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Enclosure for β24

beta24

Re: Enclosure for β24

Postby Kabal{MSU} » May 23rd, 2019, 6:45 am

cobretti wrote:Can you zoom in on the rise edge? What is the rise time?


If it helps: https://www.amb.org/forum/beta24-measurement-t3442.html AFAIR, measured slew rate was about 170V/uS.
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Re: Enclosure for β24

Postby amb » May 23rd, 2019, 8:55 am

My own slew rate measurement result was 440V/μS.
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Re: Enclosure for β24

Postby Kabal{MSU} » May 23rd, 2019, 10:25 am

Can be, that BestPav measured only one half of B24, so slew rate is to be at least doubled. I would say, B24's slew rate is enough.
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Re: Enclosure for β24

Postby mpa2 » May 23rd, 2019, 11:33 am

I measure 145 V/us. Rise time 10% to 90% (32V, Vp-p is 40 V, not 8 V as displayed - 50X probe...) about 220 ns.

IMG_20190523_201232__01__01__01_resize_38.jpg


IMG_20190523_201443_resize_82.jpg
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Enclosure for β24

Postby amb » May 23rd, 2019, 5:22 pm

Actually, with squares waves, 32Vrms is not 40Vp-p. With sine waves, 32Vrms is 90.5Vp-p (RMS to p-p conversion is 2 * 1.4142). With the high-power version of β24, you should drive your amp with sine waves up to 32Vrms output into 8Ω or a little more as long as it's not clipping (32Vrms corresponds to 170W output), then switch to squares waves, check that the top and bottom lines are 90.5+ volts apart on the scope, then measure the slew rate.
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Re: Enclosure for β24

Postby mpa2 » May 23rd, 2019, 9:47 pm

I will repeat the measurement at full power just before clipping. I've measured at lower output with 40Vpp (32V = 80% of 40 V)

Clipping started here at about 35Vrms (100Vpp) into 7 Ohms.
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Re: Enclosure for β24

Postby mpa2 » May 24th, 2019, 7:41 am

Ti, when I switch from 90Vp-p sine wave to square wave, I also switch from 32Vrms to 45Vrms, so more power is demanded. Will it still be the correct testing environment?


Here is the measurement.

IMG_20190524_171645__01_resize_60.jpg


IMG_20190524_173857__01_resize_79.jpg



18V*5=90Vp-p
Rise time 10%-90%: ~300ns
Slew rate: 72V/0.300us=240V/us.
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Re: Enclosure for β24

Postby amb » May 24th, 2019, 9:28 am

With square waves RMS is rather meaningless. The top and bottom of the square wave should be about 100V apart as observed on your scope. That corresponds to the maximum unclipped sine wave Vp-p output. Any more and you will also run the amp into clipping, except it’s hard to tell on the scope with square waves.
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Re: Enclosure for β24

Postby mpa2 » May 25th, 2019, 12:25 am

I was more concerned not to overload the transformer (250VA as far as I remember). The dummy load was getting hot pretty fast :)
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Re: Enclosure for β24

Postby Pieterh » May 26th, 2019, 10:48 pm

530 VA toroidy....I have the same.
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