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AmpCasq: an OPA1622 integrated headamp project
AmpCasq: an OPA1622 integrated headamp project
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Old 6th March 2017, 07:17 AM   #11
Idiosyncrasy is offline Idiosyncrasy  Europe
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Join Date: Jan 2015
Quote:
Originally Posted by nigelwright7557 View Post
I dropped a huge clanger when I made a similar circuit.
I hadn't kept the power supply ground separate from the audio ground and got massive hum. I had randomly mixed in power supply ground with audio ground.
The power supply needs to be on its own on one corner/side of the pcb.
Could you elaborate a little on this, Nigel? E.g., do you mean that you kept these grounds completely separate? Or did they meet in a single spot? And, if so, did you connect them using a small inductor to keep out HF crud? Also, what would be the best place to have these grounds meet?
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Old 6th March 2017, 03:51 PM   #12
AIM65 is offline AIM65  France
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AmpCasq: an OPA1622 integrated headamp project
Default BOM

Quote:
Originally Posted by adydula View Post
Aim65,

PM sent and paypal for a board....thanks! Looking forward to building up this amp.

Thanks
Alex
Great,

I'll ship it tomorrow.

I've updated the BOM, there may be some slight differences with schematic.
BOM is for Farnell, I've put Farnell's references when available.

Attached is the BOM and the schematic in a more readable pdf format.

In addition, for the ones who plan to build AmpCasq and who never did solder smd before, I can send with the pcb a previous version of the pcb for training purposes.
Attached Files
File Type: pdf AmpCasqV3.pdf (94.3 KB, 95 views)
File Type: pdf BOM_AmpCasq V3.pdf (6.9 KB, 63 views)
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Old 6th March 2017, 07:18 PM   #13
adydula is offline adydula  United States
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Do you have a part number for a dc supply? 10v-30v 300ma max,

Thanks
Alex
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Old 6th March 2017, 08:00 PM   #14
adydula is offline adydula  United States
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Nevermind....most of my existing wallworts will do!!
Alex
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Old 6th March 2017, 09:44 PM   #15
AIM65 is offline AIM65  France
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AmpCasq: an OPA1622 integrated headamp project
Quote:
Originally Posted by adydula View Post
Nevermind....most of my existing wallworts will do!!
Alex
Yes, 10 V should be enough, it use 50mA idle and up to 100/150mA with a 50 Ohms headphone playing loud. So the main adapter should not be an issue, it should even work with an AC (non rectified) adapters, 12-14V mini
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Old 7th March 2017, 07:17 AM   #16
AIM65 is offline AIM65  France
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AmpCasq: an OPA1622 integrated headamp project
Default Pcb shipped

Quote:
Originally Posted by adydula View Post
Aim65,

PM sent and paypal for a board....thanks! Looking forward to building up this amp.

Thanks
Alex
Board just shipped, delivery delay : 1 week
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Old 7th March 2017, 01:22 PM   #17
adydula is offline adydula  United States
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Great, now I have to figure out how to solder the really small parts, the 805's I have done on AGDR's ODA and other amps, but the smaller lead-less items will be a challenge to me. I have no hot air station etc...

Alex
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Old 7th March 2017, 01:36 PM   #18
OlegSh is offline OlegSh
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Quote:
Originally Posted by adydula View Post
Great, now I have to figure out how to solder the really small parts, the 805's I have done on AGDR's ODA and other amps, but the smaller lead-less items will be a challenge to me. I have no hot air station etc...

Alex
It is doable. Since PCB has big vias in the thermal pads you can solder them with the strong soldering iron from the underside. The IC should align itself on the pad due to surface tension of the molten solder, but you can correct it carefully if it is slightly off to align the pins. Once thermal pad is done use the drag method on the pins by taking a lot of solder on the soldering iron tip. Apply a lot of flux and drag the tip along the package pins. Touch up if missed something. Remember to have a lot of solder on the tip otherwise it is nearly impossible to touch and heat the pins with the bare tip.

Hope it helps.
Oleg
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Old 7th March 2017, 01:49 PM   #19
nigelwright7557 is offline nigelwright7557  United Kingdom
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Quote:
Originally Posted by adydula View Post
Great, now I have to figure out how to solder the really small parts, the 805's I have done on AGDR's ODA and other amps, but the smaller lead-less items will be a challenge to me. I have no hot air station etc...

Alex
I use SMD tweezers to hold the part.
Rest your hand on the pcb holding the tweezers to keep your hand steady.
I solder one pad first then pick up part with tweezers and solder one pin to the tinned pad. I then solder the other pin.
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Old 7th March 2017, 01:54 PM   #20
OlegSh is offline OlegSh
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Nigel, your method works for SOIC packages, SMD resistors and capacitors etc., but leadless QFN package with 0.5 mm pitch is a different story
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