is their a big difference between 6sj7 and rca's 5693?

osd1

Member
im trying to decide between rca's red 5693 pre amp tubes or nos 6sj7.

it will be paired with kt66 or el34 tubes.

the amp is a musical paradise mp301 mk2.

also is there a big difference between the red wrapped tubes and black wrapped tubes that are 5693?
 
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The big differance was original price and , the red RCA tubes where made to long life standards like Western Electric tube .
 
Part of the reason for their long life was derating - notice that all the "special red" tubes have lower voltage and power ratings than the base tubes. They probably were selected for close tolerance, possibly had some different materials for longer life.
 
Part of the reason for their long life was derating - notice that all the "special red" tubes have lower voltage and power ratings than the base tubes. They probably were selected for close tolerance, possibly had some different materials for longer life.

lol forgive my stupid question but is the above statement good or bad?
 
Was going to start a thread on this same subject, I just ordered a set of NOS RCA 5693's on Ebay for my MP301. Might as well revive this old thread.
 
Was going to start a thread on this same subject, I just ordered a set of NOS RCA 5693's on Ebay for my MP301. Might as well revive this old thread.
It is not really derating, but that the operating point is tightly specified. So, if you follow the recommended operating conditions then the 10K hour lifespan can be expected.
The Red Base RCA tubes were designed for military and industrial conditions for reliability and high vibration, etc.
 
I've had my MP301 since 2014 and still using stock preamp 6j8p tubes so i'm wondering if i'll be able to tell a difference in sound. I always order extra tubes so I guess i'll be good for 20,000 hrs. I will be using KT88's and EL34's so this will be new for me.
 
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I've had my MP301 since 2014 and still using stock preamp 6j8p tubes so i'm wondering if i'll be able to tell a difference in sound. I always order extra tubes so I guess i'll be good for 20,000 hrs. I will be using KT88's and EL34's so this will be new for me.
I know that the Bendix tubes even show a chart with expected lifespan at certain operating conditions. With the expected longest use at the conservative conditions and lesser hours as the voltage and current increased. The filament voltage is also specified to be within 3 or 5 % of nominal.
 
I use the red 5693 in my 301.
I also have the Black 6SJ7, which I recently swapped back in.
The 5693 sounds much better. Probably due to less gain. I found the 6SJ7 to be rather grating in the highs in comparison.
 
The 6SJ7 and the 5693 are essentially the same tube which means the operating points and gain are identical. As TB says above, the 5693 is "derated" to reduce the maximum allowed plate dissipation from 2.5W for the 6SJ7 to 2W for the 5693; the screen dissipation from .7W in the 6SJ7 to .3W for the 5693. This does not qualify either of these tubes as "good" or "bad" it is just a statement of fact and a reminder that running tubes at a reduced operating point can improve the life of the tube.
 
5693 tubes were ultra ruggedized build to withstand outrageous conditions and still work. If you can find this type, hang on to it. Nobody will ever make anything like it ever again.
The tolerances are tighter and the physical structures are more rigid and better supported than its non military counterpart. This may result in closer matching and lower microphonics. Ymmv. And did I mention that these will never ever be produced again at any price...
 
5693 tubes were ultra ruggedized build to withstand outrageous conditions and still work. If you can find this type, hang on to it. Nobody will ever make anything like it ever again.
The tolerances are tighter and the physical structures are more rigid and better supported than its non military counterpart. This may result in closer matching and lower microphonics. Ymmv. And did I mention that these will never ever be produced again at any price...
I know I have been on the look out for awhile and bought 4 as I only need 2.
 
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