My MoFo Build
Here's my build:
A home brew monobloc chassis for each channel, with:
MeanWell LRS-100-15 100 watt power supplys set to 18VDC (only $16.00 each, what a bargain!)
Junk box high quality 30 watt 70V loudspeaker line matching transformers, using the 8 ohm secondary as the choke. Surprisingly similar to Hammond at 0.6 ohm DCR. At 18V, I biased with a 1 volt drop across the choke for 30 watts.
Crydom HE-54-5.5 Heat Sinks, Canadian surplus, $13.00 each including freight on eBay. Although similar, these are not Amazon's cheap chinese SSR heat sinks. Very nice aluminum extrusion. Spec sheet says 0.75 deg C/watt at 30 watts and measurements prove that out. At 30 watts bias, I'm running a relatively cool 58 degrees C at the transistor case after full warmup.
I'm driving them with a tube-hybrid el cheapo $99 Monoprice amp using the headphone output. Much better sound than the hybrid's built in chip amps.
Scope shows some very slight deformation of the sine wave starting below 40Hz. Obviously the 70V transformer "chokes" are the limitation. But the sound is fabulous and the ancient Braun 5.25" 2-ways don't go that low anyway.
A shout out to Zen Mod - enjoy BA 2019 - wish I could be there, maybe next year....
Here's my build:
A home brew monobloc chassis for each channel, with:
MeanWell LRS-100-15 100 watt power supplys set to 18VDC (only $16.00 each, what a bargain!)
Junk box high quality 30 watt 70V loudspeaker line matching transformers, using the 8 ohm secondary as the choke. Surprisingly similar to Hammond at 0.6 ohm DCR. At 18V, I biased with a 1 volt drop across the choke for 30 watts.
Crydom HE-54-5.5 Heat Sinks, Canadian surplus, $13.00 each including freight on eBay. Although similar, these are not Amazon's cheap chinese SSR heat sinks. Very nice aluminum extrusion. Spec sheet says 0.75 deg C/watt at 30 watts and measurements prove that out. At 30 watts bias, I'm running a relatively cool 58 degrees C at the transistor case after full warmup.
I'm driving them with a tube-hybrid el cheapo $99 Monoprice amp using the headphone output. Much better sound than the hybrid's built in chip amps.
Scope shows some very slight deformation of the sine wave starting below 40Hz. Obviously the 70V transformer "chokes" are the limitation. But the sound is fabulous and the ancient Braun 5.25" 2-ways don't go that low anyway.
A shout out to Zen Mod - enjoy BA 2019 - wish I could be there, maybe next year....
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Hey, that perf steel is what I had kicking around the shop. This is, after all, a MoFo.
I'll take some under the hood live measurements and if my mosfets are over 60 deg C,
, I'll ventilate further.I think Zen Mod is more concerned (big word that is) about some holes underneath the heatsink itself to facilitate vertical air circulation than the cover (which is perfectly fine and looking nice as well, at least to me)...
Edit: Some guys over here are craving for a "Fugly"
Edit: Some guys over here are craving for a "Fugly"
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Thanks, ZM. I will add some holes in the wood base directly under the heat sinks. This can only help to create a "chimney effect". Good suggestion!
If wood cracks, I will just nail it together. Which reminds me, remember the nail pulling scene in Black Cat, White Cat (Црна мачка, бели мачор) - very funny!
yup
Kusturica is one hell of a Filmmaker
I adore his movies , somehow - even if (majority of them) they're sorta sad , they're still optimistic
well , living in Windy Area gives you that .....
Will try adjusting MoFo output bias by listening to the tuba player in the No Smoking Orchestra ...
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Hello gentlemen,
I will start to build my MOFO just wait for its PCB...
The care for its component selection is importante and I would like to choose the best of it.
I see in this forum, it could be possible to optimise it by using Mundorf cap.
If it is the case, which cap reference is the best?
Thank you for your advice. Musically yours, TYM
I will start to build my MOFO just wait for its PCB...
The care for its component selection is importante and I would like to choose the best of it.
I see in this forum, it could be possible to optimise it by using Mundorf cap.
If it is the case, which cap reference is the best?
Thank you for your advice. Musically yours, TYM
Money vs Sound
Hi TYM,
IMHO, this design is awesome. It's so simple, that changing components shouldn't be difficult, if you wanted to try it. Spending 20x the money to get 1.1x the "sound quality" (whatever that means) doesn't thrill me. I'd rather user my money to try building something else, or mod what I have.
Or go out for a nice dinner.
If you want to try swapping components, temporarily solder a component "on top" of the PCB (not through the hole), and you can try them out. They'll be easily removable if you're not keen on the sound.
On the input film capacitor, I doubt you will see much difference in a blind test between a 22mf Mundorf (US$125/€113) and a 2.7mf Panasonic (US$6/€5,45)
On the output electrolytic capacitor, get a Nichicon 6800mf/25V for US$9/€8,17 (#UFW1E682MHD), or something similar that handles over 25V.
I bought enough components for 2 pairs of MOFOs (with some spares), and it set me back $150/€136 in May 2019.
Kind regards,
Drew
Hi TYM,
IMHO, this design is awesome. It's so simple, that changing components shouldn't be difficult, if you wanted to try it. Spending 20x the money to get 1.1x the "sound quality" (whatever that means) doesn't thrill me. I'd rather user my money to try building something else, or mod what I have.
Or go out for a nice dinner.
If you want to try swapping components, temporarily solder a component "on top" of the PCB (not through the hole), and you can try them out. They'll be easily removable if you're not keen on the sound.
On the input film capacitor, I doubt you will see much difference in a blind test between a 22mf Mundorf (US$125/€113) and a 2.7mf Panasonic (US$6/€5,45)
On the output electrolytic capacitor, get a Nichicon 6800mf/25V for US$9/€8,17 (#UFW1E682MHD), or something similar that handles over 25V.
I bought enough components for 2 pairs of MOFOs (with some spares), and it set me back $150/€136 in May 2019.
Kind regards,
Drew
Hi Tym,
I'll second what Drew has written.
I built mine using basically the parts
outlined in Mike's article and I really
like it. The input cap might have been a
Solen but it's just something I had that
was cheap.
I find the Mofo so amusing that I
will probably build a balanced version.
Cheers,
Dennis
I'll second what Drew has written.
I built mine using basically the parts
outlined in Mike's article and I really
like it. The input cap might have been a
Solen but it's just something I had that
was cheap.
I find the Mofo so amusing that I
will probably build a balanced version.
Cheers,
Dennis