Who's the dumbest poster here - Poll

[Ben Waylin]

Those wires look awfully thin.

Which ones ?

 

[psychodave]

Which ones ?

The ones between the resistors.

 

[Ben Waylin]

The ones between the resistors.

Naw, that's 600V Teflon coated wire.

 

[psychodave]

Naw, that's 600V Teflon coated wire.

Cameron made me an attenuator years ago. He used solid wire. I’ll find a pic of it.

 

[Ben Waylin]

Cameron made me an attenutor years ago. He used solid wire. I’ll find a pic of it.

Yeah, I buy that from ValveStorm

https://www.valvestorm.com/Products/Wire

Don't forget to smash that like button, and vote for me !

 

[glpg80]

Resistors in parallel, resistance halves and power handling doubles.

Except you forgot to account for thermal degradation. That principal doesn’t work for high power dissipation resistors - you have to have a thermal coupler that acts as a safety off to prevent thermal runaway and risk of fire.

 

[Ben Waylin]

Except you forgot to account for thermal degradation. That principal doesn’t work for high power dissipation resistors - you have to have a thermal coupler that acts as a safety off to prevent thermal runaway and risk of fire.

The previous photos kind of hide it, I know..

But there's a large, finned aluminum heat sink under the power resistors (dummy load portion of circuit), and they are bolted to it with heat sink grease.

 

[glpg80]

The previous photos kind of hide it, I know..

But there's a large, finned aluminum heat sink under the power resistors, and they are bolted to it with heat sink grease.

That’s good design practice however it doesn’t nullify the need to know the RMS rating after accounting for thermal heat soak even with fans and heat sinks. Make sure you’re not building a benchtop fire starter hoping you have headroom. 250W resistors seem like a lot but they really aren’t after thermal derating. For example when I spec’d my resistor load for measuring maximum power THD of tube amps I was looking at using thousands of watts of high power resistors to get the thermal stability under control.

Just be mindful of the circuits limits and design a fail safe if you can.

 

[Ben Waylin]

That’s good design practice however it doesn’t nullify the need to know the RMS rating after accounting for thermal heat soak even with fans and heat sinks. Make sure you’re not building a benchtop fire starter hoping you have headroom. 250W resistors seem like a lot but they really aren’t after thermal derating. For example when I spec’d my resistor load for measuring maximum power THD of tube amps I was looking at using thousands of watts of high power resistors to get the thermal stability under control.

Just be mindful of the circuits limits and design a fail safe if you can.

I was interested in how this version would handle heat dissipation. Previous purely resistive units I built would get warm to the touch, after running a cranked 100w amp into it for several hours..

Amazingly, this unit barely gets above room temperature, due to the thermal mass and wattage rating of the resistors.

 

[SQUAREHEAD]

I was interested in how this version would handle heat dissipation. Previous purely resistive units I built would get warm to the touch, after running a cranked 100w amp into it for several hours..

Amazingly, this unit barely gets above room temperature, due to the thermal mass and wattage rating of the resistors.

That’s fantastic, is it more transparent than my ole Hotplate?

 

[Strandberg Junkie]

heat sink grease.

Nickname: thermal paste

Is the unit in this photo shown upside down?

 

[Ben Waylin]

That’s fantastic, is it more transparent than my ole Hotplate?

Here's a really good thread we had going on that very question on TGP a few years ago..

https://www.thegearpage.net/board/i...garding-resistive-and-reactive-loads.2044665/

 

[Strandberg Junkie]

May 08, 2019
A purely resistive load is going to work best for you if you're using it to load down a tube amp and then feed a line-level signal off the resistive load into another amp.

You don't want the static impedance load anywhere near your line level guitar signal out!

Original Power Break Was just a notched power resistor.
THD, Dr. Z, etc. started adding some filtering to the circuit but these are still static loads
in regard to what your amp out is seeing.

 

[Ben Waylin]

Here's another interesting take on it.. the Weber Mass:

 

[Strandberg Junkie]

Here's another interesting take on it.. the Weber Mass:

The Carr Mercury has a built in attenuator that uses the same method as the Weber.

https://www.carramps.com/mercury-v
Ever seen these?

https://fluxtonespeakers.com/how-it-works/

 

[Ben Waylin]

Here's another Weber Mass gut-shot..

Speaker motor, cement resistors and ceramic, sliding-disc rheostat.

 

[psychodave]

Yeah, I buy that from ValveStorm

https://www.valvestorm.com/Products/Wire

Don't forget to smash that like button, and vote for me !

Just voted for you. ?

 

[Diary of a Axeman]

The guys you asked us to vote for in this thread .... some have intelligence and some have hope to being rational or sane .

Proof that MAGA is like Kryptonite to some folks .
Picasso is a rotten soul .... kind of like a syphlitic vagina that has been ran over, repeatedly for a week, like road kill on the intellectual Freeway.... Picasso is a lost cause .... I could feel sorry for him .... but I'd rather laugh at him .

 

[Picasso]

The guys you asked us to vote for in this thread .... some have intelligence and some have hope to being rational or sane .

Proof that MAGA is like Kriptonite to some folks .
Picasso is a rotten soul .... kind of like a syphlitic vagina that has been ran over, repeatedly for a week, like road kill on the intellectual Freeway.... Picasso is a lost cause .... I could feel sorry for him .... but I'd rather laugh at him .

Asoonah Numunu !!!

 

[Ben Waylin]

The guys you asked us to vote for in this thread .... some have intelligence and some have hope to being rational or sane .

Proof that MAGA is like Kriptonite to some folks .
Picasso is a rotten soul .... kind of like a syphlitic vagina that has been ran over, repeatedly for a week, like road kill on the intellectual Freeway.... Picasso is a lost cause .... I could feel sorry for him .... but I'd rather laugh at him .

*kryptonite