No speaker?
Or with speaker?
No speaker = no load = power dissapation in the output transformer = sound.
Tubes can make noise too. Parts can move under power.
With speaker?
Possibly you have a really really bad reactive load?
Not good.
Check the impedance of your xovers, looking into the xover and see what you get. You may have very HIGH Z peaks, and/or very LOW Z dips. Both bad usually, especially with tubes.
Xovers are NOT equal with the parts placed in alternate positions!!
Like:
in--->C1------C2---->load
|
L1
|
GND
(edit: ascii representation of a 3rd order filter seems to fail when posted, assume it is an 18db/oct high pass...the "L1" is connected to ground inbetween the two caps...ok?)
is not the same impedance as the C2-C1 being reversed, unless they are the same value... check it and see fer urself. The load may see the same freq response, but the amp will not see the same load!
_-_-bear
PS. some transformers do "sing" - that can be reduced by isolation mounting, making the windings tight to the core, or better still: vacuum potting.
Or with speaker?
No speaker = no load = power dissapation in the output transformer = sound.
Tubes can make noise too. Parts can move under power.
With speaker?
Possibly you have a really really bad reactive load?
Not good.
Check the impedance of your xovers, looking into the xover and see what you get. You may have very HIGH Z peaks, and/or very LOW Z dips. Both bad usually, especially with tubes.
Xovers are NOT equal with the parts placed in alternate positions!!
Like:
in--->C1------C2---->load
|
L1
|
GND
(edit: ascii representation of a 3rd order filter seems to fail when posted, assume it is an 18db/oct high pass...the "L1" is connected to ground inbetween the two caps...ok?)
is not the same impedance as the C2-C1 being reversed, unless they are the same value... check it and see fer urself. The load may see the same freq response, but the amp will not see the same load!
_-_-bear
PS. some transformers do "sing" - that can be reduced by isolation mounting, making the windings tight to the core, or better still: vacuum potting.
Probably not a very good idea to run the amplifiers without a proper load on the transformer secondaries. Most of the noise you are hearing is probably windings in the transformer vibrating with variations in signal. (Better not be the core stack - this indicates very poor transformer construction practices.) With no load applied it is possible to get very large voltage excursions on the primary, further, driving the output tubes into the cutoff region will result in the primary acting like a flyback transformer, and very large voltages can be developed - more than enough to destroy the transformer insulation.
without any load 
I'v been repairing a sanded amp and was testing on a dummy load ( 200watts continuous on 32 ohms paralleled resitors) and could ear the dissipators sing : the transistors, the resistors even the wire 
Ger56,
If you use a nominal impedance resistor = to nominal speaker impedance, you get to see the contribution of the xover.
If you then test with the speaker in place you see the total result.
Do it with a dummy load first that is the same as the nominal speaker impedance.
Also, see if the amps "sing" with a nice easy 8 ohm dummy load??
_-_-bear
If you use a nominal impedance resistor = to nominal speaker impedance, you get to see the contribution of the xover.
If you then test with the speaker in place you see the total result.
Do it with a dummy load first that is the same as the nominal speaker impedance.
Also, see if the amps "sing" with a nice easy 8 ohm dummy load??
_-_-bear
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