What's up with dynafet boards these days?

[Dusty Chalk]

Besides, here's a picture of Shiina Ringo punching through a sheet of (admittedly probably fake) glass:

Does that even make sense? Does you suing me make sense? Does "Pfff" make sense? Does anything make sense? Ladies and Gentlemen of the supposed jury, I declare that if Chewy lives on the planet Endor, you have to acquit.

The defense rests.

[luvdunhill]

I do hope Linear Systems gets their act together in 2009

c-c-c-combo breaker

I bought $10,000 worth of parts from Linear Systems this year. I wager they don't get their act together in 2009. They will release the single version of the p-channel part in question first anyways.

[Icarium]

Damn 10k? I hope most of that is for a group buy(s) If not.. damnnn sir!

[Beefy]

assuming that the quasi-digital model of neuron activity is correct.

I'm not even close to convinced that it is correct, unless you evoke the quantum level of single electrons or ions.

The mode of transmission might be considered a form of digital...... action potentials along neurons could be seen as a yes/no, or on/off function, that cause a quantile release of neurotransmitter.

But the 'big picture' of every nerve transmission is far closer to analogue. An infinitely variable membrane potential at the start of one cell that becomes an infinitely variable membrane potential at the start of the next cell.

[luvdunhill]

Damn 10k? I hope most of that is for a group buy(s) If not.. damnnn sir!

yeah, it was for two group buys. I had the opportunity to talk with Linear several times, as we worked some special pricing on some of the form factors. I wouldn't hold your breath for the p-channel parts. Toshiba just EOLed the 2SK170 this year, so people will start switching over to the LSK170 first then the other parts may come along.

Don't forget that the Charles Hansenes and Nelson Passes of the world have 1000's of these rare parts squirreled away. This reduces the market pressure to release these parts.

Also, matched JFETs aren't the only kid in town. There are solid bipolar options out there that for example some of the phono stage manufacturers are starting to use.

[JBLoudG20]

[posty]Maple and brown sugar oatmeal, 2 pieces of toast, one cup of coffee[/posty]

[kevin gilmore]

Also, matched JFETs aren't the only kid in town. There are solid bipolar options out there that for example some of the phono stage manufacturers are starting to use.

but a matched pair of duals (a pair of pnp's matched to a pair of npn's)

is much harder to come by as bipolar.

Also there is the input bias thing for bipolar inputs.

None of this is really a problem for me, as i'm using some expensive matched quads

right now. But at $43 per front end, not really for the diy'ers.

[Beefy]

forgive me if i'm misunderstanding what you're saying, but i find the idea that transmission is somehow not important for defining the basic action of the brain to be a funny one. might as well say that a CD isn't digital because the source being transmitted was recorded in analog.

I would think of it more this way......

The CD is digital, just like the transmission/action potential is digital.

The music itself is still analogue, just like the nervous system is analogue.

You could use vinyl or some phantasmagorical analogue nerve transduction, and the music/nervous system would still work the same, because the analogue end product is the key parameter.

But I haven't done this stuff in 9 years, so my argument could be pretty rusty

and i'd hate to derail the thread.

...... seriously?

[Pars]

but a matched pair of duals (a pair of pnp's matched to a pair of npn's)

is much harder to come by as bipolar.

Also there is the input bias thing for bipolar inputs.

None of this is really a problem for me, as i'm using some expensive matched quads

right now. But at $43 per front end, not really for the diy'ers.

Is that $43 per device, or $43 for a stereo differential front end? Cuz if you could even find the 109/389, you would be paying at least that much for 2 pairs of them...

[HiWire]

Crap, now I remember this debate. So... what makes a DynaFET good, compared to a Dynahi or Dynamight? The wikipedia entry on MOSFETs isn't helping me much.

I am looking at a single-ended, low-gain application (i.e. the Grado HP-2).

[digger945]

Is that $43 per device, or $43 for a stereo differential front end? Cuz if you could even find the 109/389, you would be paying at least that much for 2 pairs of them...

I would like to know also. Worth the money if they sound good.

[Pars]

On 11/15/2007 at 0:43 AM, kevin gilmore said:

I'm waiting for linear systems to get their butt in gear and actually deliver on

lsk109's. Then the floodgates open. The lsk389 is so much better than either

the 2sk389 or the individual versions used in the B52 that it is worth waiting

to do it right. I have a dynafet prototype with 2sk389/2sj109 and it is kickass.

No matching of parts will be necessary, just stuff the board and it works.

Any ideas as to why no one could get these working? I know with the SS Dynahi around now, why bother. I was thinking about recouping some parts from the pair of boards I have built up.

[mypasswordis]

Did you ever end up trying high resistance gate stoppers on the fets like from the T2 thread (500-750 ohm)? 

[Pars]

Nope, though I haven't touched these in quite some time and can't remember what all I did. I think I might have tried lower resistance gate stoppers? I'll try to take a look, and go thru the T2 thread.


Sent from my iPhone using Tapatalk

[mypasswordis]

For your convenience  

 

[Pars]

Thanks! Yes, I was going thru the DynaFET build thread and looked at the T2 thread (finding Craig's post regarding going with 750R), but hadn't run across that post yet. I looked at the board I was tweaking and it does have 47R on it, but on the back side, directly on the gate pins. I have some 750R and will see what happens with those.

I'm trying to reacquaint myself with the jumpers and feedback choices, and have to dig the rest of it out, including schematics. It always bothers me when I can't get something to work, but don't have the background that some such as Craig do

[Pars]

Spent some time reading the build thread (and rubbing salt in old wounds

I had seen or had the T2 thread pointed out back then, and tried larger gate stoppers at that point with no luck.

After re-reading that thread, I'm not going to continue doing anything with these.

[mypasswordis]

I clearly haven't read as deeply into those threads or what you did, but did you also try only using a single pair of output devices, and then try the large gate stopper resistor? Maybe you can narrow down the problem, whether it's individual FET problems or layout or whatever else. Totally understand if you already exhausted all options and don't want to deal with it anymore.

I know there have been a decent number of boards bought in group buys over the years, but it's strange that so far there hasn't been a report of a working build. Maybe they exist but I haven't seen any posts about it. I've got a few of those FETs laying around, so it might be nice to explore sometime in the future.

[Pars]

Yes, I don't think that anyone got theirs working. Pretty large GB as well, so kinda surprising. I thought that luvdunhill had his working earlier in the thread, but I think not.

As for using a ferrite bead for this, would it replace the gate stopper, go in series with it, or? I do have some ferrite beads like these.

[mypasswordis]

As per this app note, put ferrite bead as close to gate as possible and leave the series resistor in. https://toshiba.semicon-storage.com/info/docget.jsp?did=13416

More specifics: http://www.microsemi.com/document-portal/doc_view/14693-eliminating-parasitic-oscillation-between-parallel-mosfets

You could also try messing with compensation caps like the 5pf across the global feedback resistors and putting them in other places. 

Again, I'm not sure how much of these things you already tried.