Millett "Starving Student" hybrid amp - Page 242

Is preordering still possible as stated on the beezar site?And how can I do that?
I'm really interested in building this amazing thing.

That's basically right. R2 and R4 form a voltage divider, and the mosfet's gate sits at that voltage which is ~24V or so. The fet's source will be a couple of volts lower, ~19V. Then, the heater, which is basically a resistor, will draw a certain current at 19V (V=IR). The mosfet drops the rest of the voltage that is applied to the drain, so, as long as the gate is maintained at ~24V, you could raise the voltage on the drain without changing the voltage across the heater.

Would I be able to amp PortaPros well with this? They have a 60ohm impedance. I don't know if I would need to change around the schematic a bit to make up for the low impedance.

Sorry, not for kits. Shipment of the existing kit orders is imminent. That will occupy most of my next week, I think. After that, I'll take stock of the tubes I have left and decide whether to offer more kits.

Of course, you can always order the PCB and tubes and order the BOM yourself. That seems to be a lost talent around here lately. Everyone wants a kit. I can remember a couple of years ago when we built everything around here without a kit.

Of course! I listen to PortaPros on mine all the time - it's a perfect pair of headphones to use with the Starving Student. They work just fine with Input Resistors = Pot Impedance.

Kits tend to work out cheaper. I'm building a pair of dual mono power amps at the moment and they're costing me a fortune! It's the postage from multiple suppliers, getting the wrong stuff, etc

Problem with my SSHA

all right. i'm not sure why, but my amp is pretty much silent with no imput, but if i attach an interconnect to the imput jack i get this horrible vibrating noise which with the pot at 30% sounds like a hum, but at full volume sounds like an old turntable microwave right next to your ear. if i poke around with a pin or a nail in the imput jack, i get the same result.

poking the ground does nothing, but if i touch the left or right signal, i get that noise in the respective channel. if i touch a signal and the ground, the noise dissappears (not really surprising). now, this noise turns to static if i plug my source into the interconnect, but this static popping is still pretty loud (on full volume, virtually silent with volume down), and far noisier than the amp with no imput connected (which sounds like a barely audible, and almost pleasant whoosh at full volume).

why am i getting this noise, and how come it's totally missing when there's nothing plugged in? is this oscillation? i tried putting a 1k resistor to pins 5-6 on each tube in case it was tube oscillation (the imput goes to pins 5-6 so it seemed likely) but that did absolutely nothing. is it a grounding problem, because i'm pretty sure that i've done a very thorough job of grounding..

do any of you guys know what the problem could be?

it sounds like a grounding problem to me, in my inexperienced opinion

So is the ground of the incoming signal attached to the master ground? It should be. If I am thinking right, you saying that the noise is soft with the volume down that is telling you that the noise seems to originate before the volume pot.

Read this: http://en.wikipedia.org/wiki/Ground_loop_(electricity)

Also try searching this thread the same problem has come up a couple of times already.

Hello there! Nice build! I in turn finished mine late last night (or very early this morning, rather). It's nothing fancy, just a cheap generic plastic enclosure. For the point to point wiring I basically copied the one from Pete Millett's photo. I still have to do some minor stuff (power-on LED, grounding the volume pot's body) but here are three shots from my 3 a.m. first audition session.





I must say I'm completely astounded at the sound of the amp: clear, punchy, 3-dimensional. My cheap Sony "CD Walkman" sounds gorgeous through it and it absolutely puts my previous two DIY amps to shame (Cmoy style) Thanks Pete! Now I just need a set of REALLY nice cans to go along with it...

I also want to thank Tomb for making the tubes available; it's not easy at all to come by those tubes here in MX. Then again I just saw Tomb's tutorial on building the SSH and the Hammond case looks sooo sweet ... I might just have to go and order one! Any still available Tomb?

A thought for the electronics experts out there. Has anyone tried substituting the 19J6 for some other double triode with 150mA heater current (12AU7 maybe) and a resistor in series? The cathode and plate load resistors would have to be changed too of course, but I'm just checking on the idea's feasibility, since it seems to me that these days 12AU7's are cheaper and easier to come by than the 19J6.

Cheers!

Yes, there are cases available and they'll be shipping soon.
Dsavitsk has already designed a 12AU7 replacement circuit, but that's a ways in the future. We still have a fairly good supply of 19J6's.

Do you think there will be an opportunity for those who bought the PCB's when tubes were only offered with a full kit may be able to purchase them before those ship?

Did Dsavitsk publish this replacement circuit anywhere?

I'm confused - "them" is what - tubes or cases?

Probably not. It's not been tested, either and requires a different circuit altogether. As I said, we still have PCB's and tubes for the Starving Student.

Sometimes it seems like you are more in it for the money...
don't get me wrong, I appreciate what've you done, and you've been very helpful to many people including myself.

in any case, is there a problem with publishing a circuit that you won't be selling PCB's of? There are plenty of people who do this project P2P, and obtaining tubes from sources other than you, (who doesn't sell them without the PCB,) is nearing impossible.

Nearly all of the designs that are released have already gone through a testing period.