[the_equalizer]

Wonderful! It looks like you did a really clean work in that perfboard. Really nice!

 

[bengoshi2000]

Greetings all,
 
After years of being frustrated that I can't use my AKG240's with my iPod/iPhone (or really anything else I have), I have decided to quit whining and build something... I think the Starving Student is going to fit the bill acoustically, aesthetically and most important, financially.  I have a couple of questions though...
 
I'm going to confess up front that I haven't read all 400+ pages of this thread, so please excuse me if the following questions have been previously answered.
 
1)  I want to use a different type of heatsink for the mosfets... will just about any heatsink work (as long as the mosfet is properly mounted to it) or are there some types to avoid?
 
2)  I also want to use a rotary on/off switch.  Will any ol' switch do (as long as it meets or exceeds the specs of the switch from the BOM)?  Would someone be willing to suggest an appropriate switch?
 
This will be my first foray into diy amplifiers so I'm a bit nervous about the project.  Are there any good EE for Dummies type books I could pick up?
 
Thanks in advance!
 

 

[Starfire]

 
Quote:

Greetings all,
 
After years of being frustrated that I can't use my AKG240's with my iPod/iPhone (or really anything else I have), I have decided to quit whining and build something... I think the Starving Student is going to fit the bill acoustically, aesthetically and most important, financially.  I have a couple of questions though...
 
I'm going to confess up front that I haven't read all 400+ pages of this thread, so please excuse me if the following questions have been previously answered.
 
1)  I want to use a different type of heatsink for the mosfets... will just about any heatsink work (as long as the mosfet is properly mounted to it) or are there some types to avoid?
 
2)  I also want to use a rotary on/off switch.  Will any ol' switch do (as long as it meets or exceeds the specs of the switch from the BOM)?  Would someone be willing to suggest an appropriate switch?
 
This will be my first foray into diy amplifiers so I'm a bit nervous about the project.  Are there any good EE for Dummies type books I could pick up?
 
Thanks in advance!
 

 
Yes any heatsink of sufficient size will work, if you want you can mount the mosfets to one large one as I did in my build, be sure to get the mounting kits or I just get the thermalsil (Search that in mouser) pads and some nylon screws and nuts, you want them to be isolated.  Then you can ground the heatsink for extra noise reduction.
 
Any switch will work as long as it can handle the current, which really isn't much.  I've used the volume pots that have a switch built in to kill two birds with one stone.
 

 

[thelostMIDrange]

So, just stumbled on this thread....wow is it a big'un.....this starving student is a simpler version of the minmax?  the concensus is that it sounds good and likes low ohm grado type phones too?  thanks for any quick synopsis' of this 400 page thread...

 

[bengoshi2000]

Greetings all,
I'm looking into building the 12au7 version as an option if I can't find any 19j6 tubes.  I've been reading over the schematic for that mod:  http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif
 
My question relates to the highlighted changes... Where the changes are alongside another (i.e. original design component), is the highlighted option to be used in addition to the original or in place of the original?  I know that's a rank, noobie question but I wanted to be clear before I started putting together a BOM/shopping list.
 
Also, are there any good basic electronics resources in print (or electronic) that I should take a read of before I warm up the soldering iron?
 
Thanks again!
 

 

[SpringHalo]

Quote:

Yes any heatsink of sufficient size will work, if you want you can mount the mosfets to one large one as I did in my build, be sure to get the mounting kits or I just get the thermalsil (Search that in mouser) pads and some nylon screws and nuts, you want them to be isolated.  Then you can ground the heatsink for extra noise reduction.
 
Any switch will work as long as it can handle the current, which really isn't much.  I've used the volume pots that have a switch built in to kill two birds with one stone.
 

Would this switch work? I see that it has 2A/250V AC, but only 28V DC. You say you used volume pots with switches in them, and I can't seem to find dual pots with switches (on mouser) could you link me to the one you used?
 
If I did use a standalone switch (to enable/disable headphones so they don't pop) would I need a DPST (for both channels) or could I just short the ground with it?
 


Quote:

Greetings all,
I'm looking into building the 12au7 version as an option if I can't find any 19j6 tubes.  I've been reading over the schematic for that mod:  http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif
 
My question relates to the highlighted changes... Where the changes are alongside another (i.e. original design component), is the highlighted option to be used in addition to the original or in place of the original?  I know that's a rank, noobie question but I wanted to be clear before I started putting together a BOM/shopping list.
 
Also, are there any good basic electronics resources in print (or electronic) that I should take a read of before I warm up the soldering iron?
 
Thanks again!
 

The two capacitors that are tacked in parallel to the others are output coupling capacitors. They are to be added to the current components. (I'm making a 12A_7 version too) Have fun with your build!
 
 
 
 
 
Speaking of builds, I messed around in sketchup for a while and produced my case idea! The top and bottom are maple, while the front/back plates, as well as the heatsinks on the sides (going to make them myself) are going to be made of either aluminum or steel. The switch to the right is going to be the headphone-safety switch, but I might end up getting rid of it in favor of starfire's idea, and mounting the potentiometer on the right side of the face.
 

 

 

[the_equalizer]

Quote:

Greetings all,
I'm looking into building the 12au7 version as an option if I can't find any 19j6 tubes.  I've been reading over the schematic for that mod:  http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif
 
My question relates to the highlighted changes... Where the changes are alongside another (i.e. original design component), is the highlighted option to be used in addition to the original or in place of the original?  I know that's a rank, noobie question but I wanted to be clear before I started putting together a BOM/shopping list.
 
Also, are there any good basic electronics resources in print (or electronic) that I should take a read of before I warm up the soldering iron?
 
Thanks again!
 

 
I'm not sure what exactly do you refer to when you say 'alongside another' but if you're talking about, for example, C1 and C6, where there's a value crossed with a line and another value non-crossed value next to that, then they're not to be used in addition to but in place of the original (the crossed number). 
 
So for C1 and C6 the original schematic specified 150uF electrolitic capactitors where the modified version uses 680uF caps @ 63 volts.
 
To also clarify another potentially confusing issue, parts highlighted in yellow are optional, you can leave them out if you so wish. If you DO leave them out R14, R15, R16, R17 must be substituted by a wire connection; whereas C3a, C5a, C7 and C8 need nothing of the sort, you just don't connect them.
 
Oh, and certainly anything you can read on introductory electricity and/or electronics helps. I wish I could give you some URLs but I really don't know any. Google is your friend or maybe others could chime in here.
 
Hope this helps.

 

[bengoshi2000]

Quote:

 
I'm not sure what exactly do you refer to when you say 'alongside another' but if you're talking about, for example, C1 and C6, where there's a value crossed with a line and another value non-crossed value next to that, then they're not to be used in addition to but in place of the original (the crossed number). 
 
So for C1 and C6 the original schematic specified 150uF electrolitic capactitors where the modified version uses 680uF caps @ 63 volts.
 
To also clarify another potentially confusing issue, parts highlighted in yellow are optional, you can leave them out if you so wish. If you DO leave them out R14, R15, R16, R17 must be substituted by a wire connection; whereas C3a, C5a, C7 and C8 need nothing of the sort, you just don't connect them.
 
Oh, and certainly anything you can read on introductory electricity and/or electronics helps. I wish I could give you some URLs but I really don't know any. Google is your friend or maybe others could chime in here.
 
Hope this helps.

Thank you!  That does clarify things for me.  I had been concerned that c7, c8 c3a and c5a  would be used in place of r5, r11, r6 and r12.  Now I understand now that if I use the yellow, highlighted options that they would be used in addition to NOT instead of.
 
What benefits do the highlighted additions bring to the build?  (...my apologies if this is clearly answered elsewhere and I missed it.)
 
Looks like I'm going to place some orders today!
 

 

[the_equalizer]

C7 and C8 have the effect of increasing the net gain of the tube amplification stage by removing a local negative feedback effect produced by using cathode resistors R5 and R11 to bias the tubes. Their intention is more the removal of the local negative feedback than an increase of gain; the amp has more than enough gain as it is.
 
C3a and C5a have quite a complex effect but in summary they basically improve the high end frequency response of the output stage. They're called 'snubber' caps, if I recall correctly; heavily used in power supplies to suppress noise and transients.
 
R16 and R17 help control the 'throw' of the volume pot, in theory allowing you to set the pot further ahead in its travel than you would have to set for a similar volume without the resistors (I swear that last sentence makes sense ). Say, set the pot at 12 o'clock rather than at 8 or 9 for a similar volume level. This is good because the first section of the travel for volume pots is very uneven. I believe both Dsavitsk and TomB have posted much finer and better explanations of how these work elsewhere in the thread (the search function is your friend).
 
Finally, R14 and R15 are grid stoppers. They have the intention of discouraging oscillations and some other noises in the tube amplification stage. Some builders in the thread report quite dramatic noise reductions when using them.
 
For more about why these things have the effects they do you'll have to make your way through amplification theory texts
 
Good luck with your build!

 

[bengoshi2000]

the_equalizer,
Thank you for the short explanation.  I do appreciate your considerable time/wisdom on this project (still working my way through this thread, btw).
 
My last question is what caps would be of equivalent quality to the nichicon muse es 220uf for c7/c8 (that is also available at mouser)...
 
I.E. what about this Panasonic Cap?
 
http://www.mouser.com/ProductDetail/Panasonic-Electronic-Components/EEU-FM1E221/?qs=sGAEpiMZZMtZ1n0r9vR22ZGaUoI0JcRfFCgLDbfQFjo%3d
 
Nevermind... found the Nichicon Muse ES at Mouser:
 
http://www.mouser.com/Search/ProductDetail.aspx?R=UES1C221MPMvirtualkey64700000virtualkey647-UES1C221MPM

 

[bengoshi2000]

Ok... where do you wire in the tube illumination leds and resistor?
 
http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif

 

[Beftus]

It's all in this thread: http://www.head-fi.org/t/319231/millett-starving-student-hybrid-amp/5685#post_7319936
 
Quote:

Ok... where do you wire in the tube illumination leds and resistor?
 
http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif

 

 

[bengoshi2000]

Thank you Beftus... I did a search and actually found that post, but it didn't make sense to me last nite.  Amazing what a good night's sleep and a hot morning cup of coffee will do for reading comprehension.  

 

[Beftus]

For the sake of tinkering, you can make the tube LEDs switchable. I wired a on-off-on switch between the tube LEDs, I can run them at two different levels of brightness.

 

[bowei006]

Thought about doing this.....ill start wtih a cmoy first..