#1
I'm using a lightbulb in series with my speaker to act as a cheap attenuator and compressor for my valve junior head, and it works nicely.

My only worry is that with the amount of playing I do the bulb is sure to burn out sometime, leaving the head powering an open circuit.

I have heard of wiring a suitable resistor in parallel with the speaker and light bulb but if the light bulb does burn out the net impedance will increase, will this damage the head?

Does anyone have any other ideas to prevent an open circuit from burning out the output transformer?

My idea is to run the power supply from the mains into a thermal fuse which would lie across the output transformer and in the event of the head being powered up with no speaker the OT would start to heat up and thus set off the thermal fuse,
Does anyone see any flaws with this theory?

Thanks in advance guys.
#3
Have you taken into account that the lightglobe has resistance that will add to the total impedance of the speaker? Even if it doesn't blow you are going to be putting added strain on the output.
What you need is an L-Pad of sufficiently high a power rating. Stop doing what you are doing now, it can only end in tears.
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#4
Dumbass kids...
Everyone is entitled to an opinion.

Feel free to express yours so I can make an informed judgement about how stupid you are.
#5
Quote by Cathbard
Have you taken into account that the lightglobe has resistance that will add to the total impedance of the speaker? Even if it doesn't blow you are going to be putting added strain on the output.
What you need is an L-Pad of sufficiently high a power rating. Stop doing what you are doing now, it can only end in tears.


It's the natural compression I'm looking for and the same idea has already been used by amp manufacturers in the 60's,
I know what you mean by the bulb adding resistance but its a 3 watt amp and a small light bulb, I'm not going all Tesla on this, an amp tech friend popped around this morning and checked the wiring of it and had no objections, however he said I'd have to use a mathematical formula for total impedance if I keep the resistor in the circuit
#7
Update! After wiring in a pcb and two red leds, I shorted the attenuator bulb and with some crafty wiring (thanks to Mikey) the leds now light up indicating the bulb short and an assortment of resistors takes up the load.
All tested with my new multimeter! (the only flaw with my old one is it didn't like electricity)
Thanks guys