[dsavitsk]

Quote:

To clear something up.
the 50k resistors in series with the pot do not attenuate the signal at all
 
If you need to lower the volume, put a resistor in parallel with the pot.

Maybe a picture will help.  50K input resistors with a 50K pot effectively turns it into a 100K pot where the knob only turns half way.  It also changes the taper a bit allowing you to turn the knob further for the same attenuation, and ensuring 6db of attenuation even when turned all the way up.
 

 
 
 

 

[nullstring]

Quote:

Maybe a picture will help.  50K input resistors with a 50K pot effectively turns it into a 100K pot where the knob only turns half way.  It also changes the taper a bit allowing you to turn the knob further for the same attenuation, and ensuring 6db of attenuation even when turned all the way up.  

 
EDIT: I am tired. I am going to reply to this later when I can't make more sense of things, and be sure what I am saying makes sense.
In either case, putting a 50K resistor in series will do nothing to increase the voltage divider, and therefore will not lower the volume.
 
Put 50K resistors on there should only increase the impedance.. nothing more..

 

[the_equalizer]

Quote:

 
EDIT: I am tired. I am going to reply to this later when I can't make more sense of things, and be sure what I am saying makes sense.
In either case, putting a 50K resistor in series will do nothing to increase the voltage divider, and therefore will not lower the volume.
 
Put 50K resistors on there should only increase the impedance.. nothing more..

 
That is, unfortunately, wrong. It will attenuate the signal. The portion of the signal available at the pot's wiper is a fraction proportional to the ratio of R1/R2. Where R1 = The resistance value of the upper leg resistor plus the resistance value of the 'upper half' of the pot (from the first terminal to the wiper); and R2 is the value of the 'lower half' of the pot (from the wiper to ground).
 
Try a simple experiment and insert a 1Mohm resistor in series before the pot (R16, R17) or take a look here and do the math.
 
cheers!

 

[juntom10]

I think it will work as a voltage divider...which means it attenuates the signal....
 
ps. oops. i read the_equalizer's link after i posted it lol 

 

[nullstring]

I knew I must've been mistaken to be disagreeing with dsavitsk (and others apparently, I didn't even see those posts till now)
 
I apologize and Thanks for your patience with me.
 
 
Apparently the way I had it explained to me was very wrong.

 

[the_equalizer]

I, for one, don't think there's a need to apologize

. Disagreeing with anyone is not wrong... but that's another story for another thread

.
 
What you did (putting a resistor in paralel) certainly does attenuate the signal too, but it does it by dividing the current (or "shunting" it). A side effect of it is that it decreases input impedance (just as a side effect of the above pictured voltage divider is to increase the input impedance, as you very well pointed out).
 
cheers!

 

[juntom10]

Quote:

I, for one, don't think there's a need to apologize

. Disagreeing with anyone is not wrong... but that's another story for another thread

.
 
What you did (putting a resistor in paralel) certainly does attenuate the signal too, but it does it by dividing the current (or "shunting" it). A side effect of it is that it decreases input impedance (just as a side effect of the above pictured voltage divider is to increase the input impedance, as you very well pointed out).
 
cheers!

That reminds me of my prof saying...
"Very high Zin and very low Zout  = the best "
 

 

[kellzey]

Did they ever come out with a PCB for this available for purchase?
 
 

 

[revolink24]

Yes, but unfortunately, it's no longer available.

 

[Veggiel]

Does the heatsink of the mosfet have to be insulated from the chassis if the chassis is being used as ground?

 

[Ikarios]

Quote:

Does the heatsink of the mosfet have to be insulated from the chassis if the chassis is being used as ground?

yes, you to isolate the tab from the case. you can either use a mica insulator with thermal grease and a shoulder washer for the screw you attach it to, or you can pick up a mosfet mounting kit from beezar, which has bergquist pads and all the hardware you need for one mosfet.
 

 

[dsavitsk]

Quote:

Did they ever come out with a PCB for this available for purchase?
 
 

I've been cleaning out old boxes and I stumbled upon some (3) of the original prototype PCBs. These are pretty different than what we ultimately settled upon for a design, but they do work OK ... I think.  If anyone wants one you can have one for the price of shipping and a padded envelope, ~$4.
 
Here's what they look like: http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/510#post_4403745
 
The FETs can be mounted to the case as with the final version, or, as shown, they can be used with sinks.
 
I also have my original built prototype that someone can have. Shown here (but no big sink included, but otherwise as shown with no front panel) http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/615#post_4475495
 
Yours for the shipping + a $5 donation to the Red Cross.
 
Send me a PM if interested.

 

[sailorman]

PM sent on amp.

 

[dsavitsk]

sorry, all taken.

 

[revolink24]

Wow, too bad I missed this. I'd love to do another PCB build.