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O2 headamp output booster PCB
O2 headamp output booster PCB
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Old 27th August 2017, 03:16 PM   #381
agdr is offline agdr  United States
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O2 headamp output booster PCB
Default Revised O2 Booster Board BOM posted

I've just posted a revised BOM for this project out on the Google Drive link in the first post in this thread with the rest of the DIY project materials (version 3.6 is the latest).

Just dealing with some part issues at Mouser:

* The two 10V SMD zener diodes in the protection relay circuit, D2 and D5, are being obsoleted by On Semi/Fairchild. I've replaced them with an identical part from Vishay.

* The 499K SMD resistor, R13, is out of stock at Mouser, plus they doubled the price on me. Replaced with an identical Susumu part that costs half as much.

* Mouser is out of stock of the IM26TS relays until next February, but Digikey has them and I also have them. Onlinecomponents.com is another source.

I've run a BOM scan at Mouser and I *think* those are all the significant part/price changes, but if anyone spots anything else please let me know.

Also - just a reminder since some of these are going into commercial O2's from JDS, Mayflower, etc. I would highly recommend keeping the O2 power transformer no higher than 14Vac, with at least 500mA. This goes for just plain old O2's also, without Booster Boards. Someone a few months ago mentioned in an email they had an 18Vac transformer. Definitely not recommended. Remember that NwAvGuy wasn't able to heat sink those voltage regulators in the O2. All that extra voltage just gets burned off as heat in the regulators.

More than 14Vac won't do a thing extra for you with the audio quality in an O2 (with or without a Booster Board), since the regulators limit the rails to +/-12Vdc. After the capacitors 14Vac turns into around 18Vdc unloaded or 16Vdc under full load, more than enough for the 3Vdc drop the regulators need to do their thing. 16Vdc - 3Vdc = 13Vdc, which even leaves an extra volt in case you have low AC wall voltage and takes the regulator tolerance into account.

Mouser doesn't have the AC-AC wall transformers anymore, but Jameco does (www.jameco.com):

* #171408 14Vac 500mA for $8.98
* #2138978 13.5Vac 1A for $4.95

And finally an update on doing more THD testing with the Booster Board, in addition to the QA401 tests already done. I'm waiting for Jens' new tester to ship:

DIY Audio Analyzer with AK5397/AK5394A and AK4490

Sounds like it might be September now. I also haven't had a chance yet to hook the Booster Board up to a Panasonic VP7722A I bought a few months ago. Once I get those done I'll ship a couple off for AP testing. I don't expect any significant surprises, the QA401 is already pretty good.

Last edited by agdr; 27th August 2017 at 03:29 PM.
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Old 27th August 2017, 08:42 PM   #382
agdr is offline agdr  United States
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O2 headamp output booster PCB
Default Wrong Jameco part number for 13.5Vac 1A in post above!

I just found a typo in my post above. Wrong Jameco part number for the 13.5Vac 1A wall transformer. The one above is the same thing, but wrong connector on the end. You would want:

* 2202765 13.5Vac 1A for $3.95.

The part number on the 14Vac transformer is OK. I also forgot the http:// in the Jameco link:

http://www.jameco.com

Last edited by agdr; 27th August 2017 at 08:45 PM.
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Old 10th September 2017, 03:39 PM   #383
adydula is offline adydula  United States
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Thanks for keeping this thing up-to-date!!

Alex
:>)
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Old 10th September 2017, 09:46 PM   #384
agdr is offline agdr  United States
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O2 headamp output booster PCB
Hey Alex! You bet.

I'm (slowly) working on an update to the Booster Board build instructions too. Maybe I'll get that posted this coming week (at the project Google Drive link in the first thread post). Nothing major, just some small additional tips from various questions that have come up over the last couple of years.

Last edited by agdr; 10th September 2017 at 09:48 PM.
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Old 26th December 2017, 06:48 PM   #385
CHiroshi is offline CHiroshi  Sweden
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Hi agdr!

Any news on the measurements?

I'm reviving this thread because of an strange issue I've been having lately with one of my O2s equipped with your excellent booster board. In my battery driven O2 I have the booster board with the opa140, as well as your latch board. The issue I am experiencing is that the relay on the booster is more often than not failing to click and connect the output when I turn on the amp.
When I started noticing the problem, I thought it was when the battery were discharged below a certain point. Sure enough, after I left the amp charging for a few hours, it would then turn on correctly on battery power alone. But now it's got to the point where it (the booster) doesn't turn on even with recently charged batteries. I thought maybe my batteries are getting old, but measuring them shows 9,1 and 9,12 respectively.

On AC power, everything turns on fine. I can even plug the AC adapter just to turn on the amp, then disconnect it and continue using the amp. But if I turn it off and back on again (just on batteries) the relay won't click...

Any clues? Heard of anybody else who has experienced something similar?
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Old 27th December 2017, 09:09 AM   #386
CHiroshi is offline CHiroshi  Sweden
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Quote:
Originally Posted by CHiroshi View Post
On AC power, everything turns on fine. I can even plug the AC adapter just to turn on the amp, then disconnect it and continue using the amp. But if I turn it off and back on again (just on batteries) the relay won't click...
I should add that when doing the above, I do wait at least 10-15 seconds for the PM latch to reset. Even waiting for a minute or so didn't change the behavior. And that was with the batteries measuring at around 9,1 volts each.
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Old 28th December 2017, 08:07 PM   #387
Cal42 is offline Cal42  Sweden
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Quote:
Originally Posted by CHiroshi View Post
I should add that when doing the above, I do wait at least 10-15 seconds for the PM latch to reset. Even waiting for a minute or so didn't change the behavior. And that was with the batteries measuring at around 9,1 volts each.
Admittedly, I'm on thin ice here, without much knowledge about relay power demands or having studied the 02 booster board schematic. But the behavior you describe sounds just like old batteries. They can still show high volts but without the "umph". Load them with something moderately demanding and see if the voltage drops a lot.
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Old 3rd January 2018, 07:32 PM   #388
TypodCrow is offline TypodCrow
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Does anyone here know where I can get either a build booseter board or a pcb + part kit? I've contacted agdr through the contact info on the google drive but haven't recieved a reply yet. (The store section of the website seems down as well)
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Old 4th January 2018, 05:06 PM   #389
adydula is offline adydula  United States
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Send him a pm via this site...
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Old 4th January 2018, 06:12 PM   #390
TypodCrow is offline TypodCrow
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Quote:
Originally Posted by adydula View Post
Send him a pm via this site...
I've tried this as well - sadly no response in the past few days.

Thanks
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