Millett "Starving Student" hybrid amp - Page 191

The wire will be fine,
C2 & C4 are not polarised
C1,3,5,6 are polarized

cheers
Fred

Production PCBs

Are the production pcb's available yet? Just need to know as holidays are here, im about to order my BOM from Farnell and i've only got 1 and a half weeks to complete it If they're not available yet (which I have a feeling there not) could someone please tell me if it is easy to do a point to point build? I havent built a project using a schematic yet, although I have basic knowledge on all the symbols and how the ground plane works, and I guess it would be handy on future projects.

Thanks,
-CaptHowie

I am currently doing the point-to-point build. I'd say it's pretty easy even for my first p2p. All it is, is something like (for example) R2 shares a node with C5 and C2, solder them together... node done... next node...

It sounds ok then. Is it just soldering some ends together? Some if 1 resistor was connected to a cap and another resistor, you would just solder all their ends together? Am I right? If that's it i'll happily build p2p.

yep, check out the amp on the first page of this thread, its pure p2p. Also, Pete's design uses a ground plate in combination with a p2p build too.

1. I think the gauge is more important then the material or stranded/solid. Since the wiring will be sitting still, solid should be fine. I haven't used silver wire, but isn't it more expensive? I'm not sure what benefit you're hoping to gain. I wired mine with SPC from navships.

2. I think it depends on the caps you bought. Got part #s? We can look at the datasheet if needed to find out.

My selection of wire wasn't from any hope of benefit gain but it was just what I have currently in my possession.

I also got the cap situation all figured out. Thanks guys.

ah, then your wire should be fine

glad you figured out the caps. In general, if there isn't a polarity marking on the device, it doesn't matter.

Are there any tubes left for this build out there? I have not been able to find one source. I already have a pair on the way but I don't know if they are matched or not. I don't even know what it means for them to be "matched" exactly.

Well, I got mine from thetubecenter.com and was told that they were at least from the same stock. But, they aren't. Two of them look like they're similar, but none of them are "matched".

Matched means the same brand and same design inside the tube.

Let me know once you get them, as I have an unmatched pair that I could sell if it happened to match yours. RCA or GE I believe.

Actually, matched means the same output as tested on a tube tester. In the case of the 19J6 tube, it has two triodes (amplifier tube circuits). The Starving Student ties both of these triodes in parallel, a not uncommon way to do it. However, a tube tester measures one triode at a time. I asked Pete Millett if the triodes "average" when they are tied in parallel, but he says they're most often considered "additive." So that means the sum of the tested value for each triode in a tube should be equal to another tube's sum of the triodes' tested values.

IOW, say we measure one triode in a 19J6 at 110, the second at 95. This is not uncommon - in fact, almost every 19J6 I've tested is slightly different from one triode to another. I suspect that this is the case for most dual-triode tubes. Anyway, the sum of those two triode measurements is 205. So, if I measure another 19J6 with one triode at 100, and another triode at 105, then those two 19J6's will be matched because the sum of both is 205.

Edit: All of this is at least in the case of the Starving Student where the triodes are in parallel. Another circuit may not tie the triodes in parallel and this premise may not hold true. (One of the reasons tube amp designers tie the triodes together within a dual-triode tube is for this very reason - to minimize the imbalance, or IOW, to increase the chances that two random tubes will work out to be balanced.)

edit: tomb was faster than I am, I was going to post this:
What does Matched Pair mean?

zk

Yes, good link! However, I wanted to take the opportunity to explain what matching meant specifically for the Starving Student circuit, since that's how I'm going to supply the tubes when we get to that point.

I see.

Silly of me to answer a question without knowing the proper answer. My bad!