I have ordered boards but stil to decide on going 19v or 24v. This will partner a ba3 as pre and will be used with spendor sp1 speakers that are around 90db efficiency (that are currently running very well with an audiosector 3875 amp). I plan to use whatever I build for some time so am intersted in if one version offers much more over the other. I am semi interested in going to hi efficiency speakers (probably some pi 3 from Wayne Parham) but will have to stay with the spendors (and their glorious mid-range) for some time at least. Advice on experience with other speakers and mofo/big mofo in general would also be appreciated. Many thanks Nigel.
@ Fwt1712
Guideline article about power and speakers efficiency calculation and legendary 1 Watt window courtesy of Mr Pass :
http://www.firstwatt.com/pdf/art_cas_2015.pdf
Your Sp1 are 8 Ohm impedance or 4 Ohm ? Large or moderate space room ?
Big MoFo 24V version are better choice your speakers are power greedy.
2.5 A bias = lower distortion figure at cost of bigger heat sinks and 193V.
Imho ideal amp for Your SP1 is MoFo on steroids
MoFo Turbo
Inductors who can handle huge ~ 4 A DC current , hockey puck mosfets , higer psu rails , giant heat sinks etc.
...or You find for example 100 dB efficient compression drivers with horns
if not 12" 98 dB full range drivers and 19V psu , 1.7A bias MoFo amp are perfect
Guideline article about power and speakers efficiency calculation and legendary 1 Watt window courtesy of Mr Pass :
http://www.firstwatt.com/pdf/art_cas_2015.pdf
Your Sp1 are 8 Ohm impedance or 4 Ohm ? Large or moderate space room ?
Big MoFo 24V version are better choice your speakers are power greedy.
2.5 A bias = lower distortion figure at cost of bigger heat sinks and 193V.
Imho ideal amp for Your SP1 is MoFo on steroids
MoFo TurboInductors who can handle huge ~ 4 A DC current , hockey puck mosfets , higer psu rails , giant heat sinks etc.
...or You find for example 100 dB efficient compression drivers with horns
if not 12" 98 dB full range drivers and 19V psu , 1.7A bias MoFo amp are perfect
Apologies in advance for not having read the 87 pages but I’m planning to use the MooseFET as a preamp. This preamp has a max output of 7Vrms, based on my knowledge this will get me a shy 6W output (8ohm load) when used with the regular 19v MoFo. Is this correct ?
I’m aiming for the 12W output so if the above preamp won’t get me there which one is recommended.
Placing my order today ;-)
BR
Eric
I’m aiming for the 12W output so if the above preamp won’t get me there which one is recommended.
Placing my order today ;-)
BR
Eric
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It's not just about the swing, it's also about the gain, maybe more so. My findings are that you really want plenty of both for maximum enjoyment. E.g. >18dB. My ARC preamp does great with the MoFo's, so does the cheap little Chinese Marantz clone I'm listening to right now.
My First Watt B1 XFRMR (Yep, I've got one
) also does great with my more efficient speakers i.e. >95dB
Plus, all the usual DIY suspects: Impasse, AKSA, B3 Pre...
Off-topic Aside: The B1 XFRMR + F3 combo is magnificent.
My First Watt B1 XFRMR (Yep, I've got one
) also does great with my more efficient speakers i.e. >95dB Plus, all the usual DIY suspects: Impasse, AKSA, B3 Pre...
Off-topic Aside: The B1 XFRMR + F3 combo is magnificent.
It's not just about the swing, it's also about the gain, maybe more so. My findings are that you really want plenty of both for maximum enjoyment. E.g. >18dB. My ARC preamp does great with the MoFo's, so does the cheap little Chinese Marantz clone I'm listening to right now.
My First Watt B1 XFRMR (Yep, I've got one
Plus, all the usual DIY suspects: Impasse, AKSA, B3 Pre...
Off-topic Aside: The B1 XFRMR + F3 combo is magnificent.
Thank you Michael
My speakers are 96 dB and the MooseFET has a gain of 15db so it should be a good match
Thanks for sharing the design and for your help.
BR
Eric
Finished the wiring this evening, still waiting on some larger 3mm plywood for the top.
Had to try it. Using a BA-3 preamp at the moment.
Clarity, articulate, imaging are some of the words to describe the sound.
Really nice amp, Michael.
Thank you for making it available to the rest of us, that have no design skills!!
Had to try it. Using a BA-3 preamp at the moment.
Clarity, articulate, imaging are some of the words to describe the sound.
Really nice amp, Michael.
Thank you for making it available to the rest of us, that have no design skills!!
Attachments
Awesome job David!!
The Big MoFo is a keeper, your going to really enjoy it
Time to build somethîg again,
What will be the most appropriate amp for a 96db 12inch driver (for mid/bass)
The Mofo, the Sitamp, or the sonyVfet2 ?
I tried 3 preamps just for fun. None are good for the MoFo, but it doesn't hurt to try.
BOZ-J: Surprising amount of gain, but still not appropriate for MoFo.
Parasound PHP 750II: Not good at all. Sounded thin.
BA3-Pre: A little more gain than BOZ-J (13 to 15db, not sure where I set it.) Better sound over all.
Have a B&K preamp left to try. Also have boards for another BA3-Pre; this time leaving it with original gain.
I will say this, there is an honesty about how the MoFo sounds, even at low gain levels.
I can't comment much about noise, except for there is no noise without music playing. I don't think the Mean Well SMPS is adding any noise.
This could change with higher efficiency loudspeakers. Don't know if noise will change with higher gain preamps, but I guess it shouldn't, if the preamp is designed and built correctly.
FYI- Heat sinks are 15.75"x8"x3". Heat sinks barely get warm. The edges of the heat sink are room temp.
If you are not building your own case, like I did, this project should be quick and fun with very good results.
Boards took under 20 minutes for part soldering.
Big thanks Michael!
Vince
BOZ-J: Surprising amount of gain, but still not appropriate for MoFo.
Parasound PHP 750II: Not good at all. Sounded thin.
BA3-Pre: A little more gain than BOZ-J (13 to 15db, not sure where I set it.) Better sound over all.
Have a B&K preamp left to try. Also have boards for another BA3-Pre; this time leaving it with original gain.
I will say this, there is an honesty about how the MoFo sounds, even at low gain levels.
I can't comment much about noise, except for there is no noise without music playing. I don't think the Mean Well SMPS is adding any noise.
This could change with higher efficiency loudspeakers. Don't know if noise will change with higher gain preamps, but I guess it shouldn't, if the preamp is designed and built correctly.
FYI- Heat sinks are 15.75"x8"x3". Heat sinks barely get warm. The edges of the heat sink are room temp.
If you are not building your own case, like I did, this project should be quick and fun with very good results.
Boards took under 20 minutes for part soldering.
Big thanks Michael!
Vince
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