DoubleCavers5.3

[shooter]

started spring clean and found pieces parts 
since the 2 tubes are 6SN7, went looking and found Blue Velvet's pre.  Gonna splice into the RCA stereo SS 10W PA.

gonna try something different, I'm gonna drill out the turret board for the octal, put turrets on top with tube.  Put standoffs in the 4 corners and have a piece of colored plexi or, (if it don't break the bank), glass to "cover" the parts, with hole for tubes to stick through.
layout is for 1 channel only, but they look the same 

EDIT
update layout
link to original build
http://enjoythemusic.com/magazine/equipment/1103/midmonth

[sluckey]

That's a lot of NFB on the second triode. What's on the input? Where does the output go?

[shooter]

the input, I believe, set up for "phono" in level signal, gotta do sum webin there to be sure, the "out" will get hacked into the SS PA amp

I've driven the SS amp with both line level and phono level
The "frontend" on the schematic were added for another build.

[shooter]

trying to do the PS on paper, it's not as fun as gatorclipin 

The design folk say I need 204vdc @ 40mA for feeding of the 6SN7s   
Calc my PS test Dummyload = 5.1k @ 8w
My donor tranny is XPWR050-120
Sec 250 – 0vac at 200mA
Cheatsheet shows FWB into Cap = .9 X 250 = 225v avg
Idc = Iac * .65 =  130mA dc avg

I’m trying to guess at R1 & R2
Since RL needs 204v drop, R1 + R2 drop 21v. @40mA = 525ohms


So… guessing each 330ohms with fudge factor?
Am I askin for problems with a low R big C filter stages?

Thanks

[PRR]

Why have you figured current demand from this stray-find transformer??

The current to run the 6SN7 preamp can be figured from the notated plan for the preamp. I get 57mA.

I can't believe "204V" is critical, but a little more figuring shows it runs the poor 6SN7s HOT, so we don't want more.

250VAC makes 350VDC. You want 200V or 150V drop. 150V/0.057A is 2,600 Ohms. You want two maybe three R-C stages. Total heat in droppers is a whopping 8.55 Watts! I would start with three 1K 10W resistors. That may come a little low of 204V, but best to start low and trim up.

[shooter]

I can't get the link to work, their PS is insane 
part of the 57mA you got goes to feeding a pair of 0A2's.
the notation says 40mA for 6SN7 the rest for the voltage regulators

Ya, their sonic testing showed the best results with the N7's at 70% or better.  They compromised at around 50% idle

250VAC makes 350VDC

That's where I get hung up on paper, the Hammond design sheet for rectifiers says .9X for avg, 1.4X for pk which trips me up since I'm guessing idle current near 20mA, (avg??) with peak at 40mA

I can't believe "204V" is critical

The cathode R is 326 
I cheated and found 2 carbon comp 330ohmers that measure 327 

[shooter]

Maybe I had a break-through, or break-down 

250 X1.4 = 350
250 X .9 = 225
Tranny rated @ 200mA I need 20mA to idle, 40mA max

So;
20mA = 10% of 200mA, 90% of 350v = 315vdc
Does the logic track??

[DummyLoad]

dude! XPWR050? you're trying to wedge a cat 399 into a fiat 500.   

suggestion: use a pair of 120V:6V 2A radio shack PT back2back - the 120VAC sec. will produce around 180VDC with that load.


--pete 

[shooter]

dude!

I DO, have future dreams for an upgrade, but future $'s...... 
Ideally I replace the 10wSS stereo with 2PSE /ch EL84's.

besides it's running 12deg below normal here so a little handwarmer is nice 

[PRR]

> part of the 57mA you got goes to feeding a pair of 0A2's.
> the notation says 40mA for 6SN7 the rest for the voltage regulators

I have not seen any 0A2s posted here.

I get 57mA *simply* by Ohm's Law on the plate resistors and their voltage drop.

> their sonic testing showed the best results with the N7's at 70% or better.  They compromised at around 50% idle

Well, they could just pick plate resistors which did not strain the poor little 6SN7s. Given the heavy load, hotter is better, but this is a crude approach.

> Hammond design sheet for rectifiers

Which has errors. And can easily mislead.

> says .9X for avg, 1.4X for pk which trips me up since I'm guessing idle current near 20mA, (avg??) with peak at 40mA

Cap-input rectifier filter, you only want the 1.414 *Voltage* factor.

Choke-input uses the 0.9 *voltage* factor.

I don't know why you apply these numbers to *currents*. Or why you seem to think the power supply DC current will have a "peak". The DC current in this affair is dead constant. (V1 goes up, V2 goes down, sum stays the same; also any preamp's signal current should be totally absorbed in the filter caps.)

[shooter]

here's where I stole the idea, sans PS

http://enjoythemusic.com/magazine/equipment/1103/midmonth/bluevelvet.htm

Cap-input rectifier filter, you only want the 1.414 *Voltage* factor.

thanks
scribblin notes to self 

I don't know why you apply these numbers to *currents*.

1st pass, I never paid attention to Iac vs Idc in the tranny specs before. was surprised to "see??" a scale factor like .65 which I'm thinking on paper makes most of my "designs" iffy, ie, need a 100mA, got a 120mA tranny, good, next step....

2nd pass, my quirky understanding;
I've always "seen" I, R, E as equal partners in the same equation, change 1 the other two gotta compensate, so I sorta "talk" in terms of I since the other 2 are just potential energy until they can agree and get I moving,
Ya I know, "glad I didn't have that nut case in my class "   

I do appreciate the effort though 

[shooter]

got the iron hot for 5minutes 
I screwed up my order to Doug enough I thought he'd ban me from shopping 
He still managed to re-package and have it here on the 2nd work day!!.  Been 5 work days and my PE order made it to "shipped" 

[shooter]

no parts! BUT the air had almost imagined heat, so went barn scrounging, found a nice piece of redwood.

[shooter]

sadly the Bose funded the winter avoidance acct, so I pulled the trigger for a poor mans replacement, weeded through 10 speakers <300

https://www.stereophile.com/standloudspeakers/204klipsch/index.html

[shooter]

drew the layout like I was doing a chassis build 
so cris-cross wires under.  this build already has more self induced bugs than all my others combined  , ah well, I kinda miss troubleshooting 

[shooter]

on hold for a weekish, possible snow tomorrow, and the speakers haven't been broke in 

already stole the 10W stereo, so runnin through a mono-block, close 'yer eyes and ya see separation!! 
and they ARE sweet soundin 

[shooter]

stuck all the schematic pieces together 

still breakin in the speakers, but I get dirty looks when I go downstairs 

[shooter]

took the filter stage and sent off for a Doug turret, had 2 made.
bought new cutoff wheels for the dremel, IIRC 1.5" X 3"

[shooter]

there was enough time in the day to get the board cut and jumpers in
it's 9:20 

[shooter]

It's only 8:20, but spent the day OUTSIDE
managed to get the parts ready for solder rainday

[shooter]

got tired of hauling ballast around outside so a little work indoors
 

[shooter]

waiting for whatever crap Willabe is gonna send across the big pond 
re-thinking the redwood, not ruled out yet, speakers got 100hrs sooooo....
4:20 soon, power tools down for the day 

[shooter]

on hold while the speaker out jacks show up 
That's ok, building a kayak arc so we can escape in a day or two 

Heath kit 2.0

[shooter]

Great day! Got Mama to the salt free ocean, picked up 3 new old vinyl for test driving.  Had to force the paint in the wife's oven, so far so good 

AND I started!!

[shooter]

TOOO Sunny for solder!
1 wire n a gatorclip and PS is ready for test
It musta been good    when I laid out the lines for the CRC rail 

[shooter]

repair bench waiting on parts, weather got the M month wrong!
hot iron tomorrow, maybe

[shooter]

EPIC FAIL 
the DC side was good, but the AC side, NOT.  Hummm, odd phase-shifting, but that was inside the FBloop along with some 52khz positive lobe thing 

ALL is not lost though, the sand side works just fine, the "foot_print" for the tube board is close enough for the mono brick from here;

http://el34world.com/Forum/index.php?topic=23598.0

That will drive the Altec 15" (center channel)

and in the mean time, I gotta go flip the vinyl