[tomb]

Quote:

Got a question about Q5,Q6 and VR1.
 
From post #9:
"Torque is probably too strong a word, though, because you want to tighten them so that the lock washer is obviously compressed, but not enough so that the thermal pads get cut.  There is high-voltage going through the CCS transistors, so you don't want them shorting to the heat sink."
 
 
The MJE350 and NJM2396F63 looks like they isolated,  in which case thermal pad  or paste  requires only for better heat transfer not isolation from heat sink.  Just want to be sure. Thanks
 
 

Back then, there was the possibility that other transistors could be used.  In fact, the LM317 was used during the first prototyping.  Also, there are many versions of the MJE's that have metal backs.  However, since Dsavitsk standardized on only isolated (all plastic) transistors and VR, you are correct.

 
 

 

[vvs_75]

Tom,
Thank you for the prompt respnd. Also thank you for the top-notch packaging, you guys rule!

 

[jdkJake]

All cased up and looking fine. The case itself is really nice, just needs a coat or two of paint to bring it some personality. 

 

 

 
 
I tapped out 6-32 thumb screws for the end panels, which worked great. A very easy case to tap due to it's construction.
 
The only issue with the build right now is the case itself. While it looks great and is a very nice addition to the build, with the top piece in place, I get the slight hum mentioned earlier in the thread. The hum is way low in the background, but, there nonetheless. Without the top piece in place, the amp is silent. Very silent. I am using 6J6A tubes and Grado SR225/HF-2 which expose the hum. I have not yet tried other tubes/headphones.
 
So, the good news is that the hum seems to be directly attributable to the case, at least in my build. Worse comes to worse, that can be addressed a variety of ways. I do have a couple of shielding ideas I am going to try that I will report back on.
 
In any case, this is certainly not a show stopper. It is VERY low and once the music starts, most material will make imperceptible, especially at volume. Just a bit of a shame as the case is really, really nice and the sound of this amp is oh so very sweet. I spent a good amount of time with it yesterday and brought the HF-2's to the party.  A most fine combination to say the very least.
 
Anyway, time to get creative and figure this one out.
 

 

 

[tomb]

Great pics!
 
Someone has suggested grounding the heat sinks.  That should only take a few short leads - maybe even jumpers.  If you can get to it before I do, please let us know.

 

[jdkJake]

Thanks TomB. Photos are easy when the source material is so photogenic. 

 
So, not sure what you mean by grounding the heat sinks. I went brute force and put a big hunk of copper between the tubes and the power supply.
 

 

 
Did not make a lick of difference. I moved it forward as well as back in a few different places within the amp. No change. The top lid still telegraphs the hum, which is somewhat puzzling considering the wave length at that frequency. 
 
The problem, at least from my perspective, is that big ass E-core at the back of the chassis. Once we isolate that bad boy (save for sawing the board in half), we will be cooking.
 
Serious contemplation begins now....

 

[tomb]

Whoa! I'm amazed that you tried that! Many thanks for such an effort.
 
Actually, I was thinking of perhaps running a wire lead from one of the heat sink pins underneath the PCB to a pad that was connected to the ground plane (for each heat sink). Whether the heat sinks are grounded or not depends on whether the heat sink PCB pads are connected to the ground plane.

 

[DingoSmuggler]

Looking good jdkJake. 

 
I was considering doing something similar with the chassis, but wasn't quite sure what colour I would prefer, but that satin black looks like a winner for sure.
I'm still considering trying a textured coat though on top, anyway I'll update on here whatever i end up doing.

 

[jdkJake]

Well, looks like I pulled a boneheaded maneuver that did not materialize until today.
 
I was listening to the amp (with my LCD2's actually) and shut it off to move it to another room to try out another shield I made. When I re-applied power, there was nothing, nada, zip. No AC at all.
 
Thinking that was very odd, I pulled the fuse holder to check the fuse (which was fine) and two lovely bits of metal fell out, Well, one fell out, the other had to be extracted. Looks like I was more than a bit heavy handed when I installed the fuse drawer. I must have jammed it in with enough stress that it broke the fingers that make contact between the drawer and IEC socket to pass power through the fuse. They are now too short to make contact at all. Lovely.
 

 

 
Looks like I was lucky it worked as long as it did. Oh well, I put another fuse drawer on order. I will see if I can rig up a temporary fuse holder until the replacement arrives. 
 
Let this serve as a caution. The fuse drawer is apparently somewhat fragile. That or I am far more powerful than I ever knew. 

 
So, be gentle on installation of that fuse! 

 

[tomb]

The Torpedo website is up and running!
 
 
P.S. Sorry to hear about that fuse drawer.

 

[Gabe Logan]

Got mine finished up yesterday and have been rolling between the 5694,5884 and 6J6. I now hear the imaging that you were talking about long ago tomb and is something i have been lacking in my other amps that i've previously owned.
 
Now that i've seen jdkJake's case i'm tempted to take it apart and do a paint job with wet sanding and buffing to get a mirror finish but i'm having a hard time turning it off.
 
By the way tomb on the Overview page the link to a DMM sends me to a Drip Irrigation Kit instead.

 

[tomb]

Quote:

Got mine finished up yesterday and have been rolling between the 5694,5884 and 6J6. I now hear the imaging that you were talking about long ago tomb and is something i have been lacking in my other amps that i've previously owned.
 
Now that i've seen jdkJake's case i'm tempted to take it apart and do a paint job with wet sanding and buffing to get a mirror finish but i'm having a hard time turning it off.
 
By the way tomb on the Overview page the link to a DMM sends me to a Drip Irrigation Kit instead.

What, you don't want to grow roses in that case?  I'm surprised.  Guess I'll have to fix that link.

 
 
EDIT: Should work now ...

 

[Gabe Logan]

Ha, as tempting as that sounds i'll stick with a DMM instead.

 

[funch]

Hey Jake, you gotta lay off the steroids.

 How did the amp sound with the LCD2's?
 
Again, nice case work.

 

[crappyjones123]

The box from tom is finally in my possession as of 15 minutes ago. Holy mother of all things well packaged...Tom, I hope you don't take this the wrong way but you are insane brother man. i used to think I was a fairly cautious packer but you put me to shame and swept the floor with me. 

Still waiting on the parts from Mouser but put whatever I have so far together to see how it all fit and am quite pleased so far. 

I haven't had any financial dealings with Tom in the past but I can definitely see where he gets his good name from, and deservedly so. 

Hopefully the mouser stuff will arrive tomorrow otherwise I have to wait till Tuesday to stuff this puppy. Any tips before I do anything in terms of grounding or noise/hum reduction? 

 

[glenda]

Quote:

Great pics!
 
Someone has suggested grounding the heat sinks.  That should only take a few short leads - maybe even jumpers.  If you can get to it before I do, please let us know.

I have an spud amp that is similiar to this one.  It can be worthwhile to ground the heatsinks for the heaters,  they tend to pick up the EMI from the transformers ( I saw 60hz @ -90 reduced to -100db) and this was a separate chassis.  Another thing to try would be adding  decoupling capacitors right at each heater pin (~200pf). 
 
These are just suggestion,  the emi from the torroid is generally vertical,  so it sounds like when you put the lid on it gets bounced around and picked up but the OPT.  
 
A plastic lid would be something to look for,   even plexiglass top with the sides from the stock case may be worth trying.   It is worthwhile to get rid of audible hum with Grados,  that seemingly benign low level hum adds significantly to the IMD. It is even worthwhile to get rid of non-audible 60hz hum because of its influence on IMD.  Has anyone done RMAA with/without the top on ?