If they're just ground referenced, then what's the issue? There's nothing going in or out of the neutral pins, so how does the impedance matter? No difference in sound either. Lower ESR on ceramics too.
I agree. A fully differential input as the TPA3132 has should have the same electrical characteristics on both inputs. Regardless if one is effectively tied to ground.
Mostly it's a comparison as an amp32 replacement. There are to my knowledge no other commercially available designs with as high output in the same physical size. The closest is the maxamp20 which is more than twice as big or the rather feeble Dayton DTA2 (aka the original t-amp) .
I considered film input coupling caps, but they would be massive. Some high voltage ceramics might be a good substitute, I'll have a play.
Also you're probably right, I'll switch the 0603 and 1210 caps around. The caps are 1nF 0603, 100nF 50V 0603 and 100nF 200V 1210. I included the 1210 for the lower ESR.
Yes all the inputs are biased at 3VDC. I was simply naming them as per the pinout on the chip.
I use 10uF/16V ceramics for input caps...on both input lines.
Look at page 4 of data sheet...inputs are part of the feedback path of the first gain stage.
Using a smaller cap value on the not-used-input will affect low frequency roll-off.
🙂
Look at page 4 of data sheet...inputs are part of the feedback path of the first gain stage.
Using a smaller cap value on the not-used-input will affect low frequency roll-off.
🙂
Thanks for the input guys. I'll take your word for it, so I'll leave the amps with the original caps.
I'd have no qualms about getting rid of the electrolytic coupling caps, and following Doug's suggestion I'll replace them with 10uF X7R types.
I'd have no qualms about getting rid of the electrolytic coupling caps, and following Doug's suggestion I'll replace them with 10uF X7R types.
I'm busy with some other stuff right now so I can't do anything in depth, although there is no audible difference whatsoever between the different caps.
OK, so I've been playing with the PCB editor for a bit today... My wrist hurts now.
Ditching the terminals in favor of 100th pin headers means the current ferrite bead design can reduce to 1 inch square. For the same size as it is currently, I have redesigned the board with LC output filters.
Would it be worth building both? I can't really imagine who would need a square inch amp so I may switch entirely to inductors.
Ditching the terminals in favor of 100th pin headers means the current ferrite bead design can reduce to 1 inch square. For the same size as it is currently, I have redesigned the board with LC output filters.
Would it be worth building both? I can't really imagine who would need a square inch amp so I may switch entirely to inductors.
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That looks pretty slick Doug. Out of interest, what made you decide to use Tantalums? I'm aware of the electrical and size benefits, but given how many have blown up on me for no reason I find it hard to trust the darn things.
I have also had a bad experience once...one blew up and left a mark on my shoulder. 🙂
In this case they are 25V and I only use 12V on this amp.
The case is the heat sink so I did not want to run 19V as I usually do.
🙂
Ah right, plenty of leeway then. Still that design looks very low profile, nice job.
Anyway, got a couple Coilcraft inductors to play with. I really want to minimise SMD parts on the back side of the board, so I'll be using the through hole ones. This also means I don't have to worry about getting the power traces to the other side of the board as the pins are going right through, plus it makes it easier to hand assemble. And not to mention the huge mechanical benefits of through hole inductors. I'm a huge fan of SMD but especially in something such a portable speaker set, having large bulky SMD parts doesn't make a lot of sense if it can be avoided.
Anyway, got a couple Coilcraft inductors to play with. I really want to minimise SMD parts on the back side of the board, so I'll be using the through hole ones. This also means I don't have to worry about getting the power traces to the other side of the board as the pins are going right through, plus it makes it easier to hand assemble. And not to mention the huge mechanical benefits of through hole inductors. I'm a huge fan of SMD but especially in something such a portable speaker set, having large bulky SMD parts doesn't make a lot of sense if it can be avoided.
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![IMG_20141112_105444[1].jpg](/community/data/attachments/409/409781-4a37841ef57647e0326588d8c0b1619c.jpg?hash=SjeEHvV2R-)
I've never considered that to be a huge issue on a sufficiently decoupled power bus. I never go between layers on things like the output of a switcher (and so on... Not that anyone does) and nothing on this circuit is high speed so it's not much of a problem.
Well I just bought one of these TPA3116 Class D Digital Power Amplifier Board Inductor Circuit Design 50W+50W | eBay
I know it's probably not the best TPA3116 board available but it was so darn cheap I thought it might be good to have something to compare my boards to.
When it arrives (probably next week) I'll get some proper listening comparisons done.
I know it's probably not the best TPA3116 board available but it was so darn cheap I thought it might be good to have something to compare my boards to.
When it arrives (probably next week) I'll get some proper listening comparisons done.
That's a Danzz design board, recommended for modding. Don't know how it sounds unmodded, haven't tried it.
The best one I have (unmodded) is Breeze Audio HIFI TPA3116. It sounds so good that I didn't have any real incentive for modding, and I'm using it as is (I just rewired the mute switch to act as power switch).
It's quite amazing how cheap that Breeze one is, the whole thing, in a fancy box for that price really is astonishing.
As said in the edit on the first post, all amps are now gone. I'm going to have the next version with full LC output filters and some other minor changes ready in 2-3 weeks. Price will be £22 each. If you're interested, let me know any time and I'll reserve one for you. Thanks for all the interest guys!
Also thanks to DUG, Saturnus and Irribeo on suggestions for the amp.
Also thanks to DUG, Saturnus and Irribeo on suggestions for the amp.
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