Build This MoFo!

[dBel84]

Congrats to Mike for the publication in AudioXpress - great to see this work being recognized beyond our community.

An externally hosted image should be here but it was not working when we last tested it.

 

[Zen Mod]

Mr. MR, he is.

 

[Michael Rothacher]

YouTube

🙂

 

[audiodesignguide3]

Starting now with Hammond 195T5

I am starting now the experiments with Inpol / Mofo using a very good choke the Hammond 195T5 100mA 5A

 

[jostwid]

Looking forward to your results

 

[vdi_nenna]

Same here.

 

[Cpan]

Hi, what should be the input voltage in order to achieve the max power output from big MoFo and small MoFo?

Thanks, Claudio

 

[Zen Mod]

Vpp in value of rail voltage

 

[ekosis]

MOFO style with LATERAL MOSFETS

Hi all,
I built sth like MOFO with 2SJ162 four parallel. Inductor is handmade 75 MH wire diameter 1.40mm. Psu voltage 36v, I=4.0 amps. Both measurements and sound are stunning. Also the psu reversed as required.
My question is that: Iron core or air core is better ?

Regards,
Mehmet.

 

[TungstenAudio]

I have had some disappointing results with the power supply for my MoFo. I am using the MeanWell RSP-150, 27V. It was sufficient to establish a 2.4 or 2.5 Amp quiescent current at 26V, but has excessive ripple when the amp is being driven by a 1 kHz test signal. I am seeing high levels of distortion (>3%) on the output even with very low power levels. The amp clips badly at 1 Watt. I expected a 150W supply to be better behaved than this.
Adding a 70 uF motor run capacitor to the output of the SMPS made the distortion a little worse. I already have a 100 uF aluminum polymer cap at the power input on the MoFo board, but that is all right now. Looks like I need to build a CapMx if I want to use these SMPS.

 

[Zen Mod]

don't use junk

use it for some other purpose , where it works and is not junk

 

[TungstenAudio]

I kinda thought the LRS series were the cheap junk. The RSP series looked better; at least they have built-in PFC, which the LRS series doesn't have. I have two of the 27 Volt RSP-150 left over from another project and was hoping they would work for this one.

Need to find something else, I guess.

 

[Zen Mod]

well, I'm bad at remembering what's good what's not, so I remembered that I can trust my measuring equipment more than my memory

in other words, Proof is in da Pudding



edit: now I have several amps in simulation - finished, sort of "Quarantine amps Series"

while working on ...... fifth or so , after several hours of heavy fun, being finished 70% , I had an idea to check, so started searching through some older files ....... just to find that I already finished same bloody amp, on which I'm working - 7 days ago

memory .....

 

[audiodesignguide3]

First measurements on my Inpol / Mofo.with Hammond 195T5.


18VDC 2.75A drive 6072A (near to my PF2019)

Vout = 11Vrms on 8ohm load Pout=15W Thd=1.5%


Freq. (-3dB) = 3Hz - 300KHz Cout=6800uF


Very good result to be the first.

 

[audiodesignguide3]

Here another measurement


30VDC 3.5A Pout 30W on 8ohm thd 2% 1KHz


I suggest to add another mosfet on output to reduce the power to dissipate on a single device.

IRFP150NPbF

 

[audiodesignguide3]

What is your impression from the IRLP3034 in that circuit?

Regards,
Johannes

Ciss Input Capacitance––– 10315pF


very high !

 

[jostwid]

I reiterate the question of Johannes. What about irlp 3034?
i have used it and also its small cousin the irlb 3813 which has the same high Ciss.
I am currently working on a comparison of different mosfets to see how important the input capacitance really is when they are used in follower mode.

 

[jostwid]

Thank you for the measurements. Impressive what a well done Mofo does.

 

[TonyTecson]

Ciss Input Capacitance––– 10315pF


very high !

since the gain of the mofo is 1 or less, isn't the Crss the important spec?

 

[audiodesignguide3]

Here a simulation of 3 different mosfet with 3 different input capacity.


The first 2 models give a good high frequency band and this means also a good slew rate able to follow the input driver.


The output impedance of driver here is only 670ohm like my 6072A.