Dummy - load

[JensRasmussen]

Hi all,

What sort of dummyload is best for testing amps ?

I have a ohmic load that can be used for amps up to 200 W (both 4 and 8 ohm). But is it enough to just use an ohmic load, or do I need to add a capacitor or inductor ?

What do you all use when testing ?

How about modelling a speaker with crossover, how is that done ?

thanks

\Jens

 

[Nelson Pass]

More Gratuitous Haiku:

On bench, dummy loads
For best subjective results
try loaded dummies

 

[JensRasmussen]

Thanks Mr. Pass

He he funny, but on a serius note what do you use ?

\Jens

 

[Nelson Pass]

Those big 250 watt Dales that you've seen, mounted
on old Threshold sinks.

 

[Peter Daniel]

That's my dummy load.

 

[skaara]

I make my own resistors (4 resistors, 2x8ohm and 2x4ohm) for dummyload.. I used cekas wire (this wire is used in big electric cookers, i get it when we went in factory that makes them with school..), one resistor can handle some kW I guess.

 

[Lisandro_P]

You can always dump the resistor(s) on a bucket of water... not nice, but it works like a charm

 

[JensRasmussen]

So all of you just use an ohmic load.

I guess mine is fine then

\Jens

 

[Kilowatt]

You can put your resistor(s) in parallel with a 2uF capacitor for a better test. Just be warned that some amps won't like it.

 

[JensRasmussen]

Loads of fun

Hi Kilowatt

Well, I heard from a fellow dane to put 1 µF parallel over the resistors. Haven't tried it yet, but I'll post the results (I hope that nothing will be burned)

Thanks

\Jens

 

[alfsch]

Hi,
for testing amps i made a box with some switches, to test different loads:
1. 8 ohm
2. 8 ohm
3. 0.33 ohm + 1u (MKP) series
4. 3 ohm + 22u (MKS) + 0.6 mH series

with 1/2 test: no load, 8, 4 real
with 1/2/3/4 test complex load;

with sine/triangle/square wave testing you see all problems, a amp can have... i youse this for about 15 years with success...

regards
alf

 

[phase_accurate]

Another kind of load I have seen more than twenty years ago, was at the quality control of Studer (Revox).

They clamped 4.7uF capacitors, that were soldered to a specially made adaptor plate, directly to the output clamps of some receivers and fed the amps with a signal in the 10 to15 kHz range.

You can of course not use this test to figure out the maximum power an amp can deliver but you can test it for robustness and reliability (thermal stress and stability). They were run this way for about one hour as I can remember. You could even hear sound emerging from the amps !

Please be aware if you want to try this yourself !

Regards

Charles

 

[skaara]

2uF cap and you burn some amps

 

[Kilowatt]

But a good amp will do just fine into 2uF. It's like the ultimate test of stability, do it at your own (well, more like your amp's own) risk.

Personally, I wouldn't.

 

[jleaman]

hey potter what is your power rating on yor dummy load..


I want to buildone..

 

[jleaman]

i used to havea huge dummy load 1.5 kw but i lost it it was basicaly a dryer power element and it worked awsome..

J'

 

[JensRasmussen]

Hi JasonL

My dummyload is made from 8 * 4ohm resistors, rated at 50 W each.

I have made it so I have 2 * 4 ohm 200 W (for stereo test)

I have installed banana plugs on it so it's easy to change it into 1 * 2 ohms 400 W.

Hope it helps

\Jens

 

[jleaman]

Got at pic i'd like to see it...

i should make one..

 

[JensRasmussen]

My dummyload

Hi JasonL

Here is a pic of my dummyload

\Jens

 

[yugaaa]

the best dummy load i have used is a bucket of salt water with 2 electrodes in it wich is connected to the speaker outputs