Tír Na HiFi

nige2000 wrote:

jkeny wrote:
You may be right, Nige that capacitors only slow down the current delivery in battery operation but in designing a pcb, I would consider it wise to include pads for them.

sure is easier to have the pads and not use them than the other way round

i used these for bypass on the prototype
http://ie.farnell.com/wima/smdtc04220tb ... dp/1890111
id be inclined to test something along these lines
these film type caps dont seem to have the same slowing effect that alot of caps have with the batteries

It's always good to put in provision for new discoveries i.e for new knowledge that maybe a cap is found which greatly enhances these Lithium phosphate batteries?

Yea, traditional electrolytic bypass capacitors should not be used here - I doubt they have the speed necessary throughout the frequency range. The problem of current delivery in power amps is that we need gobs of current (I've read somewhere that it is quite a bit more than is traditionally considered) for LF signal elements & very fast but smaller current delivery for HF signal elements. Considering that music signals are a simultaneous combination of both LF & HF signals this becomes a big ask & batteries seem to answer this requirement excellently.

From experience with them, I formed the opinion that lifepo4 batteries are like perfect large capacitors - they don't need to be constantly recharged in between delivery of large pulses of LF current (I believe this is the problem with most PSes - there is a certain finite recovery time for the PS caps ) & they are very fast in both LF & HF current delivery. So it's hard to know what capacitors could be used with them as they don't seem to have a weak area that needs attention.

Nige, apart from no detriment, did you notice any benefit with using these film caps (I can't see any esr figure sin their datasheet)?

dont think i ever seen a benefit of adding caps to lifepo4
no audible difference is the best result so far
maybe i havent tested the right caps yet

probably should pick out a few for testing

nige2000 wrote:dont think i ever seen a benefit of adding caps to lifepo4
no audible difference is the best result so far
maybe i havent tested the right caps yet

probably should pick out a few for testing

Yea, it's hard to beat these batteries as capacitors with other capacitors - the only likelihood is probably super capacitors but I think you tried some of these in your pc tweaking & found them not quiet as good?

jkeny wrote:

nige2000 wrote:dont think i ever seen a benefit of adding caps to lifepo4
no audible difference is the best result so far
maybe i havent tested the right caps yet

probably should pick out a few for testing

Yea, it's hard to beat these batteries as capacitors with other capacitors - the only likelihood is probably super capacitors but I think you tried some of these in your pc tweaking & found them not quiet as good?

yea used supercaps with pc and soekris dac
good results with pc and turned the dacs vref inside out
but batteries is a different league

it was very apparent with the dac during the modding stages once on battery ps that removal and replacement of electrolytic and tantalum with film smd vastly improved speed and detail
like a sponge soakage effect
its far easier to do harm adding capacitors to a lifepo4 system than good

one of the best things about finding and using caps that dont do any harm is the acceptance factor,
no one calls you an idiot when you got bypass caps :)

My second attempt with PCB. Two options implemented.

both look great
option a will allow for both option with a bridge wire between sgnd and pgnd

bet there'd be fun double blind testing these options :)

Great work Fredyrk and all.....

Yea great work, Fredyrk
I think Nige's idea of having a wire strap to change from A to B config is a good one - always good to have options!
Hard to say if there will be any audible difference between A & B - it depends on how the two channels are connected & if there is any ground noise voltages on the upstream source connected to the amp channels.

Nigel,

Thought you might have missed this:
http://www.diyaudio.com/forums/chip-amp ... -hell.html

This guy has observed what I think everyone has missed about the original GAINCARD.

They are being run at high temperatures on purpose - this fellow says 135 degrees C.

AS usual the usual folks are talking about how it won't work all the while we are talking about a product that has been sold for 15 or so years with no reputation of failure. Unbelievable in the most believable of ways.

I have a feeling this might be important.

interesting thread although seems a little odd to me, 135 celsius
maybe 135 f could be understandable
i know im never that overly impressed with the lm3875 sound cold they need about a half hour to sound at their best

by coincidence i had ran these chips at a varity of temps on my first lm3875 amp while finding a suitable heatsink for the job
i had thought they sounded best when they're very warm, but when they get hot sound got harsh and irritable
that said ive no real interest in putting the lm3875's in an oven i think its pretty much excessive