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Ebay 1200 watt amp board.
Ebay 1200 watt amp board.
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Old 26th October 2017, 02:11 PM   #11
GeorgeM59 is offline GeorgeM59
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Quote:
Originally Posted by Shhh its me View Post
It won't be 30A break rated at >60V DC.
A subject that can go off-topic as there are prior threads regarding the only reliable switch method for higher power amps - MOSFET switching.

I only mentioned this due to use of a relay.... a device sure to fail a break at the most critical time lest you destroy speakers in a worst case scenario [welded contacts] or degrade audio quality due to consequence of pitted contacts.

It's a 'red flag'. The amp maybe all well and good for what it is, but the use of a relay in output stage indicates lack of design consideration... maybe indicating other design flaws too. Relay could be replaced with MOSFET driver chip and correctly rated MOSFETs still using the existing fault indication/disconnect circuitry. Has been done as a module board by folks here to install in place of the relay....just like some folks have suffered the grief of welded relays not disconnecting a full rail DC voltage applied to expensive speakers.

Your choice. Be warned.
Can't say I even thought of using mosfets for a protection circuit but I can see the merit.
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Old 26th October 2017, 09:22 PM   #12
PRR is offline PRR  United States
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Ebay 1200 watt amp board.
8: 1200W output power
4: 2400W
Input Voltage: DC +/-28---+/-110V (recommend DC+/-100V)


This number must not be Sine RMS. +/-100V rails is at-most 100V peak, or 70.7V RMS, which in 8 Ohms is 625 Watts Sine RMS. 110V rails is <756W. More likely it is 600 Watts Sine RMS and they doubled it to look good.

Agree: this NEEDS a high-velocity fan. OK for PA use (though I would not bet a gig on it). Annoying for home hi-fi.

I'll agree to disagree about the use of a relay. They are used in commercial PA amps. I trust relays to turn-off quickly when I open the door in my microwave oven. A similar relay is used in vast quantity in my 2001 car without failure. Yes, risk is a function of possible damage, and we hate to kill expensive speakers, but I'd also hate to nuke my eyeballs when I open the microwave.
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Old 26th October 2017, 09:27 PM   #13
29285 is offline 29285  Europe
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Quote:
Originally Posted by Shhh its me View Post
It won't be 30A break rated at >60V DC.
A subject that can go off-topic as there are prior threads regarding the only reliable switch method for higher power amps - MOSFET switching.

I only mentioned this due to use of a relay.... a device sure to fail a break at the most critical time lest you destroy speakers in a worst case scenario [welded contacts] or degrade audio quality due to consequence of pitted contacts.

It's a 'red flag'. The amp maybe all well and good for what it is, but the use of a relay in output stage indicates lack of design consideration... maybe indicating other design flaws too. Relay could be replaced with MOSFET driver chip and correctly rated MOSFETs still using the existing fault indication/disconnect circuitry. Has been done as a module board by folks here to install in place of the relay....just like some folks have suffered the grief of welded relays not disconnecting a full rail DC voltage applied to expensive speakers.

Your choice. Be warned.
Could be my words!
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Old 26th October 2017, 11:31 PM   #14
GeorgeM59 is offline GeorgeM59
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Quote:
Originally Posted by PRR View Post
8: 1200W output power
4: 2400W
Input Voltage: DC +/-28---+/-110V (recommend DC+/-100V)


This number must not be Sine RMS. +/-100V rails is at-most 100V peak, or 70.7V RMS, which in 8 Ohms is 625 Watts Sine RMS. 110V rails is <756W. More likely it is 600 Watts Sine RMS and they doubled it to look good.

Agree: this NEEDS a high-velocity fan. OK for PA use (though I would not bet a gig on it). Annoying for home hi-fi.

I'll agree to disagree about the use of a relay. They are used in commercial PA amps. I trust relays to turn-off quickly when I open the door in my microwave oven. A similar relay is used in vast quantity in my 2001 car without failure. Yes, risk is a function of possible damage, and we hate to kill expensive speakers, but I'd also hate to nuke my eyeballs when I open the microwave.
Thanks for the Math. I did think it was a little optimistic although my power supply is only +-85 and with a bit of voltage drop I think around 400 watts at 8 ohm would be about all I expect. It would only ever be used for PA a couple of times a year which is why I don't want to put to much money into it.
I'm with you on the relay's but I don't want to start an argument, my thought is keep it simple and there is not much more simple than a correctly sized relay.

If I really add up the cost to build a 2 ch amp even though I have the toroids at no cost I am probably better off with one of these.
Behringer PA iNUKE NU3000 High-Density 3000 Watt Power Amplifier
Even with there 650watt boards at $100 each and $50 postage that's $250 then add a case $125 a bunch of caps $60 not to mention all the other hardware and I'm well behind. Just got to decide if the pleasure gained by DIY is worth the Australian dollars.
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Old 26th October 2017, 11:56 PM   #15
phase is offline phase  United States
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This has been covered here before in other threads; most of these boards use the 5200/1943 parts, and yet recommend higher voltages. This doesnít agree with the SOA of these parts.

Iím all over the eBay preamps and dac type boards, but I have yet to see a decent power amp to be honest. Still looking though...
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Old 27th October 2017, 12:03 AM   #16
PRR is offline PRR  United States
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Ebay 1200 watt amp board.
Quote:
Originally Posted by GeorgeM59 View Post
......probably better off with one of these.
"Behringer iNUKE"......
"iNUKE"??

Yes, even with one-off assemblies from the orient, it is VERY hard to "compete" with MASS-produced mass-market equipment in commodity work. B-ringer buys modules much like that but in ten-thousands, bundled with caps, iron, and metal-work, and gets a price far lower than you can imagine, enough to cover good profit to dealers and still undercut DIY.

And the B-ringer has a warranty-- if it fails the first gig you can demand your money back, or repairs. (Hmmmm.... 3-year from USA to Portugal, but Australia is not mentioned on the details web page... Australia does have extensive warranty law so you should have some protection.)
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Old 27th October 2017, 12:32 AM   #17
GeorgeM59 is offline GeorgeM59
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Quote:
Originally Posted by phase View Post
This has been covered here before in other threads; most of these boards use the 5200/1943 parts, and yet recommend higher voltages. This doesnít agree with the SOA of these parts.

Iím all over the eBay preamps and dac type boards, but I have yet to see a decent power amp to be honest. Still looking though...
Have you looked at these.
600-900W Module Class AB Audio Power Amplifier Board Assemble | eBay
I thought instead of using there recommended drivers use MJL4281/4302.
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Old 27th October 2017, 12:51 AM   #18
GeorgeM59 is offline GeorgeM59
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Quote:
Originally Posted by PRR View Post
"iNUKE"??

Yes, even with one-off assemblies from the orient, it is VERY hard to "compete" with MASS-produced mass-market equipment in commodity work. B-ringer buys modules much like that but in ten-thousands, bundled with caps, iron, and metal-work, and gets a price far lower than you can imagine, enough to cover good profit to dealers and still undercut DIY.

And the B-ringer has a warranty-- if it fails the first gig you can demand your money back, or repairs. (Hmmmm.... 3-year from USA to Portugal, but Australia is not mentioned on the details web page... Australia does have extensive warranty law so you should have some protection.)
They still claim a 3 year warranty here in Australia. I have used older Behringer amps before, a 2500 watt which seems to grunt quite well but the 1500 watt version seems to be a bit under it's rating.
Other plus of the iNuke is the weight 7lbs, my DIY monster would be atleast 40lbs if not more.

I was looking at these cheap things but the power rating is peak power so could be only 200watt RMS.
Skytec SKY-3000 PA Power Amplifier 3000W - DJ City
The guy at the shop couldn't tell me what the RMS was just told me it had a lot of grunt.
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