At least on the original Wiener card, I've tried to make the thing as configurable as possible. Being able to switch on/off PFFB would fall in line with that spirit, but switching it in/out changes the gain of the amp, which means I might need to futz with the gain switching on the analog input to handle both cases.
I'm toying around right now with LTspice. Right now I've got the TPA3250 modeled as an inverting amp with a 24K input resistor and a 240K output resistor, and I'm finding that adding PFFB causes gain peaking above 10KHz unless you futz with the output filter values, zobel values etc.
Also, TI also suggests a 2.7 ohm / 1uF output zobel in their PFFB app note. If you drive a pretty much worst case signal into the amp, 36Vpp / 12Vrms at 20KHz - the zobel has a Z of 8.4 ohms, there's about 1.5 amps going into that zobel and that resistor is dissipating 5.5 watts. Even with reasonable music listening levels, I'm gonna need to put down a big resistor to handle that. Running the amp with no load and lowering the C value, yeah, things go unstable real quick.
Looks like I've got a bit of work to do.
Well, have a look at 35-45kHz. PFFB needs some bw-limit on the input for not toasting the zobel in worst case.
Yup. First order of business is to get the thing no-load stable though, because when the thing goes unstable the zobel is toast anyway.
Oh, I've had a shitty conscience over these boards for months 🙂 Thankfully the christmas season has given me a couple full days to throw at these boards, which makes me feel a slight bit better.
Back at 'er right now. I made a little programmer with a SOIC test socket for preprogramming AVRs before installing it on the Wiener cards, but it's lost somewhere in this room and I can't find it, so I'm back to bed of nails programming for the time being 🙂
Got a batch of 8 stereo cards here with the SMT done. Doing the programming and some DMM tests on the bare boards right now, then building these into 8 ohm stereo cards for your order and testing them, then doing another 8 SMT place and bakes.
Sorry for the chicken scratched notes, I know a bit hard to read.
On the right side was the filter settings.
I used an Amber 3501 test set, which has a both a un-balanced and balanced input.
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From what I have read, you are supposed to use some special filters to measure Class "D" amps, which I do not have.
Update: all 8 stereo cards completed/tested/packaged. About to paste the next round.
Got an idea for a 3D printed jig which you place on top of the board, and it holds the through-hole parts down onto the board. So I stuff the TH parts in loose, install this jig, flip the board upside down, screw the PCB down onto the jig, then clip and solder all the leads in one shot. I s'pose I'd need to put a thin layer of foam in the jig to make up for tolerances in component heights and such.
Spending hours soldering the same board over and over again makes me ponder these things 🙂
Got an idea for a 3D printed jig which you place on top of the board, and it holds the through-hole parts down onto the board. So I stuff the TH parts in loose, install this jig, flip the board upside down, screw the PCB down onto the jig, then clip and solder all the leads in one shot. I s'pose I'd need to put a thin layer of foam in the jig to make up for tolerances in component heights and such.
Spending hours soldering the same board over and over again makes me ponder these things 🙂
Gary,
I recall they did the same sort of thing in the 80's when I was at Motorola, it was a vacuum thing of sorts, that put a film over the pcb to keep the THT comps in place before they went over the wave solder machine. After that the pcb went over a milling machine that trimmed all the leads. Then on to HP 3065? ICT or specialized jigs we made for functional testing. The test jigs were all hand wired, no MCU's at that time, mostly 4000 series CMOS logic state machine driven logic. It was a fun job, for a young tech, watching all the innovation in process control. They had a ceramic hybrid and FR4 smt line as well. Gone were those good ole days in this country.
I recall they did the same sort of thing in the 80's when I was at Motorola, it was a vacuum thing of sorts, that put a film over the pcb to keep the THT comps in place before they went over the wave solder machine. After that the pcb went over a milling machine that trimmed all the leads. Then on to HP 3065? ICT or specialized jigs we made for functional testing. The test jigs were all hand wired, no MCU's at that time, mostly 4000 series CMOS logic state machine driven logic. It was a fun job, for a young tech, watching all the innovation in process control. They had a ceramic hybrid and FR4 smt line as well. Gone were those good ole days in this country.
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We had a through hole line for a while at my previous job. Board were hand stuffed and wave soldered, then someone used a set of side cutters to trim all the leads. Then the machine, which was made in the 80s by a defunct manufacturer, caught fire and that was the end of that, TH board assembly was outsourced at that point. SMT was always outsourced.
You really gotta be running a large, continuous volume of boards to make it worthwhile to have an in-house SMT line these days. We've got a couple of shops here in NS which do the majority of assembly for local tech companies.
You really gotta be running a large, continuous volume of boards to make it worthwhile to have an in-house SMT line these days. We've got a couple of shops here in NS which do the majority of assembly for local tech companies.
Anyway, 8PM update: Got 8 stereo cards placed/baked/programmed. Gonna do the TH assembly tomorrow.
8 stereo cards fully built/assembled. This is all of ChuckT's stereo cards done now, and two of FJD's.
Gonna change over to doing PBTLs now. Gonna attempt to paste/place/bake 10 cards tonight, which will cover all remaining PBTLs for the group buy!
Gonna change over to doing PBTLs now. Gonna attempt to paste/place/bake 10 cards tonight, which will cover all remaining PBTLs for the group buy!
Real yeoman's work, gmarsh!
These GB builds are a ton of work for you. That sentiment comes from someone who only had to do a few cards - I can only imagine doing many. The recipients will be thrilled.
Happy New Year!!
BK
These GB builds are a ton of work for you. That sentiment comes from someone who only had to do a few cards - I can only imagine doing many. The recipients will be thrilled.
Happy New Year!!
BK
Last two PBTL's in the oven...
And at 12:30am at night, we're done.
This batch came out perfect - zero solder bridges on the TPA's and zero tombstoned parts. Still have to verify everything's good with the DMM, but that'll happen some other night 🙂 Back to the day job tomorrow AM, time to pack it in.
And at 12:30am at night, we're done.
This batch came out perfect - zero solder bridges on the TPA's and zero tombstoned parts. Still have to verify everything's good with the DMM, but that'll happen some other night 🙂 Back to the day job tomorrow AM, time to pack it in.
Correction: previous batch didn't come out perfect, I soldered a TPA3118 on backwards 😉
9/10 of the PBTLs are built/tested/working/bagged, just hot air reworked the backwards-chip card with a fresh TPA, will test when I get home. Then onto building a pile of Pro's...
9/10 of the PBTLs are built/tested/working/bagged, just hot air reworked the backwards-chip card with a fresh TPA, will test when I get home. Then onto building a pile of Pro's...
The wiener, the wiener pro
Hi, I have seen your TPA3116 Amp cards. The design is pretty well. Is it possible to send 6 "the wiener stereo" to germany? the bare board (not assembeled) is ok for me. Cost including shipping? Tax? You have also designed the wiener pro. This design uses a different TI chip. Interesting for me, is the sym input buffer for the TPA Chip and the onboard +/-12V Aux generating. Thanks
Hi, I have seen your TPA3116 Amp cards. The design is pretty well. Is it possible to send 6 "the wiener stereo" to germany? the bare board (not assembeled) is ok for me. Cost including shipping? Tax? You have also designed the wiener pro. This design uses a different TI chip. Interesting for me, is the sym input buffer for the TPA Chip and the onboard +/-12V Aux generating. Thanks
$12 CAD for a bare PCB and preprogrammed microcontroller x 6 = $72.
Shipping = $10, for a total of $82.
I've got lots of PCBs but I have to buy more microcontrollers, so I won't be able to fulfill this order right away. I'll keep you posted.
Used up the last of a container of solder paste doing the PBTLs, just cracked open a new one to paste some Pro's... no good. Vacuum seal on the top wasn't sealed, and the paste inside was pretty much dried into grey snot. And it's the only container I had left. :/
Just hand-soldered a 6 ohm Pro to see how long it would take to do, took 2.5 hours and a fair bit of rework to get it going, the TPA3250 footprint TI provided wasn't made for hand soldering and I'm kicking myself for not making my own footprint to facilitate rework. Have 12 more to build, 9 if I get the three in my rework pile going.
Just hand-soldered a 6 ohm Pro to see how long it would take to do, took 2.5 hours and a fair bit of rework to get it going, the TPA3250 footprint TI provided wasn't made for hand soldering and I'm kicking myself for not making my own footprint to facilitate rework. Have 12 more to build, 9 if I get the three in my rework pile going.