I have been playing on my boards for a while now and I am really pleased with the result. I have also delivered 250 pieces to members on a Swedish internet-forum, www.faktiskt.se and the response has been nothing but happy faces.
I'm thinking of ordering more boards now because people in Sweden has been asking for it, so I might as well ask if there is any interest world-wide also. NOTE: This is not a groupbuy, I just wants to see how big the interest are so I can guess how many boards I need to order.
Facts about the board:
3pcs LM3886 in parallel configuration, non-inverted
Servo-circuits to null the DC-offset, instead of cap's
Buffer circuit to keep the input impedance high
On-board voltage regulators (LM317T and LM337T) for the +15V/-15V for the op-ams
PCB is 2-layer, 1.6mm thick and 70um copper-weight
Size is 6.4 X 2.7 inch, or 16.255 X 6.858 cm
No measure has been done since I don't have the tools, but this is the best "Gainclone" I have ever built, and there has been a lot of them.
Power in theory is somewhere around 150W into 4ohm, 50W into 8ohm. But if you bridge two board as I do, and recommend that you do, then you'll get something like 325W into 4ohm, 170W into 8ohm. Everything depends on voltage and the capability that the selected power supply has...
Images. First, empty board:
Close-up of where the voltage regulators should be, not assembled in these images:
Connectors can be Faston-type or ordinary screw-connectors, or anything with 5.08mm (0.2 inch) leg-space:
Close-up of buffer and one servo-circuit:
Overview of assembled board (voltage-regulators missing):
To get as close to the pins as possible the caps is assembled directly on power-pins:
So... is there any interest here? Let me know...
I'm thinking of ordering more boards now because people in Sweden has been asking for it, so I might as well ask if there is any interest world-wide also. NOTE: This is not a groupbuy, I just wants to see how big the interest are so I can guess how many boards I need to order.
Facts about the board:
3pcs LM3886 in parallel configuration, non-inverted
Servo-circuits to null the DC-offset, instead of cap's
Buffer circuit to keep the input impedance high
On-board voltage regulators (LM317T and LM337T) for the +15V/-15V for the op-ams
PCB is 2-layer, 1.6mm thick and 70um copper-weight
Size is 6.4 X 2.7 inch, or 16.255 X 6.858 cm
No measure has been done since I don't have the tools, but this is the best "Gainclone" I have ever built, and there has been a lot of them.
Power in theory is somewhere around 150W into 4ohm, 50W into 8ohm. But if you bridge two board as I do, and recommend that you do, then you'll get something like 325W into 4ohm, 170W into 8ohm. Everything depends on voltage and the capability that the selected power supply has...
Images. First, empty board:
An externally hosted image should be here but it was not working when we last tested it.
Close-up of where the voltage regulators should be, not assembled in these images:
An externally hosted image should be here but it was not working when we last tested it.
Connectors can be Faston-type or ordinary screw-connectors, or anything with 5.08mm (0.2 inch) leg-space:
An externally hosted image should be here but it was not working when we last tested it.
Close-up of buffer and one servo-circuit:
An externally hosted image should be here but it was not working when we last tested it.
Overview of assembled board (voltage-regulators missing):
An externally hosted image should be here but it was not working when we last tested it.
To get as close to the pins as possible the caps is assembled directly on power-pins:
An externally hosted image should be here but it was not working when we last tested it.
So... is there any interest here? Let me know...
Count me in! I haven't tried the 3886 before and I think this is the best time to do it. Can you post the BOM?
Cheers,
Fred
Cheers,
Fred
AndrewT said:
Define "playing at"...
Pics hosted at my own server. Is it to much for your 46K modem or what are you applying?
Playing at = enormous posting without thinking about the download speed of many Forumites' Internet links.
Hi all...
Nice to see the interest 🙂
You can find the schematic here: Schematic. Traces/layers can be found here: Layers
Note: this is only recommended values, some values can most certainly be changed to fit the personal needs.
More images will be added later (if that's OK for you AndrewT).
The regulators does not need heatsinks, at least not what I have noticed. They are a bit overkill for this 4 op-amps. The servo-circuit should be LF411 or any other op-amp with low offset. The buffer op-amp is in the schematic a OPA134 but that can be changed to any other single op-amp of personal taste and flavour.
I am not sure about the price yet. It depends of how many pcb I will order. A wild guess would be somewhere between 10$ and 16$, or 7-10 Euro. That's for 1 pcb. Shipping over the pond and down under should land on 12 Euro or 20$ for weight up to 2kg's. This prices is hard to change and some might think that it's a bit high, but I'm not a big customer so it's hard to affect.
Nice to see the interest 🙂
You can find the schematic here: Schematic. Traces/layers can be found here: Layers
Note: this is only recommended values, some values can most certainly be changed to fit the personal needs.
More images will be added later (if that's OK for you AndrewT).
The regulators does not need heatsinks, at least not what I have noticed. They are a bit overkill for this 4 op-amps. The servo-circuit should be LF411 or any other op-amp with low offset. The buffer op-amp is in the schematic a OPA134 but that can be changed to any other single op-amp of personal taste and flavour.
I am not sure about the price yet. It depends of how many pcb I will order. A wild guess would be somewhere between 10$ and 16$, or 7-10 Euro. That's for 1 pcb. Shipping over the pond and down under should land on 12 Euro or 20$ for weight up to 2kg's. This prices is hard to change and some might think that it's a bit high, but I'm not a big customer so it's hard to affect.
I am also interested, the PCB is looking really good. I'd go for bridging them, so I'd need a total of 4 boards.
What can you do, if (10Mb/s/10Mb/s) is slowest internet you can have and you forget often, this wasn't so say 5 years back, for a lot people even nowAndrewT said:
Nice amp, but still it is linear, heat is probably hell when driving 4R
luka said:
Its unnecessary to cause linear amps to run hot. If yours is getting hot, its doing "more than audio." Cool and powerful can be done with linear--when its right, then NatSemi's little heatsink recommends are overly generous rather than too small.
Heat is not an issue. After 1 hour at high volume you can still touch the LM3886 without burning your finger. A guess is that they are around 45-50 Celsius.
The servo-circuits does its job really well and together with well-matched components you'll get a amp that doesn't oscillate, and that's keeping it cool.
The servo-circuits does its job really well and together with well-matched components you'll get a amp that doesn't oscillate, and that's keeping it cool.
AndrewT said:
Yeah, at least one of these images could be cropped to a third of the area without any loss of information.
Sometimes a diagram or photo really aids understanding but better to post a link for multiple photos, in what is essentially an advert, and arguably shouldn't be in this section.
Sloppy.
Is the board sloppy too?
w
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