[Gabe Logan]

Placed my order so hopefully i am one of the lucky few. Been looking forward to this amp build for quite some time but bad news is i misplaced my soldering station and can't seem to find it.
 
 

 

[DingoSmuggler]

OK, order placed.
 
I just decided to get a pair of each tube available at beezar. A bit of rolling cant go astray.

This should be a nice new years project.

 

[tomb]

Quote:

great news, I'll be placing an order this week for sure. Just need to be deciding what tubes i wish to get with it.
 
In general does this amp's sound vary a lot with the different tube options you've tried? (not referring to the mysterious noise issue)

I think it's subtle, instead of wide variances.  The best I recall when I was rolling a lot was that the 6J6 seems to have the best impact, but the 5964 may be smoother with better highs.  The 5844 sounds different than either of the other two and seemed to have an exagerated mid-range.
 
To be honest, though, I'm hoping you guys can give us a better idea of the differences and what you like.  Those are just the three types that I carry, though.  When you enter 6J6 into TDSL, you get this:
1216, 5844, 5964, 6030, 6045, 6099, 6101, 6535, 6927, 6CC31, 6J6A, 6MNN3*, CK6101, CV5046, CV8160, CV8231, ECC91, M8081, T2M05
Some of those can't be found, I think, but it still leaves a heckuva lot to pick from.

 

 
 

 

[DingoSmuggler]

When I've had a look around for torpedo tubes 

, there did seem to be some different ones here and there, but very few sources offering matched tubes. But I won't really get overly fussed about looking at what's around till I've had a play with the 3 beezar options.

 

[dsavitsk]

There is a little bit of history about this tube at http://www.r-type.org/exhib/aaa0399.htm

 

[tomb]

Quote:

There is a little bit of history about this tube at http://www.r-type.org/exhib/aaa0399.htm

Very cool!
 
 

 

[tomb]

I've posted the BOM separately right now until I get the website built.  As usual, I have it available in three formats - just in case:
TorpedoBOM.htm
TorpedoBOM.pdf
TorpedoBOM.xlsx
 
Dsvatisk wanted me to list cap dimensions, but for the time being, let's just say if you want to substitute - be certain that the substitute cap does not exceed the dimensions of the caps listed on the BOM (can be looked up on Mouser/DigiKey).  A tad overy 48mm is the height limit in the case from the top of the PCB.  Of course, just about anything will fit in C11 and C12 - the numerous alternates listed in the BOM will all fit, with the Clarity Caps probably the largest.  If in doubt, you can ask me to measure it until I get drawings/dimensions posted.

 

 

[digger945]

Transistors Q1, Q2, Q3, Q4 .... 2N5087 ... qty should read 4. 

 

[tomb]

Quote:

Transistors Q1, Q2, Q3, Q4 .... 2N5087 ... qty should read 4. 

True, but it was supposed to be a little pack (all 4) that I would sell from Beezar at 50 cents.  Unfortunately, I slipped up and didn't include that in the original listing (now changed).  I changed the description in the BOM to "matched pack of 4", but it will be a little bit tonight before I get the change uploaded because of below -
 
Dsavitsk tells me the 1N4007 might be too noisy.  So, I'm changing it back to the 1N5062, but they aren't available at DigiKey.  I'm waiting on him to tell me which one is best out of what they have.  When he does, I'll upload the BOM with the changes.  Sorry about that.

 

 

[tomb]

OK - the BOM has been updated and uploaded.
 
Changes:

1. HV rectifier back to 1N5062.  The DigiKey option is the best they have available, but we still recommend the 1N5062 (Mouser).  I will start carrying them as a selection at Beezar.
2. The comment on LED's was trimmed back.  (I didn't keep up with the design changes.)  What's important is to keep the LED RED and at a forward voltage of about 1.8V.
3. The small signal transistors (TO-92, 2N5087's - 4 needed) were edited in description to include "pack of 4" and a footnote added stating the HFE matching is not really critical, but Beezar supplies them this way, anyway (link also added).

 

[jdkJake]

TomB,
 
The link for J1 needs to be fixed in the BOM. It is currently pointing to  a Wima Capacitor. 

 

[jdkJake]

TomB,
 
Another BOM question. R4 and R5 are spec'ed at 68R, 1/2 watt. The link goes to a 1/4 watt part. Acceptable? 
 
Or go with something like: 71-RL20S-G-68?

 

[tomb]

Quote:

TomB,
 
Another BOM question. R4 and R5 are spec'ed at 68R, 1/2 watt. The link goes to a 1/4 watt part. Acceptable? 
 
Or go with something like: 71-RL20S-G-68?

Thanks for that catch on the Neutrik headphone jack.  Corrections have been made and all BOM formats have been re-uploaded.
 
As for R4 and R5, that's the old V-D military spec vs. commercial rating difference.  Those are RN60 resistors, which in everybody's book are 1/2W.  However, the RN60 is a military spec designation, so the wattage listed is de-rated by half.
 
 

 

[dsavitsk]

The 68R resistors set the CCS current.* Each should carry about 16mA and drop slightly over a volt. That means that they dissipate ~0.017W. 1/4W parts are fine so long as they are OK at high voltage and fit the board.

*The transistor's Vbe is ~0.7V. The biasing LED drops ~1.8V. The resistor will drop enough volts to make up the difference between these -- so, (1.8 - 0.7) = 1.1V, and by V=IR, 1.1 = I*68 or 1.1/68 = I = ~16mA. We really don't recommend pushing the current much higher than this, though a little lower is OK, and a little experimenting is also OK. For 18mA, you would use 62R resistors, and for 13mA you would use 85R. Anything in there is OK, but we felt that 16mA was a bit of a sweet spot.

 

[n_maher]

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