Xits X10 = liverpool half power?

[pamaz67]

Surf, at this moment I will stick with the values on the Colossal drawing.
Remember that i'm building a 30w version and so i don't necessarily want to make an exact clone.
I just would be pleased to be in the ballpark of the youtube samples of the x10.
First of all I would like to hear the thing like it has been drawn by colossal, Then I'll move from there tweaking by ear.
Remember that nobody here has the same transformers, so making an exact clone, until the transformers characteristics will be public, it's not so useful.
In any case, once I'll have the iron I'll let you know my impressions.
Ciao

[pamaz67]

did you use 1M MV pot?
Yes by now.

What about the RC filter values after the PI?
Think I'll place a filter similar to a komet 60 with a pot and see what will happen.
Did you ground the two 220k resistors?
Yes by now. I'll check the behaviour with and without ground.

Choke or 1k R?
10h choke and a resistor in series to give a little sag if needed.

What voltages are you expecting for B, B1-B5?
Not even worried from this. I'll adjust the anode voltage simply by ear tests.

[Lonely Raven]

If you guys even get close to getting the tone of the original amp, this will get bumped to the top of my To-Build list.

Seriously, I thought about selling my motorcycle to get one of these amps...

~Eric~

[Ken Moon]

Any more leads on the choke specs?

It looks very small for a MM choke - much smaller than an AC30 like this one:

[img:640:259]http://www.mercurymagnetics.com/pages/c ... hassis.jpg[/img]

or this JTM45 unit, sitting next to a smaller heyboer choke:

[img761]http://i514.photobucket.com/albums/t346 ... etch02.jpg[/img]

or even this one, for the AC15/ Night Train:

[img:800:554]http://www.mercurymagnetics.com/images/ ... in-mod.jpg[/img]

It looks to me like a little Fender choke, about the size of the 9H/120mA/120DCR heyboer unit in the pic with JTM45 choke above.

I know physical size won't tell all, but maybe this will help narrow it down.

[Gaz]

I agree with Ken, those AC chokes are over-rated and Big. Pazmaz's choice to use any 'ol choke and tune with a series resistor to taste is a good one, IMHO.

[surfsup]

Okay I think this is my final layout...my only concerns:

1) the power tube cathode ground and B lines cross under the board after the VVR3 diode to supply the B for the PI and preamp tubes

2) the bleeder resistor location under the big solens. There's 0.15" clearance around it though, should be okay

Comments? Let me know I am going to cut the G10 and start drilling this weekend. (still waiting for Edcor iron)

[pamaz67]

Supply transformer arrived.
I'll fire it up as soon as I'll mount it . I think in the afternoon.
And so, we will se what the problems are.

[angelodp]

Paolo, can you post some shots of your build. Very interested in hearing and seeing your evaluation.

Ange

[surfsup]

Paolo how does it sound?

[pamaz67]

sorry guys but I got a bad viral flu and yesterday I was unable to do anything . Today i feel a little better and I hope to do some evaluations.

[pamaz67]

so . i've done it.
a few smoke coming out of the 1kohm resistors in the supply, but I forgot I have a 30w here so I have at least to lower that resistors.
The thing is working. But let me do some other tests because i suspect there are a few things to adjust here.....
Now I' m going at lunch.
Later I'll go on with the tests.

[pamaz67]

'the actual configuration I'm using is referred to the schematic WITH both the 470kohm voltage divider between the first and second stage and the 56kohm grid leak.
my power amp is a 30 w version with 120 ohm grid resistors ( i had only them on hand)
The transformer is giving me 285v per side under load conditions.
preamp tubes 3x 12ax7 Capacitors are xicon mpp. Plate resistors dale rn65. I've lowered tha supply resistors form 1kohm to 330ohm to deal with the 4 el84. They run really hot. Not sure about them ( and I'm using 10w stuff)

First impression.
You can feel that the DNA is the one of the youtube videos, but is quite difficult ( not to say almost impossible) to dial in really clean tones.
For my personal taste the overall gain is way too high.
With the gain knob at 9.00 and a telecaster you are almost in crunch ( that is not so far from what i can see in the youtube videos using similar tone settings)
Looking at the scope, I've found that most of the distortion is generated in the PI , so I think I'll keep both the 56kohm grid leak that the 470kohm divider and I think I'll work on that voltage divider to have the possibility to get a clean tone also with humbuckers.
The Tone controls are critical. I mean they work well , but really very sensitive ( too much for me) . BTW i'll keep them this way beacuse thaey are fundamental to keep that kind of sound.
Later i'll try to push it a little harder and see what will happen.

I have to say that is not bad, but not a miracle at this stage....
I think something else needs to be done ( way too gainy......)


edit: way better taking out the 56kohm, the 470kohm divider and with 12au7 in the second position. Always difficult to get clean tones.
furthermore just a personal suspicion: I think the output transfomer should have an excellent transient beahviour to get that kind of sound.

[surfsup]

edit: way better taking out the 56kohm, the 470kohm divider and with 12au7 in the second position. Always difficult to get clean tones.

Okay, that is good info, as i am not using the voltage divider, nor the 56k, though i dont have a 12au7. I posted a bit more info on my components in my thread, fyi, if you care to look and compare. I have the slope resistor mod, too. So i hope that makes things a little more flexible WRT the tonestack

[azatplayer]

Youre gonna need that 12AU7 dude. Without the divider and the grid leak, its gonna have monstrously unusable gain with a 12AX7.
Paulo, youre having a similar experience to what i had. More gain than it should have. My suspicions have always been the controls values. I think theyre high, but we cant see what value they are in the pics of course.
Also the way the treb and bass pot interacts is weird, the treble act as almost a volume pot on your build?
What B+ are you getting, 285 aside will see you in the high 300's, could be too much voltage.
I put a cap on the entry to the third stage, .02 from memory, helped the controls even out a lot.

[pamaz67]

edit: way better taking out the 56kohm, the 470kohm divider and with 12au7 in the second position. Always difficult to get clean tones.

Okay, that is good info, as i am not using the voltage divider, nor the 56k, though i dont have a 12au7. I posted a bit more info on my components in my thread, fyi, if you care to look and compare. I have the slope resistor mod, too. So i hope that makes things a little more flexible WRT the tonestack

I tried diffferent slope resistors today and the problem is still the same. The useful range in the bass potentiometer IMO is too short, so any setting is quite difficult to reach.
Just one thing to point out. I'm trying the amp through a 4x12 cabinet , and have not tried a 1x12. Probably the bass range is too much for a 4x12 but fits perfectly a 1x12. Tomorrow I'll try a 1x12 and will see what's going on.
if it's just that i'll reduce some coupling ( or decoupling) capacitor just to lower a little bit the bass range.