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DIY Workshop » M³ headphone amplifier (part 2) amb  Headphone Council Joined: Apr. 1, 2004 |  Message [#240] posted on: 02-16-2009 12:05 AM CST (US).   |  |  OPA627 should have very low DC offset. As MisterX suggested, try swapping the opamp between channels and see if the DC offset problem moves with the opamp. |
| headphone1235 Member Joined: Nov. 7, 2008 | Message [#241] posted on: 02-16-2009 02:42 AM CST (US). | | Hey guys, nearly close to the completion of my m3 and o11 kits. I'm wondering if this opamp is suitable for the kit: http://search.di...ame=OPA627AP-ND
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| amb Headphone Council Joined: Apr. 1, 2004 | Message [#242] posted on: 02-16-2009 04:06 AM CST (US). | | Yes it is, and listed on the M³ website as a recommended opamp. |
| niksh Member Joined: Feb. 13, 2009 | Message [#243] posted on: 02-17-2009 12:49 AM CST (US). | | Hi AMB or anyone, Is it safe to run power supply 30V driving AD843 (datasheet +/-15, absolute max +/-1  ? What is the best ratio between voltage/quiescent current setting without too much heat. I know that there is a recommended voltage/max quiescent current setting. Currently, I am running M3 with 30V and 90mV quiescent current, using Q11 power supply, 40VDC/2Amp tranny with C5 4400uF and C11 2200uF on Q11; and M3 C7 3760uF. Fyi, I m running M3 mostly to drive fostex 206. |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#244] posted on: 02-17-2009 12:56 AM CST (US). | | niksh, yes, 30V is safe for AD843. As for the quiescent current, it depends on the size of heatsinks you used and how well ventilated your enclosure is. If you could still touch the heatsinks for a few seconds after fully warmed up without being uncomfortable, then it's fine. |
| niksh Member Joined: Feb. 13, 2009 | Message [#245] posted on: 02-17-2009 05:16 AM CST (US). | | Thanks AMB, that was quick, you never sleep huh? |
odilon_df Member Joined: Oct. 6, 2008 | Message [#246] posted on: 02-18-2009 05:41 AM CST (US). | | Hi AMB, please help me on some stupid think I have done: I finished my M3 an everytinhk looks fine. Operatin points adjusted , nice sound. Best regards, |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#247] posted on: 02-18-2009 05:45 AM CST (US). | | odilon_df, check your input and output wiring. |
onesandzeros Member Joined: Dec. 26, 2007 | Message [#248] posted on: 02-18-2009 06:02 PM CST (US). | | What do you folks think about burn-in? I mean, do you buy it? For drivers, with membranes that flex, I guess I can see it. But, for electronics, I'm pretty skeptical. However, my M3 has been alive for about 48 hours now, and I think its sound is improving. Hmmm. Thanks for your work on this, amb, works great with my sigma11. I figure I'll get it cased up by 2011, and then... beta22 and sigma22... |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#249] posted on: 02-18-2009 09:51 PM CST (US). | | For a class A amp, letting the circuit warm up fully makes good sense to allow it to settle into its equilibrium. But burn-in? No. I don't really believe in it, at least not for this amp. None of M³'s parts should change in any substantive way over the initial hours, days or months. With certain amps, especially those that have NOS parts (i.e., tubes or electrolytic caps) that have been sitting on the shelf for years, burn-in might rejuvenate the parts and make an actual difference. But that clearly isn't the case with this amp. |
| habba Member Joined: Feb. 14, 2009 | Message [#250] posted on: 02-19-2009 09:14 AM CST (US). | | Hi amb, on my previous post, the high dc offset problem was following the opamp. does it means that it's faulty? I've recheck everything and found out that my bass boost was at max. The voltage was lowered to 4mv, when bass boost was set to min. Increasing the vol had also increased the voltages for both the L and R channel while gnd channel stayed under 1mV. is everything fine? [Edited by habba on 02-19-2009 at 10:04 AM.] |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#251] posted on: 02-19-2009 02:03 PM CST (US). | | Yes, bass boost and volume should be all set to minimum when checking DC offset. Sounds like all is well. |
| habba Member Joined: Feb. 14, 2009 | Message [#252] posted on: 02-23-2009 11:20 AM CST (US). | | Hi amb, i have this Zz sound whenever i touch my vol knob or bass knob. [Edited by habba on 02-23-2009 at 11:20 AM.] |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#253] posted on: 02-23-2009 03:17 PM CST (US). | |
If you have a M³ v1.01 board, then please see the special notes about the ground pads near the volume pot. [Edited by amb on 02-23-2009 at 03:17 PM.] |
| wiatrob Member Joined: Jun. 4, 2008 | Message [#254] posted on: 02-23-2009 09:59 PM CST (US). | | Found the cause of the short that (temporarily) killed my sigma 11 and corrected it (pinhole in some heatshrink allowing R signal to make case contact...). A few tweaks and this baby will be complete. Sounds even better than when I had it mounted to a board- probably because it looks so much better now! Thanks! |
| habba Member Joined: Feb. 14, 2009 | Message [#255] posted on: 02-24-2009 01:34 AM CST (US). | | Hi amb, Yes i've read the special notes and done according to it, but i had connect it to IG on the input 1 block instead. |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#256] posted on: 02-24-2009 02:30 AM CST (US). | | Habba, ok, make sure that the pots are really grounded by measuring the resistance between IG on the board and the pot's metal shaft. |
| habba Member Joined: Feb. 14, 2009 | Message [#257] posted on: 02-26-2009 12:34 PM CST (US). | | hi amb, the pots shaft to IG is 0 ohm. i cant seems to find the problem. |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#258] posted on: 02-26-2009 03:21 PM CST (US). | | habba, is the power supply in the same case as the amp? And if so, is the AC ground connected to the case? I wonder if your house AC wiring might be wired incorrectly. |
| habba Member Joined: Feb. 14, 2009 | Message [#259] posted on: 02-26-2009 03:53 PM CST (US). | | the power supply is a external ac-dc adapter. |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#260] posted on: 02-26-2009 04:03 PM CST (US). | | OK. What are you using as the source (your player)? Is it AC powered? Do you still get the electric shock (either touching the amp or the player) if it's disconnected from the amp? |
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