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DIY Workshop » M³ headphone amplifier (part 2) | eddystoner Member Joined: Apr. 3, 2008 |  Message [#80] posted on: 05-03-2008 04:08 PM CST (US).   |  |  AMB, The output jack was it. DOH. what a Dummy. Anyway thank you for all your hard work on these great projects. |
hardnrg Member Joined: Apr. 23, 2008 | Message [#81] posted on: 05-08-2008 09:15 PM CST (US). | | The M^3 and s11 PCBs and other parts from amb arrived today so I finally have all the parts for the amp. So, while I was sorting out all the components and looking at the build instructions, I noticed that the 2.5" heatsinks have 2.37mm diameter pins at the PCB end. What is the point of these! Lol. Is there any way to remove these pins? I guess I could drill them out? Or maybe drill holes for the MOSFETs on the other end and tap that side instead (I could probably just leave the pins as they are in this case, haha pun). I realise there are hurdles in any project, but these useless pins! Arg! lol Maybe I can twist them out using brute force and mole grips... hmmm [Edited by hardnrg on 05-08-2008 at 09:17 PM.] |
| Beefy Member Joined: Feb. 29, 2008 | Message [#82] posted on: 05-08-2008 09:18 PM CST (US). | | Just use those pins to solder the heatsinks to the board. Much easier than tapping them...... just make sure you don't get your MOSFETs mixed up, because they are a pain to remove! |
amb  Headphone Council Joined: Apr. 1, 2004 | Message [#83] posted on: 05-08-2008 09:30 PM CST (US). | | Yes, solder the heatsink pins to the board, but just "tack" them in place with a little bit of solder rather than flooding them. This will make removal easier if you ever need to do that. |
| hardnrg Member Joined: Apr. 23, 2008 | Message [#84] posted on: 05-08-2008 09:45 PM CST (US). | | doh! well... mole grips pin removal works quite easily... I've just done one so far I have a tap/die set, and totally don't mind tapping all the heatsinks... I was prepared to do it anyway... would make removal even easier hehe edit: on second thoughts... tapping 16 holes versus just identifying the MOSFETs... hmm, I'll just use my eyes and solder-tacking maybe something to mention in the assembly guide? or am I just a big noob? [Edited by hardnrg on 05-08-2008 at 09:58 PM.] |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#85] posted on: 05-08-2008 10:14 PM CST (US). | | The heatsinks I supply are all pin-less so I didn't think to mention this. At any rate I thought it would be somewhat obvious what to do with the pins...  |
| hardnrg Member Joined: Apr. 23, 2008 | Message [#86] posted on: 05-16-2008 01:25 AM CST (US). | | Success! Just set up the amp and psu on the case's bottom panel, on a plastic tray lol... Tested with MP3 player, portable CD player w/ line-out, and now my stereo amp's Tape2 Rec Out, listening from my modified X-Fi XtremeMusic... I went with 0.1uF for the Cbb caps, and it's pretty much perfect with my HD25s at/near max, but with my HD280Pros and K701s, the bass seems a little thin, almost as if max is not much more than flat... So, I'm thinking about trying 0.068uF, 0.047uF and 0.033uF... Since I have EVERYthing else for the entire amp, and have even sent the front and rear panels away to Schaeffer, I'd like to pick some caps up from a local shop, or at work, rather than make an online order for a load of stuff I don't need, or pay 20 times the cost of the caps in postage lol, but I'm not familiar with the differences between all the types of capacitors. Can I use any metallised polypropelene or metallised polyester cap? 63 or 100V I guess... Maybe the 47nF/63V "multilayer metallised polyester film" caps? Or this 0.047uF/250V "metallised polyester film"? 0.047uF/100V "mylar film"? these links are from the not-very-informative website of where I work (one of the retail stores), so I can have a look at them more closely on Saturday, I'm sure we have loads of Wima caps! [Edited by hardnrg on 05-16-2008 at 01:28 AM.] |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#87] posted on: 05-16-2008 03:06 AM CST (US). | |
Basically, yes, as long as the cap will fit properly in the board space. Polypropylene is preferred, teflon or polycarbonate types are also very good but hard to find. Polyester (mylar) is considered a step down for this application, but still far superior to any electrolytic or ceramic types. |
| hardnrg Member Joined: Apr. 23, 2008 | Message [#88] posted on: 05-17-2008 12:40 AM CST (US). | | Ended up finding some polystyrene axial caps, which after a little research appear to be as good or better than polypropolene for audio path applications at the range of values I was considering (33nF to 0.1uF). I picked values of 50nF and 68nF since I'm not sure which one will extend the bass sufficiently on the K701s. I thought passing the input signal from my modded X-Fi to the M³ via my stereo amp would remove the DC offset through internal coupling, but apparently it doesn't! My X5L has even worse DC offset. So, the only sources I have without DC offset are my CD players and maybe my Vestax mixer for my turntables. Looked into the considerations of input capacitors and ended up downloading MicroCap to simulate various values of the RC couple and it looks to me as though 3.3uF and upwards has a negligible bass roll-off and minimal phase distortion.
Hopefully the stock levels are right and I can use my computer as a source (well, and any other line level source lol) after work So far I'm very impressed with the clarity of the M³, it really has demonstrated that proper amplification improves the sound of headphones, some more than others of course. I think once I tweak this bass curve and sort out the input coupling, the sound should be perfect with all my headphones, and it will just be a case of cosmetics (like, having more than just the base panel and maybe attach the knobs and switch [Edited by hardnrg on 05-17-2008 at 12:42 AM.] |
Ferrari HeadWizer Joined: Apr. 29, 2006 | Message [#89] posted on: 05-17-2008 02:26 PM CST (US). | | hardnrg, I have taken a look in my parts bin an found some boxed polycarbonate caps (MKC), 6.8uF/100V. This type is quite compact for 6.8uF (see pic). If you want a couple to try, PM me. I will drop it in the mail for you, for free of course.
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| hardnrg Member Joined: Apr. 23, 2008 | Message [#90] posted on: 05-17-2008 03:50 PM CST (US). | |  YGPM |
| LMiller Member Joined: Mar. 1, 2006 | Message [#91] posted on: 05-27-2008 04:57 PM CST (US). | | Several months ago I built the M3 and it went very smoothly. Lately I have been doing some critical listening tests and the M3 is fantastic on simple acoustical music, but seems distorted with complex signals. I think it is sometimes referred to as sibilance. Cymbals are especially distorted. I do not hear this distortion through my speakers (Martin Logan SL3 or headphones with my simple Millet amp). I listen with Grado 125. I am thinking the problem is either with a capacitor (not good enough) or the bias is not right, but it is set to the spec. Where should I begin to look? |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#92] posted on: 05-27-2008 08:10 PM CST (US). | | LMiller, do you have other headphones to try? Grados are rather bright-sounding headphones and may be the reason. |
| LMiller Member Joined: Mar. 1, 2006 | Message [#93] posted on: 05-27-2008 08:18 PM CST (US). | | I only have the Shure in ear ETC series and the Senheiser noise canceling earphones. They are OK but not great, but I'll give a listen tonight. |
| hardnrg Member Joined: Apr. 23, 2008 | Message [#94] posted on: 05-29-2008 07:58 PM CST (US). | | I had it working perfectly this afternoon, and then the wires on the (off-board) bass pot snapped off, one snapped, fixed it, another snapped... and so on...  Rewired the pot and the sound is perfect in the left channel, but sounds kinda out of phase and clipping in the right... I have a 10MHz digital scope, and can make some pre-rendered test signals in SoundForge... This is so annoying... it was working perfectly, surely it must be the bass pot wires, but I've reflowed all the joints several times and no difference The headphone jack socket is just tethered to the PCB with the three output wires, so maybe somehow the left one got damaged... *facepalm* digged out my PortaPros and the amp is fine... three of my more expensive headphones aren't so fine though lol... luckily two out of three are less than a year old... [Edited by hardnrg on 05-30-2008 at 11:46 AM.] |
| hardnrg Member Joined: Apr. 23, 2008 | Message [#95] posted on: 06-28-2008 12:47 AM CST (US). | | I'm still having trouble finding the suggest series of capacitor for Cbb, but with value of 47nF (or possible up to 68nF) in the UK. I've asked WIMA several times over about 4 weeks about how to get them, and they offered to send samples via Anglia(UK), a components distributor, but this never happened... Looking at Farnell's selection of polypropelene caps in this value range (47-68nF), I find a load of X1/X2/Y2 suppression caps that are metallised polypropelene film, but are these actually not suitable as their intended application is for suppression? Trying to make a more educated guess, I see some Vishay MKP caps: 47nF/160V: MKP1837-347-161-G 47nF/400V: MKP1840347404M Would these be ok? At the moment I'm using some random 47nF/250V polyester film caps for Cbb, so I'm sure anything would be an improvement lol |
dougigs HeadWize Fanatic Joined: Sep. 21, 2005 | Message [#96] posted on: 06-28-2008 01:55 AM CST (US). | | Suppression caps are fine if they fit in the space... most polypropylene caps are used for line suppression. If you're ordering from Farnell and you're looking for 0.047uF (47nF), may I suggest part number 1166885 - - a really excellent polypropylene capacitor. If you're looking for 68nF, then 1166094 is a great choice, as is 1166886.
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| hardnrg Member Joined: Apr. 23, 2008 | Message [#97] posted on: 06-28-2008 02:30 AM CST (US). | | Ah fantastic... thanks for the recommendations! I think I might buy them all... two of your recommendations are the MKP1837 series that looked to be very near the suggested ones when comparing datasheets, but I had no idea if that meant they were actually good or not... Time to spend £20 at Farnell again haha... Brilliant... polypropelene caps ordered at last, along with DP relay so my mute delay has instant off and a few TO-220 clip on heatsinks for overkill. Will have it complete this coming week and be able to show it off, and more importantly, get to listen to my K701s properly again instead of through the HP out of my speaker amp [Edited by hardnrg on 06-28-2008 at 04:44 AM.] |
| dougigs HeadWize Fanatic Joined: Sep. 21, 2005 | Message [#98] posted on: 06-28-2008 05:46 AM CST (US). | | I doubt you'll notice much difference between these and the polyester ones... while theoretically more stable and less leaky (by a very slight margin), the polypropylenes aren't going to be much different in low-frequency applications. As DIYers, I do think we should use the best possible parts we can obtain in every location, so I too would use polyprops instead, but I'd be interested in knowing if you can perceive any difference. |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#99] posted on: 06-28-2008 06:17 AM CST (US). | | The Cbb caps are in the global NFB loop. When the bass boost pot is in the minimum ("flat") position, the caps are shorted by the pot. But when bass boost is turned up, the caps become sort of "coupling" caps (albeit with a pot in parallel) that pass signal from the bass frequencies and up in the feedback loop. Thus, if there is a one capacitor location that could use something nice, it's this one. Personally, I almost never use bass boost so this is not an important issue. |
| dougigs HeadWize Fanatic Joined: Sep. 21, 2005 | Message [#100] posted on: 06-28-2008 06:51 AM CST (US). | | When I have the Sennheiser 650s plugged in, I wish there was a bass CUT. |
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