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Primaluna evo 400 - unmatched tubes

Hi
quick history....i recently borrowed a primaluna evo 100 from the local store and loved it so bought the evo 300 and immediately bought 4 matched KT150's for it, but then 2 weeks later wish i bought the evo 400 ! so my local store let me return the 300 (small restocking fee) and now i have the 400. Sounds like a lot of $$ but I'm thinking this is a lifetime purchase so have justified it that way ;-)
Because I had 4 KT150s that i bought for the evo 300 i decided to buy another 4 so i could fill the 8 tube requirement of the evo 400. I'm driving magnepan .7's so more power the better. By the way the primaluna sounds great with these speakers....I've found a low end i'd never heard even when driving with 150wpc solid state and the sound is very natural, pleasant, and unfatiguing to my ears. The KT150's in my system sound much better than the EL-34's. They sound fuller and more spacious. I sat there last night and kept wanting to play just one more song....they drew me in. The choice of tubes is related to the speaker being driven so the EL-34's may sound better on a different speaker. 
Anyhow to the issue......when i installed the 8 tubes in the amp i totally forgot they were actually 2 matched quad sets so in effect i have mixed them up. Will it matter? should i have put in a matched set per channel? Will the autobias feature negate any issues?
The 2 sets were bought from different suppliers but i don't think there would be any different markings as they were both tung-sol branded. 
mid-fi-crisis
oldhvymec
5,101 posts
 
You look real close, I bet you can figure it out.

It will have to do with distortion, more than anything. Auto bias, is usually by groups of 1,  2 or 4.  1 would be fine, but in pairs, or quads, YES it can add distortion..

Do you see why? It will average between two or 4 and adjust, between the average

Individual autobias there is no average, an lot less distortion..

BUT will have a reject point of overall tube health by some means.
A led, or something will or will not light up.

Look close, get a mag/glass their different.. TOOL marks....

Regards


three_easy_payments's avatar
three_easy_payments
2,097 posts
 
Upscale marks the measurements on the tube boxes they sell you.  Just make sure they are somewhere in the same ballpark.  Over time your tubes will no longer match as they begin to drift anyway...hence auto-bias kicks in on your amp.  I wouldn't obsess unless the measurements were wildly different which I wouldn't expect from the same brand of new release tubes.
jjss49's avatar
Ag insider logo xs@2x
jjss49
6,612 posts
 
listen to rar1/rich above

that is the right answer
oldhvymec
5,101 posts
 
listen to rar1/rich above

that is the right answer

How do you figure that, two sets of quads, You have no idea where their at.  At best, current matched at 10-20% per quad. NOW You want to mix the Quads too up. YES it make a difference. The reason for the match. LONGEVITY and clarity.
.
Geezzz how long you been using valves, 5 minutes. I have some in use for over 50 years... MATCHED...500 hours not matched...

Most don't mark the boxes or valves, especially bulk sellers and buyers..
SOME do. It doesn't make them a good or bad seller. Most like me have a way to current match and make sure they're BALANCED...

I don't like marks on my valves, glass or base unless it's an indexing marker.

Look at the tool marks, listen to the OLD MECHANIC.. That is what I did..
for 47 years.... I know I can, the question is, can this help you. 

IT DOESN'T MATTER.. lol  Bad mechanic.....Bad answer....Sit in the corner. Time to learn....

Your ears, your money....

Regards...
gs5556
1,241 posts
 
It doesn't matter if the tubes are matched in the Prima Luna. The adaptive bias circuit sets the idle bias current of the output tubes by sensing a voltage drop across a resistor. That voltage modulates a transistor to either increase or decrease the current to set it and then keep it at spec value. If the tubes are unmatched, or they change with age, the individual transistor for each tube adjusts accordingly. Doesn't matter how off spec the tubes are mismatched as long as they can be adjusted to maintain the design idle current.


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