Xits X10 = liverpool half power?

[Masco]

I see, too, that he has a leg sandwiched between the bell cover and the laminates on the standups. Is this something special he does or is this stock MM? Anybody?

The leg between the bell end the laminates is how Mercury does it, nothing special there. XITS iron is custom wound or at least relabeled for them.

One thing I hate about MM when ordering iron w/ stand-up legs: They snap off the excess threds for the bell and legs at the nut. This makes it difficult to remove the legs and/or end bell if you happen to want to mount in a different fashion. It also pretty much renders the bolts useless if you want to use them for mounting through the chassis.
-Just a heads-up when ordering.

[rhinson]

the output trannie in the pics looks to be about the size of the merc ac15 style trannie---probably the larger 1 1/4" sized stack. also, i'm wondering about the "cut" cap of 100pf across the grid loads. i think it's probably a resistor/cap combo in heat shrink-----probably something like the standard 250k pot turned up halfway----maybe a 120k resistor in series with the standard .0047uf cap. if it's just a cap no need to heatshrink it. rh

[Structo]

The note w/ the first photo in the directory says "Sadie in X10 clothing".

So, were not really looking at X10 guts, but a Sadie instead?

Strange looking coupling cap coming off of V1's plate.

http://www.soniccraft.com/relcap_rte_capacitors.htm

rel-cap. appears to be a polystyrene from the description. also the amp can't be a sadie because the sadie 1st stage is an ef86 according to their site. rh

Yes those are polystyrene

Isn't the cathode resistor on the PI a 1K2 and the tail a 47K?

[rooster]

Er...polystyrene and tin foil, not just polystyrene. I think this is nothing new, but this is not what wattstubeaudio.com is selling. That version does not use metal foil in it's construction.

I should have mine this Wednesday, BTW, and right now sonic craft has a 15% off sale going on. They still hose you for the shipping, $9.95 for 1oz. of caps. I hate that kind of thing.

Anyway, I will report back on these, and yes, I have the caps from wattstubeaudio to compare them to.

[Colossal]

SCHEMATIC UPDATE

1) Removed 100pF fizz cap across PI grids
2) Added fixed cut circuit as seen in latest photos (heat shrunk)
3) Added a couple of comments

[rooster]

Wow, looks nice. I still question V2 and the gain there. Are you satisfied with the 56K resistor and the exit of the signal from the plate resistor? This just seems like a something that 'chokes' the signal more than a higher value resistor (220K?) and a cathode exit.

Too, the MV circuit I would still like to see in person. From day one some were ready to accept the pair of 220K resistors as being in the circuit and attaching to ground - in parallel with the MV. OK, I did some simple math here and it seems this would work IF the MV pot were a dual 1M type and not the 250K value of the LarMar MV. The math says that the overall parallel resistive value would be 180K then as the grid leak value when the MV was on '10' - this would be totally fine I think. (Using the LarMar value pot the grid leak would be 117K - too far off the traditional mark I think.) ...So maybe this dual 1M MV option should at least be listed on the schematic, Colossal?

Still, good job on trying to decipher a schematic from gut shots, I must say Colossal, and thank you for such a tidy PDF!

[M Fowler]

Dave, great job on that schematic buddy, thank you.

[surfsup]

Is anyone/everyone interested in helping me guiney-pig this amp? I would like to build it but the PT values escape us. My thought is with the VOX night train having a similar setup and running plates at 330V, it might be similar and to shoot for a B+ of around 350 fro some wiggle room on the voltages. Would that be a safe assumption? I don't plan to use PRPs like in the sadie, just regular ol' 1/2watt carbon films and some sozos.

So what I'm asking is what would your guesses be for the PT?

Collosal I also have a XLS of the list of materials (just component type and value) if you want it I can email it to you.

[Colossal]

Is anyone/everyone interested in helping me guiney-pig this amp? I would like to build it but the PT values escape us. My thought is with the VOX night train having a similar setup and running plates at 330V, it might be similar and to shoot for a B+ of around 350 fro some wiggle room on the voltages. Would that be a safe assumption? I don't plan to use PRPs like in the sadie, just regular ol' 1/2watt carbon films and some sozos.

So what I'm asking is what would your guesses be for the PT?

My guess would be like Rhinson's in that it is closer to Voxy PT values; so higher than the usual "18W" iron at 280 or 290-0-290. I would guess 300-0-300 and maybe plates around 360V.

We do know that the cathode bias resistor for the X10 is 125R so the voltage can't be too smokin' hot as it's probably running close to max dissipation for each tube already. There are "sag" resistors in front of each diode in the rectifier which are 1k apiece. This would add some voltage drop.

[Colossal]

Wow, looks nice. I still question V2 and the gain there. Are you satisfied with the 56K resistor and the exit of the signal from the plate resistor? This just seems like a something that 'chokes' the signal more than a higher value resistor (220K?) and a cathode exit.

Rooster, check out the enclosed photo (click on it to zoom in and you can see the 56k value pretty clearly). I'm pretty sure about 56k being the input grid leak on V2. Let me know if you see otherwise. I think Azatplayer noticed this first when we were looking at the first gut shot photos to come out from Fat Sound.

Two, the MV circuit I would still like to see in person. From day one some were ready to accept the pair of 220K resistors as being in the circuit and attaching to ground - in parallel with the MV. OK, I did some simple math here and it seems this would work IF the MV pot were a dual 1M type and not the 250K value of the LarMar MV. The math says that the overall parallel resistive value would be 180K then as the grid leak value when the MV was on '10' - this would be totally fine I think. (Using the LarMar value pot the grid leak would be 117K - too far off the traditional mark I think.) ...So maybe this dual 1M MV option should at least be listed on the schematic, Colossal?

Sure, that seems reasonable. Martin Manning added something a few pages back on this issue. We have never been sure if those 220k/220k post-PI grid leaks were grounded but the consensus was that a) they are and b) that they would be operating in parallel with the PPIMV. We all assumed that the LarMar PPIMV is 250kA||2M2 but as you have observed, the total grid leak drops to about 117k under those conditions. This is reasonable, but as you have noted certainly not "traditional". I can add the comment to the schematic that the Master Volume pot could be dual-250kA or dual-1MA.

Still, good job on trying to decipher a schematic from gut shots, I must say Colossal, and thank you for such a tidy PDF!

Dave, great job on that schematic buddy, thank you.

Thanks guys, hope it is of use! I defer a lot of credit to Azatplayer who sorted out a lot of values with his keen eye and has even mocked up a test amp on his bench based on the values we derived in the early discussions (pages 1-4 or so of this thread) just to test some of the assumptions.

[rooster]

OK, I see this. You do have it correctly then, my bad, and thanks for posting the closeup.

Please carry on.....

[surfsup]

colossal sounds like I'll have to talk to azatplayer if he breadboarded one already!

My guess would be like Rhinson's in that it is closer to Voxy PT values; so higher than the usual "18W" iron at 280 or 290-0-290. I would guess 300-0-300 and maybe plates around 360V.

Okay bear with me (thinking aloud). Its a full wave so 300-0-300 will put:
600*0.7= 420VDC at B+ but there's some resistors in there (two 1k 5W)

If B2 were to be 360V and B+ is 420:
B2 = 420 - (voltage drop of one 1k 5W) =
B2 = 420 - (i * 1k) = 360V
i = 60/1000 = 60mA

This is all for one power tube at a time because it is pushpull right? so the 60mA is for one power tube and both 12ax7s, which would be about 5mA so the ptube is drawing roughly 55mA for the screen and plate?

[rhinson]

Is anyone/everyone interested in helping me guiney-pig this amp? I would like to build it but the PT values escape us. My thought is with the VOX night train having a similar setup and running plates at 330V, it might be similar and to shoot for a B+ of around 350 fro some wiggle room on the voltages. Would that be a safe assumption? I don't plan to use PRPs like in the sadie, just regular ol' 1/2watt carbon films and some sozos.

So what I'm asking is what would your guesses be for the PT?

My guess would be like Rhinson's in that it is closer to Voxy PT values; so higher than the usual "18W" iron at 280 or 290-0-290. I would guess 300-0-300 and maybe plates around 360V.

We do know that the cathode bias resistor for the X10 is 125R so the voltage can't be too smokin' hot as it's probably running close to max dissipation for each tube already. There are "sag" resistors in front of each diode in the rectifier which are 1k apiece. This would add some voltage drop.

well i was actually just talking about the ouput trannie there

but i'd guess he uses a vox/18watt marshall style power trannie. that's the reason for the 1k in series with the hv sec winding----so he can use these without a rect tube to drop the voltage and still be in the good range to not stroke out the tubes--also benefit from the more solid low end and faster response the diodes give. i'd say it's probably a 290-0-290 n.l. --probably 31 or 30ga wire for the wind. my guess is he tries to keep it under 340v on the plates at idle, given there's a 125ohm cathode resistor, unless he just likes to run them hot as hell, and that's not out of the question! rh

[amplifiednation]

SCHEMATIC UPDATE

1) Removed 100pF fizz cap across PI grids
2) Added fixed cut circuit as seen in latest photos (heat shrunk)
3) Added a couple of comments

Collosal, amazing job on this schematic. I am in for the build. That amp sounded great in the clips and looks fun to build. Your design is very well laid out. Great great job.

Surfsup, if you have the excel sheet for bom I would love to team up on the build guinea pig.

[angelodp]

Taylor, I think you have been bit. Go man go. I am lusting on that amp as well.

Ange