It's not mine. but I have made three of them."Yuanjing" Gainclone 3886 - eBay amazing value ? Ebay kit. It doesn't look like it is available at the moment.
Anybody have any preferences/boards they like for soft start and speaker protection? PCBs that is. I'd like to put them together myself.
LM3886 x2 + opamp preamplifier 68W 4 ohm amplifier PCB - eBay (item 320428786669 end time Mar-20-11 20:11:57 PDT)
No parts included but that's what I just ordered. I'd rather gather my own parts to avoid getting fakes etc.
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Are you aware that you may have to change a few resistor values on that speaker protection board, depending on the supply voltage you use?
I think you also need about 12v dc to operate speaker protection, and your supply ac from the transformer for soft start. I doubt you will have to change any resistors, they have a wide margin for the ac. I have used one and they are very good.
I'm glad Jim's Audio are still doing the boards, because he has no kits for sale at the moment. Still, you can use your own parts. Before you buy any parts you need to view page three of this thread and the further mods suggested by Linuxguru who has worked intensly on this project. Good luck to the Law!
The 12 V for the speaker protection relays are created on the PCB. The resistor in series to the relay coils is one you have to change according to the supply voltage. Then you need to adjust the sense resistor for the AC voltage so that the relays fall off before the switch-off pop occurs. 0-45 k correspond to 4-67 V AC supply. The µPC1237 works from 3,4 V supply voltage, so there is another resistor to adjust from 8k-20k corresponding to 25-60 V DC supply.
For lack of further information you may take the 28 AC marking on the PCB as indication of the voltage for which the resistors were chosen.
Noob question but is it possible to wire this board to a DVC Subwoofer, one channel per coil? Otherwise is it possible to bridge this board?
Yikes. I think I'm going to have to read this over a few more times. 😱.
So if I run it at 28V, the components are fine, but if I run it at 22V-25V, I may need to change things.
I only need about 30-35W per channel @ 8ohms so I don't think I'll be using the full 28V+ transformer. I'm thinking 25V at the moment.
So let's see what that does with the resistors...
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You should be fine. That protection board looks really good value, I've been working on one myself, and components alone come to about £8, let alone the PCB. I may have to order a couple to try out.
Yeah I thought it looked pretty well made for $10USD. I've seen far worse for the price.
You guys still sure about switching out the resistors? I have no problem doing it, I just have to make sure to put them in my ginormous Mouser order.
I would sugest you use a simple 12v transformer for the speaker protection.
You then only have to take a wire from your 22-0-22 transformer for the soft start. It's that simple.
I recommend reading the µPC1237 datasheet, around which the protection is built.
Take a look at the photos in the link. There are two 12 V DC relays with 320 Ohm coils in parallel and there is a 270 Ohm resistor in series. How much voltage will the relay coils see, if you use a 12 V transformer (plus additional rectifier and smoothing cap)? Maybe 6 V DC? Will they ever turn on when the relay datasheet specifies 9 V as Operate Voltage?
Or calculate backwards. When the relays need 12 V DC, how much voltage do you need at the 270 Ohm resistor to get that? Around 32 V DC?
Wow this is more complicated that I was anticipating when I bought it! Alright, so I've settled on a 25V transformer...
I'm a bit confused. You can probably tell I'm a newbie. This will be my first serious project so it's a bit of a challenge already.
I'm confused because the board's silkscreen says 28V AC, not 12V etc. I'd like to use a 25V transformer, but then would I have to swap out that resistor for a lower value? Say 220ohm or 180ohm?
I'm not sure exactly how to calculate it...Thanks for all of the insight. I would never even looked into it.
Sorry, I thought it was the same as the board I used. It seems it is not. On my board you had the 28v ac on one side and 12v-0 dc on the other. Sorry to confuse
Oh actually mine might be...but I don't have it yet. From the pictures I can only see one 28VAC.
EDIT: Ah yes...I see what you were talking about. There is a "V" popping out from behind one of the relays. So...I have to have a separate PSU to use this? I don't mind, but I'm just curious.
I also don't have a soft start board, if that matters....but if someone can direct me to one on eBay/online store, I'll buy it, (if I need to).
I'm just curious as to how Skodaboy has his running on Page 22. I don't see any separate supply although I do see a capacitor in line to something...But I see no other transformer or supply board. Could it have something to do with him using only a 15V Transformer?
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There's a thread on this speaker protection board that I started here:
http://www.diyaudio.com/forums/chip-amps/164061-speaker-protection-board-ebay.html
I traced and posted a schematic. There is some discussion that might be useful. I bought 4 of these boards all under $10 cdn, including shipping. Can't build it for that.
Cheers.
http://www.diyaudio.com/forums/chip-amps/164061-speaker-protection-board-ebay.html
I traced and posted a schematic. There is some discussion that might be useful. I bought 4 of these boards all under $10 cdn, including shipping. Can't build it for that.
Cheers.
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