Sure amplifier power tests |
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studio45
Old Croc Joined: 16 October 2007 Location: United Kingdom Status: Offline Points: 3864 |
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Posted: 19 June 2018 at 1:43pm |
Hi all, thought I'd start a thread just for this.
I tested my Sure "2x300w" boards AA-AB32191, which is based on the Texas Instruments TAS5630 chip. Sure claim to have measured 300 watts at 4 ohms and 10% THD - so, clipping quite severely. This would be an output voltage of 34.6v RMS, 48.92v peak (assuming a sinewave, that last 0.92v probably gets flattened out) The 1% THD power is given as 166 watts into 4 ohms. I wanted to verify those figures. There are two problems with that 300 watt figure. Firstly it seems to indicate that the amp board under test was able to swing its output nearly rail-to-rail with some degree of comfort. Neither of my boards seem to want to do that at all. Secondly, the board's protection system must have been disabled, as both the units I have enter "shutdown" mode if you try to drive them to anything like 10% THD at the output. No more than a few cycles of minimal clip are tolerated. I guess by using peak-hold meters you could capture a little data, but it's hardly representative of real-world use at that point. So I spent some time running my boards up into a 4 ohm dummy load from a stiff 48.1v supply, which did not sag during testing. The highest output voltage I could measure before clipping was 25.5v RMS/ 36.05v peak. This equates to about 165 watts. Attempts to measure a higher figure with an amount of clipping included, were defeated by the protection system. So their 1% THD figure seems accurate which is nice to know. But there was I thinking I had 600 watt amps.... Also, during these tests my current meter was indicating approximately 20 amps being drawn from the battery to produce the 165 watt output sinewave. 20Ax15.5v = 310 watts input. 165 out/ 310 in = 53% efficiency. Barely better than class AB. Even taking into account the efficiency of the power supply (claimed >85%) it seems low. Should be seeing more like 75% in-to-out. At the end of the day, I'm not saying these amps don't do the business. I guess I'm mostly surprised at how much sound my speakers do make, given these rather low power figures. However, I would be interested if anyone else with Sure modules could run them up into a load on a scope real quick and find out some real world figures? Especially if we can shed some light on these claimed efficiency ratings. Party on ;) |
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Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
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amlu
Young Croc Joined: 30 November 2009 Location: london Status: Offline Points: 740 |
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i put a metered distro on last outdoor speaker action, active ld dave system, was properly shocked that you can run a proper forest doof doof boom boom using less than 400watts,
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bitSmasher
Old Croc Joined: 23 June 2012 Location: Melbourne Status: Offline Points: 2295 |
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I bought myself an old 'scope that can take 50v, to do this sort of testing... One day I'll get to it, and post pics / results
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https://www.instagram.com/batteryacidsoundsystem/
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slaz
Old Croc Joined: 27 November 2009 Location: London E2 Status: Offline Points: 2713 |
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Yeah well I've always been a dubious of that "600W" from a chip amp .... I'd guess 600W was once observed for a fraction of a second whilst running a board to destruction at 55 Vcc or something. But 165W is still a very decent o/p from such a compact module. My ST508 Sure board claims 100W + 100W >4R - doubt if thats "real world" - but it sure as hell sounds loud and good and clean run directly from a 6S LiPo pack ... and has done so reliably for years now ....
Edited by slaz - 27 June 2018 at 11:07am |
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REMEMBER....POLITICIANS AND DIAPERS SHOULD BE CHANGED OFTEN AND FOR THE SAME REASON
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carlosdelondres
Registered User Joined: 21 June 2012 Location: London Status: Offline Points: 243 |
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I'd love to measure my Sure boards, but don't have a scope or dummy load setup. Been thinking I ought to get a usb scope of some sort as I seem to keep needing one, if you could point me in the direction of a decent one and describe your dummy load I'd be happy to test my boards - I have one of these and one of these http://store3.sure-electronics.com/2-x-400-watt-class-d-audio-amplifier-board-compact-t-amp in my micro system amp box. I'd be really interested in test results on some of their higher power boards - has anyone any experience of boards like this: |
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studio45
Old Croc Joined: 16 October 2007 Location: United Kingdom Status: Offline Points: 3864 |
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For a load I used two 8 ohm 100mm voice coils in a bucket of water, and my scope is a school-lab style Tektronix 50MHz model, last calibrated in 1991.
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Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
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carlosdelondres
Registered User Joined: 21 June 2012 Location: London Status: Offline Points: 243 |
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cheers. Will scrounge up some bits and test at some point. Off to a field for the weekend with the battery system now though... By the way, does the 2x300w board have a red led which lights and gets brighter as the amp is pushed up? If so, do you have any idea what it is indicating - clip, level, limiter, current draw or something? Off completely at lower levels...
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