PT CT light bulb to ground

[Andy Le Blanc]

Been noodling on the bench, and I just couldn't resist.
The amp I'm fiddling with uses generic 50W fender replacement trans..
There's been quite a bit on the forum with vvr and other ways to drop the
B+ supply to power tubes, zener strings, and light bulbs.

So I tried lifting the CT of the PT and dressed it through a standard medium
light socket and fired up the amp to "see" and "hear" what happens.

100w bulb; amp ran fine, measured around 4v ac at the ct, slight drop in the
supply V DC..... The bulb eventually got warm, there was thermal noise
from the bulb as it barely heated.

60w bulb; amp again ran fine, measured around 18v ac at the ct, slightly more
drop in the supply V DC.... the bulb light faintly, heated, no noise

The 60w changed the presentation of the amp, in a nice way, still had the
power but the tone color was different, It was a surprise, there might be something to it.

I've read about other "bulb" applications, they are utilized as a CCS or a
constant current source, it seems to be valid approach even for a guitar amp.
There is a usable voltage drop and a degree of current regulation.
I'll try a few different wattage's too and see about the V drop at the ct.

[Structo]

What was that amp we talked about recently that used the light bulbs for attenuation/ scaling?

Seems it had several for different amounts of attenuation.

[Andy Le Blanc]

Oh geez..... wasn't that far back. About "Samamp".

A single 15w all most fully lit, 98vac at ct, really quiet, the tone suffered.

A single 25w half lit maybe, 68vac at ct, 10th or 8th the power still usable
tone and response.

A half dozen bulbs sockets and switches, parrallel connected between the ct,
and ground, just add or remove a given number of bulbs for the attenuation,
seems to work.

[Andy Le Blanc]

light bulbs seem to work as power attenuator, simple vvr.

I still need to gig one out to know, it sounds good in the shop.

So .... anybody got an idea to chassis mount a socket

[Jana]

I'm thinking one or more of those old style porcelain light bulb sockets--a real Uncle Fester creation. For full visual effect you should probably use one of those triode tubes with the anode (?) that clips onto the top of the tube like a spark plug would. A row of knife switches to select which bulb(s) are in the circuit would be a nice touch.

[CapnCrunch]

Hey Andy,

After you put Jana's suggested contraption together, you should dress up like Doc from back to the future. Video your gig and post it here It would awesome!

[Wayne]

light bulbs seem to work as power attenuator, simple vvr.

I still need to gig one out to know, it sounds good in the shop.

So .... anybody got an idea to chassis mount a socket

Just drill the hole a little bigger to accommodate your larger "pilot light" - everything should work out just fine

W

[Andy Le Blanc]

That's a hoot

be careful of what you wish for.

The BIGGEST tube I have is a light bulb from a search light or architectural illumination,

110 V...... doesn't sound impressive yet, right?

check it out.... guess the watts.

[FunkyE9th]

I think you need to get one of those bathroom light fixtures with a built fan, you get attenuation and cooling, all in one.

[Structo]

Whoa!
That is cool!

Is that a metal halide light bulb?

Check out the screen grid on that bad boy!

[Andy Le Blanc]

It's a GE G96 120v 10K w, and as far as I can tell its just a big light bulb.

It has temperature stamp on it 3350 k, crazy....

[Wayne]

We've got 120V 1000W halogens here at work but hands down, you win the prize!

I wonder if 3350 K refers to the color. Isn't lighting color measured in Kelvins?

W

[Lonely Raven]

We've got 120V 1000W halogens here at work but hands down, you win the prize!

I wonder if 3350 K refers to the color. Isn't lighting color measured in Kelvins?

W

3350k would probably be the color temperature. That would be a very warm yellow.

[selloutrr]

Cheap mounting

http://cgi.ebay.com/Leviton-Threaded-Ca ... 5ae00da8dd

http://cgi.ebay.com/Porcelain-Lamp-Hold ... 5198d1849c

[angelodp]

3200k is a 'normal' light bulb color temp. Thats right Kelvin. Its all relative to what you record the light on, but a camera that has a symbol for 3200k.. a light bulb.... will see that 3350k as slightly cool, compared to the 3200k.
Warm ( yellow-orangy ) would be 2800k.

Daylight is 5500k - average.

Cheers A