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Old 13th October 2013, 04:37 AM   #121
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I left the amp turned on during night with some music playing on very minor volume just to make sure that the chips aren't getting hot during long usage. Then I played some music in loud volumes and its playing fine.

The transformer 24-0-24 was feeding all the 5 LM3886 boards and the 200W sub board. Now my question is why do I need separate transformer if the single 24-0-24 is doing the job fine? The performance is acceptable so far.

Second transformer I have is a 23-0-23 with an additional 18-0-18 tapping which I got for sub crossover and I think I can skip that crossover since my compute can control the sub. Using second transformer means separate PSU and more space requirement and it will weigh lot more. If I can keep the single transformer than I can think to bind all the stuffs together in one single cabinet.

Please share your suggestions on it.
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Old 14th October 2013, 03:13 AM   #122
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Quote:
Originally Posted by Jack Sparrow View Post
The transformer 24-0-24 was feeding all the 5 LM3886 boards and the 200W sub board. Now my question is why do I need separate transformer if the single 24-0-24 is doing the job fine? The performance is acceptable so far.

Second transformer I have is a 23-0-23 with an additional 18-0-18 tapping which I got for sub crossover and I think I can skip that crossover since my compute can control the sub. Using second transformer means separate PSU and more space requirement and it will weigh lot more. If I can keep the single transformer than I can think to bind all the stuffs together in one single cabinet.

Please share your suggestions on it.
Guys. please share your opinion on the above and also help me sorting out these issues:

1. The usual humming and hissing noise issue which I was facing earlier has gone and when I turn on the 5XLM3886, they don't give hint like something is turned on. But when I tried to observe the noise by by putting my ear near to the driver, minor kirrrr kind of noise was present there and a very-very mild hum was also there. It is very-very minor and doesn't interfere while listening audio and doesn't feel at usual sitting position but I would like to delete it as well.

2. My sub makes my sub driver to pop out loudly when it is turned on which will damage the driver sooner or later, I have a speaker protection module which I tried to add between the amp and the speaker but it didn't work. The cone pop out effect wasn't there but sound also got muted, no audio signal was passing through. I checked the volts and those were fine. This is the module I have:

spkr protection diagram.jpg

spkr protection.jpg

Whats maybe the problem? I checked the connection and those were according to the diagram and the markings given on the board.

Is there is some other easier solution to protect the driver?

3. Due to odd size of the heatsinks, I had to dump the old idea of the amp cabinet and now thinking about this simpler 2-piece thing:

cabinet layout4.jpg

Total dimensions of the cabinet : (W)430mm X (L)300mm X (H)180mm

It can accommodate - 5X3886, 1Xsub amp, 2Xtransformers, 2XPSU circuits on one board, and some other added modules by making some arrangements.

Last edited by Jack Sparrow; 14th October 2013 at 03:29 AM.
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Old 14th October 2013, 04:55 PM   #123
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Guys, please help me out there, especially in sorting out the speaker protection module issue mentioned in the previous post.
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Old 14th October 2013, 09:01 PM   #124
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Check the relay. Does it get energized when you turn on the device.
You must be hearing some clicking noise of the relay. If not there is some issue with the circuit.
Check the voltage across relay it should be close to 12v. Double check the wiring.
The circuit has a "loss of ac detector" you need to connect the ac output of your transformer. I.e before the rectifier to the circuit.hope you must have done the same. Post pics of the wiring lets see the same.
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Old 15th October 2013, 01:57 AM   #125
Minion is offline Minion  Canada
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To test the DC speaker protection disconnect the speaker output from the Protection circuit but keep the power supply connected to the protection circuit , Then connect a DC power source of say 3v-5v (Maybe 2 or 3 AA batteries in series) to the speaker inputs on the Protection circuit and listen for the Relay to Switch , you should hear it click every time the DC is connected to the Protection circuit .....

Generally speaking the loud pop you hear when you turn on the power isn't going to hurt your speaker , it is generally a extremely short DC burst to your speaker which isn't enough to harm the voice coil , though the Protection circuit is very useful for protecting your speaker in case of some sort of chip failure and clipping ... Many times when a chip fails it will output half the supply rail to the output which will fry your speaker in about 15 seconds ....
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Old 15th October 2013, 02:37 AM   #126
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Quote:
Originally Posted by saraswat View Post
Check the relay. Does it get energized when you turn on the device.
You must be hearing some clicking noise of the relay. If not there is some issue with the circuit.
Check the voltage across relay it should be close to 12v. Double check the wiring.
The circuit has a "loss of ac detector" you need to connect the ac output of your transformer. I.e before the rectifier to the circuit.hope you must have done the same. Post pics of the wiring lets see the same.
The diagram has marking for +/-37v, ground and ac inputs. I connected ground form rectifier to ground and +/- 27 after rectifier to the +/- of he circuit. Then connected amp and speaker lines to the circuit.

Now you say i should connect the AC. There is only one point for AC line, then doesn't it mean that I should connect one of the 24v supply from tranny to the AC line and the (0) to the ground? Please see the diagram of the circuit I posted in my earlier post and help me out understanding the connection.



Quote:
Originally Posted by Minion View Post
though the Protection circuit is very useful for protecting your speaker in case of some sort of chip failure and clipping ... Many times when a chip fails it will output half the supply rail to the output which will fry your speaker in about 15 seconds ....
Hmmm... Didn't think about that. Then what is better fail safe alternative.

When I start the amp, the sub driver's cone come out with a loud sound, it just feels scarey and makes me worried, its not normal pop out sound, its too loud.

Last edited by Jack Sparrow; 15th October 2013 at 02:44 AM.
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Old 15th October 2013, 10:55 AM   #127
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As you are saying you have already connected the dc supplies of +-37v to the board and the ground connection aswell. You just need to connect any one of the tranny's secondary ac output to the ac input of the board, ensuring the ac is not above 27volts. Leaving this connection will not allow the circuit to work. The circuit encorporates a delay network of capacitors and transistors, whenever the circuit will detect the ac signal from transformer it will energize the relay after a short span of time (delay) depending upon the value of the capacitor. This will prevent any switch on thummps arising due to transients. The role of the circuit here is that it will connect the speaker to the amp through the relay after a short period of time where in the amplifier circuit has been stabilized and there are no dc offsets or transients at the output. And immediately when the power is removed the ac signal is lost which will instantly swtich off the transistors driving the relay. And the speaker terminals are shorted to ground . Thus elimanting switch off sounds if any. This will protect your speaker from excessive excursion, and mechanical failure of the driver.
Also as a suggestion use a subsonic filter with this filter which will protect the driver from excessive excursion below 18hz.
secondly dont use the same psu to supply all amps. Built seperate psu for all channels. This will eliminate cross channel interference. I will suggest building a seperate psu for your sub with its dedicated trafo. Also better to use several filter caps in parallel rather than one single high value capacitor. For example ..better to put 4 pcs 4700uf capacitance in parallel than using one single 22000uf capacitor. This will handle transients in sound much more faster than one single cap. As bigger caps will take more time to charge.
Hope you will find it helpful...
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Old 15th October 2013, 11:48 AM   #128
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Thanks saraswat, that is indeed helpful So you mean I will have to connect AC from transformer along with ground and +/- supplies? So total for power inputs need to be connected there? I thought either use AC or DC.

About the separate PSU for each channel, I think that won't be feasible/practical here, that will need lot of space for each PSU since there will be 5 + 1 PSU for 6 channels. Though can build a separate PSU for sub and I have few items ready with me for that - 2X10000uf caps, 35A bridge rectifier, 2X0.1uf.

Last edited by Jack Sparrow; 15th October 2013 at 11:56 AM.
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Old 15th October 2013, 02:29 PM   #129
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Yes you are right now. You have to connect all ac and dc inputs together. I.e all 4 together.

Atleast keep two seperate psu for left and right channel. One for subwoofer and built another for remaining channels. This is bare necessary. You can have everything in a very compact space if you design it properly.
Will share some of my amp pics. You will get an idea.
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Old 15th October 2013, 03:43 PM   #130
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Thanks saraswat, will try the speaker protection module again tonigh and will report back.

I also have a readymade PSU which takes multiple input and outputs but that got fried during my testings. Will try to fix that by replacing fried caps and will also replace few caps and the bridge rectifier with higher ratings. If that starts working back then that can be used for my sub+crossover.

The one I already made can be used for rear+center channels. and I can think about separate PSU for front left and right.

Waiting for your ideas with pics so that I can plan how can I fit them in the limited space of the cabinet.

BTW is it necessary to use separate transformer for the SUB? Right now all of the amps are running through single 24-0-24 transformer and I didn't notice any degradation in sound quality.

The cabinet I am thinking is a packed type and I am thinking of using one fan in the cabinet, I have a fan which I removed form a computer SMPS, how much power supply does it need? If I use a single transformer for all the amps then I can put a smaller transformer if that is required to feed the fan. I have few small transformers rated between 9v to 12v but those have only two supplies, there isn't any ground in them.

Last edited by Jack Sparrow; 15th October 2013 at 03:57 PM.
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