1482Esq

[shooter]

followed Sluckeys link for dark on 1482, found Platefires take, it's getting colder so...

still sketchin, my OT is 1250:8 so I gotta do some creative figurin for PA tubes n speakers.

[DummyLoad]

followed Sluckeys link for dark on 1482, found Platefires take, it's getting colder so...

still sketchin, my OT is 1250:8 so I gotta do some creative figurin for PA tubes n speakers.

what's wattage spec on that OT? 1/2 primary Imax? the latter is usually a longshot spec. (rarely given).


--pete

[PRR]

> my OT is 1250:8

Seems unlikely.

[shooter]

Seems unlikely.

It was late 

It's Edcor (no number yet), 1250:4 at 250mA 25W.
I used it in a QSE el84 audio, bought 2, one left, n......
leaning to EL34's again, but I don't have any.
6V6 I have, got 2 16ohm speakers n 1 8ohm but it's a couple hours before my brain wants to get serious 

[DummyLoad]

6CW5 - 200V B+ in AB1 with a 8 ohm secondary load.

http://www.nj7p.org/Tubes/PDFs/Frank/093-GE/6CW5.pdf

[jjasilli]

where is this link?  followed Sluckeys link for dark on 1482

[shooter]

http://el34world.com/Forum/index.php?topic=25020.0
Pg1 rely 33

also, this IS an experiment, the OT IS for SE, with a 40% tap for screens, but as an experiment was gonna try and use it PP and balance the PI's 68k's for ~~symmetrical a/b.

[shooter]

2shots of espresso and a coffee later;

looks like 6V6 will get close into a 32ohm(2X12 16ohm ea) load based on a quicky look at datasheet

[DummyLoad]

NOT P-P but just a suggestion. seems like it would work - it has a god reference. :p


--pete

[shooter]

 

60W pdiss!!! 

I do have a PSE 6V6 sketched, if I got the datasheet correct should want ~~ 2500ohms plate. (2X12 wired as 8ohm)
the main reason for PP (not a big fan:), I can add Steve's tremolator, which keeps it 1482esq 
not sure where I'd be able to use it to wiggle pre-amp/driver tubes if I went PSE

[shooter]

Gonna stick with the PP, added Sluckeys tremolator circuit, probably use the extra 1/2 tube to convert TS recovery stage to DCCF.

I borrowed with impunity Platefires NFB circuit.  He has it at 8ohm tap, i'll be using the 4ohm, will my divide by 2 math work as starting points for the R's in the NFB circuit?

thanks
dave

[jjasilli]

I'm not getting how this amp is 1482-ish

[shooter]

cuz that's where inspiration hit me 
once  that thing happens, as an artist I've learned to go with it
so, following "why so distorted", link to Platefire, lightbulb, ........... 

[DummyLoad]

Gonna stick with the PP, added Sluckeys tremolator circuit, probably use the extra 1/2 tube to convert TS recovery stage to DCCF.

I borrowed with impunity Platefires NFB circuit.  He has it at 8ohm tap, i'll be using the 4ohm, will my divide by 2 math work as starting points for the R's in the NFB circuit?

thanks
dave

sqrt2 * Rfb @ 4ohm = Rfb for 8ohm. to go the other way, take the inverse - 1/sqrt2 * Rfb @ 8ohm = Rfb @ 4ohm 


--pete

[shooter]

Thanks Pete, now to find the sqr root key   

[shooter]

Squared the roots, tweaked the schematic.
any flashing red lights I missed? Or like me, dim bulbs? 
(PS rail R's are just placeholders till tweaking time)

[SILVERGUN]

tweaked the schematic.

Don't forget to label V1,2,3 so none of these crazy kids try to use all 12AU7s

[sluckey]

any flashing red lights I missed?

Hopefully there will be one inside that optocoupler. I'm really interested to know if that will wiggle the 6V6s in a strong good way. Keep us posted.

BTW, when did you get back into push/pull?

[shooter]

Don't forget to label V1,2,3

they are labeled V1A, V1B.....tube type optional
N ya, 1 or 2, maybe 3 will be AU7, what of it 

when did you get back into push/pull?

I haven't really, I'm just faking it 
trying to use up the weight laying around the house, It has been ~~ 4yrs since the last time so guess I wanta see if I still can 

[PRR]

> any flashing red lights I missed?

There's no NFB until you ground the other side of the secondary.

Using a 1.25k OT as a 8k OT is liable to shave two octaves of bass. (However it is a hi-fi OT so it may end up OK for gitar.... downside is it is about 4X the weight you really needed.)

[DummyLoad]

Thanks Pete, now to find the sqr root key   

X^y is your sqrt key. sqrt is 2^.5

--pete

[PRR]

.

[DummyLoad]

.

[DummyLoad]

back on topic...

buy some EL34.   

EL34s with 32Ω secondary load is near to perfect fit for wonky OT.

see mullard EL34 datasheet.

--pete

[sluckey]

.

[shooter]

 
HA, I used the Y fishhook X one,

The NO NFB I think Platefire designed like that hence the funky Center off switching.

N buying is out for now, I spent my Christmas money on SS heavy metal etal 

[shooter]

I found Platefires P2P layouts, NICE work!  If anyone has done a board version for reference 

downside is it is about 4X the weight you really needed.

Cost about that much more also 
I am willing to entertain a swap with someone all SE geeky  (pm me)

[PRR]

.

Well, yes, mine defaults to Sci mode; but I figured it probably comes up in BASIC mode for most people.

I have a slipstick and a TI-30, so I don't use WinCalc often. Is there a way to lose that wide useless side-bar?

BTW, calculators with Square Root have been under $2 for like 20 years now. I have seen 50 cents. Dollar stores often have a SqRt calc cheap. My grocery store has a $2 SqRt calc but they want $4 for it. If you want a "real" calculator, WalMart sells the TI-30(Xa) for about $9. Try to get it to turn-on and do something to show the decimal point-- for several years they used dots too small for anybody who was booted out of school a long time ago.

[shooter]

Is there a way to lose that wide useless side-bar?

Not that I've found.  when I was trying to teach myself Python I tried to CALL the calculator sub, hung the system.  moved on to the call for a usb port, really trashed the system, gave up on learning C 

[shooter]

I stole this question from this link
http://el34world.com/Forum/index.php?topic=25086.50;topicseen

Hey I have a layout question

?

stole a couple pics from current threads

the real question, does anyone know, have any "best practices" for spaghetti builds?
the 1482 layout is spaghetti type example

I get the P2P clean, well thought.......
but I've looked at these type "examples" and cannot find ANY "discernible patterns"

thanks
dave

[shooter]

Did some chip throwing on the table saw, I like sawdust better!

for now, terminal strips, in some logical arrangement on the underside of top.  bottom will slide in "tracks" on the main chassis (previous casting:), sides caped with wood, copper lined 

toying with Dougs BJ tube board suspended below so ~ 1/3 of the 12??7s are visible    NOT built for gigging 

[shooter]

re-worked layout, edited a perfectly good layout for my use Thx 
no BJ board, lots of metal work 

[sluckey]

Don't you wish you had Visio?

There are several real P2P amps on my website, some simple, fairly clean, also some boogers. Don't let the Maggie M10-A scare you!

BOO!   

[shooter]

Don't let the Maggie M10-A scare you!

HA;
I rode the 7Sea's, climbed vertical rock for fun, taught other ppls teens!  not much left to scare me 
I will take a look, thx

[shooter]

 
ok, I was wrong, the orange fuzzy stuff from Chester's Chevy van was kinda creepy 

[shooter]

got 2 free "blanks" from my office supply Ladies, they like me 

1st doodle, lookin like spaghetti 

[shooter]

from here;
http://el34world.com/Forum/index.php?topic=25086.0
I grabbed the trem.tst, then got confused 

It's a semantics confusion, Isn't the original INT closer to "bias very" and the circled INT "signal very"?

thx
dave

[sluckey]

I have no clue what you just said. 

[shooter]

from what I've learnt/learning there are 2 basic tremolo "insertions" one type "bias vary" usually at the grid of fixed bias tubes with 2 mixing R's

the other "type" insert at cathode of a pre-amp

I'm trying to get the "proper terms" in my head or on paper.

I have 1 type "mixing/blending" with signal
the other type altering the tubes bias causing the signal to "alter" at trem rate NOT mix.

your schematic "seems" to be both types, just trying to note which is called which.

[sluckey]

I'm a little more clear headed this morning.      Now I understand. But, in my mind both are bias vary circuits. One circuit varies the bias voltage on the cathode of a small signal triode. Not much trem signal amplitude needed. The other varies the grid bias voltage on the power tube. It's true that the grid voltage is normally zero, but that's only half the info. The bias on the output tube is the difference in voltage on the grid and cathode, and that may be 15 or 20 volts. Now put a slow moving 20V_pp sine wave on the grid and the grid voltage slowly swings + 20V, centered around zero. Seems like bias vary trem to me.

[shooter]

I'm a little more clear headed this morning.   

mee2    although that means back in the crawl space n tin-knockin 

your explanation is "where I'm at" sept wiggling the grid of a self biased PA tube, that one's still full of squirrels n bats.
Rk typically sets bias, G1 AC signal "just" gives the tube something to amplify (input sig +/- trem signal) not alter "bias" 

[sluckey]

G1 AC signal "just" gives the tube something to amplify (input sig +/- trem signal) not alter "bias"

The AC signal on any amplifier grid absolutely does vary the tube bias. That's how amplifiers work. Small ac voltage on the grid varies the bias and causes current through the tube (and plate resistor) to vary. This varying current through the plate resistor causes a larger varying voltage to be dropped across the resistor. Abracadabra. You have gain.

Let's do it differently... No signal, just a linear pot on the grid of a cathode biased tube. (Just for shits and grins let's call the pot INT.) We have a +12v on the top side of the pot and we have a -12V on the bottom of the pot. With the pot set to the middle we send zero volts to the grid. Let's call this the quiesent state. Zero volts causes some current to flow through the tube. A certain voltage will be dropped across the cathode resistor and a voltage will be dropped across the plate resistor. Everything just sits like that in a quiescent state. Now crank the pot all the way down to -12V. This will cause the tube to conduct much less, the cathode voltage will decrease and the plate voltage will increase. Notice that the plate voltage did just the opposite of the grid voltage. It's inverted. Now crank the pot all the way up to +12V. The tube conducts heavily. Cathode voltage goes up. Plate voltage goes down. Inverted again.

If you're still awake, try this... Crank that pot back and forth about 5 times per second. What do you think happens? Are you varying the bias? Could you call this bias vary tremolo?   

It makes no difference if you vary the voltage on the cathode or the grid. The results are the same because bias is defined as voltage difference ***BETWEEN*** grid and cathode.

[shooter]

If you're still awake

 
ok, the bats n squirrels have been replaced by happy birds singing! 

so now back to my original thought that got me all sideways 

IF I use a BIG wabble on G1 experimenting should I keep an eye on tube current since SE bias is typically "set" for 90 -100 % dissipation or is the low duty cycle "low enough" not to push dissipation to worrisome places   

LUNCH BREAK 

[sluckey]

IF I use a BIG wabble on G1 experimenting should I keep an eye on tube current since SE bias is typically "set" for 90 -100 % dissipation or is the low duty cycle "low enough" not to push dissipation to worrisome places

Nope. Just build as if there were no tremolo. Ground the grid resistors or just set the INT to zero. BTW, the wiper of the INT pot is a great place to put the footswitch. Set the bias as you normally would. Then lift the junction of the grid resistors from ground and connect to the wiper of the INT pot. If it turns out you have too much intensity your ears will tell you. If so, just put a resistor in series with the top side of the INT pot. Experiment with resistor value until you have a suitable intensity without "whoop whoop" or thumping/pumping in the speaker. And if you really want to prevent the grids from going positive, just put a diode across the INT pot so it clips the positive half cycle of the tremolo signal.

[shooter]

just put a diode

I like it!

I'm gonna use pull on INT pot for trem on/off and pull on speed pot for swamp on/off
BUT I need long thread mounting, that's a hunt for another day 

thanks for the clarity, I'll try not to ask any goofy questions for 2 days 

[shooter]

updated doodle
change notes next 

[shooter]

found ~ 6 errors 
wired 3 more circuits, came up with a question;

the trem circuit needs 5 "fly" wires, any downside to using cat5?
If I fly the hypotenuse ~ 6", if I skirt the sides ~ 15"
if cat5 is out any downside bundling and taking the long way ?

thanks
dave

[sluckey]

I'm sure silvertone would have specified CAT5 if it had been around in the '60s.   

[shooter]

 
I was 'ol ppl shoppin today at lake M.  looked EVERYWHERE for a press-board, press-cardboard box for the chassis 

that said, I want a 5E3 killer 
1st pass will probably fall short with the OT, but I'm an optimist 

none of the trem wires seem to carry sensitive stuff and I still got 100's of ft left. 

[shooter]

On paper I’m soldering 68K at pin 2, jumper 2 to pin 7

Has anyone found the single R problematic compared to 2 R’s?

Thanks
Dave