[morsel]

M³ development is closed. Thanks to everyone who participated.

It is a few hours early, but there have not been any new issues since yesterday, so the time feels right. We will let you know when boards are available.

 

[amb]

An update: The M³ boards are in the queue to be manufactured. The ETA is about 2 to 3 weeks. I will announce the web site where you can get the boards and some related parts when it is ready.

 

[BradJudy]

Good news. I may have to build this one for giggles and then sell it or my PPA.

 

[z2trillion]

yay!!! this is going to be so much fun. [edit] what color are the boards? [/edit].

 

[amb]

Quote:

Originally Posted by z2trillion what color are the boards?

It's going to be the ubiquitous green soldermask with white silkscreen.

 

[n_maher]

oh no... just what I needed... another project...

 

[steinchen]

on http://elvencraft.com/mmm you recommend the Aavid Thermalloy 531202b00000 2" heatsinks, I'd prefer 531202b02500 with pins. Do they fit ? The pcb seems to have the holes drilled for pin mounting.

Is there a benefit in taking silver mica caps for C1 and C3 instead of generic NP0 / C0G ceramic caps ?

 

[amb]

Quote:

Originally Posted by steinchen on http://elvencraft.com/mmm you recommend the Aavid Thermalloy 531202b00000 2" heatsinks, I'd prefer 531202b02500 with pins. Do they fit ? The pcb seems to have the holes drilled for pin mounting.

You can use either style. The pin-style means that you'd solder the pin
to the pad below to secure it, however it will be a lot harder to remove. The style that we recommend has holes in the heat sink which you can use with screws. I run a #4-40 tap for about 3/8" deep into the holes and use #4-40 machine screws. You could also use self-tapping screws if you wish.

I now recommend 1.5" high versions of these heat sinks (Aavid Thermalloy 531102b00000) which are comfortable with 80mA of bias. 2" is of course fine if your case has enough clearance inside.

Quote:

Is there a benefit in taking silver mica caps for C1 and C3 instead of generic NP0 / C0G ceramic caps ?

The pin spacing on the board for these are on 0.1" centers, and the Kemet Golden-max C315 series multilayer ceramic NP0/C0G fits well. If you could find silver mica caps that fit, they will also work.

 

[tingj]

Would someone here be willing to build one of these for me? I would pay the cost of parts plus a build fee -- whatever is considered reasonable.
Thanks. Hopefully this is not a violation of etiquette.
Jess
handsurgeon at gmail dot com

 

[steinchen]

just two more questions:

what are the requirements for the power supply ? With 3x 80mA + 3x 14mA (ad843) + 3x 2mA (OpAmp classA bias) + LED + ... the amp will draw about 300mA quiscent current in idle mode. How much will I have to put approximately on top of that for the dynamic load into a K1000 ? How much current should the psu at least provide ?

Are bigger values than 1uF for C2 reasonable ? Since they are for stabilizing the voltage drop and lowering impedance bigger should be better.

 

[amb]

Quote:

Originally Posted by steinchen what are the requirements for the power supply ? With 3x 80mA + 3x 14mA (ad843) + 3x 2mA (OpAmp classA bias) + LED + ... the amp will draw about 300mA quiscent current in idle mode. How much will I have to put approximately on top of that for the dynamic load into a K1000 ? How much current should the psu at least provide ?

The K1000 is a medium impedance (120 ohms) headphone and will not cause the amp to drop out of class A at max voltage swing, so the amp will not be drawing any more current than quiescent at max output. So, a power supply capable of of 0.5A should be sufficient, although I'd be happier with 1A. The K1000's low efficiency means that you will need a lot of voltage swing capability to get loud. I suggest using a 36V power supply and opamps that could handle that and swing close to rail-to-rail.

Unfortunately, the AD843 is a poor choice for the K1000 because it can't swing very close to the supply rails before clipping. In fact, the AD8065 can swing a smidge more voltage with a 24V supply than an AD843 on a 36V supply. The AD823 may be a good candidate here, with rail-to-rail swing and able to handle a 36V supply.

Quote:

Are bigger values than 1uF for C2 reasonable ? Since they are for stabilizing the voltage drop and lowering impedance bigger should be better.

I have done all sorts of measurements and listening with different values of C2 and concluded that a larger capacitance provides no benefit. Even a 0.1uF cap works just great.

 

[jamont]

Quote:

Originally Posted by amb doobooloo, the Lansing MicroPak series do not have any ventilation holes or slots, neither do the Hammond 1455 series. This makes the cases unsuitable for use with this amp. The MOSFET heatsinks get warm, and the heat need to escape. I am working on enclosure solutions. Watch this thread for more info when I have more to share.

Any progress to report here?

 

[Syzygies]

I understand that the M³ was never intended to be portable, yet I see people on planes all the time who think that 8 lb laptops (the 90's are calling! they want their laptop back!) are portable.

Can anyone imagine using a 20 AA cell travel power supply with the M³? I'd in fact prefer to outboard the battery pack, as a modular alternative to an outboard AC power supply. The M³ just gets hot, it's not a fire hazard, right?

(I know I should consider a PPA, that will in fact be next once the new boards are out and I finish my PIMETAs and MINTs. The M³ just looks very, very cool. I'm faithful to one woman, why should I be faithful to one amp?)

 

[Voodoochile]

Quote:

Originally Posted by Syzygies I'm faithful to one woman, why should I be faithful to one amp?

Uh-oh... that one is just screaming 'custom title'.

[size=xx-small](no, I don't deal with custom titles... just an observation)[/size]

 

[amb]

jamont, as far as Hammond 1455 series goes, the 1455T2201 or 1455T2202 can be used if you run with a lowered quiescent current (set to <= 50mA per channel), but this is in my opinion less than optimal as the MOSFETs do like to run with more bias. However if you must use this case then you'd have to make some compromises. Maybe make a custom top plate with ventilation holes...

As for Lansing, the Micropaks are out because none are big enough, but there are some Graybox B series cases that could be used and they can be ordered with ventilation panels.

Par Metal 20 series still looks to be the best bet, and maybe someone here could spearhead a group buy after the board comes out. I have gotten some quotes from Par Metal. Single orders of a custom sized case is going to cost about $70 but in quantities of 10 or more it drops to less than $40 each. Quite reasonable.

Larry ar Larocco Audio is still working on a quote for a beautiful custom case for this amp. I'll report when I hear more from him.

Syzygies, the temperature gets warm, but not dynahi-hot. The MOSFETs have a beautiful tendency to self-regulate in this respect. But You will need a pretty hefty battery pack to supply 0.3A for a prolonged period of time. You can do your own calculations and see how long would 20 AA cells last.