New sound of new valves

Quick question about new valves. I've never changed the power tubes in my amp before and my existing set are starting to get a bit long in the tooth. I've just a got a matched quad (Svet 6550C) from Watford Valves. The replacements are nominally identical in every way to the original set. However, they sound dire. A really congested sound, very harsh in the treble and subjectively quieter - although this could be an artifact of the congested sound. This isn't subtle - it's night and day. Is this just the fabled 'burning in' period? Cheers = John

 

run them for a while then check the bias ,valves do need running in.
ray

 

The Svet 6550C is a good tube. You will definitely hear an improvement after 20 or 30 hours. What are they going in?

 

WAD6550 - it's only ever had Svets in it.

 

My Svet 6L6GC sounded really bad when I first put them in, then mellowed out after 20 hours or so. Tube "burn in" is not uncommon in my experience. Some tubes sound great from new, many do not.

 

Perhaps you could also consider that your old set of valves may still be in their prime, I've never changed output valves until I've had reason to believe that one or more of them are knacked - i.e. noticeable loss of sound quality or, as was the case for me last time, an impressive mini fireworks display! Both times I did replace output valves there was an instantly noticeable improvement in sound, but to be fair neither times were the replacements identical.

I'd pop the old ones back in and keep the new set for another day, there are plenty of vintage amps still in service that still seem to work fine on their original valves, so they must be able to work well past their nominal optimum number of hours....

 

That's what I've done! The main reason I got them is that my income tends to fluctuate somewhat and I didn't want to risk getting stuck with no amp when they finally die. I just wanted to be sure that the new ones weren't dud but was surprised by the difference. Having mostly owned SS gear, I was a bit skeptical about 'burning in' of components since IME it's usually your ears that are burning in. I'm obviously wrong about OP tubes! Live and learn.

 

I suppose you still have the old tubes as a reference? After 50 hours, do a comparitive listening test and if the new ones still sound crap, flog'em as the best thing sinced sliced bread on eBay and try something else.

DT