perhaps 3 times the output, so say 150-180W. But, these numbers are for continuous RMS outputs - dynamic or short-term "peak" outputs will be substantially higher. I reckon that a bridged setup will drive my ATC's quite well

When sizing the torroid, a factor of two is a good starting point. But, it depends on the application - for a PA amplifier, you might want to increase it. For home use, you might get away with a smaller one. Unless you listen to heavily compressed music, you rarely need the full output power - it's there to deal with peaks. For the stereo bridged amplifier amplifier I'm thinking about (using 4 PCB's), I reckon 500VA will be enough

Cheers,

Mark
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Old 11th May 2004, 10:35 AM   #6
roibm is offline roibm  Romania
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me too

and I like black. black is cool. imagine black pcb, black heatsinks, black case, black toroid



yeah, and another point... what is a kit?
one channel bridged? or two channels bridged?
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Old 11th May 2004, 12:33 PM   #7
BrianGT is offline BrianGT  United States
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Quote:
Originally posted by bigparsnip
Brian, if you do go ahead with this, and are offering a component kit, is it likely you will be using the Mills MRB-5 power resistors at all? Just if you are I would also be interested in buying a bunch of these seperately, to use as output resistors for my Aleph-X (preferably 0.33 or 0.22 ohms).

Alternatively, if anyone knows where you can buy these off the shelf I would really appreciate it if you could let me know.
I will keep this in consideration when ordering parts. This shouldn't be a problem if I go for the Mills resistors.

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Old 11th May 2004, 12:50 PM   #8
BrianGT is offline BrianGT  United States
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Quote:
Originally posted by mhennessy
I'm curious - looking forward to seeing the prototypes. Personally, I like red.

But is there an option to order just the LM4780 PCBs? For my application, I won't need the rectifier boards. I guess the answer to this might be "no", as I guess you get all 5 boards made on one piece of FR4...

Bridging a pair of these boards will give you double the voltage swing, which is 4 times the power in theory. Unfortunately, losses will reduce this to perhaps 3 times the output, so say 150-180W. But, these numbers are for continuous RMS outputs - dynamic or short-term "peak" outputs will be substantially higher. I reckon that a bridged setup will drive my ATC's quite well
Mark,

You can find the prototype pcb pictures in this thread, where the idea of the layout was created:
http://www.diyaudio.com/forums/showt...330#post391330

The pcb set will be created on a single pcb set, with scoring to allow for the boards to easily be broken apart, just as with my current LM3875 order:
http://www.briangt.com/gallery/nigc-kit
It will consist of 5 boards on one, instead of 3. Having 2 power supply boards will easily allow for building monoblocks from one pcb set. The bridging pcb hasn't been finalized yet.

When bridging with the LM4780 layout, keep in mind that it is actually a bridged-parallel configuration, which seems to be the optimal high-power solution with the chipamps.

Here is a picture of the amplifier board layout. The power supply board will be similar to the last one from the LM3875 group order.

Wiki signup:
http://www.diyaudio.com/wiki/index.p...CB+Group+Order

--
Brian
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Old 11th May 2004, 12:56 PM   #9
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Brian, I like what I see BUT the signal ground (red) trace should go more left and directly to the OG pad. Than you have got a perfect pcb!

BTW: Where are the decoupling caps? Can't see any.
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Old 11th May 2004, 01:20 PM   #10
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Quote:
Originally posted by peranders
Brian, I like what I see BUT the signal ground (red) trace should go more left and directly to the OG pad. Than you have got a perfect pcb!

BTW: Where are the decoupling caps? Can't see any.

Wouldn't connecting SG and OG pads with bottom layer trace trace take care of that?

There is no coupling caps, as they are not required here. All the amps I build now don't have coupling caps either. I used them before though.
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