Millett "Starving Student" hybrid amp

[lynxkcg]

Originally Posted by JamesL

Do the mosfets get particularly hot?
I have some smaller heatsinks lying around and maybe I could recycle those.

My thermomoter that I have only goes up to 120 deg. F and it was well on it's way higher. I'm using 2 inch heatsinks but they're on top of a wood case, so it can't dissipate like a metal case would.

Off topic: when everyone mentions "bypassing" an electrolytic cap, is that just hooking up a film or PIO cap like a vitamin q in parallel with the electrolytic? (sry I'm still new to all this).

[JamesL]

Originally Posted by lynxkcg

My thermomoter that I have only goes up to 120 deg. F and it was well on it's way higher. I'm using 2 inch heatsinks but they're on top of a wood case, so it can't dissipate like a metal case would.

Off topic: when everyone mentions "bypassing" an electrolytic cap, is that just hooking up a film or PIO cap like a vitamin q in parallel with the electrolytic? (sry I'm still new to all this).

Thanks, guess I'll be looking to use the bigger heatsinks...

And yup. some info here too

[keiths]

Originally Posted by m0b1liz3

Hello Keiths, at what point in the diagram did you take off the wires for your LED?

Here:



I'm using a 20k resistor which gives a current of 2.4mA. This seems to make the LED bright enough. The resistor dissipates 0.11W at that current, so a 0.25W resistor is fine.

Originally Posted by m0b1liz3

I was also wondering if mounting the heatsinks inside the case is a bad idea. I am not even sure if I can fit mine but I thought it could be a good idea if travelling. Would just have to unplug the tubes and put the box in a bag.

I don't know. I was thinking the same for the next one I'm to build. The heatsinks on mine don't seem to get particularly warm. (I'm using 2" x 1" sinks with a thermal resistance of 3.6°C/W). I might try mounting them with 1/2 the heatsinks sticking out of the back of the case.

[Ferrari]

keiths, an LED is usually working in a forward-bias condition with current flowing from anode to cathode (the LED is much happier if you rotate it 180 degrees).

[nsx_23]

Shame that I suck at electronics at the moment....

[keiths]

Originally Posted by Ferrari

keiths, an LED is usually working in a forward-bias condition with current flowing from anode to cathode (the LED is much happier if you rotate it 180 degrees).

Opps

I've fixed the schematic. (I'd wired the LED the right way round)

Thanks.

[scompton]

Finished my build. I'll post pics later. The only problem I have it that the volume is backwards. I wired it according to a post in another thread.

With the shaft facing me

• Right pins are connected to the RCA jacks
• Middle pins are connected to pin 5 of the tube socket
• Left pins are grounded

What have I done wrong?

[TimJo]

Originally Posted by scompton

The only problem I have it that the volume is backwards. I wired it according to a post in another thread.

With the shaft facing me

• Right pins are connected to the RCA jacks
• Middle pins are connected to pin 5 of the tube socket
• Left pins are grounded

What have I done wrong?

Sounds correct provided the solder lugs are pointing down (5, 6, 7 o'clock if you will). If they are pointing up as described, then they are backwards.

[scompton]

Sounds correct provided the solder lugs are pointing down (5, 6, 7 o'clock if you will). If they are pointing up as described, then they are backwards.

They're pointing up so they were backwards. Works great now. Thanks. Pics later. Right now I have a honey-do list.

[joe_seattle]

Can anyone recommend a good-looking and not too expensive enclosure that will fit this amp well?

I saw those fantastic BB size cases on smallbear, but they seem to be tiny. Are they for sure too small? I'd like a nice looking aluminum case ideally or some metal case that could be easily painted.

Oh...and does anyone know of a place that does the drilling for you? I found frontpanelexpress, but it would be about $80 for what I want - which I guess isn't too bad since it was anodized gold aluminum with all the holes cut. GOLD! :-)

[pmillett]

Hello everybody -

I finally got around to making a "Starving Student" photo gallery on my web site. Nothing fancy, basically I just stole all the pictures out of this thread.

Starving Student Headphone Amp photo gallery

Hopefully I'll have time to keep it updated. I've been in Japan for half of the month of July.

On the upside, I gathered lots of info to update my Akihabara info...

Parts in Asia

Pete

[scompton]

I have one tube glowing very bright and the other not so bright. What can cause this? Where do I need to test?

The channel with the bright tube has a loud buzz, music doesn't play though it.

Edit: I just realized that the tube started glowing bright after I closed up the box. I assume something shorted or a solder joint broke.

[elliot42]

I finished machining my case yesterday. It's aluminium from an old hard drive with the guts ripped out. Machining it was really easy with a stepped drill bit (which I got yesterday, wonderful tool). The case is black but is a bit scratched (it's pretty old) and I may give it some paint later on, but for now it looks fine.

I might post some progress pics, but will definitely post pics when it's done, hopefully by the weekend. I'm also using the heatsink from a Pentium 3 Slot 1 card; it's a decent size and should keep the mosfets (which I'm still waiting for in the post) nice and cool (you'll all see the size of it soon, it does look good though).

[n_maher]

Pete's gallery reminded me that I'd never posted a picture of my amp after mounting the knob, d'oh! As luck would have it I had the amp home with me this weekend for a little tweaking so I busted out the camera and here it is.





And just to be a tease I decided to take a couple of photos of my amp with the starving pcb prototype that I've got ~90% populated.





I should have it done and maybe even cased up by next weekend. I know it's been a while since anyone posted updates on where this is at. Just know that we're still working on it and simply don't want to put something out there that isn't well and completely thought out.

[scott_fx]

i built one chan of the amp so far, powered it up and it sounds really great; though, it's not very loud. at full volume it's not as loud as my ipod's internal amp. also, the volume control tops out at about half way. i'm not sure if these are related or not, could it be as simple as not having wired the pot correctly?

any advice guidance would be great. i can't wait to have this finished, i may build another one learning from my mistakes!