Torpedo III Build Thread

[dsavitsk]

Plastic is good. I think you'll be surprised at how good the box caps are. But if you aren't, the best option is likely a small (0.1u?) bypass across the top of the box cap. Otherwise, you might look for 4.7u/300V caps that will fit and use 8 of them.

 

[FallenAngel]

Plastic is good. I think you'll be surprised at how good the box caps are. But if you aren't, the best option is likely a small (0.1u?) bypass across the top of the box cap. Otherwise, you might look for 4.7u/300V caps that will fit and use 8 of them.

 
I'm already heartbroken because those were about $160 CAD
I'll see if I can return them, hopefully.
 
I looked around and the Obbligato were some of the smaller caps I found.
 
I'll keep looking.

 

[HiGHFLYiN9]

Doh! 

 ...guess you could use two of em

 

[FallenAngel]

  Doh! 

 ...guess you could use two of em

 
https://media.giphy.com/media/pRElAzlflnRYI/giphy.gif

 

[tomb]

Plastic is good. I think you'll be surprised at how good the box caps are. But if you aren't, the best option is likely a small (0.1u?) bypass across the top of the box cap. Otherwise, you might look for 4.7u/300V caps that will fit and use 8 of them.

 
Nice CAD work, Doug!  (Even though FA is sorely disappointed.)  I was on my smart phone all day, so all I could do was look at the drawings and estimate.

 

[tomb]

 

  Doh! 

 ...guess you could use two of em

 
https://media.giphy.com/media/pRElAzlflnRYI/giphy.gif

 
You probably don't want to hear this suggestion, but you could cut out a rectangle in the top of the case.  fierce_freak did that a couple of pages back.  He was concerned about heat, but it might take a very little rectangle to give two center caps more headroom, allowing all of them to squeeze together more closely side-to-side.
 
This is also drastic, but you might be able to cut two slots in the PCB to allow two of the caps to "sink" lower into the case.

 

[tomb]

Nope - won't work by slotting the PCB.  There's not enough room under the PCB.  The CAD file says the rectangle in the top of the case would have to be 0.9 inches wide per cap, or 2.09 inches all the way across, give or take a few fractions of an inch:
 

 

[FallenAngel]

   
You probably don't want to hear this suggestion, but you could cut out a rectangle in the top of the case.  fierce_freak did that a couple of pages back.  He was concerned about heat, but it might take a very little rectangle to give two center caps more headroom, allowing all of them to squeeze together more closely side-to-side.
 
This is also drastic, but you might be able to cut two slots in the PCB to allow two of the caps to "sink" lower into the case.

 
I love the idea, but the board has a signal from R10/R12 moving forward through the middle as well as some signals along the side. I might really have to suck it up, lose some money and return the caps. I'll mess with it and see where it goes but I don't know how well it would go.

 

[JamieMcC]

Can I ask  if there are any measurements for the actual voltages that C7 and C10 see and what potential consequences would be if one failed would it be terminal for the amp or just a case of replacing the failed capacitor?

 

[dsavitsk]

If the amp is running as expected, they have around 150V across them. At startup, or if the tube is not conducting for some reason, they'll have 225V. And if the regulator fails, they could see close to 300V or so.

If one fails, you still have the transformer between you and the high voltage. The transformer is not rated for high voltage, so it is not to be counted on for any protection. And it could be damaged.

If a cap failed shorted, you could probably expect some transistors to overheat and be damaged. A short to ground should blow the fuse before the power transformer is damaged.

Do not use under specified caps just to get them to fit. The difference in sound is almost insignificant, and if you think it makes a huge difference, build or buy a different amp.

 

[JamieMcC]

If the amp is running as expected, they have around 150V across them. At startup, or if the tube is not conducting for some reason, they'll have 225V. And if the regulator fails, they could see close to 300V or so.

If one fails, you still have the transformer between you and the high voltage. The transformer is not rated for high voltage, so it is not to be counted on for any protection. And it could be damaged.

If a cap failed shorted, you could probably expect some transistors to overheat and be damaged. A short to ground should blow the fuse before the power transformer is damaged.

Do not use under specified caps just to get them to fit. The difference in sound is almost insignificant, and if you think it makes a huge difference, build or buy a different amp.

Understood and thank you.

 

[drfindley]

I put in the new PT and it's now whisper quiet. So much better! The stock tubes still aren't my favorite. A little too shouty in the upper-mid-range. Right around the snare drum level. Playing "Steady as She Goes" by the Raconteurs hits it hard on the first note.
 
So I did some tube rolling and my favorites are some Amperex E180CC/7062 from a McIntosh solves the problem and sound quite lovely. 

 

[FallenAngel]

Finished my build with upgraded transformers and it does sound quite wonderful.
 
Just one thing - at about 50% volume through UE700 IEMs (very efficient, fairly low impedance - http://www.innerfidelity.com/images/UltimateEarUE700.pdf ), there starts to be a slight hum/buzz in the background. At this level, it's already pretty damn loud when music is playing, and it increases as the volume goes up.
While music plays, it's obviously not noticeable, but with nothing there at ear-splitting levels, you can certainly hear it.
 
Is this expected at all, or am I unlucky with my build?
 
I'm seriously not expecting to use this amp for IEMs, that would be overkill, I'm curious how it'll handle the Grados I'm getting soon.

 

[tomb]

  Finished my build with upgraded transformers and it does sound quite wonderful.
 
Just one thing - at about 50% volume through UE700 IEMs (very efficient, fairly low impedance - http://www.innerfidelity.com/images/UltimateEarUE700.pdf ), there starts to be a slight hum/buzz in the background. At this level, it's already pretty damn loud when music is playing, and it increases as the volume goes up.
While music plays, it's obviously not noticeable, but with nothing there at ear-splitting levels, you can certainly hear it.
 
Is this expected at all, or am I unlucky with my build?
 
I'm seriously not expecting to use this amp for IEMs, that would be overkill, I'm curious how it'll handle the Grados I'm getting soon.

NO, it is not expected at all.  I've built quite a few of them already and my Ety's are wonderful through the T3.  Needless to say, my Grado HF-2's have been my go-to cans for years.  Everything Doug designs sounds great with Grados.
 
I suspect you have a bad tube(s).  Is it in both channels?  If you swap the tubes, does anything change?  They may just need a re-seating, too.

 

[FallenAngel]

 
NO, it is not expected at all.  I've built quite a few of them already and my Ety's are wonderful through the T3.  Needless to say, my Grado HF-2's have been my go-to cans for years.  Everything Doug designs sounds great with Grados.
 
I suspect you have a bad tube(s).  Is it in both channels?  If you swap the tubes, does anything change?  They may just need a re-seating, too.

 
Thanks Tom.
 
I'll do a little debugging and see how things go.
 
As you may know, I'm hosting a meet in less than 2 weeks so I'm incredibly busy getting things prepared for it. This was my first listen with the IEMs and I have no idea of details. For all I know, it might be my source because I get intermittent noise anyway. I'll make sure to try it with my "reference testing system" that's darker than black with custom PSUs. It's a little one-box build I made with a DAC, Pre-Amp, Headphone Amp and disconnected POT to make sure nothing enters the signal. I only use it for testing as it's overall a half-decent system I don't want to showcase.
 
I'll update in a few days when I have a chance to debug.
 
Thanks again.