Xits X10 = liverpool half power?

[pamaz67]

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.

Sorry I don't remember the voltages by now and don't want to check it again just now ( it's midnight here).
I'm not positive that the problem lies in the control values. I mean, that one is a standard ac30 tonestack and I always found the ac 30 ( and ac50) controls a little bit weird to set.

I have to shut off the amp and think a little bit.

[surfsup]

Is it too gainy because of too much bass? If the bass pot itself is a culprit. I have a few values here I can try. Would duncan's tone stack help simulate this circuit? Or does it only work for fender/marshall types (I never used it)...btw I'm glad to hear you're in the ballpark though!

I just checked my stash, I have two old 12au7 from RCA and some 12at7s as well.

[Andy Le Blanc]

been following this thread...

there's a few variations of that tone stack used by differnt mfg.,
the range in values I've seen...

hi/lo 1m/1m 500k/500k 250k/500k 100k/250k

[pamaz67]

been following this thread...

there's a few variations of that tone stack used by differnt mfg.,
the range in values I've seen...

hi/lo 1m/1m 500k/500k 250k/500k 100k/250k

you are right Andy.
i was checking some old ac30 schemos and often found the 500k .
Tomorrow I'll try with other pots and we will see.
In any case once again I think that it requires almost an HIFI OT to have that sound. Such a tight attack is not something you get on a "cheap guitar iron".
Or you need to have a very high plate voltage on all stages. That is not the case seems to be.

[pamaz67]

Hey guys . I cannot find a picture where the cathode caps in the preamp are "certified" to be 25 uF.
I suppose they can be lower, as the tone with 2,2uf is less muddy, although always generous on the low side.
I'm convincing myself that the plate voltages are on the high side, to be so crispy.

[pamaz67]

tested different tonestack pots.
the best combination so far is 250k hi 500 lo. Tone Caps not changed.
but the gain problem remains.
In any case with this tone stack and with 2,2uF cathode caps I'm starting to hear interesting sounds with some of the feeling i can see in the videos.

[surfsup]

"with 2,2uF cathode caps"

So you now have 2u2s on both V1a and V1b? Did you try a lower value or was 2u2 the lowest you tried?

I noticed some comments about the "large oversized" transformers specifically wound for Michael at Xits and how those help 'tighten' the low end. I believe you said you were using a 280-0-280 PT, what was your OT?

Do you still feel higher voltages will help? What are your voltages?

[pamaz67]

"with 2,2uF cathode caps"

So you now have 2u2s on both V1a and V1b? Did you try a lower value or was 2u2 the lowest you tried?

I noticed some comments about the "large oversized" transformers specifically wound for Michael at Xits and how those help 'tighten' the low end. I believe you said you were using a 280-0-280 PT, what was your OT?

Do you still feel higher voltages will help? What are your voltages?

So, the voltages just now are around 320v on the el84 plates ( 35 mA each tube) , 240 on B+3 220 on b+4 210 on b+5.

furthermore : are we sure that b+4 and b+5 are tapped from B+3?
Could it be that b+4 and b+5 are tapped directly from b+2 as in an ac30?

@surfsup: I'm using a 4kohm ac 30 clone transformer , but in this week i'll get a different one, always 4kohm, but with with different windings.

[Masco]

Interesting reports, thanks for sharing findings/documentation Surfsup and Pamaz67.

Hopefully, we'll have all the details when Azatplayer reports back if he ever receives delivery of his X10.

[Andy Le Blanc]

there's critical values for bypass, 2 to 5 uf is about right.
If you run into hum issues, then you go larger...

[surfsup]

paolo,

"furthermore : are we sure that b+4 and b+5 are tapped from B+3?
Could it be that b+4 and b+5 are tapped directly from b+2 as in an ac30?"

If this was the case, why would the X10 have a dropping resistor between B3 and B4

In the photos:
B3 is connected to B4
B4 is connected to B5

If what you say is true, then wouldn't the two 1k0Rs both be connected to B2, instead?

Did you try lower values than 2u2 for first tube cathodes?

The caps on the sadie say 0617H on them, and Vishay has only one cap with this designation, a wet tantalum 56uF, which seems large since you tried 25u and 2u2 is better:

http://www.vishay.com/docs/40143/dscc0601.pdf

The pics are from fatsound guitars so you'd assume they are of a production amp shipped to them for resale and photos.

[img:800:531]http://www.fatsoundguitars.com/store/am ... guts-4.jpg[/img]

[Lonely Raven]

That's amp porn right there! ^^^^

[azatplayer]

They are sprague premium elytics.

[Gaz]

Paolo, about the gain - are you using a 1MA or 500kA pot for the gain control? If the pots are unverified, I would assume 500kA in a design like this. Must admit though, the Fat Sound video made the amp appear as though it had very little clean headroom with the guitar's volume up, so 1MA could be correct still.

[pamaz67]

Paolo, about the gain - are you using a 1MA or 500kA pot for the gain control? If the pots are unverified, I would assume 500kA in a design like this. Must admit though, the Fat Sound video made the amp appear as though it had very little clean headroom with the guitar's volume up, so 1MA could be correct still.

I'm using a 1MA.
To me it's really crucial to understand at least a couple of things:
1) How the original tone control works
2) the supply voltages.

I'm convincing myself that the amp could sound very well, but the tone and volume sweet sposts are really difficult to dial in, no matter if the tone pots are 1Mohm or 250kohm or whatever.....
Regarding the clean sound, being the overdrive coming mostly from the PI, and having found low voltages over there, I'll try to raise the supply of the Preamp section and PI, just to understand if the trick could be in that area.

I know it's not in the direction of the perfect clone, but if I have al little spare time today, I'll try an express tonestack, just to understand how it works in this context.