I was originally only trying to add some factual information to the thread. But, it seems like some people are too smart to learn, and too clever to be fooled by the Audio Illuminati....
Bless their oxygen-free tinfoil hats and OPA627 ELF detectors.
-k
For those planning on ditching the 2A included AC adapter in favor of a 5A supply from Goodwill (or elsewhere), Parts Express has the Lepai LP-2020A+ for $19.88 without power supply. I may have to break down and include one in my next order to see what all the fuss is about.
This question is for Ken Kantor, if he ever returns to this thread.
I have a question about the capacitor for the charge pump switching pins 31 and 32.
The data sheet for this device does not give a lot of details about these pins other than they operate at 300Khz and to use a .1uF cap.
I was reading up on other charge pump devices trying to glean some information about what kind of capacitor to use in this type of ,"flying capacitor", location.
Most of the data sheets recommended a very low ESR capacitor and also using ceramic in many cases.
I was wondering if this Tri-Path 2020-20 requires the same type of cap or if it even matters at all. I found two caps that I think will fit the requirements. I will go with the cheaper one if it makes no difference, not that they are that expensive in the first place.
It would be nice to hear from someone who has experience designing with these chips.
Thanks for any help you can give.
Tri-Path data sheet
http://www.kafka.elektroda.eu/pdf/tripath/TA2020.pdf
C9, on Lepai) "Flying Capacitor" ceramic option.
http://www.mouser.com/ProductDetail...=sGAEpiMZZMuAYrNc52CMZKQW5e6risl1KbnDAtO5T1k=
Cheaper polyester option. The impedance graph @ 300Khz looks to be about 1 or 2 ohms.
http://www.mouser.com/ProductDetail...GAEpiMZZMv1cc3ydrPrF0%2bjlB8SXIRuNETHDW9yLSA=
p.s. Why do I want to replace the caps?
1) My two Lepai amps came with what looks like a hodgepodge of capacitors that probably should have been thrown in the recycle bin.
2) Convert the outputs for an 8ohm load (.22uF caps), 4 ohm load .47uF caps seem to be the stock default.
3) Practice soldering on my cheap stuff so I don't mess up the stuff I care about. :thmbsp:
A charge pump is used to conveniently generate a low current supply voltage above the level of V+. In our case, this voltage is used to bias the output stage so it can be run all the way up to the rail.
The main thing you want in a charge pump cap is low inductance and, to a lesser extent, low ESR. (In this regard, a charge pump cap requirements are similar to those of a supply bypass cap.) While I don't know the inductance of your suggested cap, Ls is not generally a forte' of that style of cap. The flip side of this is that the inherent limitations of ceramics, such as tempco and linearity, are mostly immaterial for charge pumps. Meanwhile, because 300KHz is not a super high frequency, there is a good chance your cap will work, (possibly at a slightly reduced pump voltage.)
Bottom Line: It should be easy to get decent 0.1uF ceramics for less than a quarter. That's what I would use. Alternatively, you could try your stacked film cap, which will probably work.
Hope this helps!
-k
Thanks Ken, That's very helpful.
Now I have to figure something else out too. I was looking over this thing and found they used 1uF electrolytic cap instead of the .1uF MLCC cap called out in the documentation for the bias cap on pin 14. :screwy:
http://www.profusionplc.com/images/data sheets/eb-ta2020.pdf
The 1uF lytic is fine. The .1uF MLCC would be smaller and easier to use in an auto-insert machine, but possibly more expensive. I wouldn't sweat it.
-k
You did, Sir.I was only trying to add some factual information to the thread.
You did, Sir.
Thank you. :thmbsp:
Wow this is a great resource. I just picked up a lepai 2020A+ to fiddle with. One mod I haven't seen that I am considering is to turn down the gain on the tripath 2020, since I will be using it with 8 ohm speakers and the amp output is garbage above 6 to 8 watts or so, in this case. Would best way be just using smaller values for the two Rf resistors?
Wow this is a great resource. I just picked up a lepai 2020A+ to fiddle with. One mod I haven't seen that I am considering is to turn down the gain on the tripath 2020, since I will be using it with 8 ohm speakers and the amp output is garbage above 6 to 8 watts or so, in this case. Would best way be just using smaller values for the two Rf resistors?