Retube breakin in

[joeling]

Gents,

Looking for some clue as to the break-in time required after a retube. My ref110 is well broken after having logged in more than 2000hrs with the original 6550 tubes. Replaced them with the KT120's about 60+ hrs ago. Still feeling not quite settled. Any ideas ? How long before everything settles in?

Regards,
Joe Ling

[cmalak]

Tubes do not need extended break in period. I would say after 20-30 hrs you should be fine. What you should check Joe is tube bias drift. If there is drift it usually happens in the first 100 hrs so I would check it now and again after another 50 hrs. After that, I would check it maybe once a qtr to make sure everything is ok. Good luck

PS: I am still using 6550s in my Ref 110. Any thoughts on what you are hearing different with the KT-120s? Thx

[joeling]

Thanks for the quick reply. So far, I'm not that impressed. Still sounded a little shrill after 60hrs. Might to have to check bias as per your advise though. I might even swap back the other set of 6550's that has about 1600hrs on them to compare. This is contrary to what other have to report though. Maybe my ears need checking...

Down to 1 ref 110 for the time being. Silly me left one stereoblock switched on & not hooked to any load the whole night. Next day, plug them back to the system & heard a loud cracking sound. Quickly switched it off & now thinking of sending to the dealer to do a health check.

[cmalak]

Joe...sorry to hear. I would certainly send them to dealer. If you heard a very loud crack sound that could be 1 or a couple of blown resistors. If you take the cover off and inspect the board, you will be able to see a blown resistor(s). Good luck.

[PHC1]

I didn't think you could just drop the KT120s in place of 6550s.

[cmalak]

Originally Posted by PHC1

I didn't think you could just drop the KT120s in place of 6550s.

Serge...in ARC's case you could for their more recent amps.

[PHC1]

Originally Posted by cmalak

Serge...in ARC's case you could for their more recent amps.

Good to know Cyril. I know they draw more filament current and autobiasing amps will not bias them quite properly. Some fixed bias amps may or may not have the range to bias them properly either.

[ronenash]

Originally Posted by joeling

Thanks for the quick reply. So far, I'm not that impressed. Still sounded a little shrill after 60hrs. Might to have to check bias as per your advise though. I might even swap back the other set of 6550's that has about 1600hrs on them to compare. This is contrary to what other have to report though. Maybe my ears need checking...

Down to 1 ref 110 for the time being. Silly me left one stereoblock switched on & not hooked to any load the whole night. Next day, plug them back to the system & heard a loud cracking sound. Quickly switched it off & now thinking of sending to the dealer to do a health check.

Did you smell a something burned when this happened? If so it might be the catode resistors. If not you could try to see if it operates fine and if not send if for repair.

[TMcD]

Originally Posted by joeling

Gents,

Looking for some clue as to the break-in time required after a retube. My ref110 is well broken after having logged in more than 2000hrs with the original 6550 tubes. Replaced them with the KT120's about 60+ hrs ago. Still feeling not quite settled. Any ideas ? How long before everything settles in?

Regards,
Joe Ling

Mine sounded better in my Ref 110 from the moment I put them in, there was maybe 10 hours of break in. Check the bias and make sure all the tubes are ok, for example make sure none are cloudy. I did have a tube go and it did sound a touch shrill after that.
It is a nice upgrade, enjoy.

[cmalak]

Originally Posted by PHC1

Good to know Cyril. I know they draw more filament current and autobiasing amps will not bias them quite properly. Some fixed bias amps may or may not have the range to bias them properly either.

Serge...ARC recommended biasing them at the same level as the 6550 which basically means the current draw from the KT-120s was well below their rated max, extending the tube's life. That is why subbing out the KT-120s for the 6550s in the recent ARC amps did not result in a material jump in the rated output of the amp. IN the most recent amps designed around the KT-120 tubes (Ref 150 and Ref 250), ARC is probably drawing a little bit more from the tubes based on the new circuit designs which is why the rated output goes to 150wpc and 250 wpc from 110 and 210 wpc.