dirt cheap load box

ICBM

DJH83004 said:

Agreed IC they are ideal whenever the amp output is not sufficient to have any significant heating effect on the element (hence changing the resistance), and even then I am only talking about if you are trying to take accurate otput measurements at a given frequency. Some of the 2kW PA amps make them cough a bit though 

I don't think there is very much variation of resistance with temperature for a typical kettle element - as Dave measured, the cold resistance of his 2.4kW kettle is 25 ohms, and it will be 24 when hot... at least if water-cooled .

A fan heater with a suspended wire element might be a bit more affected though.

DJH83004

Agreed IC,  was thinking more about the old style 1kW tubular heating elements in placed series which do actually start to give off a dull glow when pushed hard!  

pintspiller

+1 on the Rat. Though I plugged my 100w Marshall into it and it hasn't worked since. Lol.

olafgarten

pintspiller said:

+1 on the Rat. Though I plugged my 100w Marshall into it and it hasn't worked since. Lol.

How far was the amp turned up? The amp power rating is usually how much power it outputs clean, distorted it can be double that, and sometimes more. It's possible that you overloaded the dummy load and damaged the amp. The dummy load is only rated for amps up to 50w.

ICBM

pintspiller said:

+1 on the Rat. Though I plugged my 100w Marshall into it and it hasn't worked since. Lol.

The amp, or the load box?

olafgarten said:

The amp power rating is usually how much power it outputs clean, distorted it can be double that, and sometimes more. It's possible that you overloaded the dummy load and damaged the amp. The dummy load is only rated for amps up to 50w.

Exactly, and if you put too much power into it you will simply burn out the resistor in the load box leaving an open circuit - which is quite likely to damage the amp as well.

Plectrum

Sporky said:

Do different kettles affect the sound? 

Only if you leave the fish in. Then you get a lot more bass.

ecc83

The middling power rating of some soaks bothers and annoys me. The actual resistors are not that expensive so a "50W" box could easily contain 100 watts worth of resistors and the Arcol allycalds at least I know have massive overload capacity, like 1000% for one second!

Yes, 100W Rs in a small box WILL get bloody hot if you abuse it but it will not open circuit and bugger your amp!

We are in an age of "near enough" engineering! If it struggles past the warranty period, "who" give a ****k!

Dave.

pintspiller

@olafgarten @icbm the load box stopped working. I had forgotten about the 50w limit and just cranked the Marshall. The feet melted and there's no audible drop in use.

ICBM

pintspiller said:

@olafgarten @icbm the load box stopped working. I had forgotten about the 50w limit and just cranked the Marshall. The feet melted and there's no audible drop in use.

Were you using it with a speaker cab as well? In that case the amp would be OK. It does sound like you've burned out the resistor.

ecc83 said:

The middling power rating of some soaks bothers and annoys me. The actual resistors are not that expensive so a "50W" box could easily contain 100 watts worth of resistors and the Arcol allycalds at least I know have massive overload capacity, like 1000% for one second!

Yes, 100W Rs in a small box WILL get bloody hot if you abuse it but it will not open circuit and bugger your amp!

Totally agreed. Even a 200W allyclad resistor is not that expensive or that big, and there's really no point pissing about trying to save a few quid on the load when if it fails, it could blow the amp's output transformer.