Headphones Amp

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ruffrecords

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Clearly no one knows what I'm talking about.
That is exactly it. To make any op amp single supplied all you need to to is make the negative rail ground and bias the op amp +ve input to half the rail voltage. The op amp itself knows absolutely nothing about split rails.

Cheers

Ian
 

Newmarket

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Hmmmm, I don't doubt that with that amount of copper it would handle 250mW but that is a lot of real estate that cannot be used for tracking.

That's always the thing with small SMT power stuff. Yes - it will work with enough copper attached and via stitching etc - but that is effectively adding to the size of the "composite component" and in many cases it negates the size advantage.
It also often requires the soldering of a "Powerpad" on the bottom of the device.
And its often at least implied that this pad needs to be connected to 0V for proper 'datasheet' operation.
That really needs top be done with the proper equipment - very likely a sub contract manufacturer - which may not be ideal for short run / low volume kit.
I'll happily DIY 'standard' SMT - well down to 0603 wrt chip components - but there's a limit.
I kinda like the small finned heatsinks that you can stick on top of components.
 

abbey road d enfer

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The sources are transformer balanced. To use a single pot on a balanced signal you connect the ends of the pot to the hot and cold. The output is from the cold and the wiper. I am sure you know this.
Then it means you separate the debal and amplification functions. It answers part of the questions I asked earlier.
 

MidnightArrakis

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That's always the thing with small SMT power stuff. Yes - it will work with enough copper attached and via stitching etc - but that is effectively adding to the size of the "composite component" and in many cases it negates the size advantage.
It also often requires the soldering of a "Powerpad" on the bottom of the device.
And its often at least implied that this pad needs to be connected to 0V for proper 'datasheet' operation.
That really needs top be done with the proper equipment - very likely a sub contract manufacturer - which may not be ideal for short run / low volume kit.
I'll happily DIY 'standard' SMT - well down to 0603 wrt chip components - but there's a limit.
I kinda like the small finned heatsinks that you can stick on top of components.
[I'll happily DIY 'standard' SMT - well down to 0603 wrt chip components] -- Some years ago I once designed an 8-layer PCB that was only 1.25" square (31.75mm square) for the U.S. Dept. of Homeland Security that had over 205 components of the -- 0201 -- size, placed on both sides of the PCB!!! It also had a 256-pin micro-BGA, some 64-pin PLCC's, a couple of standard 8-pin DIP's (one of which had a self-contained microphone) and a couple of 64-pin dual-row micro-header connectors!!! Two of the internal layers consisted of "Split Power & Ground" planes and all of the routing was done using 4-mil tracks & spaces.

Yeah.....this is off-topic, but I saw the 0603 comment and I just thought I would mention one of my 0201 experiences. SORRY!!!

/
 

Newmarket

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[I'll happily DIY 'standard' SMT - well down to 0603 wrt chip components] -- Some years ago I once designed an 8-layer PCB that was only 1.25" square (31.75mm square) for the U.S. Dept. of Homeland Security that had over 205 components of the -- 0201 -- size, placed on both sides of the PCB!!! It also had a 256-pin micro-BGA, some 64-pin PLCC's, a couple of standard 8-pin DIP's (one of which had a self-contained microphone) and a couple of 64-pin dual-row micro-header connectors!!! Two of the internal layers consisted of "Split Power & Ground" planes and all of the routing was done using 4-mil tracks & spaces.

Yeah.....this is off-topic, but I saw the 0603 comment and I just thought I would mention one of my 0201 experiences. SORRY!!!

/
Well I'd design it but don't ask me to assemble it by hand !
 

MidnightArrakis

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Well I'd design it but don't ask me to assemble it by hand !
[Well I'd design it but don't ask me to assemble it by hand!] -- HA!!! The client that I did this PCB for was a defense contractor and they -- DID -- assemble this board by hand in-house.....as it was a "one-off" design and they certainly didn't want to trust any outside contract assembly firms to put this PCB together!!! On some of the other PCBs I had also designed for this client, they had me place an 0.062" hole underneath the larger SMD components, which allowed them to stick a fiber-optic camera up there so they could "see" the backside of the component lead solder joints for completeness and reliability issues. I had spent nearly 2-1/2 years designing "Dept. of Homeland Security" PCBs for this defense contractor and some of them were just downright "spooky and weird", but I am also glad that I got to design them all for The U.S. of A.!!!

/
 

Newmarket

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[Well I'd design it but don't ask me to assemble it by hand!] -- HA!!! The client that I did this PCB for was a defense contractor and they -- DID -- assemble this board by hand in-house.....as it was a "one-off" design and they certainly didn't want to trust any outside contract assembly firms to put this PCB together!!! On some of the other PCBs I had also designed for this client, they had me place an 0.062" hole underneath the larger SMD components, which allowed them to stick a fiber-optic camera up there so they could "see" the backside of the component lead solder joints for completeness and reliability issues. I had spent nearly 2-1/2 years designing "Dept. of Homeland Security" PCBs for this defense contractor and some of them were just downright "spooky and weird", but I am also glad that I got to design them all for The U.S. of A.!!!

/

How do you (they) assemble a BGA 'by hand' - and inspect it (usually done by X-ray) ?
 

ccaudle

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How do you (they) assemble a BGA 'by hand' - and inspect it (usually done by X-ray) ?

I suspect that anything with a small BGA and 0201 components is not literally assembled "by hand" but rather by a small prototype oven instead of an assembly line. I have replaced a small number of 0201 components by hand before, and it involves multiple attempts and much cursing and throwing small components across the workbench. It would be physically impossible to install 200 components on a board that size with a soldering iron, you have to use either hot air bath, or IR reflow.
 

MidnightArrakis

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I suspect that anything with a small BGA and 0201 components is not literally assembled "by hand" but rather by a small prototype oven instead of an assembly line. I have replaced a small number of 0201 components by hand before, and it involves multiple attempts and much cursing and throwing small components across the workbench. It would be physically impossible to install 200 components on a board that size with a soldering iron, you have to use either hot air bath, or IR reflow.
[much cursing and throwing small components across the workbench] -- HA!!! Reading this made me laugh out loud and chuckle!!! GOOD ONE!!! But, I have also experienced the same "professionalism" while sitting at my workbench!!!

Since all of the PCBs I had designed for this defense contractor were for The Department of Homeland Security and were basically "classified" projects, I was never able to witness any of the actual physical assembly and/or -- HOW -- these PCBs were assembled. I was just given a set of schematics, a BOM and some mechanical parameters and then I provided them with a ZIP file of GERBER and N/C Drill files. What happened after that..........I have no idea!!!

One of the projects that were a part of all of the DHS PCBs involved me designing a tiny GPS receiver so that the GPS receiver, its battery and its antenna could all fit within a hollowed-out cavity within a piece of 2X4 lumber!!! When the company that created the shipping crates that were used to transport arms and missiles from the U.S. mainland to our various U.S. military bases overseas, one of the pieces of lumber that were used to create the shipping crate had this GPS receiver hidden within it. So.....after these crates of ammunitions, arms and missiles made it over to the foreign ports and were in transit to the actual military base and if the trucks became hijacked by "The Bad Guys", the U.S. military could track the crates' whereabouts and either send out a "Special Ops" team to recover these crates or call-in an airstrike to blow the crates up to "Kingdom Come" along with any "Bad Guys" who happened to be nearby!!! I liked that part!!! I never realized that just being a "Senior PCB Designer" could have such an impactive relevance on the overall world events!!!

/
 

Bo Deadly

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One of the projects that were a part of all of the DHS PCBs involved me designing a tiny GPS receiver so that the GPS receiver ... the U.S. military could track the crates' whereabouts
Assuming this isn't all just BS, did DHS happen to ask you to sign an NDA perhaps? You do realize that the "Bad Guys" have Internet too right?
 

Newmarket

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I suspect that anything with a small BGA and 0201 components is not literally assembled "by hand" but rather by a small prototype oven instead of an assembly line. I have replaced a small number of 0201 components by hand before, and it involves multiple attempts and much cursing and throwing small components across the workbench. It would be physically impossible to install 200 components on a board that size with a soldering iron, you have to use either hot air bath, or IR reflow.

Yes - I agree about the oven. I guess it depends what is meant by "by hand". I guess you can test it by function . But for Hi-Rel stuff it should be inspected properly
On v small components - replacing is probably than building from bare board ? Saying that because I assume that a stencil and solder paste / manual hot air gun would be used for that.
 

JohnRoberts

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Years ago while visiting my contract manufacturer at the time, he showed me a board populated with 0201s... I took his word for it that those black specs were resistors. :unsure:

I could imagine a hot air gun blowing them off the PCB.

JR
 

ruffrecords

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How do you (they) assemble a BGA 'by hand' - and inspect it (usually done by X-ray) ?
The normal way would be to dab the solder paste on the pads the roughly place each component on them. Then surface tension in the oven pulls them into line. No way would anyone assemble it a component at a time with a soldering iron.

Cheers

Ian
 
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Newmarket

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The normal way would be to dab the solder paste on the pads the roughly place each component on them. Then surface tension in the oven pulls them into line. Now way would anyone assemble is a component at a sime with a soldering iron.

Cheers

Ian
Yes - surface tension will align stuff.
But I think some keyboard/finger trouble with your last sentence there.
 

Newmarket

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Years ago while visiting my contract manufacturer at the time, he showed me a board populated with 0201s... I took his word for it that those black specs were resistors. :unsure:

I could imagine a hot air gun blowing them off the PCB.

JR

They can be tacked in place with 'SMT adhesive'. Or if not the 'wet' paste will tend to hold them.
But I do still tend to use a hot air pencil from above to minimise sideways force.
One problem with the paste for small scale DIY is that it does tend to 'go off' and dry up in a fairly short time.

With the very small chip resistors I don't like not being able to read the value. But that's the same with most SMT chip caps of any size. You get to recognise a wrong value cap by its height !
 

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