The Kuartlotron - keantoken's simple error-correction superbuffer

[danielwritesbac]

Originally Posted by Destroyer OS.

I hope this is your sense of humor; that or you're going to send me a $3k hot air bed station....

It is either that smaller layout or the added coil for the cost of a fast thing in an overlarge size. Seems like the needless coil is cheaper at the moment.
I did mine coin size with through-hole parts, just because that's what it looked it like it needed. Well, it was triple layer and not the prettiest thing; but, I've still got to say that when it is small enough, then the coil is not needed. I was told that it was supposed to be fast, so I built it for fast. Well, you wouldn't do otherwise. But, if you did, that's when you need the extra coil.
Sure, the new SMD things are awful, at least 1/3rd off the mark; however, they're a lot better than a foul layout. And, for a fast thing, a foul layout is one that is too big.
In this application, there is some leeway to consider using SMD parts.

[jameshillj]

What does a non-foul layout, fast thing, 1/3rd off the mark 'SMD things' (transistors?) sound like? Any better than a 'normal' slow thing with the 1/3rd 'on' devices? 100Meg Hz response?

[ammel68]

Originally Posted by jameshillj

What does a non-foul layout, fast thing, 1/3rd off the mark 'SMD things' (transistors?) sound like? Any better than a 'normal' slow thing with the 1/3rd 'on' devices? 100Meg Hz response?

LOL...

[keantoken]

If the transistors are slower, then that could adversely affect stability. The effect of the inductor can be simulated to work without parasitics added, because the inductors is compensating for the slowness of the transistors, not for layout.

The total trace length of the PCB inductor is 48cm. If it were adjusting for layout inductances, that would be too large (several times larger than the longest trace on the board), especially since the ground plane reduces trace inductance.

In terms of capacitive parasitics, the transistors themselves still have more capacitance than the traces that connect to them, so are the limiting factor. But the inductor isn't really compensating for the transistor capacitances. It's compensating for the junction transition time. The B-E junction behaves like an inductor at RF and this can cause too much phase shift even if Cbe is very small. This is why some circuits are near impossible to stabilize when you only think in terms of Cob or Cbe.

So again, even for inductances the transistors are probably slower than the layout.

I imagine the inductor plays little purpose except for edge cases, but having it there improves reliability in some cases and in simulation even improves distortion. If anything about layout worries me, it's pcb leakage. I forget what the general value is but I thought somewhere around 500Mohm+1pF or something like that. But that is swamped even by the 100k+15pF input impedance, and most DIYers don't seem to have had a problem with it.

[keantoken]

So, the new PCBs arrived. I'm looking for someone who can test a pair within a week or so, since I'm not sure when I'll get to it.

[RCruz]

I would be glad to help please pm me.

[Theodosis O.]

Ηι,

How can we check that the BC550c/BC560c we have are from ON Semi ?

Is there a special code on them ?

[keantoken]

It's hard to describe since the current ones have very similar lettering. Mine have 3 lines:

BC560
C
[code]

The lettering has changed in the past. Some of my old ones have the FC lettering which is omitted on the new ones.

[ammel68]

Originally Posted by Theodosis O.

Ηι,

How can we check that the BC550c/BC560c we have are from ON Semi ?

Is there a special code on them ?

Even though this listing has ended, look closely at the photo.
8 X Matched ON Semi BC550 BC550C BC560 BC560C LOW Noise Audio Transistor | eBay

Those are original ON Semi '550/'560s. I know since I have many of each.
If the markings aren't similar, they're probably made by some other manufacturer and/or fakes.

[keantoken]

For the Kuartlotron they should be from Fairchild, not OnSemi. The difference won't break it, but they are less suited for the current Kuartlotron.