[liamstrain]

 
 
Quote:

Tomb:
As for the ground loop question - it's a good thought (not a silly question!), but we have tested the amp with the PCB completely isolated from the case and with no source connected.  It made no difference.

 
In this case, the poster indicated that the hum ONLY appears when the case lid is on, when the PCB is isolated, there is no hum. So that's why I wondered if a drain from the case would correct it. 
 
Sorry for posting about it in the other thread.

 

[tomb]

Quote:

 
 
 
In this case, the poster indicated that the hum ONLY appears when the case lid is on, when the PCB is isolated, there is no hum. So that's why I wondered if a drain from the case would correct it. 
 
Sorry for posting about it in the other thread.

No problem!  I just wanted to be sure that we all had the benefit of the discussions concerning the Torpedo.  Thank you for re-posting your comment.

 
About your comment though, maybe I'm not reading it correctly - or it could be semantics.  However, I think jdkjake was stating that there is no hum when it is uncased - iow, bare PCB sittting on a table.  That's slightly different than isolated.  What I stated in the Pics of Your Builds thread is that we (Dsavitsk) have definitely tested it isolated - in the case, buttoned up - but with no ground point on the PCB touching the case.  That made no difference.  As in, the hum was still detectable.  We've also found that the hum is still there - just not as detectable - when the lid is off, but when the PCB is sitting in the bottom half of the case.  So IOW, the case bottom contributes to the issue as well - just not as much.
 
Admittedly, this is my own perspective from jdkjake and Dsavitsk (except for noting the hum with just the case bottom - that was me).  So, maybe they can confirm whether I've portrayed the scenarios correctly.
 
 

 

[jdkJake]

Quote:

About your comment though, maybe I'm not reading it correctly - or it could be semantics.  However, I think jdkjake was stating that there is no hum when it is uncased - iow, bare PCB sittting on a table.  That's slightly different than isolated.  What I stated in the Pics of Your Builds thread is that we (Dsavitsk) have definitely tested it isolated - in the case, buttoned up - but with no ground point on the PCB touching the case.  That made no difference.  As in, the hum was still detectable.  We've also found that the hum is still there - just not as detectable - when the lid is off, but when the PCB is sitting in the bottom half of the case.  So IOW, the case bottom contributes to the issue as well - just not as much.
 
Admittedly, this is my own perspective from jdkjake and Dsavitsk (except for noting the hum with just the case bottom - that was me).  So, maybe they can confirm whether I've portrayed the scenarios correctly.
 
 

Yes, I am stating that in my situation, there is no hum when uncased - low, bare PCB sitting on the table. I have run it with just an iPod as an input to take out any other potential grounding and/or ground loop issues. 
 
I had not noticed a hum with just the case bottom, but then again, the hum even with the top case on is extremely low. Certainly not a show stopper, but, rather something that would be nice to isolate and resolve to make the amp that much better.
 
I have a set of 5964's to try out as well. Just kind of overloaded this weekend. Today is our annual "Pork Extravaganza" New Years feast, so, do not expect much from me today beyond a smile and a full belly.  

 

 

[vvs_75]

 
[size=medium]I’ve been enjoying my Torpedo for two days, the more I listen to it the more I like it!

[/size]
[size=medium]I wanted it for my work rig, so it fits the purpose very well.[/size]
 
[size=medium]In my case I would not call the hum as an “audible” hum at all. My ipod hiss is louder then the hum. It’s very low and I only can hear that its there when I move the top cover On and OFF while the amp is on (no music playing in complete silent room). [/size]
 
 

 
[size=medium]I grounded the heat sinks during the build, so I can't  comment how much it does contribute or help with the hum. Also I am using a choke instead of R2 and vintage NOS ECC91 Mullard tubes.  My plates are very stable at 129/130 VDC.[/size]
 
[size=medium]Thanks everybody who contributed to this project and happy building!

[/size]
 
 

 

[tomb]

Quote:

 
[size=medium]I’ve been enjoying my Torpedo for two days, the more I listen to it the more I like it!

[/size]
[size=medium]I wanted it for my work rig, so it fits the purpose very well.[/size]
 
[size=medium]In my case I would not call the hum as an “audible” hum at all. My ipod hiss is louder then the hum. It’s very low and I only can hear that its there when I move the top lead On and OFF while the amp is on (no music playing in complete silent room). [/size]
 
 

 
[size=medium]I grounded the heat sinks during the build, so I can comment how much it does contribute or help with the hum. Also I am using a choke instead of R2 and vintage NOS ECC91 Mullard tubes.  My plates are very stable at 129/130 VDC.[/size]
 
[size=medium]Thanks everybody who contributed to this project and happy building!

[/size]
 
 

Nice pics and glad you're enjoying it!  Maybe it really is focused primarily on that case lid (I assume that's what you meant when you typed "lead"), but I could swear I still heard it - not as much, though - with just the bottom.  Your feedback is much appreciated and thanks for trying the heat sink grounding.
 

 

[vvs_75]

 
Quote:

Nice pics and glad you're enjoying it!  Maybe it really is focused primarily on that case lid (I assume that's what you meant when you typed "lead"), but I could swear I still heard it - not as much, though - with just the bottom.  Your feedback is much appreciated and thanks for trying the heat sink grounding.
 

I meant "lid, cover" not "lead"

.
 
 

 

[n_maher]

You people and your fancy cases...
 

 

[funch]

OK, I'll bite. Where did that Hammond come from?

 

[tomb]

Quote:

OK, I'll bite. Where did that Hammond come from?

The Hammond was the case used for the early prototypes - about 7 of them.  They were "special" order, too - with an extrusion length of 13 inches.  Of course, none of them were custom machined.  What you see in the pic above was all Nate's own mill work.  Some of this is detailed in the Torpedo History on the Torpedo website.
 
I still have several of the cases, but design changes after those first prototypes lengthened the PCB to 14 inches and it got wider, too.  That's one of the reasons we went to Context. 
 
 

 

[jdkJake]

Not been a good week for me.
 
Until the replacement arrives, I "fixed" my fuse drawer, reassembled everything and immediately blew a fuse. Measured less than 2ohm between B+ and ground.
 
Luckily this design is so clean and straightforward. I lifted R5 and R4 to isolate the high voltage supply and still had the short. Not much was visible, everything looked to measure okay. I even lifted/removed a few other components to be sure that no solder/metal chip had worked it's way into anything.
 
Turns out I was heavy handed once again. The center lug used for one of the bottom standoffs is right next to the main high voltage supply line to the amp portion of the board. I was using a stainless #4 flat washer at that location to bring the standoff to the correct height. Seems I torqued the screws a bit too tight and the washer pierced the solder mask. For that location, you might want to consider a nylon washer (which I have switched to using) or be careful not to over tighten.
 

 
Anyway, back in business.  

 

[jdkJake]

Probably wondering what the purple wires are in the picture above.
 
I also went ahead and grounded all the heat sinks. I returned them back to the transformer ground pin (pin #6).
 

 
Subjectively, it might have helped a little bit. Hard to say. I need to get some better test gear to help with measuring progress. I will work on that soonest.

 

[jdkJake]

Oh, and I also went ahead and decoupled the heaters.
 
The only caps I had in the parts bin around 200pf were some wima 220pf film caps. So, in they went.
 

 
No real change. BTW, note the nice use of nylon flat washers on the standoffs.  

 

[jdkJake]

Oh, and one more thing.
 
I decided to up the ante on the shield a bit. Never know what you have in the garage until you really start looking.
 

 
That is steel. 3/16 flat steel 

. Wrapped in electrical tape.
 

 
It was a b---- to cut clean. The Dremel with a cutting wheel did most of the work after my arm almost fell off trying to use a hack saw. Gotta love power tools. Still was too tall for the case to close correctly.
 
In any case, it was mostly a cool experiment. Did not change anything, but, I want to try it further down a bit, closer to the output transformers. I'll let you know.
 

 

[crappyjones123]

Finished the build today. Powered on with no issues. Playing some tunes right now but I have a bad case of the hum with hd650s . Persists with ibuds as well. Just a constant volume hum that stays even with music playing. I have the a/c unit just on the other side of the door so it's not completely quiet of an environment and it is still quite bothersome. With music without quieter passages it's easier to forget about it but with a lot of my music where there are pauses it is quite noticeable. 
 
Going to sleep now. Will try it tomorrow with the lid to see if it is indeed less that way. Will also try the choke instead of the resistor tomorrow. Just wanted to try to get a working project tonight. 
 
Sq wise so far, it is extremely clean with dumont 5964 tubes. Oddly enough it sounds non tubey to me. Might be the tubes but coming from a warm lush amp it's a change of pace. Very very clean vocals. Barring the hum issue it is a pretty nice amp. Hopefully that issue gets sorted out soon. Excellent amp Doug. Thanks to Tom for the excellent kit.
 
 

 

[dsavitsk]

That sounds like a lot more hum than expected. With the lid off, it should be basically inaudible. Putting the lid on increases it some, but if it is to the level of quite bothersome, then something else is likely going on.