PT CT light bulb to ground
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PT CT light bulb to ground
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.
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.
lazymaryamps
Re: PT CT light bulb to ground
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.
Seems it had several for different amounts of attenuation.
Tom
Don't let that smoke out!
Don't let that smoke out!
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- Location: central Maine
Re: PT CT light bulb to ground
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.
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.
lazymaryamps
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- Joined: Sat Dec 22, 2007 1:16 am
- Location: central Maine
Re: PT CT light bulb to ground
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
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
lazymaryamps
Re: PT CT light bulb to ground
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.
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Re: PT CT light bulb to ground
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!
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!
Re: PT CT light bulb to ground
Just drill the hole a little bigger to accommodate your larger "pilot light" - everything should work out just fineAndy Le Blanc wrote: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
W
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- Joined: Sat Dec 22, 2007 1:16 am
- Location: central Maine
Re: PT CT light bulb to ground
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.
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.
lazymaryamps
Re: PT CT light bulb to ground
I think you need to get one of those bathroom light fixtures with a built fan, you get attenuation and cooling, all in one.
Re: PT CT light bulb to ground
Whoa!
That is cool!
Is that a metal halide light bulb?
Check out the screen grid on that bad boy!
That is cool!
Is that a metal halide light bulb?
Check out the screen grid on that bad boy!
Tom
Don't let that smoke out!
Don't let that smoke out!
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- Location: central Maine
Re: PT CT light bulb to ground
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....
It has temperature stamp on it 3350 k, crazy....
lazymaryamps
Re: PT CT light bulb to ground
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
I wonder if 3350 K refers to the color. Isn't lighting color measured in Kelvins?
W
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Re: PT CT light bulb to ground
Wayne wrote: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.
Jack of all Trades,
Master of None
Master of None
Re: PT CT light bulb to ground
Cheap mounting
http://cgi.ebay.com/Leviton-Threaded-Ca ... 5ae00da8dd
http://cgi.ebay.com/Porcelain-Lamp-Hold ... 5198d1849c
http://cgi.ebay.com/Leviton-Threaded-Ca ... 5ae00da8dd
http://cgi.ebay.com/Porcelain-Lamp-Hold ... 5198d1849c
My Daughter Build Stone Henge
3200k is normal
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
Warm ( yellow-orangy ) would be 2800k.
Daylight is 5500k - average.
Cheers A