On 03/12/2015 19:41, Gareth Magennis wrote:


"N_Cook" wrote in message ...

The owner cannot detect a difference. Other than different gain settings
are obvious, how to set up and test? . I've not put a scope on there
yet, but what set of parameters to confirm there is a difference,
compressor or no compressor, max or min of contour settings, what sort
of level and frequency of presumably over-driven input? Test not
requiring guitar input and ear-drums, as then it becomes
subjective/musical ears required.
The valve actively tests fine.

Incidently seriously crap "engineering" on the speaker outlet board,
especially as it is PbF. 2 legged 1/4 inch socket, no extra dummy legs
for mechanical strength, so 2 simple active PbF joints supposed to hold
the pcb and 2 thick unconstrained supply wires , laughable.





There is a lot of audible difference between the valve stage and the
transistor stage in the HA3500, it's deliberately designed in.
If the owner can't hear this there is no point in him owning such an amp.


As for "testing" this stage, I would have to ask why do you need to
test this stage?
What do you hope to achieve by doing so?
How are your results actually going to make any sense?



Sometimes there is just no substitute for a pair of ears and a brain.




Gareth.



So how does he or I determine whether things are as they should be or
that there is some failure with one or both of those channels?
I'll put a scope on there and suck it and see with different sine f and
levels of input and different other control settings.