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morsel  Headphone Council Joined: Mar. 21, 2002 |  Message [#1] posted on: 10-12-2005 10:54 AM CST (US).   |  |  This is the new M³ Build Discussion thread. Old Head-Fi M³ Build Discussion |
amb Headphone Council Joined: Apr. 1, 2004 | Message [#2] posted on: 10-12-2005 03:02 PM CST (US). | | Welcome to the new (old) world  If you had already built M³ amps, this is a place to show it off too. Post pics of your work for all to enjoy. For those of you who had not been following the M³ project, we have two "official" websites: here and here. Here is a picture of an assembled M³ board:
[Edited by amb on 10-13-2005 at 04:56 AM.] |
| ottopig Member Joined: Oct. 12, 2005 | Message [#3] posted on: 10-12-2005 06:10 PM CST (US). | | Well, here we are. Nice design to both of you. I'm casing up my second MMM now. |
n_maher HeadWize Fanatic Joined: Dec. 15, 2004 | Message [#4] posted on: 10-12-2005 08:11 PM CST (US). | | Well, I guess I'll get the ball rolling: Here's the M3 that I finished late last night. It's actually for a friend but was nothing more than a box of parts last weekend.
My M3 is about to start getting cased now that I added one of these : |
| DigiPete Member Joined: Oct. 12, 2005 | Message [#5] posted on: 10-12-2005 08:29 PM CST (US). | | Hi Nate, What case is that? Looking for a case for my Dynamight I am assembling. DigiPete [Edited by DigiPete on 10-12-2005 at 08:29 PM.] |
rjkdivin Member Joined: Sep. 11, 2005 | Message [#6] posted on: 10-12-2005 09:30 PM CST (US). | | AMB, Morsel, I have another idea.....but not sure if it makes any sense from the electronics point of view. I would like to add an output chip-amp (like these: http://www.audiosector.com/lm3875.shtml ,a gain clone....or something), after an M3 to drive some small speakers. So the M3 becomes essentially a pre-amp. But I don't necessarily want to up-power the M3 as some have done, because the primary use would still be as a stock M3 head amp. I would just use a front panel swich to select between the Phone Jack, or the Power Amp stage for output to some speakers. Is this even possible, or are there signal/impedence matching issues that are beyond my current level of understanding? My actual goal here is to add this option into my upcoming 'Super Walkman' project with an M3, CDRom Controller and Transport, DAC, and possibly the Chip-Amps all in one case.....probably a home theater type computer case. |
| n_maher HeadWize Fanatic Joined: Dec. 15, 2004 | Message [#7] posted on: 10-12-2005 09:30 PM CST (US). | | That's just a bone stock/standard Par Metals 20 Series case (http://www.par-metal.com) with dimensions of 16"x12"x3" with a full anodized finish. They make nice cases but are a pain to deal with some times - it'll take 2 to 3 weeks to get a case and they wont tell you when you'll get it, it'll just show up one day. HTH, Nate |
| n_maher HeadWize Fanatic Joined: Dec. 15, 2004 | Message [#8] posted on: 10-12-2005 09:35 PM CST (US). | |
You might want to consider just using a switching headphone jack - that's the way I wired up a preamp/headamp that I built. It was very simple to do (I'm no genius) and saved having yet another switch to worry about. Also, it avoids confusion since as soon as the headphones are plugged in the amp ceases to be a preamp and enters headamp mode. Nate |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#9] posted on: 10-12-2005 11:02 PM CST (US). | | I guess this depends on what kind of output power you're looking for. Uprating the M³ to about 6W/channel is not difficult and doesn't detract its usability for headphones (see the "Other options" area on my M³ website). And you'd be surprised how much sound 6W makes (provided that the speakers aren't terribly inefficient and the room is not large). The M³'s MOSFETs are quite up to the task of dumping current into the speaker load if the power supply is also capable. Adding another chipamp adds more boards, heatsinks and more complexity, you also have to deal with another power supply with higher rail voltages. This would make sense only if you want more power than 6W/channel. There is no problem with impedance matching or such. The M³ has ultra low output impedance, very low noise and moderate gain, so it is a very flexible, "drive almost anything" amplifier. Not only is it a headphone amp, it could also serve nicely as a preamp or a small power amp. |
ericj HeadWize Fanatic Joined: Aug. 1, 2005 | Message [#10] posted on: 10-12-2005 11:36 PM CST (US). | | The M3 is a board I've considered buying. Sometimes the challenge of working out my own point to point layout on perfboard is a nice break from work, and sometimes i just need the simple success of a properly filled board. I'm curious about the process of matching the fet pairs. I'm sure it's probably linked somewhere off amb's site, but i don't see it. What sort of instrumentation is required? I read somewhere, i think, about needing multiple DMMs to do it? I have a few feature rich DMMs. I am also recently the proud owner of a gently used Wavetek LCR55, a steal on eBay for only $20something. I'd love to have a genuine excuse for owning it :-) |
| skyskraper HeadWizer Joined: Aug. 7, 2005 | Message [#11] posted on: 10-13-2005 12:52 AM CST (US). | | you can buy the mosfets and a few of the others from amb matched in pairs already! but this is the article he links to about matching |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#12] posted on: 10-13-2005 01:13 AM CST (US). | | Regarding mosfet matching, the P-channel devices tend to have a bit higher Vgs than the N-channel. From a small handful, chances are you will not find many matches closer than 0.3V or so. Fortunately, the M³ is not sensitive to small mismatches. |
| morsel Headphone Council Joined: Mar. 21, 2002 | Message [#13] posted on: 10-13-2005 01:36 AM CST (US). | | If you can spare a bit more case height for taller heat sinks, or are willing to thermomechanically couple the heat sinks to the case lid, going with more power is the route I suggest. Use OL, OR, and IG for the preamp outputs, and OL, OR, and OG for the headphone outputs. Use 36Vpp rails and an opamp that can handle the voltage. Jumper D1 or replace it with a studlier diode. |
| diablo9 Headphone Council Joined: N/A | Message [#14] posted on: 10-13-2005 03:08 AM CST (US). | | take the exodus and joining you guys  M3 is on my "definitely-to-build" list, just after I finish my current 5+ projects.  |
| rreynol Member Joined: Oct. 13, 2005 | Message [#15] posted on: 10-13-2005 07:34 AM CST (US). | | 
Hopefully, I'll be able to work on the matching STEPS this weekend (the 1455N16 case next to the M3 in the second picture). |
| meat Member Joined: Feb. 17, 2003 | Message [#16] posted on: 10-13-2005 09:27 AM CST (US). | | Hey Nate, Can you recommend a switching headphone jack? |
| skyskraper HeadWizer Joined: Aug. 7, 2005 | Message [#17] posted on: 10-13-2005 10:25 AM CST (US). | | Neutrik NYS215 from Mouser or partsexpress |
| n_maher HeadWize Fanatic Joined: Dec. 15, 2004 | Message [#18] posted on: 10-13-2005 10:29 AM CST (US). | | Sure you could use something like mouser part # 550-22302 or 568-NYS212 - those are the two that I prefer but I'm sure there are many others. If you want to see a picture of each just let me know. The first has a chrome nose, the second has black. In fact the second part number is the one picture on the M³ that I posted on the first page and also looks like the one Randy used in the M³ picture above. HTH, Nate [Edited by n_maher on 10-13-2005 at 10:30 AM.] |
| rreynol Member Joined: Oct. 13, 2005 | Message [#19] posted on: 10-13-2005 12:02 PM CST (US). | | The chrome nose one looks like this.
The other is all black and is the one I used in the M3 pictures |
| meat Member Joined: Feb. 17, 2003 | Message [#20] posted on: 10-13-2005 01:12 PM CST (US). | | That is the one I have, but I did not know it was switching. So you just hook up 3 wires to the board and 3 go to the RCA jacks? Does it matter which ones go where? |
| rreynol Member Joined: Oct. 13, 2005 | Message [#21] posted on: 10-13-2005 02:07 PM CST (US). | | Accidental double post. [Edited by rreynol on 10-13-2005 at 02:18 PM.] |
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