Millett "Starving Student" hybrid amp - Page 128

Hello I'm new here

Hello everybody and happy new year !

I just read all the thread (it took me some time !) and I'm very interested by this Starving Student headphone amp.

I've already built a preamp (UGS balanced preamp, seems well known in some DIY community), and I'd like to add a small headphone amp after it, maybe in the same box (I have room). The jack socket would command a relay that will switch the signal out from the preamp to the head amp instead of the power amps.

I also use a Sony MDR-CD1700 which is a 32 ohm AFAIK.

Do you think the Starving Student would be ok for this purpose ? Or does it require some modifications to accept the output of a preamp instead of the output of a source directly ?
I would at start suppress the volume pot because I would use the preamp's control. What else should I think of ?

Thanks in advance for your advice !

I use a CD1000 with this amp (though a higher current active ground version) and a preamp and have no issues. You could potentially just put a resistor in the signal path to attenuate if you are doing a one box solution (no need for a potentiometer).

Germania, did you get my pm? Just wondering if you have sent out my cable.

Thanks

Isolated RCA jack advice

I'm getting my Mouser order together, and I had a question about the input jacks. Several people have recommended isolating them from the chassis and using a star ground. I'm planning on doing this, but I'm having some trouble figuring out the best way to do this.

One option is to just buy non-isolated jacks, like the ones in the original BOM, and then buy either a grommet or a shoulder washer and flat washer from the hardware store. But I'm not even sure if it's common to find washers that would be the proper size. Frankly, it's also less convenient than just ordering from Mouser.

The other option is to order isolated jacks from Mouser. Kobiconn has jacks in black and red that come with "insulating nylon washers" (Mouser P/N 161-2002 & 161-2003). But on the data sheet, the washers are flat. That won't work so well, I think. Switchcraft has a jack (Mouser 502-3501FPX) that can be isolated by purchasing separate shoulder and flat washers (502-S2207 and 502-S1564, respectively). That works out to $2.34 per jack. I'm not too concerned about the money, but I'm wondering if I'm missing out on an obvious solution here. Are isolated jacks so uncommon that Mouser would only carry one, or am I missing something. Any advice?

Mouser just doesn't carry much in the way of RCA jacks, you'll probably want to source them somewhere else if you decide to use isolated jacks.

I broke down the circuit into major parts and then redrew simplified versions that were easier for me to keep in my head. It made it a lot easier to keep track of what I was connecting and how they related. Maybe somebody else will find it useful, although here it is still in quick and dirty form.

I've finally completed mine, so here it is:


I have yet to get a knob, because I don't want to use a store bought one, and random household objects can't really be converted to knobs with the tools I have... also, I haven't erased the pencil marks yet.


That is a view of the bottom. I had to attach a fan in order to compensate for the fact that the MOSFETs are on the inside. HOWEVER, when the fan is on, it causes a bastardly buzz in the right channel (and less in the left). It is very noticeable, even at the lowest volumes. My guess is that it is causing the wires to vibrate or some crap like that, but then again I don't see how that could affect sound... If anyone can tell me how to fix it while getting to keep my fan, I would be in your debt P.S. the fan is running off of its own power supply.
P.S.S how hot should the heatsinks be? because when I touch the (un-insulated) screw that holds the plates to the case, it kinda burns


internal shot! specs are: dale resistors, Nichicon FG output caps bypassed with WIMAs, Elna Silmic II power supply caps, the film caps are these: Reliable capacitor PPFA series.
alps rk27 pot (which I accidentally wired backwards), copper point to point wiring (the reason some are insulated and some aren't is because all the wire was cannibalized from random cables, and I switched wire 4 times or something), 1/4" input and output jacks, and a pair of sylvania 19J6 tubes donated by HeadFi-er Dandi. Thank you so much Dandi!


night shot
This thing sounds fantastic! My grados used to be plugged into my computer speakers, because they have an integrated amp, and they sounded pretty lifeless. Now my setup is computer->SS->cans, and the sound is so much warmer and more lively. There was an immediate improvement in soundstage and separation of instruments. The clarity, depth, and power of the bass has improved a lot, although because my cans are grados, I still use Winamp's equalizer for a bass boost. Sibilance seems to be more under control now. Also, this thing is ridiculously loud. I listen to my cans at maybe 20% louder than conversation level, and I can barely move the knob past lowest without becoming uncomfortable with the sound level. Maybe its just the whole low impedance 'phones thing.
The only drawbacks other than the fan problem is that point to point wiring is such a pain without those little helping hand clips or whatever they're called.

congratulations Dr. that last picture is nice the tube glow and the wooden case are fantastic.

I am no DIY'er but me thinks you might have continued problems with putting a fan in the case. If you haven't maybe put the fan on it's on power supply, perhaps it could be external to the nice case you have??
Enjoy the music!
Cheers

The fan is outside of the case, on the bottom (courtesy of rubber cement). It is on its own power supply, a 3v 500mA wall wart

@Dr Evil Dan

Nice looking amp, very unique. If you can't find a knob maybe go for one of these wooden ones:

Radio Daze-Reproduction Knobs

Hey Dr Evil Dan, cool box. What did it used to be? I love off the wall cases.

It used to be a box for a doll, which is why it has wallpaper on the inside
The part I used is only half of it though, it used to be two identical sections that were connected by a hinge. the bottom covering is from the other half. Upon further consideration, the color of the box in the pictures is all wrong :\
the one below is much better (but I still have to erase those pencil marks!)

Hey, thanks. I was thinking about using a wooden knob, and those are really nice. I was also thinking of using a shiny brass knob type thing, to match the color of the headphone jack. Like this one: http://www.minksemporium.com/Brass_Knob_4.jpg
they only problem is attaching it




man I hate pictures... The amp looks so much less ugly in real life

I just received my tubes.
I need sockets then I'll be good to build when I get back from Sydney.

Can't wait!!

gonna try and take mine apart again tonite. i am preety much a n00b at this and cant much remeber what i learnt in high school will the capacitors need discharging?

Anything over 25V is dangerous from what I know (not testing that myself), 48V can possibly be lethal. You would feel it if a cap on this project were to discharge into you as I believe they are all seeing the full voltage at points. You can make a discharge circuit easily though, I need to make one myself.

http://www.repairfaq.org/sam/captest.htm#ctdtk