Tír Na HiFi

I know you are busy since this happens every year when you lay low

BUT

the drama is killing me.

And a group buy? You must really have some confidence in this thing's goodness!

Can't wait for the revelation.

Me too.

Perhaps he could do what Apple does and post some 'reveals'? So a close-up on one component to give a teaser for what's in it?

I would be happy knowing the output device.

i thought all the details was in this thread
http://www.tirnahifi.org/forum/viewtopic.php?f=8&t=3810

The amp itself is quite simple and another fine example that simplicity combined with a stellar power supply provides exceptional results
And yes it really is proper good im really happy with it

The mini group buy is just to facillitate sharing of this design so others can benefit from the result of this amp experiment
It sure is really nice to see others enjoy what youve built

Don't know how that got by me.

Now to take a closer look ...

Now I realize I did not see this since I rarely look elsewhere than COMPUTER AUDIO. Kept scouting the index page for the thread .... (I am identifying as a dumbass today)

Thought you might have tried something other than the LM3875, not that I have anything against them.

Now I see where the ideas for charging more than 2 cells in series came from - you were already at work on it.

Only wasp in the sun tanning oil I can see is the ESR of all of those batteries in series.

jkeny mentioned the OPTIMA which in comparison to four 26650s has a much lower ESR. I cannot imagine the 26650s in series having a faster rise time than the OPTIMA so I am a little skeptical.

In singles and doubles I, too, have found the 26650 incomparable. And as far as space requirements there is no comparison.

Maybe I did not look as closely as I should have. Are there series strings in parallel, too?

I know when I used the LM3875 I used 2 pair PANASONIC 12 volts SLAs in series for 24 volts, positive and negative. Assuming eight 26650s in series you are getting up there in ESR. You are using 10 cells per phase so is this for 16 or 32 volts? If for sixteen volts then much of my complaint is answered. I thought running low voltage supplies with the LM3875 was the suggested mode for low sensitivity speakers?

Of course, what is heard is all that matters but it would argue with what is assumed to be the "magic" quality of the 26650 with a rather typical, if not higher than typical, power supply ESR.

rickmcinnis wrote:Now I realize I did not see this since I rarely look elsewhere than COMPUTER AUDIO. Kept scouting the index page for the thread .... (I am identifying as a dumbass today)

Thought you might have tried something other than the LM3875, not that I have anything against them.

Now I see where the ideas for charging more than 2 cells in series came from - you were already at work on it.

Only wasp in the sun tanning oil I can see is the ESR of all of those batteries in series.

jkeny mentioned the OPTIMA which in comparison to four 26650s has a much lower ESR. I cannot imagine the 26650s in series having a faster rise time than the OPTIMA so I am a little skeptical.

In singles and doubles I, too, have found the 26650 incomparable. And as far as space requirements there is no comparison.

Maybe I did not look as closely as I should have. Are there series strings in parallel, too?

I know when I used the LM3875 I used 2 pair PANASONIC 12 volts SLAs in series for 24 volts, positive and negative. Assuming eight 26650s in series you are getting up there in ESR. You are using 10 cells per phase so is this for 16 or 32 volts? If for sixteen volts then much of my complaint is answered. I thought running low voltage supplies with the LM3875 was the suggested mode for low sensitivity speakers?

Of course, what is heard is all that matters but it would argue with what is assumed to be the "magic" quality of the 26650 with a rather typical, if not higher than typical, power supply ESR.

I wouldn't get too hung up on ESR, in isolation. It's an indicator of the current delivery capability of a battery but that's not the only criteria of importance (& remember the impedance of the wire (length * resistance per cm) will almost definitely raise the final ESR measured at the LM3875s PS pins) . Most SLA batteries can deliver a large current - they need to be able to do this for engine cranking duties.

But there are two other issues to be aware of - the noise generated internally as the battery is delivering current - this is the noise of the internal chemical reaction. a SLA (sealed lead acid battery) has lead plates (cathode?) that react with the sulfuric acid to produce current - a noisy reaction (have you seen the bubbling on the plates?) & also not the fastest reaction to turn on/off for transient current delivery.

On the other hand, A123 & all nano-technology batteries have very small particles (ferrous nano-phosphate) that act as the cathode - a much faster & less noisy chemical reaction so should be (substantial) lower noise floor & substantially faster transient response current delivery.

Putting these batteries in series reduces the ESR but probably doesn't greatly affect noise or transient response?

Im pretty sure none of the 26650s ive bought are genuine a123 and ive bought quite a few from different sources so really the a123 data sheet cant really apply to them
i hear no differences in any of them and thats whats important
ive 100 cells now ordered so we shall know soon enough
tbh its not something i was worried about in the slightest

nige2000 wrote:Im pretty sure none of the 26650s ive bought are genuine a123 and ive bought quite a few from different sources so really the a123 data sheet cant really apply to them
i hear no differences in any of them and thats whats important
ive 100 cells now ordered so we shall know soon enough
tbh its not something i was worried about in the slightest

hmm now I wonder how they would perform with my tpa amp. a 19v lifepo pack and a matching smps charger?

nige2000 wrote:Im pretty sure none of the 26650s ive bought are genuine a123 and ive bought quite a few from different sources so really the a123 data sheet cant really apply to them
i hear no differences in any of them and thats whats important
ive 100 cells now ordered so we shall know soon enough
tbh its not something i was worried about in the slightest

yep, I agree - most of the LiFePO4 cells use nano-technology, whether A123 or another brand.

A 100 cells on order? Are you setting up shop?