bad tubes or transformer?

I was wondering if there are ways of differentiating between a bad tube and the distortion transformers produce when they get too much input ? is there any way to find that out by listening to the sound/distortion without any expensive testing hardware? Would i still hear much distortion even on low levels if the tubes would be faulty?
I heard tube testers are not that reliable to find out bad sounding tubes..
Just wondering if i need to replace them in my vari mu.. 

kill the side chain and see if it cleans up as a straight amplifier.

otherwise, more info needed.

transformer
level into transformer
etc

What if it's a power supply fault?
Always good to confirm the supply is in working order

emrr said:

kill the side chain and see if it cleans up as a straight amplifier.

otherwise, more info needed.

transformer
level into transformer
etc

Click to expand...

well i loaded a song into cubase and put it on -10dB, it can't be digital distortion

vigortronix vtx 102-003 and vtx 102-007 (http://www.vigortronix.com/InputmicrophoneAudioTransformers.aspx)

it is a commercial compressor so psu is not the problem

-10dbfs in Cubase???? Feeding the compressor??

weiss said:

well i loaded a song into cubase and put it on -10dB, it can't be digital distortion

Click to expand...

What converter? -10dBfs is typically between +8 and +14dBu, that's a huge input level for most compressors.
I think you need to be more accurate in your description; why is it you ask? what made you suspect something's wrong?

it is a commercial compressor so psu is not the problem

Click to expand...

? You mean it's made by a company that makes things that never fail?

Vigortronics (knock-off of OEP transformers) are probably not the optimum choice for line input/output at the levels you want a vari-mu compressor to handle. They claim 1% distortion, yet does not tell you anywhere under what conditions this is.

The OEP data for the "original version" of this series was something like 1% for 1mW at 30Hz - which, for a 1:6.45+6.45 input transformer, translates into levels even lower than standard consumer levels. There is a good reason why they can do these so affordably.

High distortion even on low level signals could also be from poor composition core material.

This is all guesswork - but on a vari-mu compressor the main source of distortion is usually poor balancing of the input stage: As we depend on a nonlinearity of Gm vs. gain for variation, this nonlinearity must be very much the same in the twin input pair in order to cancel out and not turn into distortion when de-balanced. All vari-mu's have trimmers for minimizing this misbehavior.

Jakob E.

abbey road d enfer said:

What converter? -10dBfs is typically between +8 and +14dBu, that's a huge input level for most compressors.
I think you need to be more accurate in your description; why is it you ask? what made you suspect something's wrong?
? You mean it's made by a company that makes things that never fail?

Click to expand...

i don't think anything is wrong, i just wanted to know if there is any way of telling the tubes aren't okay anymore, how would one be able notice that and do the transformers distort actually? i set the output of my DAW to 0db VU so it is -18dbFS -10db from the track so in total  -28dB FS

weiss said:

i set the output of my DAW to 0db VU so it is -18dbFS -10db from the track so in total  -28dB FS

Click to expand...

I don't understand this; there's nothing like 0dB VU. Norm of VU scale says 0VU=>+4dBu.
Are you really monitoring levels with a VU meter? (physical or emulation).