[smeggy]

Oooh, good news indeed!

It'll be nice having a real board

 

[zkool448]

Quote:

Originally Posted by luiztfc /img/forum/go_quote.gif Guys, I'm trying to build the Starving, but I'm having a hard time to finding these 19J6 tubes. Are missing?

Hang in there, luiztfc. It looks like it won't be very long before beezar.com will officially start selling the kits

 

[n_maher]

Quote:

Originally Posted by -=Germania=- /img/forum/go_quote.gif Here are some readings I just took using my auzen soundcard on my computer. Not the best, but the readings seem pretty darn good.

Loaded, unloaded, output level? Those pictures are pretty worthless without more information.

Quote:

No fancy cables, just good ole' Beldens for the readings.

Let me know when you start to be able to measure the difference cables make. If anything other than shielded vs. unshielded shows up you've got big problems.

 

[-=Germania=-]

Unloaded, didn't have any 32 ohm resistors to represent the headphones that I own and actually listen to.
Stock opamps.
Output level was set for front speakers at 100% as was the line-in used for input.
Amp was right at the very middle of the potentiometer, using the lower gain, as this is my normal gain used, though usually I sit at 11 o'clock because I don't listen very loudly for the sake of keeping my hearing.

Yeah I know that this isn't a fair indication without putting on an appropriate load, just didn't have 32ohm resistors on hand. Will pick some up for testing purposes. The belden cable combined with connectors on the amp had a bit more than 1.2ohms per channel on the signal line, but I really don't think that would have affected much. Just using beldens because they are what I have left over as spares and it is a standard. Besides, me doing anything about cables would go against MOT, sorry!

This is connecting to the back of my computer which is a pretty electrically and mechanically noisy place despite using a thick steel/aluminum case, additional damping foam and dynamat, and large fans running at low RPM's. Still has a low level of audible noise that is impossible to be rid of in a tower.

Even with a 32 ohm load, I doubt that the overall freq response graph would change drastically in terms of shape. The distortion will likely change a bit, again, I doubt that it would be all that huge. I think the point right now is more along the lines of it not being distorted and the response being pretty even. Again, I will take readings with all of the proper settings and loads, but this was something done spur of the moment.

Cheers!

 

[rds]

Quote:

Originally Posted by n_maher /img/forum/go_quote.gif Let me know when you start to be able to measure the difference cables make. If anything other than shielded vs. unshielded shows up you've got big problems.

First you have to upgrade the wires in your scope

 

[holland]

Quote:

Originally Posted by -=Germania=- /img/forum/go_quote.gif Unloaded, didn't have any 32 ohm resistors to represent the headphones that I own and actually listen to.

Personally, I think a 10K to 20K cathode resistor is too much. What you should measure is the voltage on the plate of the triode and the cathode, that is pin 1 and 2, and pin 7. I would bet you're all out of whack, operating in a not so good part of the tube.

Another personal IMHO. What I did was remove the plate resistor (33K stock) and put a CRD there. I just used what I had, but I think (it's been a while and can't remember what I figured the operating point to be) 0.25mA per triode is the stock configuration. I used a 0.56mA CRD, as that's what I had on hand. Use the stock 2K cathode resistor. If you bypass, I would just use a large value low voltage cap. I have a 1000uF/16V. You need to have the cap be much larger than the cathode resistor or you start to shelve the frequency response....which is what dsavitsk was indicating when you start to bump the cathode resistor up to 20K along with a low value cap (220uF or so). Not to mention, again, that a 20K cathode puts the operating point in a not so great spot.

If you really, want you can use the stock cathode of 2K, put a 5K 20 turn trimpot in parallel, use a 0.5mA-1mA CRD on the plate and then dial in the trimpot so that you have the plate voltage at 1/2 B+. Watch for thermal drift for a 1 day fully enclosed as if it were the final build, if steady you should be able to remove the interstage cap (0.1uf-0.22uf) and the voltage divider (2 220K resistors) which sets up the gate voltage of the mosfet. The plate will set it up. It just needs to be higher than the heater voltage, and enough to "turn on" the mosfet. The output cap will block the DC, as normal.

I'm not sure I would do the latter option as there are probably things I don't understand about tube operation, but it wouldn't hurt to try.

One other thing, which I did. Change R13 to 1K, and make C1 and C6 1000uF. You will need the lower R13, especially if you try to push more current through the tube than the stock configuration. With stock configuration, larger caps and lower R13 you should get about 1V more for B+ and not affect the filter adversely. It's not much, but with such low B+ anything helps when you try to move the operating point.

 

[luiztfc]

Quote:

Originally Posted by zkool448 /img/forum/go_quote.gif Hang in there, luiztfc. It looks like it won't be very long before beezar.com will officially start selling the kits

Ok, but isn't there any other tube that can replace the 19J6?

 

[tamasic1]

if you go back a dozen pages or so there is a few passages about a replacement and the modifications for it. Except for an ebay snag you're pretty much screwed on the 19j6.

Larry the tube guy says: Getter Done!

 

[Logistic]

Quote:

Originally Posted by luiztfc /img/forum/go_quote.gif Ok, but isn't there any other tube that can replace the 19J6?

I posted a guide to use the 12sr7/12sw7 tubes about 10 pages back. Just search this thread for 12sr7.

 

[Hayduke]

Quote:

Originally Posted by kuroguy /img/forum/go_quote.gif I work with a schematic and a highlighter, coloring in the lines and components as I install them. when the schematic is completely highlighted, you're done.

I used a printed copy of the schematic and highliters also, but I highlighted first to make it easier for me to see which components were connected together. Basically I wanted to see each "piece" of the circuit. I can't find my color coded schematic now, but I seem to recall I only need 6 colors, so there were only 6 "pieces" of the circuit.

When I built the amp, I just drew an "X" through each piece or section as I built it.

 

[luiztfc]

Quote:

Originally Posted by Logistic /img/forum/go_quote.gif I posted a guide to use the 12sr7/12sw7 tubes about 10 pages back. Just search this thread for 12sr7.

Thanks, I'll look into it. And just a last question: is there any possibility that the 19J6 model name can differ in different countries?

 

[tomb]

Quote:

Originally Posted by luiztfc /img/forum/go_quote.gif Thanks, I'll look into it. And just a last question: is there any possibility that the 19J6 model name can differ in different countries?

There is a 5J6 and 6J6 in the same series - they even share the same data sheet. However, the "5" and the "6" represent 5V and 6V heater requirements, a far cry from the 19V of the 19J6. IOW, they're useless for the SSMH.

 

[cactus friend]

Just so everyone knows, I was able to order two same brand 19J6s from Jack at thetubecenter.com - not sure how many they have, but it's worth a shot if you're hunting them down.

Edit - answered my own question again ..

 

[tomb]

Quote:

Originally Posted by cactus friend /img/forum/go_quote.gif Just so everyone knows, I was able to order two same brand 19J6s from Jack at thetubecenter.com - not sure how many they have, but it's worth a shot if you're hunting them down. Also, a quick question: Those black o-rings around the holes for the transistors (for instance, in Nate's build), what are those called and where could I find some? Pardon my ignorance - thanks!

Rubber Grommets ...

 

[cactus friend]

Haha, thanks, Tomb. The name slipped my mind for a second until I checked out the BOM to refresh myself.