Mark III power tube question

[Skyless7620]

I got my Mark III (green stripe-simul) checked up a month or so ago by my tech here in the city (certified Mesa tech, cool guy and knows his stuff).

Long story short, I've got 4 brand new 6l6's inside and seem to prefer my older set (same tubes too, STR440 6l6's). I'm pretty sure it's the tubes, but as much as I like the sound I'm getting out of my amp now there's just something about the sound I was getting before that had some MOJO to it (The tech told me the tube pairs were mismatched Y G Y G instead of Y G G Y and the voltage was whack due to a severed ground in one of the powertube sockets aparently. That might not be the exact words he used, but it was something like that).After the fix the highs seem more separated from the overall sound and less focused.

Is it the tube set I have or is it more likely that I'm a freak who enjoys the sound of his amp when it's really out of whack?

 

[Boogiebabies]

Your not losing your mind. Certain mismatches in the bias can cause extremely nice harmonics.
Sometimes up to 10-15mA's in difference can get you a nice swirl and not cause too much hum from the imbalance.

 

[Skyless7620]

So how can I try and go about getting the sound back? Can I mismatch the pairs again like they were orginally (Y-Z-Y-Z) or do I risk damaging my amp this way? I don't mind wearing tubes out a bit faster if it means better tone so long as I'm not damaging my amp permanently.

 

[stokes]

As well as what BB said,it could also be where the new tubes bias point sits.I have seen tubes that were the same rating as the prior set differ by as much as 15ma's or so.There is a fairly wide range in what Mesa calls "safe".Mesa is known for being biased on the cold side,so one set could be sitting at,say,30ma's and then they sell you a "matched" set that runs at 20ma's,could make a big difference in the tone.That is the main reason I always recommend adding an adjustable bias and scrapping the Mesa plan,get yourself some good NOS tubes and bias them where they sound their best.If the old tubes sound better,I would just put them back,the same way they were.If they sound better than the new ones,you obviously didnt need new ones,no?

 

[Boogiebabies]

So how can I try and go about getting the sound back? Can I mismatch the pairs again like they were orginally (Y-Z-Y-Z) or do I risk damaging my amp this way? I don't mind wearing tubes out a bit faster if it means better tone so long as I'm not damaging my amp permanently.

You can try the mismatch and see if the magic comes back.

 

[Bustangs]

How hard is it to set up a mark 3 to adjustable bias?

And along these lines of getting the voltage to the "sweet spot" is that basically what a variac is doing by dropping the input voltage to the entire amount to change the anount of current hitting the tubes?