Juma's Easy-Peasy Capacitance Multiplier

[jkuetemann]

I did one based on the work of MrEvil:

Simplified MrEvil / PMI Capacitance Multiplier

[AndrewT]

Originally Posted by xrk971

................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.

[xrk971]

Originally Posted by jkuetemann

I did one based on the work of MrEvil:

Simplified MrEvil / PMI Capacitance Multiplier

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.

[dobrivoje]

Originally Posted by xrk971

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.

[xrk971]

Cubie 2 looks like a fine design. Another great one from Juma.

[xrk971]

I see the IRFP044 n channel being used here on both rails:

[Mooly]

Originally Posted by xrk971

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.

[xrk971]

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?

[Mooly]

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)

[xrk971]

So what are we looking for in a FET that is optimal?