Xits X10 = liverpool half power?

[rhinson]

You can see in that last pic of the head version, (its an early design, before he dropped the divider and grid leak resister), there is a resistor heatshrinked into the shielded cable return from the treble wiper.
Could be just a grid resister of maybe 10k or so, or something more to isolate the tone circuit.
Yes Paolo, it was far from optimum. There is still some mystery to be unfolded for sure!

i bet it's more than 10k. probably follows something like the komet and does a 220k, then with a 56k or so in concert to knock down the gain so you don't drive the el84's so hard. you might even try the komet tone pot values--perhaps he used the fender/vox hybrid idea here that others have used. rh

[rhinson]

opps--sorry. should have read down further. looks like you're already trying to knock it back a bit with a 220k---i think this is probably the way to go here. rh

[Masco]

Why not make use of the unused triode to add a Normal channel? You could mix it after the 220k from the treble wiper and eliminate the 56k since there will be another mixing resistor after the wiper on the normal volume pot.
Just a thought - a triode is a terrible thing to waste...

[Gaz]

a triode is a terrible thing to waste...

LOL

[azatplayer]

Ahh good work paolo, glad youre getting somewhere.
Im just in tweaking stage of a single ended komet ive been working on for a while. That 220K in series is a very important part of the circuit, between gain stages, even without the use of a divider.
Very cool. I might try a SE version of the Xits!

[Gaz]

Might anyone be able to elaborate (technically) on its effect on the tonestack's operation? Otherwise, it's just a grid stopper.

[pamaz67]

news of the day.
I know it's not correct from a clone point of view, but putting the 220k resistor and instead of the 56k grid leak an 82k grid leak will allow you to have the same tone and the gain will span from cristal clear to high saturation.
I'll leave it there. I think it's a nice improvement.

[pamaz67]

Might anyone be able to elaborate (technically) on its effect on the tonestack's operation? Otherwise, it's just a grid stopper.

I suppose (the first thing that comes to my mind) it's the miller input capacitance of the tube that kills the correct way of working of the tone stack.
The added resistor is isolating the tone stack from the input capacitance of the tube in the freq range that we are interested in.

[surfsup]

I checked my stash and I only have 1/2w 220k Xicon CFs (350V) and two 1/2w 220k PRPs (500V). I'm concerned about the 1/2w. I assume it's okay, but not being sure what the screen voltage would be on the third stage and such a high resistance, would a 1/2 watt resistor work?

[pamaz67]

I checked my stash and I only have 1/2w 220k Xicon CFs (350V) and two 1/2w 220k PRPs (500V). I'm concerned about the 1/2w. I assume it's okay, but not being sure what the screen voltage would be on the third stage and such a high resistance, would a 1/2 watt resistor work?

whichever you like will be ok

[surfsup]

I would assume if a 220k/82k combo is not on hand, any two resistors that form a similar value voltage divider would work that creates a Vout/Vin = ~27%.

Vo/Vi = 82/(82+220) = 0.27

EDIT: Hmm, maybe not because of that pesky tonestack and this acting in parallel.

It might also be better to have the resistors attached directly to the tube pin but in this graphic I believe it shows what you did to get things working properly:

[img:600:600]http://chicagocadcam.com/ChrisHahn/sche ... _V_div.jpg[/img]

[pamaz67]

that's correct.
you may want to try any value between 47k and 150k .
the sound will be almost unaffected, but you'll be able to get a wide range of gain.
if you want to keep the originality of the design it's always possible to place a switch at the 82kohm resistor

[Colossal]

Guys, in that schematic showing the greyed out resistor, that resistor used to be there on the version 1 X10. It is now greyed out showing that it has been removed from the version 2 X10 and the tube has been changed to a 12AU7. I just left it on the drawing to show the version history as the drawing changed according to available data.

If you want to build the amp to the original specifications (like in the X10 video demos by Greg V and Fat Sound), then that resistor should be added (56k). There is a gutshot of the original that shows this resistor. If you decide to use the 56k grid leak/divider, then you could switch V2 back to a 12AX7 if you wanted. It would be interesting to see how the amp behaves with an AX7, AY7, and AT7 in that position.

[azatplayer]

How far off are you Surfsup?

[surfsup]

How far off are you Surfsup?

I went through my stash and I have a 220k/82k pair both CF 1w so I'm good. I also have a 120k/47k pair which is about the same ratio.

If you meant in B+ rail voltages, I have a 22k and a 1k, both 3W to put before the PI, if I go with the 1k, I get eerily close to the voltages as Paolo:

Me - Paolo:
329 - 335
322 - 330
317 - 313
287 - 287
272 - 271

If you mean how close to completing, UPS says Edcor iron is showing up tomorrow. However, my 30w radioshack s/iron is not soldering to the turrets well, so I ordered a higher powered one a few days ago but it won't be here till next week.