[tomb]

  The one thing I was wondering is if I used an all plastic box then just used the perf board as the the central grounding point would that be bad? I basically bought one of these and it has a metal top and a plastic top I was back and forth about how to do grounding thinking that it might be better to mount to plastic and then have the grounds all go to the perf board. I guess It's something I can always re-work if it doesn't work out well.

There is no ground plane or solid plate on that perf board.  The pads are simply tied together with traces in certain instances.  It's not the same thing as a ground plane or plate.  There are other issues, as well.  I apologize for continuing to harp on it, but seriously - you have two tube sockets with 14 connection points and two MOSFETs with 6 connection points, plus heat sinks that have to be mounted.  None of those will work on the perf board.  In addition, you have four caps - perhaps eight if you use the bypasses - that will span 3 to 5 of those holes in the perf board with their leads, much less the physical size of the caps' cans themselves.  You also have 5 components in addition to this that all need panel mounting.  In addition to the tube sockets, MOSFETs and capacitors, that represents another minimum of 13 leads going from those components to somewhere on the perf board, perhaps several more than that.  At some point, having a little board with holes in it doesn't give you much advantage.
 
Like I said the last time, draw it out.  This isn't the Starving Student, but it might give you some ideas with that perf board: http://benfeist.com/wp-content/uploads/2012/12/a47_assembly_and_schematic.png
 
  If you can make it work - fine, but I have doubts. Good luck.

 

[Danthrax]

I understand your concern but I think you are misunderstanding my intention with the perf board. I don't plan to have major components mounted directly to it, it's more of a collection space to tidy things up a bit so it's mostly going to be point to point. But I'm stating to think that's a bad idea. My other though was to use the larges sets of traces as a point to tie all the grounds into but I'm guess the concern is that there isn't enough copper there to handle the power going through it? I'm assuming that there would likely be a greater advantage in reducing overall cabling length inside the box though. I'll probably pick up some terminal strips and use those with the metal plate as well? or do you think I should just use the terminal strips and a plastic cover? This was a rough non-spaced out version of all the parts I was going to mount to the board (ignore r3 and r9 I'll attach those to the mosfet): http://imgur.com/0RmpySH

 

[Fishline]

Having built a couple of the original 19J6 version (P2P) of the amp a few years ago, I thought I'd try another P2P 12AU7 version.  I basically used the same case and heatsink as what's on instructable.  Just finished wiring everything.  Turned it on and no sound was coming out of the left channel.  I measured the 48v and 12v points indicated on the schematic and got 45v and 12v in both channels.  Pin 1 of both MOSFETs measure 14-15v.  I tried reflowing the solder at anything that might be suspicious but to no avail.  Can anyone offer some idea of what to try?  I'd very much appreciated it!

 

[Fishline]

Never mind... i solder the wire to the headphone jackfor the left channel to the same side of the jack as the right channel and gnd, and voila! Sweet music! All is well.

 

[Fishline]

Never mind... i solder the wire to the headphone jackfor the left channel to the same side of the jack as the right channel and gnd, and voila! Sweet music! All is well.

I actually forgot about the mica insulation for the MOSFETs. I just put a thin layer of thermo compound on the back of the MOSFETs before bolted them to the heatsink. Would thatbe ok? I've run the amp for a few hours already and everything seems just fine. What can go wrong without the mica?

 

[tomb]

 

Never mind... i solder the wire to the headphone jackfor the left channel to the same side of the jack as the right channel and gnd, and voila! Sweet music! All is well.

I actually forgot about the mica insulation for the MOSFETs. I just put a thin layer of thermo compound on the back of the MOSFETs before bolted them to the heatsink. Would thatbe ok? I've run the amp for a few hours already and everything seems just fine. What can go wrong without the mica?

 
It's probably OK with just thermal compound, but more importantly - did you use an insulating washer on the MOSFET tab?  That's where the short will occur - between the MOSFET tab and the screw.  This happens because the inside of the hole on the heatsink often has very little anodizing, or it creates a short with whatever the heat sink is mounted on.

 

[Fishline]

It's probably OK with just thermal compound, but more importantly - did you use an insulating washer on the MOSFET tab?  That's where the short will occur - between the MOSFET tab and the screw.  This happens because the inside of the hole on the heatsink often has very little anodizing, or it creates a short with whatever the heat sink is mounted on.

Hmmm, i just bolted the MOSFETs onto the heatsink directly. I ran it all day yesterday and left it on overnight. It still runs just fine today. If there is going to be short, wouldn't it happened already?

 

[vapman]

Hmmm, i just bolted the MOSFETs onto the heatsink directly. I ran it all day yesterday and left it on overnight. It still runs just fine today. If there is going to be short, wouldn't it happened already?

There's nothing wrong with this. My Yamaha M4 power amplifier which has been running beautifully every day since the very early 1980's does this.
 
edit: Didn't notice you didn't have a washer. Add one. I thought this was a post about if having a MOSFET that close to the heat sink is safe or not.

 

[tomb]

 

It's probably OK with just thermal compound, but more importantly - did you use an insulating washer on the MOSFET tab?  That's where the short will occur - between the MOSFET tab and the screw.  This happens because the inside of the hole on the heatsink often has very little anodizing, or it creates a short with whatever the heat sink is mounted on.

Hmmm, i just bolted the MOSFETs onto the heatsink directly. I ran it all day yesterday and left it on overnight. It still runs just fine today. If there is going to be short, wouldn't it happened already?

Not unless you breathe on it.

 

[Fishline]

OK.  I've pulled the insulating washers from the 1st SSMH I built to put in the new one.  I don't see them listed in the BOM.  It should be Mouser part # 532-4880SG, correct?  I dug that out of the Mouser order history from 6 years ago.  Amazing they kept that record.

 

[tomb]

  OK.  I've pulled the insulating washers from the 1st SSMH I built to put in the new one.  I don't see them listed in the BOM.  It should be Mouser part # 532-4880SG, correct?  I dug that out of the Mouser order history from 6 years ago.  Amazing they kept that record.

 
I always provided heat sink hardware kits as a special product from Beezar and that's how it was listed - as a kit.  Self-serving, I guess, but then who else has ever supplied socket-head machine screws for heat sink mounting kits?  In addition, the shoulder washers I supplied were genuine Aavid, glass-filled shoulder washers.  Most kits supply the cheapest of machine screws and a cheap nylon shoulder washer that can often distort and compress upon torquing down the assembly.
 
If that means my BOM was not as detailed as it should've been, so be it.

 

[Danthrax]

Well I finished the first one I planned on making: http://imgur.com/a/n9LTx , this one is actually using some 18j6 tubes instead of 19j6 (had them from a friends failed build) when I make the better one I plan on laying things out a bit better but overall this wasn't too bad, I may go back and try to tidy up the wires a bit but most of the long runs are going to ground and it looks a lot busier than it really is due to the small size. I'm also going to throw some jb weld on heatsink connectors as they really didn't want to solder to the metal plate. I'm thinking I may just go with a plastic plate for the new build but I'm still not sure. The thing that surprised me is that with a 100k pot the sound was still rather loud really quickly I would say an 1/8 of a turn on the knob was dangerously high volume on some lower impedance headphones and I wasn't really expecting that, even when I added in 50k resistors on the rca input it still seemed rather high. I also noticed a bit of a noise floor when using these with my Sony MDR 7506 (is it bad when $80 headphones become your test/beater headphones?), but it was not audible with my q701 or he400i. The radioshack I went to didn't have any terminal strips but I'm going to check another one today and get some, I may redo some of the grounding on this build to see if I can reduce the noise floor a bit.

 

[Fishline]

In case anyone find this helpful, here's my project on mouser (grand total of $63):
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=0b0ae93f48
​(Can mouser projects be shared like this?)
 
This is for the 12AU7 version.  It includes everything (case, heatsink, etc.) except wires, tubes, tube sockets, and the CISCO PSU.  It's basically the version as seen on Instructables:
http://www.instructables.com/id/Headphone-Hybrid-Tube-Amp-SSMH/
 
Some notes:
1. There is a smaller Hammond case that can be used, but the heatsink will occupy the entire top of the that case, so holes will need to be drilled on the heatsink for tubes to poke through if you go with the smaller case (~$4 cheaper).  The case has several color options (BK for black, RD for red, YL for yellow, etc.)
 
2. I put in the Alps RK097 pot/switch combination.  It's about the same price as the Alpha, but has the builtin switch.  Saves a separate switch and drilling another hole in the case for it.

 

[tomb]

Well I finished the first one I planned on making: http://imgur.com/a/n9LTx , this one is actually using some 18j6 tubes instead of 19j6 (had them from a friends failed build) when I make the better one I plan on laying things out a bit better but overall this wasn't too bad, I may go back and try to tidy up the wires a bit but most of the long runs are going to ground and it looks a lot busier than it really is due to the small size. I'm also going to throw some jb weld on heatsink connectors as they really didn't want to solder to the metal plate. I'm thinking I may just go with a plastic plate for the new build but I'm still not sure. The thing that surprised me is that with a 100k pot the sound was still rather loud really quickly I would say an 1/8 of a turn on the knob was dangerously high volume on some lower impedance headphones and I wasn't really expecting that, even when I added in 50k resistors on the rca input it still seemed rather high. I also noticed a bit of a noise floor when using these with my Sony MDR 7506 (is it bad when $80 headphones become your test/beater headphones?), but it was not audible with my q701 or he400i. The radioshack I went to didn't have any terminal strips but I'm going to check another one today and get some, I may redo some of the grounding on this build to see if I can reduce the noise floor a bit.

Input resistors are keyed to the volume pot impedance. 50K resistors assume a 50K pot. You should be using resistors in increments of 100K for a 100K pot.

 

[Danthrax]

Ok that makes sense, without the 50k it was way worse but it's still not ideal, I was under the impression that using a 100k pot to begin with would allow for a little more play, but I guess I was wrong. Thanks for all the help.