[tomb]

 
Quote:

OK, I have it all build except for the replacement JFETs for the ones I killed, They are on there way..   Oh and RB14L/R are just carbon for now till I put in another order for stuff..  
 

 

Looks like you've done a great job!  You did a great job on cleaning up the JFET holes, too!

 

[Aalelan]

Quote:

Quote:

Originally Posted by Listen2this1 /img/forum/go_quote.gif Well I will give it a shot.

The last time cetoole and I discussed it, he's pretty much been using his MAX to drive a couple of desktop speakers (8ohm). That's mostly because he's into all sorts of electrostatics these days

, but he still uses the MAX for his orthos, too. At any rate, 8 ohms is fine for a MAX (within reason, of course - it's still a headphone amp).

I know this is an old thread but it begs the question that has been in the back of my head..  If I wanted to drive some external speakers how do I do the math to figure out what will work?  I'm still a little confused on the whole Ohm math and what the Max MOSFET can do..
 
I know its a headphone amp but I can think of a few situations where here at work on the weekends I would not want to be tied to my headset.

 

[BoilermakerFan]

 
Quote:

I know this is an old thread but it begs the question that has been in the back of my head..  If I wanted to drive some external speakers how do I do the math to figure out what will work?  I'm still a little confused on the whole Ohm math and what the Max MOSFET can do..
 
I know its a headphone amp but I can think of a few situations where here at work on the weekends I would not want to be tied to my headset.

 
We've covered it briefly, but the MOSFET-MAX will do over 2W into 8R.  So any speaker with a sensitivity of 91dB or greater should sound fine near field.
 
There are ways to get more power through the MAX, but you really need to run 2-1/2" heat sinks on the V-reg and DBs.  If your willing to swap over to a new chassis, then you can have some higher power fun.
 
I forget the exact bias level, but at some point over 80mA or so the small signal transistors leave their optimal points on the curve and need to swapped out to BC446C/BC546Cs that can handle the higher current.  The V-reg needs to go from a 317 to a 338, and the poly fuse needs a bump.  Depending on how high you bias, then the transformer may need a little bump too.  I haven't tried it on my MOSFET-MAX yet, but on my Liquid Gold, IRF540s biased out at 215mA at 55degC on 2-1/2" heat sinks.  They should be able to run at a similar bias and temp point in the MAX though.  It really doesn't change the peak power output significantly, just keeps the amp in Class A a lot longer and lets the amp pass more current when necessary. 
 
I'd also be a little gun shy on trying to push BJTs much higher than stock when driving speakers too.  There shouldn't be any problems stock, but cranking up the bias on a modded amp and then driving speakers always opens that little door of risk to thermal run away. 
 

 

[Aalelan]

Ok, this may not be the right thread but its related...  I got my parts in for my GrubDAC tonight and put it all together.  How does one go about debugging issues??  I plug it into the USB and the laptop does not see any new hardware, nor will the LED light up.  I have gone over it with a magnifying glass and I dont see anything..
 
The only odd thing is I had one SMD cap left with nowhere to put it, but I think it might have been an error on Tom's kit.. the bag said among the other spots C5, but C5 is one of the three big thru hole caps..
 
Can someone point me in the right direction?
 
 
EDIT:
Oh yeah!!! Its alive!!  well still not the Grub

 

[jdkJake]

Quote:

 
EDIT:
Oh yeah!!! Its alive!!  well still not the Grub
 

 
Great news Aalelan (well, the MAX part anyway)!
 
Now to case it up! Keep the pictures coming.
 
jk
 

 

[tomb]

Quote:

Ok, this may not be the right thread but its related...  I got my parts in for my GrubDAC tonight and put it all together.  How does one go about debugging issues??  I plug it into the USB and the laptop does not see any new hardware, nor will the LED light up.  I have gone over it with a magnifying glass and I dont see anything..
 
The only odd thing is I had one SMD cap left with nowhere to put it, but I think it might have been an error on Tom's kit.. the bag said among the other spots C5, but C5 is one of the three big thru hole caps.. </snip>

You need to post this in the GrubDAC thread so that cobaltmute can see it and offer support.  Offhand, the first thing I'd suggest is to see if you can measure 3.3VDC at the 3.3V test point (referenced to Gnd).
 
P.S. I hope that doesn't mean I packed an extra SMD cap in everyone's order, but it's possible.

 

 

[Aalelan]

Dangit  turns out it might have worked before farting around with it, its looking like Windows 7 does not like it and thats all I have here at the house.. brought home and old crappy laptop from work and booom! recognized it..  
 
Man I get trigger happy, I better go hook it up and make sure sounds come out of it now.  Just ask Tomb about me being took quick to do things
 
EDIT..
 
Yep and the GrubDAC sounds AWSOME!!!  Just need to figure out my Windows 7 support issue

 

[funch]

Quote:

Dangit  turns out it might have worked before farting around with it, its looking like Windows 7 does not like it and thats all I have here at the house.. brought home and old crappy laptop from work and booom! recognized it..  
 
Man I get trigger happy, I better go hook it up and make sure sounds come out of it now.  Just ask Tomb about me being took quick to do things

Gee, I thought that I was the only one to do the knee-jerk thing.

 Can't count how many times I've had to drop back and punt after jumping to
a wrong conclusion.

 

[tomb]

Quote:

Dangit  turns out it might have worked before farting around with it, its looking like Windows 7 does not like it and thats all I have here at the house.. brought home and old crappy laptop from work and booom! recognized it..  
 
Man I get trigger happy, I better go hook it up and make sure sounds come out of it now.  Just ask Tomb about me being took quick to do things
 
EDIT..
 
Yep and the GrubDAC sounds AWSOME!!!  Just need to figure out my Windows 7 support issue

 
I don't think Windows 7 the issue - the grubDAC works first time, every time on my Windows 7 PC.

 

 

[Aalelan]

Quote:

 
I don't think Windows 7 the issue - the grubDAC works first time, every time on my Windows 7 PC.

 

Yeah, I figured it out alittle bit ago...  I guess there was a problem on my first try as it had shutdown the USB HUB in my laptop, the device was stopped (oops)  restarted the USB hub host service and bam! there was the grub...  Been Playing some Led Zepp FLAC's through it and its rock'n!!!
 
Thanks for all your help Tom!!  I know I have pestered the poo out of you the last few weeks

 

[jdkJake]

Forgot I had these on the camera.
 
Some "night" shots. This was before I painted the top, so, the vent holes are not black. Still, pretty cool. The blue really lets you see the heater filament.
 

 

 

 
 
jk

 

[Aalelan]

GrubDAC all mounted, Just need to figure out how I want to case it up
 
PS running at 27v  Tube Bias is 13.5V  and MOSFET bias is at 180mv
 

 
One of many Night shots I took the other night, saw JK put his up and figured i would share one too
 

 

[jdkJake]

So what do you think of the sound of your new combo?

What phones are you using?

jk

 

[Aalelan]

 
I love it!!  as for phones, I don't have a good pair yet/anymore  I used a set of Bose comfort quite 2 on it and it was amazing!!  
 
Suggestions on a sub $200 set that would go well with the MAX?

 

[jdkJake]

Wow, that's a loaded question!

There is a whole forum dedicated to answering it as well.

Personally, I built this version to act as my main amp for Grado's. In that regard, I am extremely pleased. That being said, Grado's have a very distinct sound and opinions on that sound are all over the board. Suffice to say, I like them, particularly on this amp which really brings them to life.

I haven't really hooked up my HD650's as I do not want to change out the tubes yet. Just lazy I guess. That and I am really enjoying my grads right now. I am sure I will get to the HD650's sooner or later and let you know what I think.

jk