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Juma's Easy-Peasy Capacitance Multiplier
Juma's Easy-Peasy Capacitance Multiplier
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Old 13th October 2016, 04:42 PM   #11
jkuetemann is offline jkuetemann  Canada
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I did one based on the work of MrEvil:

Simplified MrEvil / PMI Capacitance Multiplier
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Old 13th October 2016, 05:25 PM   #12
AndrewT is offline AndrewT  Scotland
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Originally Posted by xrk971 View Post
................I don't think there is an issue with current yet - 12amps with IRP240/9240 is quite high already. I don't know too many amps that pull that much current......................
most 8ohms speakers can demand transients that exceed 12Apk.
4ohms will demand even more.
If the amplifier is any good it will pass that transient demand back to the capacitance feeding it.
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Old 13th October 2016, 05:27 PM   #13
xrk971 is offline xrk971  United States
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Juma's Easy-Peasy Capacitance Multiplier
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Originally Posted by jkuetemann View Post
I did one based on the work of MrEvil:

Simplified MrEvil / PMI Capacitance Multiplier
Click the image to open in full size.

Thanks, Jason. I don't know enough to understand why it has so many transistors though - are there added benefits like lower dripeout voltage or better ripple control vs the Juma "Easy Peasy" circuit? I submit, the Juma circuit is dead simple, still.
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Old 13th October 2016, 05:35 PM   #14
dobrivoje is offline dobrivoje  Serbia
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Originally Posted by xrk971 View Post
Click the image to open in full size.

This is like an F5 with the venerable 2SK1058 and 2SJ162 lateral FET. Will have to try it one day.
Sorry X, I made a mistake. There is no cap multiplier here.
Also, this amp has v2 (Class A) Cubie2
and v3 (Class AB) Cubie3.
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Old 13th October 2016, 05:56 PM   #15
xrk971 is offline xrk971  United States
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Juma's Easy-Peasy Capacitance Multiplier
Cubie 2 looks like a fine design. Another great one from Juma.
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Old 13th October 2016, 06:07 PM   #16
xrk971 is offline xrk971  United States
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Juma's Easy-Peasy Capacitance Multiplier
I see the IRFP044 n channel being used here on both rails:

Click the image to open in full size.
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Old 13th October 2016, 06:14 PM   #17
Mooly is offline Mooly  United Kingdom
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Juma's Easy-Peasy Capacitance Multiplier
Quote:
Originally Posted by xrk971 View Post
Hi Mooly,
Thanks for the simulation! Wow - that is indeed very effective and confirms my experience and data from the Fluke. I was wondering if it was just missing bandwidth but this appears to be a very sound topology. Loss of headroom probably not an issue for someone wishing to listen to music as lower volumes where hum is audible.
Your welcome

Here is the same set up but now with a 10 ohm load that is being pulsed. The rise and fall times of the pulse are slow (100ms). Curious that there seems to be some oscillation in vout now.

The current in the load is at the right hand scale.
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Old 13th October 2016, 06:29 PM   #18
xrk971 is offline xrk971  United States
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Juma's Easy-Peasy Capacitance Multiplier
Mooly,
I think this is why I have heard that the K multipliers lose their effectiveness for class AB dynamic loads, but in class A where the current glow is pretty stationary it makes a big difference with line induced ripple hum. Would it help to make C2 33mF and C1 2.2mF? Maybe follow something similar to the circuit in Post #16?
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Old 13th October 2016, 06:38 PM   #19
Mooly is offline Mooly  United Kingdom
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Juma's Easy-Peasy Capacitance Multiplier
Maybe. One thing though, with a FET having a high gate impedance at the frequencies involved, the R/C network can be much reduced. A 1meg and 2.2uf cap seem to give similar results, even a 10meg and 0.22uf does.

(the oscillation is actually nothing of the kind... silly me ! Its just the 100/120 Hz ripple looking suspicious because of the x axis time scale. FET choice is important in minimising this)
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Old 13th October 2016, 06:44 PM   #20
xrk971 is offline xrk971  United States
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Juma's Easy-Peasy Capacitance Multiplier
So what are we looking for in a FET that is optimal?
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