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Old 22nd October 2013, 07:02 AM   #3511
aborza is offline aborza  United States
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Hi all,

I am a bit late to this party but I have a question. If the O2 is built for desk top use without the protection circuit and without batteries, and if you leave the AC on all the time (like a wall wart) but switch the DC to the amp will you still get a big thump on turning on-off? I know that is not a plan suggested by the designer, but it would make for a much simpler build.

If the DC is switched and a snubber is placed across the switch will that soften the turn on-off thumps? Any thoughts?

Thanks.
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Old 22nd October 2013, 08:55 AM   #3512
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Yes you can bypass the Power Management. You can connect h/p after the amp is powered up & disconnect h/p before turning OFF, so need to keep them ON 24X7.
Quote:
Originally Posted by aborza View Post
...If the DC is switched and a snubber is placed across the switch will that soften the turn on-off thumps? Any thoughts?...
If your switch is of good quality, the amp will have minimal ON/OFF thump. My personal observation is "toggle" switches are better than "push" switches. As for snubbers theoretically they should help.
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Old 24th October 2013, 04:55 PM   #3513
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right have built the amp as instructed, worked fine for about an hour cased up, then went all weird and distorted and then stopped working all together, have gone though all the issues listed here and nothing works at all, the amp dont work unless the batts are installed aswell, seems like a utter waste of time and effort of a kit
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Old 24th October 2013, 05:23 PM   #3514
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In this case I might be in agreement.
Do you want to fix it or junk it?
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Old 24th October 2013, 08:29 PM   #3515
swalter is offline swalter  Switzerland
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Quote:
Originally Posted by themadhatta View Post
right have built the amp as instructed, worked fine for about an hour cased up, then went all weird and distorted and then stopped working all together, have gone though all the issues listed here and nothing works at all, the amp dont work unless the batts are installed aswell, seems like a utter waste of time and effort of a kit
Right, that would be the first of 1500+ kits that is not working (after decent troubleshooting)... and this are only the ones I sold during the last two years.

First thing to check would be if the power supply circuitry is working, you mentioned the amp works only with the Batteries installed? Can you post some measurements and high res pics of the board (bottom and top side)?

Thx, Stefan
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Old 24th October 2013, 09:36 PM   #3516
ddashk is offline ddashk  Scotland
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just finished mine. no need for a review but i will just say this.
hot of the press O2+Neil Young's Old Man on my trusty ipod 3g and the sweet taste of my free lollipop makes for one of the most satisfying feelings.
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Old 24th October 2013, 10:05 PM   #3517
aborza is offline aborza  United States
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Quote:
Originally Posted by availlyrics View Post
Yes you can bypass the Power Management. You can connect h/p after the amp is powered up & disconnect h/p before turning OFF, so need to keep them ON 24X7.

If your switch is of good quality, the amp will have minimal ON/OFF thump. My personal observation is "toggle" switches are better than "push" switches. As for snubbers theoretically they should help.
Thanks for your reply, but what I want to know is whether keeping the power supply on 24/7 and switching (on or off) the DC supply to the amps at board level will minimize the thumps.
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Old 25th October 2013, 04:57 AM   #3518
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Quote:
Originally Posted by aborza View Post
Thanks for your reply, but what I want to know is whether keeping the power supply on 24/7 and switching (on or off) the DC supply to the amps at board level will minimize the thumps.
Yes it will itwill minimize the thump.

Case I
You keep PS AC adapter ON 24/7 & use FP switch to turn amp ON/OFF-minimal thump.
Case II
You turn AC adapter ON & use FP switch to turn amp ON/OFF-minimal thump (same as above)
Case III
FP switch is in ON position & you turn ON AC adapter- Loud thump, worst case is AC half cycle.Even if you plan to keep AC power supply ON 24/7 there may be situation of momentarily supply failure (lasting just under a second) or brown outs resulting in large thumps.
The batteries in O2 also act like "online UPS" to eliminate Case III type situation.C1(1uF) is also useful in reducing power ON thumps
The "minimal thump" will still be more than O2 using standard BOM.
BTW High impedance, low sensitivity h/p are more immune to power ON/OFF transients than low impedance, high sensitivity h/p e.g. IEMs.Other well designed desktop amps usually employ some sort of relay mechanism to connect h/p after the PS has stabilized & disconnect the h/p in case of supply failure/turn OFF/ DC at o/p type situation.

NwAvGuy: O2 Details
Attached Images
File Type: png o2 turn on transient into 600 ohms[2].png (53.3 KB, 147 views)
File Type: png o2 turn off transient into 600 ohms[2].png (60.6 KB, 145 views)
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Last edited by availlyrics; 25th October 2013 at 05:10 AM.
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Old 25th October 2013, 06:16 AM   #3519
aborza is offline aborza  United States
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availlyrics,

As a result of your reply I went to the schematic for a closer look. Silly me, I did not understand that FP meant Front Panel.

I assumed the O2 switched on and off at the AC input. I was wrong. It switches DC at the board level after the regulators/batteries. Exactly as I plan to do. But as NwAvGuy says, even doing that will result in large start up thumps without the protection circuit.

I am rolling my own PCB with no protection circuit and no batteries. I will leave it on 24/7 and use a snubber, FWIW, right on the board. Also, I will put a constant load on the regulators to keep them fully regulating when the DC is turned off. I hope the combination will moderate the thump on turn on and off. Of course there will be no protection for brown outs and power losses except for what the snubber might do.

Thanks
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Old 25th October 2013, 08:35 PM   #3520
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ok so i sent my board off to a friend for him to have a 2nd look to see if i missed anything and appears r14, r20 are wrong they are marked as if they are 10k but read 268r and 269r i am slightly confused with a wtf face i have checked the codes 56789746373823 times just to be sure and tested with a few dmm's and they all read the same, would these cause the amp not to work??
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