That is something unicorn like rare
Most likely it is a combination of lower that required temperature an excessive amount of paste or/and poor quality or dried off solder paste and oxidized pads.
As for package name - they can call it any way they want, it still does not have leads. DFN would be more accurate though - Dual(Quad) Flat No-leads package
Can recommend to preheat a PCB from the bottom using hot plate or preheated (perhaps and iron or toaster can do a job. Or even a BBQ...)
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Solder time
Hi Alex,
Good news: I read you’re very close to use your brand new air gun!. One issue with those VSON and WSON packages is that visual inspection can’t guarantee the chip is well soldered. Thus, rather than soldering all the parts, crossing fingers and firing up supply, I used a step by step approach described here:
I hope this may be useful,
Chris
Hi Alex,
Good news: I read you’re very close to use your brand new air gun!. One issue with those VSON and WSON packages is that visual inspection can’t guarantee the chip is well soldered. Thus, rather than soldering all the parts, crossing fingers and firing up supply, I used a step by step approach described here:
- Step I
Solder LM27761, C3, C4, C9, C13
Provide +5.5 with external PSU between 7805 pin3 and a GND. If you do not have and external adjustable PSU, populate board with 7805, C8, C10, C25, C16, R12, R17, CON1, place a wire between M1 anode and 7805 pin1 and plug your DC to adapter into CON1
You should have -5.1V on W1
Provide +5.5 with external PSU between 7805 pin3 and a GND. If you do not have and external adjustable PSU, populate board with 7805, C8, C10, C25, C16, R12, R17, CON1, place a wire between M1 anode and 7805 pin1 and plug your DC to adapter into CON1
You should have -5.1V on W1
- Step II
Solder LP38798, C18, C19, C22, R20, R21
Power up, then you should have +5V on W3
Power up, then you should have +5V on W3
- Step III
Solder OPA1622, C17, C23, C20, C21, R18, R13, R19, R14, R11, J2
Power up, check W5 and W2 for near 0V DC
Plug a can and, with your finger, touch the PCB on pin1 then on pin7 of OPA1642 which is not installed for now. You should hear some hum in both ears
Power up, check W5 and W2 for near 0V DC
Plug a can and, with your finger, touch the PCB on pin1 then on pin7 of OPA1642 which is not installed for now. You should hear some hum in both ears
- Step IV
Remove the wire between M1 and 7805, solder the rest of the parts. C11 and C12 are not used, HF drop is made at input by C5 and C6.
- Step V
Chris
Hey Chris!
Thanks, this info is useful to me!! I dont have any real "great" measurement tools except for a el cheopo voltmeter / ohm meter....I do have lots of experience building and soldering etc...35+ years as an electronics tech at IBM and other companies...I am SLOW and methodical, been burnt many times, I check and recheck, measure all the components I can before install etc..
This is especially important to me with this build and Sergey888's "crocodile" which is my next poject after yours.
The air gun has shipped, the parts are in Farnells "pending" stage....hope they will come in a week or so as well.
I will practice on a few old pc video cards, removing and soldering using the paste to get the hang of it.
I also before powering up etc.. I usually look at the connectivity via the schematic from the pins to where they are supposed to go,,but cant do this with these ic's!! ha!
Thanks Again!!
Alex
Looking forward to "hearing" what this one sounds like compared to all the other stuff I have here.
Thanks, this info is useful to me!! I dont have any real "great" measurement tools except for a el cheopo voltmeter / ohm meter....I do have lots of experience building and soldering etc...35+ years as an electronics tech at IBM and other companies...I am SLOW and methodical, been burnt many times, I check and recheck, measure all the components I can before install etc..
This is especially important to me with this build and Sergey888's "crocodile" which is my next poject after yours.
The air gun has shipped, the parts are in Farnells "pending" stage....hope they will come in a week or so as well.
I will practice on a few old pc video cards, removing and soldering using the paste to get the hang of it.
I also before powering up etc.. I usually look at the connectivity via the schematic from the pins to where they are supposed to go,,but cant do this with these ic's!! ha!
Thanks Again!!
Alex
Looking forward to "hearing" what this one sounds like compared to all the other stuff I have here.
RV1A and RV1B directly for positive input of the amplifier, does it cause noise by keeping an input impedance unstable?
Would not it be better to put a capacitor between them with a resistor to earth to keep an impedance stable and block DC current through the potentiometer?
RV1A and RV1B directly for positive input of the amplifier, does it cause noise by keeping an input impedance unstable?
Would not it be better to put a capacitor between them with a resistor to earth to keep an impedance stable and block DC current through the potentiometer?
back online, sorry for delay
A cap in serial (assuming it has a the right value) wont change the variability of the impedance seen by the positive input. The resistor you mention will be in parallel, which according its value, may have various effects : from nothing (high value R) to (low value R) large modification of volume pot behaviour, input filter frequency modification (Xfeed and HF ones) and also drop of amp input impedance.
About noise : this is a power amp not an instrumentation or high sensitivy one (mike, tape head, MM, MC) and you need a volume pot somewhere in the path...
AmpCasq
Hello Felipe,
Thanks for your interest.
Yes, those are the rights BOM and schematics; some tends to increase value of C23 and C17 to hundred of uF.
Ok for two boards, are you confortable with SMD soldering ?, I can also add a third board, an earlier version with some issues, to be used as a trainer board for SMD soldering.
Please PM your adress, shipping is 2,20€ for Europe, I'll send you my Paypal account.
Regards,
Chris
Hello Felipe,
Thanks for your interest.
Yes, those are the rights BOM and schematics; some tends to increase value of C23 and C17 to hundred of uF.
Ok for two boards, are you confortable with SMD soldering ?, I can also add a third board, an earlier version with some issues, to be used as a trainer board for SMD soldering.
Please PM your adress, shipping is 2,20€ for Europe, I'll send you my Paypal account.
Regards,
Chris
Each board is a complete stereo headamp based on one OPA1622. For which specific usage do you require 4 chips ? which kind of arrangement ?
Based on my measurements on my board with the +/- 5V supply, OPA 1622 can drive up to 3Vpeak on 32R//1nF load with no 'visible' distortion (I didn't have FFT capabilities for now) which is consistent with datasheet.
That mean it should be able to drive most of 'common' cans. If you have a more 'specific' one, try it !, results could be interesting. Maybe it will require an higher supply voltage for OPA 1622 (as OlegSH did, if I remember well) and larger pcb heatsink surface; or maybe it will require to parallel some OPA1622 as seen in Johnc124 OPA1622 thread.
Chris
I run my OPA1622 headmap at +-6V rails since my target headphones are 32 Ohm. I agree with Chris that high impedance headphones would probably require higher supply voltage and higher gain to reach the desired SPL. It all depends on the sensitivity of a particular model and how high is the headphones impedance. In most cases more current output capability will not be necessary, IMO. It may be pleasing having headphone amp capable to deliver high output current (enough to drive 8 Ohm speakers to listenable levels) but I do not see where it can be needed practically.
Regards,
Oleg
Regards,
Oleg
You can't, they're really different, one (1622) is targeted to drive headphone or line due to it's low distortion and output drive abilities , other is a high performance, low noise fet opamp (1642). They do not have the same package, you won't be able to solder the 1622 in place of the 1642.
You can easily replace the 1642 by most of 'good quality for audio' fet opamps, you can't replace the 1622.
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