TUBES

Elliot is correct. These tubes are small, they last multiple thousands of hours. Particularly when you first get into tubes it is a little disconcerting. It is power amps that have shorter a tube life. But with modern equipment even these are getting longer. It is likely you will not face any tube problems soon. Personally, I would either not worry about it and just order a full complement if something fails or order a full complement and put in the closet. I have quite a pile of tubes I ordered just in case and traded the equipment before a tube went out. 

see how matched they are.


To properly match tubes you need a curve tracer.

…..well the Mac gear from the 60’s is known to be very gentle on tubes, don’t assume every designer this astute……and yes, i have both a 1961 MC240 and 1965 MX-110Z…..both w mostly origional small signal tubes….but not all, your milage may vary….

Mac was also thru the seventies famous for walk in performance clinics…mostly power output tubes got changed….but some small signal as well….

enjoy the journey 

be cautious

you can ’maintain’, ’improve’, or ’RUIN’ the sound of excellent tube equipment, or go broke chasing nirvana blindly.

you want to have a spare or two on hand, matched pairs are nice, however, tubes do sound different, so if you like what you are hearing, perhaps spares of that brand/model.

tube break-in: In, no signal, leave on for 60 hours, done, now listen.

tube source: Brent Jesse let me swap, after 60 hours break-in, and gave me a refund for the price difference, all I paid to switch was the extra shipping.

tube bias: some equipment has easy and safe adjusters, even meters, mine has internal adjusters, hard to do, danger, potential harm to me and/or the unit. Bias is not critical IMO, if it sounds great, bias is smart, but I never bothered, may or may not bias my Cayin.

for instance: My Cayin Amp.

1. Came with 6550’s (seller said biased for them). Sounded great, after a while I chose and swapped in some KT88’s. I prefer their sound (bias unchanged).

2. came with 4 absolutely identical looking 6S tubes, but actually 2 6SL7; 2 6SN7. They were marked properly, but somehow I put two in wrong place, sound got awful, balance way off. My fault, blew a 10,000 hr tube in it’s near infancy I bet. A used tube from my mess-o-tubes (cases, boxes, drawers), sounded great again, but not matched.

Picked a pair of expensive highly rated ones (thinner/taller/chrome tops, never repeat that mistake). Hated the sound, broke in, still hated the sound. I would have rejected the Cayin if it sounded like that. Picked new ones like my old used one, they sound great. It could have gone from bad to ok, or bad to worse, I felt and still feel lucky.

be cautious.