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DIY Workshop » M³ headphone amplifier (part 2) | dualxeon Member Joined: Dec. 8, 2008 |  Message [#200] posted on: 12-24-2008 04:23 PM CST (US).   |  |  can I to know M3 broad resistor hole sizes |
amb  Headphone Council Joined: Apr. 1, 2004 | Message [#201] posted on: 12-24-2008 05:24 PM CST (US). | |
For PCB v1.01, all resistors have 0.032" holes except R9, which have 0.04" holes. Actual hole sizes are likely to be slightly smaller due to the through-plating. |
| goldfish2 Member Joined: Dec. 30, 2008 | Message [#202] posted on: 12-30-2008 11:41 AM CST (US). | | Hello all, I am currently at the planning/research stage of building an M3 and sigma11 headphone amp and have a question re earthing. Since the sigma 11 is a floating design with no earth connection, its my understanding that the amplifier/psu combo takes it's earth reference from whatever source is plugged in. Since the two sources I am likely to use are both completely isolated from earth (a turntable and an iPod), should I provide a proper earth connection somewhere to save the whole thing charging up and giving me a nasty shock? Thinking about it now, this is especially pertinent with the turntable, those PVC records charge up nicely! |
| goldfish2 Member Joined: Dec. 30, 2008 | Message [#203] posted on: 12-30-2008 11:42 AM CST (US). | | PS Many thanks to AMB and the whole community for this and all the other great projects! |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#204] posted on: 12-30-2008 05:00 PM CST (US). | | goldfish2, you won't get shocked unless something goes wrong. But note the M³ website's "Wiring & ground" section on how ground should be wired... |
| jackhsu Member Joined: Dec. 9, 2008 | Message [#205] posted on: 12-31-2008 08:50 AM CST (US). | | Hi AMB, here is a simple, and maybe stupid question. I have some 470uf/50V caps in stock and my question is whether I can use two of these caps to replace the 3 330uf/50V caps specified for C7? The total capacity will be 50uf less and I don't know if this change will affect the performance in any way. Thank you. |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#206] posted on: 12-31-2008 01:54 PM CST (US). | | Yes, no problem with that. That's why there are different hole configurations on the board. |
| jackhsu Member Joined: Dec. 9, 2008 | Message [#207] posted on: 12-31-2008 11:52 PM CST (US). | | I found some shops offering matching service for caps. Has anyone tried matching caps and found it useful? Their argument seems convincing but I am not sure if it makes any difference worth the money and efforts, particularly for the M3 I am building. [Edited by jackhsu on 12-31-2008 at 11:55 PM.] |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#208] posted on: 01-01-2009 01:00 AM CST (US). | | I can't think of a good reason why there is a need to match caps, except for CbbL and CbbR (match for capacitance) so that the bass boost curves are as close as possible between channels, but 5% tolerance caps are good enough to make that superfluous. |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#209] posted on: 01-02-2009 02:53 PM CST (US). | | Just a heads up (brought up by aos in the ε12 thread). For the 2N3904 transistors Q5+, Q2L, Q2R and Q2G, don't order Fairchild's version with the C suffix (i.e., 2N3904CTA) because it has a non-standard pin-out. The non-C suffix version is fine. |
| dualxeon Member Joined: Dec. 8, 2008 | Message [#210] posted on: 01-16-2009 12:51 PM CST (US). | | I have got 3 pcs 0.1uF filter caps.where I shall put on my M3 headphone amp can got improvement. |
| dualxeon Member Joined: Dec. 8, 2008 | Message [#211] posted on: 01-16-2009 12:52 PM CST (US). | | I have got 3 pcs 0.1uF filter caps. where I shall put on my M3 headphone amp can got improvement. |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#212] posted on: 01-17-2009 01:38 AM CST (US). | |
I am not sure what your question is. If they are not on the M³ parts list and there is no position on the board for them, then they are not needed. |
wyatt Member Joined: Jan. 24, 2009 | Message [#213] posted on: 01-25-2009 02:23 PM CST (US). | | I've been listening to my recent build of an M-cubed with a Sigma11 power supply running 24V. It seems a little ringy on some piano solo passages above middle C. I suspect I need to change the C1L and C1R values but want to run this by everyone to see if my thinking is correct. The build is stock parts from the parts list provided by AMB with OPA627 opamps. The second pot was used as gain control as the volume knob attacked too quickly. Using the bass boost calculator I used 3.32K for R3/R4 so the 50K gain pot would give me gain between 2 and 17. I used the stock 33pf for C1L and C2L but I find that the Grado SR325i phones I'm using need the gain control turned all the way down to 2. The Grado box says they are 32 ohm with 98 SPL. I assume that and the CD player I'm using for input account for the need for low gain. The notes in the Parts List say "If your voltage gain is 4 or lower, increase C1L and C1R to 47pF." Could this be the reason for the ringing? I don't have a scope so have to rely on my ears. In all other respects the amp performs wonderfully. I'm still re-listening to my music collection to hear all the stuff that was missing before Big thanks to AMB and morsel for this gem. And big thanks to all the posters on this forum. Your experiences helped me greatly in taking on this project and getting a working PSU and amp on the first go. |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#214] posted on: 01-25-2009 02:28 PM CST (US). | | I would recommend that you change the C1L and C1R values to 47pF. That said, the effect of this is all in the ultrasonic frequencies (makes the square wave response better). I doubt it would actually be audible as what you call "ringy on piano solo". |
| headphone1235 Member Joined: Nov. 7, 2008 | Message [#215] posted on: 01-25-2009 09:36 PM CST (US). | | I just finished my m3 amp board and I'm stuck on attaching the heat sinks. Can anyone recommend me any screws that don't need me to pre-drill holes into the heat sinks? I currently don't have a power drill to make the holes bigger on the heat sinks so any help would be greatly appreciated. |
Mister X HeadWize Fanatic Joined: Jul. 23, 2003 | Message [#216] posted on: 01-25-2009 09:50 PM CST (US). | | #4 by 1/2" self tapping pan head screws are fine. |
| Mister X HeadWize Fanatic Joined: Jul. 23, 2003 | Message [#217] posted on: 01-25-2009 09:50 PM CST (US). | | Double postage.  [Edited by Mister X on 01-25-2009 at 09:50 PM.] |
| headphone1235 Member Joined: Nov. 7, 2008 | Message [#218] posted on: 01-28-2009 02:53 AM CST (US). | | Thanks for your help. |
| wyatt Member Joined: Jan. 24, 2009 | Message [#219] posted on: 01-28-2009 04:48 PM CST (US). | |
That was an interesting change. I couldn't quickly get the correct replacements so I tried some caps that turned out to be 200V X7R rated. The sound was affected in a bad way. Seemed compressed, the soundstage was blurred. Today I got the correct C0G parts and all is great. AMB, you were correct: I really couldn't hear any difference. I imagine the piano solo is just the material not the amp. Everything else sounds better than fine so it's likely I just never could hear the source flaw before. Now I'm trying to learn why the wrong type of cap made such a marked difference. |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#220] posted on: 01-29-2009 12:11 AM CST (US). | | C0G caps are superior to X7R for compensation purposes. They are thermally much more stable, and have better high frequency characteristics. |
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