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Enclosure for β24

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Re: Enclosure for β24

Postby amb » May 19th, 2019, 12:57 pm

Very nice!

The overshoot in the square wave may be a factor of measuring each of the differential outputs separately relative to ground. It is minor, but if you want to tame it, you can increase the value of C1 and C2 slightly.
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Re: Enclosure for β24

Postby mpa2 » May 20th, 2019, 12:44 am

Hi Ti,

C1 and C2 are of course not easily accessible any more :) I'll try to make more tests to see if there are any signs of instability.

BTW, how high would you go with test frequency concerning the Zobel Network? I mean, at 300 Khz Cz is only 11 Ohms, and with square waves we have higher harmonics. With no load connected, could one toast the Rz?
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Enclosure for β24

Postby amb » May 20th, 2019, 12:49 am

Unless the amp goes into some kind of oscillation, there should be very little energy at 300KHz or above under normal operating conditions, so I don’t think Rz would be in any danger. Of course you need to exercise caution while testing with square waves at high output, but that’s not anything like “normal operating condition”.
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Re: Enclosure for β24

Postby mpa2 » May 20th, 2019, 1:07 am

Sure, I mean under testing conditions. Like 1 Vpp square wave input at 300 Khz.
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Re: Enclosure for β24

Postby amb » May 20th, 2019, 1:19 am

1Vpp won’t be a problem at all.
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Re: Enclosure for β24

Postby mpa2 » May 20th, 2019, 7:23 am

Please correct me if I'm wrong.

1Vpp square wave in x Gain (20) = 20 Vpp out = 10 V RMS Vout. At 300 Khz reactance Xcz~Rz, so power dissipation at Rz would be ~ (1/2*Vout)^2/10 = 2.5 Watts.
Last edited by mpa2 on May 23rd, 2019, 12:20 pm, edited 1 time in total.
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Enclosure for β24

Postby amb » May 20th, 2019, 9:26 am

Oh, I misread your post. I thought you meant 1Vpp at the output. Yes, 1Vpp would result in 20Vpp at the output, and it will indeed stress Rz if it’s a square wave with very fast edges.
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Re: Enclosure for β24

Postby mpa2 » May 22nd, 2019, 12:55 pm

Looks better with a differential probe and 7 Ohms dummy load.

IMG_20190522_211659-01_resize_26.jpg


So I hope I don't need to tamper with C1 and C2 :)
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Re: Enclosure for β24

Postby amb » May 22nd, 2019, 12:58 pm

There you go, the square wave looks perfect. No need to mess with C1/C2.
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Re: Enclosure for β24

Postby cobretti » May 22nd, 2019, 3:54 pm

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