PP to SE

[DummyLoad]

I'll make one billion dollars. Mmmwwwuuuuha, Mmwwwuuuuhaaaahaaa, Mmmwwwuuuuhaaaaahaaaaahaaaahaaaaaa!!!!!

oh lordy no... another plotting total world domination. 

it'll cost the little guys too much money in legal fees to enter a patent fight

and the only folks that come out ahead in such paltry litigation are the lawyers... win or lose, they get paid.

some days i hate the modern world...

back to the switch topic, pyotr belov was showing me an amp he designed this afternoon that has a selector to switch from 1 tube SE or 2 tube SE or 2 tube P-P and, 4 tubes P-P, all P2P hand wired built in one of the original hoffman chassis with the welded-on end plates. it used a stacked multi-pole rotary switch that switched the primary and secondary taps.

--pete

[printer2]

Sorry if you covered it but I only skimmed the posts and did not get too involved with the theory. Here is a Class A P-P and SE amp I built while I was taking part in a $100 guitar amp challenge. The important switch is the one on the top of the PI output. Turn off this signal and the top output tube coasts and the bottom one delivers the power. No need to change impedance.

[jeff]

I'd suggest putting the switch after the cap only to keep the high voltage off the switch, but I'm paranoid.

"I was taking part in a $100 guitar amp challenge"
What's that?
Are you saying the amp only cost $100 to build?

[printer2]

With just the Tweed tone control it would have been. The rules were you had to account for the amp parts not including the chassis or box and the parts had to be generally available, no closeouts or one of a kind buys. I never used the actual parts as listed but given the prototype with the similar parts I used it should work.

Not bad idea on the switch.

[HotBluePlates]

I promised the name of transformer that could provide both SE and PP service from one piece of iron.  Lundahl model LL 1663.  It has two seperate coils on the primary side.

If you look at Lundahl's Output transformers, all of them are specified for SE or PP operation.

But if you look closely at the ratings, you see that the two primary halves (or multiples of two, for primary windings with additional sectionalizing) are placed in series for PP or parallel for SE.

You will also see that the power handling capability for push-pull operation is generally about 5 times that of the same transformer in SE mode.

It's not magic, but the same things we've always said: a chunk of the core's ability to handle magnetic flux for signal is eaten up by the unbalanced d.c. when used as a SE transformer. That's the main reason why the big power handling difference for the two modes for the same Lundahl transformer. The same thing will happen with a Fender transformer...

[PRR]

Also I think that series is custom-gapped for your desired DC current, near-zero )push-pull) to 450mA (huge SE).

[HotBluePlates]

...

[sluckey]

a different example is 100w is twice the power (measured logarithmically) of a 10w amp.

Would you please explain that statement?

00dbm = 1mW
10dbm = 10mW
20dbm = 100mW
30dbm = 1W
40dbm = 10W
50dbm = 100W
etc, etc...

A 100W amp has 10 times the power of a 10W amp. Or stated logarithmically, a 100W amp has 10db more power than a 10W amp. Logarithmically speaking, an amp that has twice the power of another amp has 3db more power.

So, you can see my confusion.

[DummyLoad]

a different example is 100w is twice the power (measured logarithmically) of a 10w amp.

Would you please explain that statement?

00dbm = 1mW
10dbm = 10mW
20dbm = 100mW
30dbm = 1W
40dbm = 10W
50dbm = 100W
etc, etc...

A 100W amp has 10 times the power of a 10W amp. Or stated logarithmically, a 100W amp has 10db more power than a 10W amp. Logarithmically speaking, an amp that has twice the power of another amp has 3db more power.

So, you can see my confusion.

or in terms of dB Watt; 0dBm = 1mW = -30dBW

0dBm is power referenced to 1 milliWatt
0dBW is power refereneced to 1Watt

1W = 0dBW, so then
10W = +10dBw
100W = +20dBW -

so, 10W to 100W is still +10dB >.

10W = 10dBW now double power to 20W = 13.01dBW

yes, i'm confused as well.... 

--pete

http://www.rapidtables.com/electric/dBW.htm

http://designtools.analog.com/dt/dbconvert/dbconvert.html

http://www.radio-electronics.com/info/formulae/decibels/dBm_dBW_table.php

[HotBluePlates]

Forget I said anything...

We're getting way off topic into things that don't relate to the original post