[dsavitsk]

Quote:

  The Torpedo looked like it would be a excellent match for the Denon's also but still seems to be in some sort of late prototype stage for some reason.
 

It's actually in a waiting for parts that have been delayed due to the earthquake in Japan stage.  Shouldn't be too long, though.

 

[dsavitsk]

Quote:

Does the final design accommodate a flexible B+/bias scheme to accommodate such a wide variety or are they really that close in construction/performance?

They are all pretty much similar enough to be considered the same tube, but there are definitely manufacturing differences between them. TomB has found that different tubes sound (and measure) a bit differently.
 
You can change CCS current and bias within certain limits, and the instructions will explain how to do that.  The default build will be set where we feel the amp performs best, but it is certainly something that can be experimented with.
 
Here's a basic schematic for anyone interested: http://www.ecpaudio.com/images/torpedo_schematic.png

 

[jdkJake]

Here's a basic schematic for anyone interested: http://www.ecpaudio.com/images/torpedo_schematic.png

Thanks much for posting the schematic.

So, the LED used to bias the cathode must be bypassed just like if it was a simple resistor to prevent negative feedback (at least as I understand it). What I do not under stand is what the transistor on the cathode brings to the equation. What does this do that a simple resistor (or LED in this case) does not do?

 

[dsavitsk]

The transistor is a shunt regulator that biases the tube. The LED biases the shunt.  The bypass cap is probably unnecessary, but is left in for experimentation.

 

[Rescue Toaster]

dsavitsk,
DC heaters? I see what looks like a second bridge rectifier in there. And is there a reason you return the opt to ground instead of the cathode?
 
Those custom opt's from edcor look just great.
 
 
 
Oh and offtopic, on your site, the HPDAC6 page is missing.

 

[Beefy]

Quote:

dsavitsk,
DC heaters? I see what looks like a second bridge rectifier in there. And is there a reason you return the opt to ground instead of the cathode?
 
 

Without wanting to speak for the designer......
 
Yes, I'm pretty sure it had DC heaters. On early prototypes, you could choose where to connect the OPT - either ground or cathode - with a jumper.
 
 

 

[Rescue Toaster]

Also interesting, these are dual triode tubes. Are the sections being paralleled or does it just use half the tube? If so, is there any way to switch which section is used?

 

[dsavitsk]

Yes, DC heaters.
 
The triode sections are in parallel which reduces the tube's rp by 1/2.  We looked high and low for an inexpensive and common triode with sufficient gain and sufficiently low rp to work in the design. This was about the only one.
 
We did try connecting the OPT to the cathode rather than ground, and whatever the theory says should work, it just didn't sound as good. The shunt gives the lowest Z and the fastest recovery, and to everyone who tried it it measured and sounded better than any other option.
 
No idea what happened to the HPDAC6 page.  Here's a picture, though: http://www.ecp.cc/images/HPDAC6.jpg

 

[Rescue Toaster]

Interesting.
 
Actually my favorite part of the whole thing might be the form factor. Most true tube amps are large, wide and boxy shaped. Doesn't sit well on a desktop next to a computer. My next amp I've been trying to make into a more long and skinny shape, though probably a good deal taller than the torpedo.

 

[DingoSmuggler]

This project looks very interesting. Built a whole bunch of SS things but still yet to venture into the world of tubes.
I'll definitely keep an eye on this one.

 

[dsavitsk]

 
Quote:

It's actually in a waiting for parts that have been delayed due to the earthquake in Japan stage.  Shouldn't be too long, though.

We got the parts! A bit unexpectedly, actually which caught us off guard as we thought they were coming in in September.  So, a few more things to do, a website to put together, and we are about there.  We do appreciate everyone's patience.

 

[Riverback]

Great news! Is there an ETA on the first production run?

 

[DingoSmuggler]

Sweet!!!
 

 

[Beefy]

Good news. I'd love to just see a BOM at this stage, and intended kit contents. PCX has a 20% off sale ending soon, and it would be great see if it is worthwhile picking up parafeed caps, sockets, etc.

 

[tomb]

At a minimum, we were talking about a "Short Kit" that would include xfmrs, PCB, case, pot, and probably sockets.  It will include the voltage regulator now, too, of course.  I'll have a selection of tubes, too, but those could be separate as well, allowing people to choose and buy what they want (or get them elsewhere).  Dsavitsk and I were debating about whether I should offer a complete kit, perhaps just offering the Short Kit for the first 30 or so.    Any opinions on which direction the kits should go from you guys?