[jdkJake]

Thanks TomB, thanks dsavitsk.
 
Mouser order is on the way. I picked up the choke as well as the resistors for R2, so, I might experiment a bit. I am in the middle of another big project right now, but, I am making time for this one. I am really curious to hear a true, transformer-coupled build.
 
I am also set on tubes. John Kendall was selling two-for-one 6J6A (still is), which, at a cost of a buck a piece (recently bumped to $1.25 a piece), makes voicing this amp a solid bargain. I now have a lifetime supply. 

 
I have three 6J6A "orphans", so, if anyone needs to match a construction, let me know. I also  splurged a bit and bought some de-luxe 5964's as well (just under $5 a piece). I seem to be particularly partial to Sylvania tubes and could not resist. In any case, I am set.
 
Looking forward to the build!
 
 

 

[tomb]

Quote:

Great work as usual guys.  I still enjoy the heck out of my prototype.

We must be doing good to deserve your attention over here these days.

  Seriously, thanks for the good words.
 
 

 

[tomb]

Running a little behind as usual.  My daughter's hot water heater went out this weekend.  I was only able to get the plumbers into her house today.
 
I hope to get some of the short kits shipped tomorrow.  Thanks for your patience.

 

[n_maher]

Quote:

We must be doing good to deserve your attention over here these days.

  Seriously, thanks for the good words.
 
 

What, a Mod can't lurk?
 
And yes, you're doing great work. 

 

[tomb]

Well, as usual - I was behind in getting these kits out.  However as of today, every order has been shipped.

 
EDIT: Now, back to work on the website.

 

[Gabe Logan]

Good news!. Excited to hear how it sounds and even bought a new solder station to replace the one that magically disappeared on me.

 

[tomb]

Just a note about the LED's used to set bias and current - I noticed that one of you bought several LED's from me on one order. Not trying to single anyone out and they will remain namelesss, but ... this is just to be certain that purchase wasn't for the Torpedo.  You need to stick with the RED LED's that are recommended on the BOM.  To explain, I don't think Dsavitsk would mind my quoting a section out of one our e-mails:
 
Quote:

... [size=11pt]the plate current is set by ((Vf - Vbe) / R4) With a red LED, you get (1.8 - 0.7) / 68 = 16mA. If this were a blue LED with a 3.3V drop, it would be 38mA which would a) not work and b) likely cause the power transformer to burn up[/size].

So in the Torpedo, the voltage drop of the LED is all important and is usually dictated by the color of the LED.  I assumed that the particular customer was purchasing them for something else, but as I said, just in case ...
 
There's more background, but I'll let Dsavitsk elaborate if he wishes.

 

[DingoSmuggler]

I bought some white LEDs with my torpedo kit, but they weren't for torpedo usage

 

[tomb]

Quote:

I bought some white LEDs with my torpedo kit, but they weren't for torpedo usage

Oops - I wasn't trying to identify who you actually were!  I just wanted to make certain for everyone, since as Dsavitsk said, different LEDs could be potentially damaging to the amp. That's not to say other LEDs can't be used, but we should get a check and approval on them before substituting them.

 

[DingoSmuggler]

Oops - I wasn't trying to identify who you actually were!  I just wanted to make certain for everyone, since as Dsavitsk said, different LEDs could be potentially damaging to the amp. That's not to say other LEDs can't be used, but we should get a check and approval on them before substituting them.

yep, I realise that. I was just easing your concerns by assuring you that I was using the correct LEDs

 

[dsavitsk]

As I said to Tom, we designed this around red LEDs with a 1.8V forward voltage drop. On the CCS, and I hesitate to say this, you could potentially use different colors but you will have to adjust the current setting resistors. For instance, if you used an led with a 3.3V drop, then for a 16mA CCS you would need (3.3 - 0.7) / 0.016 ~ 162R resistor. However, red led's, in general, have a much lower impedance than blue or white which makes them a better choice for CCS performance, and you can't see these parts anyway, so there is no advantage to fancy colors.

Similarly, for biasing the tubes, red led's set the bias at (1.8V + 0.7V) = 2.5V, which seems to be a good operating point. Much lower than that, such as with an IR led, and the tube is more likely to draw grid current leading to higher distortion. Higher and it will push the plate voltage too high which may lead to clipping. Plus, the AC performance of red led's is, as above, advantageous on this position.

This is a DIY circuit, and we encourage experimentation. But, please be sure that you know what you are doing, understand the risks (to yourself and the hardware) and make smart choices. Other led's are not, in our judgment, going to improve performance.

 

[jdkJake]

Unexplained ordinance arrived today. That was an interesting conversation.
 
"Hon, a package came for you today. Did you really order a torpedo?!?"
"Um, perhaps I should explain, it's not what you think...."
 
Anyway, the short kit arrived today expertly and thoughtfully packaged. TomB and Beezar continue to have the best shipping and handling bar none.
 
TomB/dsavitsk, any chance of getting the schematic posted or PM'ed? The build is much more enjoyable when I can follow along from the hymnal.
 
 

 

[tomb]

Quote:

Unexplained ordinance arrived today. That was an interesting conversation.
 
"Hon, a package came for you today. Did you really order a torpedo?!?"
"Um, perhaps I should explain, it's not what you think...."
 
Anyway, the short kit arrived today expertly and thoughtfully packaged. TomB and Beezar continue to have the best shipping and handling bar none.
 
TomB/dsavitsk, any chance of getting the schematic posted or PM'ed? The build is much more enjoyable when I can follow along from the hymnal.
 
 

Thanks for the kind commenst.  As for the schematic, I am working on the web site during every spare moment.
 
A question, though, how the heck did you get a Guvment Employee Postal Worker to deliver a package to you today?

 
 

 

[dsavitsk]

There is an "unofficial" schematic at http://www.ecpaudio.com/Torpedo.shtml with parts labeled. I'll get a power supply up later, and Tom should have the website up soon.

-d

 

[dsavitsk]

A question, though, how the heck did you get a Guvment Employee Postal Worker to deliver a package to you today?:blink:

I had a USPS package delivered on Christmas morning last year. I tried to invite the deliverer in for some breakfast, but she had other packages.