Output tubes' current or negative voltage?

[Le Basseur]

Got an Fender Concert combo on annual service/checkout/retubing/bias.The owner bought a new (unmatched) pair of Electro Harmonix 6L6GCs (I don't want to comment his choice for now).
The original bias circuit is the "balancing" one,in spite of my repeated verbal efforts to convince the owner to accept the installation of a suplimentary trimpot as to be able to raise/lower the overall bias voltage.
I checked out both the first grids' negative voltages AND the current passing through each tube (by the means of a 1 Ohm/0,5% resistor that I placed in the cathode of each tube) and I noticed that wether I manage to get an equal current consumption,the negative voltage is different (-47,6VDC vs.-51,4VDC).If I go the "equal voltages" way,the current readings are odd,even greater differnces that I'd expect.
As I always used only matched output tubes (I match them myself,don't care too much about "factory matched" stuff),I'm a little confused right now....what's more important in a situation like the one from above?
(...but please,don't tell me that I'd have to go with a matched pair...I know this already)
Any comment is welcome,regarding some pure theoretical aspects like "...-equal currents are more important because...." ,as I'd like to find out what'd you do in such a situation,what choice is the fairest to you and what practical results (sound,tube life) I'd expect.
...therefore....equal currents or equal negative voltages?
Thanks,

[tubeswell]

My two cents worth is that; given that 'factory fixed biasing' (like PV for example) is done on a conservative basis with biasing resistors designed to run the bias not too high so anyone can slap in replacement tubes, I'd say go with the voltage, provide the highest bias isn't too high. Unmatched tubes can can a cool slight phasey effect, even if they are a bit hummier than 'matched' ones

[Enzo]

With the amp powered down, measure the resistance of the OT primary from center tap to either plate. If those resistances differ, there is your difference. SOme transformers are wound with one wire adn a tap in the center, so one half of the primary is wrapped around the other after the tap. The same number of turns is a longer piece of wire then, and thus higher wire resistance.

And which would I prefer? VOltage or currents? The voltage doesn't matter, balancing the currents is the point of setting the bias. I'd average them and set it in the middle. 34ma and 38ma = 36ma for the amp in my book. Bias is not really as critical an adjustment as most folks seem to think. If ther is a balance control, set it for minimum hum.

[Gregg]

I'm using EH tubes all the time most of them 6L6EH. The truth is these tubes are very rugged and maybe among the best current production tubes. The tone is good as well. At least this is my experience with EH.
The other truth is nobody really knows how they are matched. There are some numbers on the labels but what voltages they refer to is unknown which means they are not matched for any voltage. That's why I always use two bias trimmers to cover almost any situation.

[Bruce / Mission Amps]

I'm using EH tubes all the time most of them 6L6EH. The truth is these tubes are very rugged and maybe among the best current production tubes. The tone is good as well. At least this is my experience with EH.
The other truth is nobody really knows how they are matched. There are some numbers on the labels but what voltages they refer to is unknown which means they are not matched for any voltage. That's why I always use two bias trimmers to cover almost any situation.

This is the reason I like to buy my tubes from MOJO Musical Supply... their tube testing is with a jig setup that tests them at +400vdc to 450vdc and it has a variable bias supply so when they say the tube is a, say 28... it probably means that at +400vdc to 450vdc and some negative fixed bias the tube is idling at 28 ma.
Regardless, I always find the tubes I buy from them with in a specific "number" range, always work perfectly in the 5E3 kit amps I put them in.