[DingoSmuggler]

Quote:

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.
 
 

To me your hum issue sounds somewhat worse than other peoples, perhaps a ground loop issue?
What's you're source, could its signal ground be connected to AC ground?  Can you try with a different source?
 
 
in other news...
...I'm still waiting for Auspost to send a kangaroo over from sydney to perth with a torpedo kit in its pouch.
If the kangaroo survives the long trip across the nullarbor, i might see my amp this afternoon at best, or maybe tomorrow if its an older kangaroo.
Lets just hope they haven't sent a wombat, or I'll be waiting a long while - damn equal opportunity laws.
 

 

[Gabe Logan]

The only hum i hear is during startup but after that it fades away and it is very quiet.

 

[tomb]

 
Quote:

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.
 
 

I would agree with the others that something else must be going on. It may be that set of tubes is bad. Have you tried a different set?  Also, this is pure conjecture, but after having built 3 of these so far, it seems that there is a bit of burn-in that goes on.  When I finished the production version in this thread, I was alarmed at the hum I first heard.  However, it's never been as bad since and subsided to the level of minor-nuisance that everyone seems to be confirming. I can't offer a technical explanation for it - maybe the transformers quieten down after a few hours.
 
If it doesn't improve appreciably, though, please post again. We may need to investigate other possibilities for you.
 
 
P.S. For the same reason the tubes pick up interference from the transformers, it also means they are pretty susceptible to adjacent power sources. If you have the Torpedo next to a CD player/receiver/PC/etc.where the item's transformer is located, it will definitely pick up the hum.
 

 

[crappyjones123]

The amp is located next to quite a bit of electronic equipment. I will try the amp in a quiter place when I get home today. Last nights tests were with an iPhone and iPad yielding identical hum levels. This morning I tried te amp without the top cover on and the noise was reduced a LOT. i can still hear it over the ac but it was a lot less than with the case on. I'll try grounding the heatsinks after a different set of tubes and a few different sources. 
 
A few observations on construction -
 
1. Place the warning regarding grounding the volume pot a little earlier for impatient twits like me. fat fingers and tight spaces don't like each other. 
 
2. It might be better to test how many spacers are needed for the standoffs prior to board population. As of right now the screw that is going in from the bottom of the case sticks out too much from the bottom as most of the spacer is taken by the pcb screw. 
 
None of the above are mission critical and require better planning on the builders part. Just my thoughts on the process.

 

[jdkJake]

Quote:

The amp is located next to quite a bit of electronic equipment. I will try the amp in a quiter place when I get home today. Last nights tests were with an iPhone and iPad yielding identical hum levels. This morning I tried te amp without the top cover on and the noise was reduced a LOT. i can still hear it over the ac but it was a lot less than with the case on. I'll try grounding the heatsinks after a different set of tubes and a few different sources. 
 

When you try your tests with the cover on and the HD650, please leave the volume level ALL the way down (full attenuation) and note the hum level with  BOTH positions of the front panel impedance switch.
 
I suggest you float the inputs (nothing connected) when you make your observations. That will eliminate the potential for any ground loops whatsoever.
 
Try the above in the quietest room available.
 
Thanks.
 

 

[crappyjones123]

650s plugged in. high impedance. no source. volume all the way down first. then volume all the way up. as quiet as i will have a listening environment. 
 
case on - hum as before. 
 
case off - very low hum but audible nonetheless even with the a/c unit going outside the door. but now i can hear white noise and little staticy sounds. probably the tubes. but it sounds like wood crackling. the staticy noise is not constant like the hum. comes and goes. 
 
hum gets more prominent, with and without the case when the volume is turned up. 
 
 
all the above conditions but this time a battery powered macbook air is used for a source. same observations as above. 
 
 
low impedance and same conditions as above
 
case off - no audible noise or hum with the volume pot turned all the way down. the hum is audible with the volume pot all the way up. 
 
case on - the hum returns with the case being held an inch above where it sits. stays at the same level regardless of the position of the volume knob. 
 
same set of tubes as last night. i figured i'd post this just in case someone can troubleshoot from the above clues. has anyone noticed improvement with high z phones after using the choke vs the resistor at R2?

 

[HiGHFLYiN9]

 
Quote:

You people and your fancy cases...
 

Haha, good to see you on here Nate! Yours is very pretty too, and unique!
 

 

[tomb]

Quote:

650s plugged in. high impedance. no source. volume all the way down first. then volume all the way up. as quiet as i will have a listening environment. 
 
case on - hum as before. 
 
case off - very low hum but audible nonetheless even with the a/c unit going outside the door. but now i can hear white noise and little staticy sounds. probably the tubes. but it sounds like wood crackling. the staticy noise is not constant like the hum. comes and goes. 
 
hum gets more prominent, with and without the case when the volume is turned up. 
 
 
all the above conditions but this time a battery powered macbook air is used for a source. same observations as above. 
 
 
low impedance and same conditions as above
 
case off - no audible noise or hum with the volume pot turned all the way down. the hum is audible with the volume pot all the way up. 
 
case on - the hum returns with the case being held an inch above where it sits. stays at the same level regardless of the position of the volume knob. 
 
same set of tubes as last night. i figured i'd post this just in case someone can troubleshoot from the above clues. has anyone noticed improvement with high z phones after using the choke vs the resistor at R2?

Your tubes are bad.  Contact me via e-mail or Beezar and I'll send you a replacement set.  The intermittent static/crackling is pretty much a confirmation.  Although, you should be able to confirm this yourself by swapping them out.
 
Actually, the hum should be even quieter with high z phones and yes, I do believe the choke makes it quieter - regardless of impedance.  If you read closely in this build thread or on the website, you'll see that I recommend the choke, period.
 
 

 

[jdkJake]

 
Quote:

650s plugged in. high impedance. no source. volume all the way down first. then volume all the way up. as quiet as i will have a listening environment. 
 
case on - hum as before. 
 
case off - very low hum but audible nonetheless even with the a/c unit going outside the door. but now i can hear white noise and little staticy sounds. probably the tubes. but it sounds like wood crackling. the staticy noise is not constant like the hum. comes and goes. 
 
hum gets more prominent, with and without the case when the volume is turned up. 
 
 
all the above conditions but this time a battery powered macbook air is used for a source. same observations as above. 
 
 
low impedance and same conditions as above
 
case off - no audible noise or hum with the volume pot turned all the way down. the hum is audible with the volume pot all the way up. 
 
case on - the hum returns with the case being held an inch above where it sits. stays at the same level regardless of the position of the volume knob. 
 
same set of tubes as last night. i figured i'd post this just in case someone can troubleshoot from the above clues. has anyone noticed improvement with high z phones after using the choke vs the resistor at R2?

Okay. You are getting different results from my unit. Something appears to be different.
 
When I use HD650's with no source and the case employed, the volume setting (attenuation setting) makes no difference in the quantity of the hum. The amp is dead quite, save for the hum, at any volume setting**. Only changing the impedance switch changes the relative volume of the hum, which, is louder on the high impedance setting with the HD650. Removing the case top makes it quieter and removing the bottom, quieter still. So far, this is the only headphone that has allowed me to hear the bottom of the case make a difference. Totally uncased, the amp is truly dead quiet regardless of headphone (at least of what I own), impedance setting or volume setting.
 
I think you have something else going on if you hear a hum with the unit uncased. Especially if it changes with the attenuator setting. Have you tried out a different set of tubes? Any pictures of the board to share?
 
BTW, I am using the choke. Have not tried a resistor at R2 yet.
 
**note, I did have one HIGHLY microphonic 6J6A, which, picked up just about anything that came near the tube. You could tap the table the amp was on and hear it. Tapping the tube directly (gently) was seriously loud. It was also 'staticy'. That went away with a different 6J6A tube.

 

[jdkJake]

On a different topic, I have been running 5964 tubes (Sylvania-labeled Gold Brand) the last couple of days. They are very nice and are a bit different in presentation from the Westinghouse-labeled 6J6A I had also been using. The Sylvania are quite a bit more extended and detailed on the high-end. Not necessarily thinner, but more high-end focused while retaining plenty of low-end presence and control.  The 6J6A seem a bit more, lacking for a better word, robust. As TomB has remarked previously, the 6J6 seem to be a bit more dynamic as well. Either one is a fine tube and it really comes down to personnel preference. 
 
I will say this much about the 5964 I am using, the first pair I put into the amp measure very close on the plate (122.7/121.3). Closest so far right out of the box. I will have to check/measure for how close they actually match in output, but, they seem quite close on subjective listening.
 
Good stuff.

 

[DingoSmuggler]

OK package arrived yesterday, and things got underway. Thanks to TomB for the great packaging. I'll be popping bubble wrap for weeks

 
Soldering to the vias connected to the ground plane on this thing was certainly interesting. That massive ground plane sucks heat away faster than you can say torpedo. Mincy lil' 25W irons need not apply.
One of those tube sockets gave me a hell of a time, but i managed to get it as straight as i possibly could, although its still a bit wonky. Also its pin 4 hole is half closed over, but i've tried plugging and unplugging tubes, and it seems to still work fine.
Got to buy some M3 fasteners today and I should be able to finish things off.
 

 

[crappyjones123]

I replaced the tubes today with ge 5844s and I can't hear any hum without the top cover and the impedance switch at low. At high I can hear it but it is low. Low enough to where I can kinda hear it throughout the range of the pot with no source. With an iPhone as source, it is there but I can't hear the hiss of the iPhone anymore. I'm guessing the hiss was from the old tubes not the source as I can't hear any static or pops that I heard with the dumont set. Also left the amp on today and will do so tonight so whatever needs to settle, does so. Sound with the 650s is tight and clean. No distortion with the volume pot at 12 o'clock (I can't go higher than that) without hurting myself. 
 
The top cover is being made prettier (I hope) so I will see how it behaves with the case on and the new tubes. Hopefully I will have time tomorrow to install the choke as well. 
 
I realize there is no subjective way to explain what I hear but the hum is certainly a lot less than what I had with the previous set of tubes (thanks for catching that Tom). 
 
For now it plays music Quite well. 

 

[tomb]

Quote:

OK package arrived yesterday, and things got underway. Thanks to TomB for the great packaging. I'll be popping bubble wrap for weeks

 
Soldering to the vias connected to the ground plane on this thing was certainly interesting. That massive ground plane sucks heat away faster than you can say torpedo. Mincy lil' 25W irons need not apply.
One of those tube sockets gave me a hell of a time, but i managed to get it as straight as i possibly could, although its still a bit wonky. Also its pin 4 hole is half closed over, but i've tried plugging and unplugging tubes, and it seems to still work fine.
Got to buy some M3 fasteners today and I should be able to finish things off.
 

I'm sorry about that tube socket.  The quality control is not so good sometimes.  They're wrapped in that wax paper stuff when I get them from China and I don't have time to check them all.  Every once in a great while, the ceramic gets molded badly and the tube pin holes get covered up, as you stated.  I would recommend the tip of a sharp knife such as an X-acto.  Ream the hole out by twirling the tip of the knife in the hole.  You have to be careful, though, if it's bad enough you could crack the entire top half of the socket.  If it's unsuitable, let me know and I'll send you another.
 
 

 

[tomb]

Quote:

I replaced the tubes today with ge 5844s and I can't hear any hum without the top cover and the impedance switch at low. At high I can hear it but it is low. Low enough to where I can kinda hear it throughout the range of the pot with no source. With an iPhone as source, it is there but I can't hear the hiss of the iPhone anymore. I'm guessing the hiss was from the old tubes not the source as I can't hear any static or pops that I heard with the dumont set. Also left the amp on today and will do so tonight so whatever needs to settle, does so. Sound with the 650s is tight and clean. No distortion with the volume pot at 12 o'clock (I can't go higher than that) without hurting myself. 
 
The top cover is being made prettier (I hope) so I will see how it behaves with the case on and the new tubes. Hopefully I will have time tomorrow to install the choke as well. 
 
I realize there is no subjective way to explain what I hear but the hum is certainly a lot less than what I had with the previous set of tubes (thanks for catching that Tom). 
 
For now it plays music Quite well. 

I'm glad it's better.  As I said, the static and pops were definitive that it was the tubes.  There's no way you should be hearing that on the Torpedo.
 
I got your address and I'll have another pair shipped out to you on Friday. 

 
 

 

[crappyjones123]

Mom just walked in the door. Saw the topless torpedo and asked what it was. Naturally, I asked her to sit in my chair and gave her my headphones. 
 
"Oh wow! This sounds nicer than my headphones [iBuds]. How much did it cost?" 
 
$XXX.XX
 
"WHAT??? DO YOU KNOW HOW MANY HEADPHONES I COULD BUY FOR THAT MUCH MONEY???" 
 
Good thing she doesn't know how much the jh16s cost