Well, seems like you hit the trap.
Two of these 3 amps use MLCC, one is using foil.
THD vs frequency is another story. MLCC (usually) tend to increase at low frequencies, yes.
Hi Christian,
I was trapped like gmarsh. I was sure the Foil cap was the winner on this bench.... Can you do a test with Tantal cap ?
Well, they might be winners in a different amp situation. The unanswered question is, if these foil used is not suitable due to inner construction (stacked vs. wound) and/or geometrical size and location regarding noise pickup.
Regarding differential dc-bias, this is ~zero for the interlink coupling as the AFE output and TPA32XX input are biased at ~6V, so the influence not the biggest concern.
I can't test tantal for several reasons. 1st, the measurements are done in a lab in denmark, i sent the amps to. 2nd, i don't use tantal in any way due to:
https://www.sourceintelligence.com/what-are-conflict-minerals/
Regarding differential dc-bias, this is ~zero for the interlink coupling as the AFE output and TPA32XX input are biased at ~6V, so the influence not the biggest concern.
I can't test tantal for several reasons. 1st, the measurements are done in a lab in denmark, i sent the amps to. 2nd, i don't use tantal in any way due to:
https://www.sourceintelligence.com/what-are-conflict-minerals/
oops... I missed a couple of posts here. Sorry for going back a little.
I can't remember if you already said. Maybe you could recall us the capacitors references you used ? As you say, all caps are not born equal.
TPA325x input bias is AVDD/2 = 7.8/2 = 3.9V
Opamp bias is 6V. The "interlink" caps should see 2.1Vdc bias.
While we talk about dc-blocking caps, no one here seems to use TI's suggested electrolytics (Panasonic EEE-FK1C100R) eventhough they prove to have very good results on the EVM, are cheap and small.
question to the builders : What are your reasons to use other caps ?
ps: Yuan-Jing announced some months ago a TPA3251 board at $38. Status was "coming soon". Today status changed straight to "sold out"
probably impossible to meet the anounced price point !
interesting.doctormord said:
I can't remember if you already said. Maybe you could recall us the capacitors references you used ? As you say, all caps are not born equal.
uhmm.... sure about that ?
TPA325x input bias is AVDD/2 = 7.8/2 = 3.9V
Opamp bias is 6V. The "interlink" caps should see 2.1Vdc bias.
While we talk about dc-blocking caps, no one here seems to use TI's suggested electrolytics (Panasonic EEE-FK1C100R) eventhough they prove to have very good results on the EVM, are cheap and small.
question to the builders : What are your reasons to use other caps ?
have you noticed that in their latest design, the TPA3255 EVM, 3R3 resistor was replaced by a 10µH inductor. Seems that TI is learning as well5th said:
ps: Yuan-Jing announced some months ago a TPA3251 board at $38. Status was "coming soon". Today status changed straight to "sold out"
probably impossible to meet the anounced price point !
Data for the MLCC:
Capacitors | details for GRM21BR71E105KA99# | Murata
Have a look at dc-bias and ac voltage rms.
Capacitors | details for GRM21BR71E105KA99# | Murata
Have a look at dc-bias and ac voltage rms.
Correct, they told me they need to find a reliable source for the TPA3255 and they do sell the TPA3251. However, I want (not need) more power. I never know what kind of speaker I will buy in the future.
I agree with you. Very strange that there is NO 3251 makers out there other than Sinewave and their price is little high (at least to me).
Is the cost of TPA3251/3255 chip A LOT more than the 3116?
TI published few days ago an appnote to design ClassD LC output filter.
The TPA3251 EVM is used to measure about 20 different inductors.
Worth reading
http://www.ti.com/lit/an/slaa701/slaa701.pdf
App notes are published out of order
This one is about selecting the most linear inductor. The best (Wurth) is large and expensive.
A previous recent appnote explained how to add a Post filter feed back (PFFB) on TPA3251 to lower the non-linearities of inductors. One of the acclaimed benefit being that a less performing cheeper inductor could be used with better overall amplifier results.
Has anyone an idea for the optimal compromise for a coil selection with PFFB ?
The TPA3251 EVM is used to measure about 20 different inductors.
Worth reading
http://www.ti.com/lit/an/slaa701/slaa701.pdf
App notes are published out of order
This one is about selecting the most linear inductor. The best (Wurth) is large and expensive.
A previous recent appnote explained how to add a Post filter feed back (PFFB) on TPA3251 to lower the non-linearities of inductors. One of the acclaimed benefit being that a less performing cheeper inductor could be used with better overall amplifier results.
Has anyone an idea for the optimal compromise for a coil selection with PFFB ?