It plays music. 
I did a listening session with it and my DIY F5. (I will drop the "DIY" from here on for brevity, by keep in mind that all 3 amplifiers mentioned are DIY versions.)
First let's get the expectation bias out of the way: I expected the J2 to notably tame the sometime over-aggressive highs of the F5, with a slight loss of control in the bass. Basically 1/2 way between an F3 and F5.
I found the J2 to be much closer to the F5 than expected. There was some pull-back of the in-your-face nature of the F5's highs, but not much. My daughter summed it up well: the F5 would be great for music class because it made it easier to pick out the individual instruments, but she'd rather listen to the J2.
On the other hand there was more difference in the bass than I expected. The J2 felt like it went deeper. Not a hair deeper, but notably deeper. (My test speakers are old Gale 4s -- a ported two-way design.) The bass might have also had a bit more warmth (ie: been a little more rounded), but this difference was subtle.
It was a bit hard to match volume levels as the J2 has more gain.
Cheers,
Jeff.
I did a listening session with it and my DIY F5. (I will drop the "DIY" from here on for brevity, by keep in mind that all 3 amplifiers mentioned are DIY versions.)
First let's get the expectation bias out of the way: I expected the J2 to notably tame the sometime over-aggressive highs of the F5, with a slight loss of control in the bass. Basically 1/2 way between an F3 and F5.
I found the J2 to be much closer to the F5 than expected. There was some pull-back of the in-your-face nature of the F5's highs, but not much. My daughter summed it up well: the F5 would be great for music class because it made it easier to pick out the individual instruments, but she'd rather listen to the J2.
On the other hand there was more difference in the bass than I expected. The J2 felt like it went deeper. Not a hair deeper, but notably deeper. (My test speakers are old Gale 4s -- a ported two-way design.) The bass might have also had a bit more warmth (ie: been a little more rounded), but this difference was subtle.
It was a bit hard to match volume levels as the J2 has more gain.
Cheers,
Jeff.
Latest sketch up, FW and modushop 4U form factor.
I talked to a rep. from extruder. Tooling is a one time charge, $1200-1800. Bare extruded product is ~ $6.5/kg. FW form factor ~ 3 kg for a 30cm piece while 4U form factor is ~ 3.5 kg for a 30cm piece. Still need to add machining and anodizing. Est. max. total of $84 (FW) or $90 (4U) + shipping @ minimum order of 90 pairs (180 pcs) of 30cm length.
Biggest cost would be shipment. By air to UK would be ~ $15/kg, est. $115 for a pair of FW form factor, $130 for 4U. Still looking for better alternatives.
Comments or suggestions?
I talked to a rep. from extruder. Tooling is a one time charge, $1200-1800. Bare extruded product is ~ $6.5/kg. FW form factor ~ 3 kg for a 30cm piece while 4U form factor is ~ 3.5 kg for a 30cm piece. Still need to add machining and anodizing. Est. max. total of $84 (FW) or $90 (4U) + shipping @ minimum order of 90 pairs (180 pcs) of 30cm length.
Biggest cost would be shipment. By air to UK would be ~ $15/kg, est. $115 for a pair of FW form factor, $130 for 4U. Still looking for better alternatives.
Comments or suggestions?
Attachments
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I agree with 4U/400, but I think the 5-fin version looks better. Even if it's a bit lower thermal transfer, the 4U/400 form factor should still give plenty.
8 x 3.8mm through holes at 1", 3", 5", 7", 9", 11", 13" and 15"?
Tap ends of extrusion for M4, or leave that as an exercise to the builder?
Looking good!!!!
8 x 3.8mm through holes at 1", 3", 5", 7", 9", 11", 13" and 15"?
Tap ends of extrusion for M4, or leave that as an exercise to the builder?
Looking good!!!!
Thanks ZM. 
Which is preferred M4 or M5? I think 4 x M5 is better to hold a front/back plate.
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dimension of the board mounting flange?
Hi,
I have J2 boards on order with the present group buy, and am planning on building with the 4U x 400mm Dissipante chassis.
I was thinking of just adding 6mm thick angle iron to the heatsinks to create the flange.
how far out from the heatsink does the board mounting flange need to be?
In other words, what are the dimensions of the board mounting flange on either the original or planned extrusions?
Thanks,
Matt in Minnesota, USA
Hi,
I have J2 boards on order with the present group buy, and am planning on building with the 4U x 400mm Dissipante chassis.
I was thinking of just adding 6mm thick angle iron to the heatsinks to create the flange.
how far out from the heatsink does the board mounting flange need to be?
In other words, what are the dimensions of the board mounting flange on either the original or planned extrusions?
Thanks,
Matt in Minnesota, USA
Yes the flange do add to weight and package volume, 0.4 kg for 400mm length. Est. cheaper by ~ $20 per 400mm pair shipped by air.
Thanks ZM.
Which is preferred M4 or M5? I think 4 x M5 is better to hold a front/back plate.
I think M4 is plenty, but M5 would work too. Anyone know what the Modushop cases use?
It also occurs to me that leaving this to the builders wouldn't be a great idea since the gap in the 'C' channel means a straight-fluted tap is going to be really tricky (and most folks probably won't have a spiral fluted tap).
Cheers,
Jeff.
The original is 1-3/4" wide, with the holes set back 1/2" from the front. But it's wider than is required -- 1-1/2" would be fine too.
Use thermal paste between the angle and the heatsinks, and bolt it down in at least 4 places (and 6 or 8 would be better).
Cheers,
Jeff.
4U 5-Fin Sketch, with and without flange.
4U5F/400 with Flange :
Est. weight 4.4 kg/pc.
Min order 126 pcs = 63 pairs.
Est. cost max $80 / pair.
Est. ship to UK by air ~ $160.
Est. total $240 / pair.
4U5F/400 without Flange :
Est. weight 4 kg/pc.
Min order 140 pcs = 70 pairs.
Est. cost max $75 / pair.
Est. ship to UK by air ~ $135.
Est. total $210 / pair.
Shipping rate has price break at 10, 20, 30, 50, 70 and 100 kg.
Note: prep, production, machining and anodizing is estimated to take between 8 to 12 weeks.
4U5F/400 with Flange :
Est. weight 4.4 kg/pc.
Min order 126 pcs = 63 pairs.
Est. cost max $80 / pair.
Est. ship to UK by air ~ $160.
Est. total $240 / pair.
4U5F/400 without Flange :
Est. weight 4 kg/pc.
Min order 140 pcs = 70 pairs.
Est. cost max $75 / pair.
Est. ship to UK by air ~ $135.
Est. total $210 / pair.
Shipping rate has price break at 10, 20, 30, 50, 70 and 100 kg.
Note: prep, production, machining and anodizing is estimated to take between 8 to 12 weeks.
