I’m starting on another MoFo but this time using an SLB SR power supply. Will be fed by Antek AS-3222 which will provide about 25v at 3A. With the SLB SR, I am getting less than 1mV rms ripple as measured with 8ohm 100w Dummy load.
Here is scope shot of input (yellow) to pass-BJT and output (red) of the ripple eater:
I will be using JPs64’s Excellent MoFo boards:
Will drive with an Aksa Lender pre running at about 27dB gain with a 48vdc power supply.
Here is scope shot of input (yellow) to pass-BJT and output (red) of the ripple eater:
I will be using JPs64’s Excellent MoFo boards:
Will drive with an Aksa Lender pre running at about 27dB gain with a 48vdc power supply.
Oh right. Sorry, didn't realize I had to download from an external page. The link didn't exactly stand out.
Happy to report my MoFo channels are working! Pics to come, once I get the mounting sorted out.
Many thanks to everyone, especially vunce for providing PCBs.
Next up is to build a pre based on the Korg Nutube.
Kind regards,
Drew
Many thanks to everyone, especially vunce for providing PCBs.
Next up is to build a pre based on the Korg Nutube.
Kind regards,
Drew
A quick question: It looks like it would be very easy to get more output voltage swing with higher power supply voltage (and input voltage swing). Is the limit here the increased distortion shown in the original article, or is that increased distortion at max power reflecting an approach to clipping?
Thanks, Skip
Thanks, Skip
The limiting factor is heat removal. I ran mine at 37.5v and 4.35A - that's 163w per channel. Had to use an IXYS MOSFET, CPU cooler and fan but was getting upwards of 49w. Of course, you will need a clean preamp that can drive 57vpp.
Last edited:
Thanks, I think I'll go ahead with the higher voltage, biasing to allow the choke to work and use huge sinks and fans if needed.
Skip
Skip
Moving along on build specs: It looks like I'll be aiming at 34-36 VDC and about 3.4 amps. Can the IRFP250 handle this, and even if it can, is there a better choice? I noticed the max Vgs is +- 20V. I'm not up to much effective interpretaion/understanding of data sheets, but this looks like it might be touchy at my voltage/current target.
Skip
Skip
The IXTK88N30P can handle 600w dissipation vs the IRFP250’s 214w. A TO-264 case also has capability of dissipating more. I would suggest a CPU cooler with heat pipes in order to remove 120w from the MOSFET die quickly enough.
joining the club
Hi all,
MR, thanks for the design. Here is my attempt to build the amp.
Custom ordered choke not the Hammond ones (different specs from the Hammond). Voltage drop across the choke is about 2.7 volt (2 ohms Rdc). Modded a bit to adjust with available components in my drawer. Currently set to about 1 A bias (fluctuating AC mains) and of course, the HS gets really hots after ten minutes of music play. Hunting for bigger HS now.... 🙂
Once getting a bigger HS, higher bias current will be exercised.
Cheers !
Hi all,
MR, thanks for the design. Here is my attempt to build the amp.
Custom ordered choke not the Hammond ones (different specs from the Hammond). Voltage drop across the choke is about 2.7 volt (2 ohms Rdc). Modded a bit to adjust with available components in my drawer. Currently set to about 1 A bias (fluctuating AC mains) and of course, the HS gets really hots after ten minutes of music play. Hunting for bigger HS now.... 🙂
Once getting a bigger HS, higher bias current will be exercised.
Cheers !
Attachments
Thanks Mike for the optimistic news.
Your DIY work share is " the light " to many audio hobby amateurs.
Hooray! 😀
I hope the “Tunnel” gets full sunlight very soon Mr. MR 🙂
I’ve been thoroughly enjoying the MoFo since the day it was born!!
Thank you.
I’ve been thoroughly enjoying the MoFo since the day it was born!!
Thank you.
So good to hear from you Mike! Hope things continue to get better.
Thank you for the Mofo. It totally rocks!
Dennis
Thank you for the Mofo. It totally rocks!
Dennis
Would it be possible to build a Mofo With Npn transistors? A Bifo? I got some nice 35 year old battery charger electronics, large heatsinks with 3 x MJ 802 already mounted.