Xits X10 = liverpool half power?

[azatplayer]

Just checked some of Greg V's demos, led to Fat sounds site on the Xits X10
Gees great sounding amp. Had a look at FS's great pics and theres a lot of liverpoolish looking action going on, particularly the three gain stages, no CF.
PPIMV as well, which seems to work nicely.
Its made me think about a build... but closer examination of the pricing.. and why would you build it! Its beautifully constructed, great to look at, and not a lot of cash.
Anyone got one/played one?
Pretty sweet, could be the perfect clubber.

Demo http://www.youtube.com/watch?v=f2S_jh_z ... r_embedded

Fat sounds pics http://www.fatsoundguitars.com/store/am ... s-amps.php

Sure looks like a pool to me. Apart from the input stage

[chopstuck]

This has "something elusive" I can't put my finger on but it has to be the BEST demo of an amp I have heard on the net.

So you think it's a two holer liverpool type of amp ? I need another project....

I happen to love the 2xEL84 flavor and this seems to capture all that and and whole lot more than the top boost pre I have been using for a few years.

Anyone have an Idea of the topography ? Here is a link to the gorgeous website. LOTS of info too.
check out the demo on YOUtube
http://www.youtube.com/watch?v=KGpIRj6M ... re=related

and let me know if I'm nuts but this amp really hits a nerve....in a good way.

http://www.fatsoundguitars.com/store/am ... s-amps.php

[azatplayer]

I ended up ordering one... the price at the time was really good, theyve since gone up with the demand.
Still have to wait till at least years end for it.
You can just about make the circuit from the pics of the guts. Voltages aside, the stuff you cant see, im sure can make an educated guess.
From the clips the master looks like it works a real treat. Interesting version of PPIMV, the 220k bias R's are left in the board, but the PPIMV looks to have the 2.2M R's on it. Im guessing theres no ground at the end of those 220k's.
Theres a voltage divider on the treble return to the third gain stage, pair of 470K's. The tonestack is fed from the 2nd gain stage. Looks like a real easy mod from a rocket. But its got odd controls. The treble pot acts as a gain of sorts, as its controlling the amount of signal to that 3rd gain stage.
Good thing i have enough to keep me consumed with other builds till mine is ready!

[RevD]

15-18 watt 2 holer EL84 amps are one of my favorites too. I played in a blues band as basically a rhythm/second lead player and the cut from those amps just would flat do it. I'd get decent cleans turned down and dimed (in a larger club) that nice over the edge EL84 sound. My builds have mostly been lite IIb 18 watters, and towards the end of that band a TMB 18 watter. I'm currently modifying the non-tmb channel on that amp with a 5879 pentode for the early ac15 sound with a bit less microphonics (and cheaper albeit a tad less gain) than the EF86. I still will have to rubber mount V1 and it'll have the 6 way rotary switch for tone. I love these amps, they were great for Funk with a strat in the quack position. The TMB/Plexi sort of channel just flat rips and gives up the good british tones. I use a Eminence Wizard (built in a combo amp which used to be one those peavey transtube SS's, I love flips!) which is a really efficient speaker and have even played it on outside stages on small events and it was WAY loud even outside.
This one sounds very good, heck I'd be real happy with one of these. Hope to hear some more clips when you get yours! Good luck with it.

Regards,

RD

[C Moore]

I have to tell you, Greg V is a very talented and toneful player. He has done several great demos. Not saying the amp can be overlooked, but if I were looking for a guy to demo one of my builds......

[Colossal]

That is an awesome sounding amp. It might be fun to tease out the component values for the X10 based on the Fat Sound gut shots and see what makes that amp tick (although Azatplayer has done a lot of the legwork already! Nicely done dude). It is interesting to contrast the sound of the X10 to the typical 18W tube rectified fare. You can hear the fast response of this amp; it's got that real zing on open B/E strings.

Greg V's demos are excellent and what really turned me on to the 15-18W 2xEL84 amps was his demo of the RetroKing 2x12 combo. His Tele and SG both sound really good. His playing is unique and he's got great chops and phrasing. These EL84 amps really seem to suit him. I was pretty much a "plexi" type player but seeing these EL84 demos has really piqued my interest and I'm excited to try some builds out. I've got some nice Heyboer iron wound for a couple of 18W projects.

[Darkbluemurder]

The tonestack is fed from the 2nd gain stage. Looks like a real easy mod from a rocket. But its got odd controls. The treble pot acts as a gain of sorts, as its controlling the amount of signal to that 3rd gain stage.

I agree. The third stage is definitely fed from the treble pot though that long white shielded cable. Whether the controls are odd I don't know but if they have the Vox values the symptom would exactly be that - turn the treble knob down and the low mids strongly increase which feels similar to a gain increase.
The signal leaves the third stage through that coupling cap (I guess it is a 0.022uf - the same as the PI grounding cap) to the PI which has Vox values. There is a snubber cap across the two 220k power tube grid leaks - probably 100pf. PI couplers are 0.047uf.

So my guess on the topology is

Input - V1a - Vol2 (=preamp gain) - V1b - Tone Stack with Vox values - V2a - PI with PPIMV - PA cathode biased - no NFB.

So it is not the Liverpool topology but the third stage may be the same. In the video it appears that the amp does not hiss as much as a Liverpool which would be a good thing. It is indeed closer to a Rocket but instead of the cathode follower before the tone stack there is that third gain stage. And Greg V is definitely a hot player.

Theres a voltage divider on the treble return to the third gain stage, pair of 470K's.

Where did you see that?

Cheers Stephan

[azatplayer]

Sorry Stephen my mistake, typing late.. its the gain volume control returning thru the pair 470Ks to the second stage. then off to the tonestack.
The input cap from third stage to PI is a .01uf.

What about that type of MV arrangement with the 220k's still in tact? I did a PPIMV on a rocket build sans the 220k's. Im wondering what the diff is leaving that divider setup in tact? I see the guys at metro often put that snubber on the grid bias R's rathwer than across the load R's, works the same but is oft done when using a PPIMV from what ive gleaned. Reason?

I confess i changed a rocket build to this same spec, couldnt get it fiz free, and figured the pots had to be the culprit, my guess was the 1megs are the wrong value?

[Colossal]

What about that type of MV arrangement with the 220k's still in tact? I did a PPIMV on a rocket build sans the 220k's. Im wondering what the diff is leaving that divider setup in tact? I see the guys at metro often put that snubber on the grid bias R's rathwer than across the load R's, works the same but is oft done when using a PPIMV from what ive gleaned. Reason?

Hey Azatplayer, I've been trying to sort this out myself. I question whether that arrangement of having that 100pF(?) cap across the PI plates or across the grid leaks is the same because in the second arrangement, the pF cap is separated by the 0.047uF output caps. So if the fizz cap is across the PI plates, high frequency is being shunted to ground via the plates. If the fizz cap is across the grid leaks (but the grid leaks are not connected to ground as *may* be the case with the X10), then highs are getting phase cancelled, like a cut control. Or am I way outta my element here? (STFU Donny, you're way out of your element).

Also, do you guys know what's going on the right of the board? Is that big black resistor next to the PS caps a sag resistor (since the amp is SS rectified) or is that the (unbypassed) power tubes cathode bias resistor. Also, what is that little black Sprague cap doing on the far right? It looks like it may be paralleled with a resistor underneath (and barely visible), in which case maybe that is the cathode bias resistor and bypass cap. The pair of diodes on the right edge of the board and associated resistors appear to be powering the LED status light.

[Darkbluemurder]

What about that type of MV arrangement with the 220k's still in tact? I did a PPIMV on a rocket build sans the 220k's. Im wondering what the diff is leaving that divider setup in tact? I see the guys at metro often put that snubber on the grid bias R's rathwer than across the load R's, works the same but is oft done when using a PPIMV from what ive gleaned. Reason?

I confess i changed a rocket build to this same spec, couldnt get it fiz free, and figured the pots had to be the culprit, my guess was the 1megs are the wrong value?

I believe they put the master volume pot in parallel to the existing 220ks. The disadvantage by using a dual 1MA pot for this purpose is that at lower settings you have much more series resistance between the output coupling caps and the power tube inputs which (1) hurts fidelity, (2) makes the grid lines more sensitive to picking up noise and (3) may add fizz to the tone. Therefore the dual 250kA pot in place of the 220k resistors is the (I better should say "my") preferred solution. To ensure the integrity of the connection to ground (in cathode biased amps) or to bias (in fixed biased amps), safety resistors of 2.2M should be used between the wiper and ground of each pot section.

I used snubber caps on the PI plates on some amps and used cut controls on other amps but rarely I tried both in the same amp. Putting the snubber after the PI coupling caps allows a low voltage cap to be used.

Cheers Stephan

[Darkbluemurder]

Also, do you guys know what's going on the right of the board? Is that big black resistor next to the PS caps a sag resistor (since the amp is SS rectified) or is that the (unbypassed) power tubes cathode bias resistor. Also, what is that little black Sprague cap doing on the far right? It looks like it may be paralleled with a resistor underneath (and barely visible), in which case maybe that is the cathode bias resistor and bypass cap. The pair of diodes on the right edge of the board and associated resistors appear to be powering the LED status light.

I believe the big black resistor is the power tube cathode resistor and that little black Sprague cap is the power tube cathode cap. It would make sense to have them separated since the resistor gets hot.

On the far right I see two diodes that appear to be the rectifier. I am not sure what the smaller black resistors in series with the diodes are for.

Cheers Stephan

[Darkbluemurder]

[quote="azatplayer"]Sorry Stephen my mistake, typing late.. its the gain volume control returning thru the pair 470Ks to the second stage. then off to the tonestack.
The input cap from third stage to PI is a .01uf.

[quote]

No problem, I see it now, thanks! The original Dr. Z Prescription used a 220k pair at that point.

And yes you are correct. The PI input and grounding caps are 0.01uf, not 0.022uf as I thought initially. Same set up as Matchless DC30 and TopHat Club Deluxe.

Cheers Stephan

[Colossal]

I believe the big black resistor is the power tube cathode resistor and that little black Sprague cap is the power tube cathode cap. It would make sense to have them separated since the resistor gets hot.

Darkbluemurder, I *think* I can see a resistor below (in parallel) to that black Sprague cap (see enclosed JPEG with notes). This leads me to believe that that it is the R/C pair for power tube cathode bias. But you are right, that resistor would get hot.

Second, the series diodes (between the big black resistor and the black Sprague cap) has got to be the rectifier. The black series resistors in series with each pair of diodes is dropping secondary AC a little and providing a little sag. My guess, if the Sprague cap is actually paralleled to the cathode bias resistor (it's definitely paralleled with SOMETHING and I think that resistor below it is *barely* visible), then that big black resistor to the right of the blue Sprague PS caps is a sag resistor which full wave rectifier goes into (makes a left turn) then from the sag resistor to the standby/power/off switch.

Finally, I think the two diodes on the far right are for powering the LED indicator, at least one of them is. There is a pair of carbon film resistors on the end of those diodes at the back right corner. You can see the wire from the standby/power/off switch to the LED and down to the diodes/resistors.

This is my best guess anyway.

[azatplayer]

Good guess it is Dave! I concur with this theory. I reckon i can see a wirewound about the same size as the ones feeding the rec diodes.
Looks like a pair of 100 ohm R's artificial centre tap from the led diodes/heater wires to ground. I used an led on my last build for something different, ran a diode from one heater tap off the phase inverter, used a dropper after it, and the other side to ground.
What still puzzles me with the PPIMV is i can see 2.2M R's on the dual gang pot, so one would have to assume its a 250k dg pot, and theres a black wire to ground coming from the pot so there can not be a ground reference at the end of the 220k pair. So, what are they there for? I gonna have to sub some in to an amp and find out!

[Colossal]

Good guess it is Dave! I concur with this theory. I reckon i can see a wirewound about the same size as the ones feeding the rec diodes.

Yes, just barely visible near that white wire and the black Sprague cap.

Looks like a pair of 100 ohm R's artificial centre tap from the led diodes/heater wires to ground.

Ah! The 100R tap makes sense! That's gotta be it.

What still puzzles me with the PPIMV is i can see 2.2M R's on the dual gang pot, so one would have to assume its a 250k dg pot, and theres a black wire to ground coming from the pot so there can not be a ground reference at the end of the 220k pair. So, what are they there for? I gonna have to sub some in to an amp and find out!

I've enclosed a PDF of what I can guess from the gutshots. I *think* that DG 250kA/2M2 Master Volume pot is grounded to the cathode bias R/C pair. You can just see a black wire running the DG pot, it disappears under the power on/standby/off switch and then you see it run just under the turret that the black Sprague cap and R are connected too.

I can't quite make out what the grid resistors are on the power tube grids. The bands look brown-brown-something or red-red-brown but those don't add up to be grid resistor values that seem "normal".

For the big black sag resistor, 100-130R would approximate the sag of an EZ81. I have no clue what it is though. I can't make out the value on the black Sprague atom cap for cathode bypass but we could look up the TVA line and approximate its physical size using the bigger Blue Atom caps for reference and ferret out its value. My guess would be 100uF/50V or so (?).

I am pretty certain the PI plate loads are 100k/100k to give some imbalance and a lot of 2nd order harmonics to the power amp. This is done in the 18W variants.

[EDIT: Attachment deleted. Schematic to be fully drawn and reposted]