Critique my schematic, please

[Jag]

WOW!

I got all of that Bruce!!! Thanks, that's why I asked the question, to get a lesson.

[daz]

Ok, i have another question. Why do i need the choke? Can i do without it? Why am i asking? Because i just recieved 1/2 my parts order which included the choke. God god man ! I've had amps with chokes, but not like this. This Effing thing is huge ! It's bigger and much heavier than my 18 watter's OT. The PT is of course heavy as is the OT, and between the 3 of them i'm gonna need a forklift to carry this thing. Tell me again why i need this $32.00, 50 pound chunk of metal?

[Paul P]

Tell me again why i need this $32.00, 50 pound chunk of metal?

In my amp it reduces AC ripple on B+ from 3v rms to .07v rms. Seeing as
1mv is audible I think they're pretty useful.

Hammond says your choke weighs 3 lbs .

Paul P

[daz]

Thats about right, 3 Lbs. The chokes i've seen seem like they probably weight 8 Oz. I can't understand why this one has to be so friggin big. Chassis is gonna be stressed with all this weight. Probably should have looked for a punched steel one.

[Paul P]

Yours does seem to be pretty heavy. My choke, 3H, 100 ohms,
90 ma (I think), is not much smaller than yours but weighs about
one pound. I see weight as a good thing when it comes to amps.

Paul P

[daz]

I must admit it seems to be true in that the best sounding amp's i've owned have had a lot of heavy iron. If thats the case this thing should sound very good because the iron weighs a ton. I'll probably have a good 30 lbs of iron and the rest will be the speaker and cabinet.(and i use a EV12L !) should be a back breaker. I don't like them, but i may have to make this a head instead of a 1-12 combo. at my age a 80-100 Lb amp is not a pleasing thought.

[Bruce / Mission Amps]

Thats about right, 3 Lbs. The chokes i've seen seem like they probably weight 8 Oz. I can't understand why this one has to be so friggin big. Chassis is gonna be stressed with all this weight. Probably should have looked for a punched steel one.

That is a pretty big choke...
Since you own it just use it.
EL34s will need a bigger screen choke (one that can handle more screen current then say a pair of 6L6s).

I was just messing with a custom built amp on my bench and measured the maximum screen current across a 1K screen resistor in a 4 x 6V6 amp.
At full power (about 48 watts and flat out, fully distorted and so that there was no more measurable voltage across my dummy load) each 6V6 tube was pulling 11ma in their screens.
The amp builder used huge 5 watt resistors on the sockets, probably because he read on the Internet you have to have this big ass resistors to be safe....
.011a ^2 x 1000 ohms = about 1/8 to 1/4 watt. In this amp I have no problem using small 1 watt resistors for this application.
Anyhow, add all four of those screen currents up plus the four preamp tubes and the choke is handling 44ma in screen current and about 6ma in the three preamp tubes and 6 ma in the 12AT7 reverb driver.
56ma.
He is using the correct sized choke... about 90 ohms, 70-90ma 3-4Hy choke.
That means that the choke is running at around 1/3 watt and it weighs about 5 or 6 oz.

[daz]

I imagine antique elec. supply would let me return it for another. Is there a particular model/value that would work as well and not weight a ton? My marshall chokes were always much smaller. why is this one so big? I was told elsewhere that 20H/100ma is what i need and that i could go lesser on both specs but it wouldn't be a good idea. Is this thing just abnormal size-wise for a choke with those specs?