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New Millett Hybrid MiniMAX (what happened to this thread?) - Page 2

post #16 of 1944
just took a quick look, so other than component sizes/values, etc, the circuit design differences are basically half the power caps, no tantalum, added series resistor after PS? otherwise it seems pretty much the same MAX goodness in half the size. nice. I'm possibly missing anything, anything?
post #17 of 1944
Well, I am in on this - not because I need an(y) additional amp(s), or don't have enough to do, but rather to support the continuing DIY efforts of these exceptional designs. And the exceptional efforts of those who make this possible.

Too bad commercial realities make this such a conflict. But, we DIY will _never_ buy commercial amps, and, to the extent it is felt that this curbs sales of other products is, at best, misguided. Easy enough for DIY to be blamed if sales start to slip amongst the commercial builders, I guess.

Perhaps it is at the margin that the superior design of these products now so tempts the usual buyer to do this that is the real threat, rather than believe more people overall will now have an amp.

My opinion only.
post #18 of 1944
what pabbi1 said...
post #19 of 1944
Quote:
Originally Posted by ruZZ.il View Post
just took a quick look, so other than component sizes/values, etc, the circuit design differences are basically half the power caps, no tantalum, added series resistor after PS? otherwise it seems pretty much the same MAX goodness in half the size. nice. I'm possibly missing anything, anything?
Yes. The primary differences are in the PS grounding scheme, the overall layout with much shorter traces, but most importantly - our proposed high-level of integration with a pre-machined case.

Also, the output coupling film caps have much more room. It'll be nice to install a couple of Vitamin Q's horizontally - just as any other component.

Necessarily, there will be fairly rigid requirements on the panel-mounted parts, but we'll make certain that the availability is high. The rear power switch is probably the critical thing - most everything else is the same. (That's a smaller knob that I used from Partspipe, too.)
post #20 of 1944
I'll probably skip the case for now and wait for a machined one(hopefully). I probably wouldn't get the case done till way after its available anyway...

Also, would those be the .22 or 0.18 VQs?
post #21 of 1944
Quote:
Originally Posted by ruZZ.il View Post
I'll probably skip the case for now and wait for a machined one(hopefully). I probably wouldn't get the case done till way after its available anyway...

Also, would those be the .22 or 0.18 VQs?
0.18uf's - can't have everything. It's a tight squeeze as it is. However, the 0.22uf's should have a very short knee if you want to do that.

Yeah, I can see this is probably going to work out with no one casing theirs until the machined version is ready. I have a lot of work to do.
post #22 of 1944
Oops - first mistake! A user over on DIYForums pointed out that I left a 1-1/2" sink in for the PS on the BOM.

It's fixed, now - can't have anything over an inch with this case.
post #23 of 1944
Quote:
Originally Posted by ruZZ.il View Post
I'll probably skip the case for now and wait for a machined one(hopefully). I probably wouldn't get the case done till way after its available anyway...
Yeah, same for me. I love the prospect of a DIY project with no casework involved.
post #24 of 1944
Quote:
Originally Posted by cetoole View Post
Yeah, same for me. I love the prospect of a DIY project with no casework involved.
I hear that, especially after chipping the perfect paint job on my Bottle Head Seduction last night, and then messing it up even more trying to touch up the paint.

Oh well, it's the sound that matters, not the looks, right?
post #25 of 1944
Found another mistake - updated the BOM to use the Schottky MBR360 axial rectifiers. These should enable us to center mount the tip jacks.
post #26 of 1944
Quote:
Originally Posted by cetoole View Post
Yeah, same for me. I love the prospect of a DIY project with no casework involved.


That is the essence of what I think sets this apart.
post #27 of 1944
Quote:
That is the essence of what I think sets this apart.
Also, it's awesome. I love the compact design.
post #28 of 1944
Quote:
Originally Posted by cetoole View Post
Yeah, same for me. I love the prospect of a DIY project with no casework involved.
I'm sold!
post #29 of 1944
Quote:
Originally Posted by tomb View Post
I've posted the layout, schematic, and BOM on the MiniMAX home page.
A couple things I noticed reviewing the preliminary BOM and the schematic.

1.) CM2 appears to have been removed from the circuit, but it still shows up on the BOM.

2.) The labels for RB13 and RB14 appear to have been swapped on the MiniMax as compared to the regular Max, so the BOM should be updated to reflect this. (Or maybe you'll want to revise the schematic and the silk screen on the production run for consistency's sake?)

3.) CM3 now specifies a 470μf capacitor, which is a change from the 330μf on the Max. Is this correct?

Otherwise, things look good to me. I plan to put in an order with Mouser and Digi-Key tomorrow.
post #30 of 1944
Quote:
Originally Posted by TimJo View Post
A couple things I noticed reviewing the preliminary BOM and the schematic.

1.) CM2 appears to have been removed from the circuit, but it still shows up on the BOM.

2.) The labels for RB13 and RB14 appear to have been swapped on the MiniMax as compared to the regular Max, so the BOM should be updated to reflect this. (Or maybe you'll want to revise the schematic and the silk screen on the production run for consistency's sake?)

3.) CM3 now specifies a 470μf capacitor, which is a change from the 330μf on the Max. Is this correct?

Otherwise, things look good to me. I plan to put in an order with Mouser and Digi-Key tomorrow.
CM3 is correct. It's a bit more safety factor than is probably needed under normal circumstances - resulting in something like a 45 second delay (from memory w/o a stopwatch). However, there are various scenarios - testing, setup, kids with itchy trigger fingers - where turning the amp on and off within a minute or so will result in less than half the delay time. With the 330uf capacitor, cutting that delay time in half gets into the danger zone.

I hope this increased delay doesn't irritate some folks, but the tubes aren't at their best before several minutes/half-hour, anyway. BTW, I've used 470uf on every productoin MAX I've built. Note that this is also tied to RM2 at 1MegaOhm. If you adjust RM2, then CM3 must change as well to result in the same RC product. So, we're really recommending an RC product of RM2 and CM3 of 470ohms-farads.

CM2 is a good catch - we'll have to get an explanation from Colin on that one. He's probably decided that it's redundant.

Likewise, the RB13/RB14 swap - a good catch. My guess is that we'd need to correct the silkscreen on the production board. That would keep things consistent with the regular MAX. Again, we'll see what Colin suggests.
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