Dummy load , high power audio, add ons ?

[N_Cook]

50V , low wattage lamp (or seriesed lower V ones) (assuming normal testing
is 10 to 20W range) to visually show if the volume is set too high, also if
high level high f oscillation on the output; sacrificial, fusewise, if
overdriven.
AC voltmeter , preferably autoranging for possible overload situation, to
measure/long term monitor the RMS power.
High power speaker pot (plus droppers) leading to a low quality ,
sacrificial ( for intitial maybe problematic testing) small speaker, for
basic possible intermittant sound, on/off, indication. Can be switched out
by plugging in a good quality speaker for audio monitoring of quality of
sound issues in otherwise known good amp.
Provision for coupling in a scope for distortion monitoring, when necessary.
Any other add-ons that others know of ?

 

[Arfa Daily]

50V , low wattage lamp (or seriesed lower V ones) (assuming normal testing
is 10 to 20W range) to visually show if the volume is set too high, also
if
high level high f oscillation on the output; sacrificial, fusewise, if
overdriven.
AC voltmeter , preferably autoranging for possible overload situation, to
measure/long term monitor the RMS power.
High power speaker pot (plus droppers) leading to a low quality ,
sacrificial ( for intitial maybe problematic testing) small speaker, for
basic possible intermittant sound, on/off, indication. Can be switched out
by plugging in a good quality speaker for audio monitoring of quality of
sound issues in otherwise known good amp.
Provision for coupling in a scope for distortion monitoring, when
necessary.
Any other add-ons that others know of ?

I also have a box I made which has a stereo input, switchable to
paralleled-channel mono, with two switchable and variable basic ranges of
zero to low, for low level instrument simulation such as guitar pickup, and
zero to high for line level tests. It also contains two 600R line
transformers to produce 'balanced' outputs for testing amps with a balanced
XLR type input. I have a special Speakon adaptor which has a built in
standard 1/4" jack so that the test speaker can have a normal jack plug on
it, and if I get an amp for repair that has Speakon outputs, as many of the
higher power heads have, it's just a case of plug in the adaptor first.

I also have a little box that I made that has a 'normal' edgewise meter, and
a centre zero edgewise meter and a 3 pin plug for setting and checking the
bias balance on Fender Twins.

My load tester has a built in very heavily attenuated 4" 'squeaker' with
volume control, for monitoring intermittent faults, and jack-switched
'through' output for a genuine speaker. It also has a crude power meter
based on measuring the voltage across the load. This stays in circuit if the
through socket is used to connect a real speaker. There is a BNC connector
to hook directly to my 'scope.

The loads are force-air cooled, and relay switchable for 4,8 and 16 ohms.
When the tester is switched off, the relays drop out, and it defaults back
to 16 ohm load, so you don't accidentally overload the next one on the
bench. I also put in a double bar-graph display, monitoring output waveform
+ / - either side of zero, with a level control. The idea was to be able to
immediately see any lack of symmetry in the output waveform, but I've only
ever had one instance where it did its job. Still, it looks pretty, pumping
away on the front panel, and it soon catches your eye if it stops, and
you've got the squeaker turned down ...

Arfa