Correct.
If using just 2 coils in PBTL, they need to do 1.4x times the current for the same wattage in 2R compared to BTL 4R.
As you double the output power due to PBTL 2R capability, the inductors needs to be rated 2x times the current handly than 4R BTL when pushing.
If using 4 inductors, no re-rating is needed.
The plan is to use the PBTL configuration into a minimum of 4 ohm load with a max output of 120 watts power or less. So it looks like the 4 inductor implementation would be best for sound quality reasons.
Keep in mind, that PBTL distortion (at 4R) is a bit higher than BTL.
At 10W:
BTL: 0.0035%
PBTL: 0.009%
I wouldn't hear that anyway. 😀
At 10W:
BTL: 0.0035%
PBTL: 0.009%
I wouldn't hear that anyway. 😀
So your saying as long as I keep the impedance up above 4 ohms and I could use an 8 ohm voicecoil that bridged mode would be the better choice. The amp will never see a 2 ohm load so I don't have to plan for that. I get to specify the voicecoil impedance so can ideally pick anything I want within reason.
I guess EMI standards and cost are the main issues for commercial designers but diyers are more concerned about placing coils too close (mutual inductance) or emi induced noise. I reckon that simply fitting alternate coils above/below the pcb would mitigate this enough to be a non-issue, and if not, some deflective shielding, so the biggest issue is sourcing or making the coils and then testing them to avoid the psychology of "It sounds better cos I made it".
Worth having a look at 10 year old discussions about air cores and mitigating RF using ERS paper:
http://www.diyaudio.com/forums/class-d/95740-shielding-charlize.html?perpage=25&pagenumber=2
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(Unshielded) Air core inductors in output filter, best broadband jammer ever. 🙂
Let's see the results. 🙂
Let's see the results. 🙂
Indeed - results! But things are progressing slowly - haven't even persuaded my other half I need two new 250VA toroids for the (shh... two) new amp(s). When that does happen, or if, the next thing is to hook up the scope to the 10K:10K trafo and see what's happening with input/output voltages across the audio band.
An idea occurred to me - you could present this to her as 'I'm thinking of DIYing my transformers, I just need this (expensive,bulky) toroidal winding machine and some cores and wire. Or do you think its easier to just buy the finished product?'
I like the thinking, kind of a bait and switch... this hobby is so challenging. ;-) I reckon new duvets and Hello Kitty covers will probably be the kind of Faustian deal I'm forced into.
3251 chinese commercial offer
Has anybody tried one in the meantime? I am curious.
Has anybody tried one in the meantime? I am curious.
The man sold already 8 of them on Ebay. They are in stock again, as I write this.
TPA3251D2 2CH Class D Audio Amplifier | eBay
I ordered mine on the 24th February, tracking shows it landed in Heathrow Airport yesterday, so I may see it tomorrow!
I ordered mine on the 24th February, tracking shows it landed in Heathrow Airport yesterday, so I may see it tomorrow!
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Yes, I have seen it.
I hope Yatsushiro is willing to share his findings when he gets his board?
Of course. It won't be scientific
, but I can compare it against the TPA3250D2EVM, various TDA7498s and a plethora of TPA3116's.
3eaudio. Your vendor posts are now here:
http://www.diyaudio.com/forums/vendors-bazaar/305060-tpa3251d2.html
Please restrict all sales to this single Vendor thread. You may request a change of thread title if needed. Just report post#1 and state what the title should be.