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Cary SLP 05 - When To Replace Tubes?

Hi

I have a Cary SLP 05 preamp. recently, I changed some power cords on source components and added a USB and SPDIF reclocker. The overall result was the bass became resonant and boomy, so much so that my ears ring after prolonged listening. It could be a power cord mismatch but i have a feeling power cords do not alter the sound that much.

I suspect it may be the tubes getting old. I use NOS RCA Grey Glass GT’s for the quad and Sylvania GT’s in the balanced positions. They are about 5 years old with playback time of 5 hours every weekend (estimated 1,250 hours of use) and measured in the mid to high 90’s when I purchased them. I do not have a tube tester.

Does anyone know what the lifespan for these tubes are and if it’s time for a replacement set? I am guessing if it is time’s up, I’ll need to replace all 6.
mikey8811
brf
1,715 posts
 
What you have described does not sound like worn out tubes.  As tubes age, dynamics become compressed and the highs roll off.  

Perhaps the changes to your system is now allowing the tubes to show their true colours, but that is pure speculation.  5 years and the number of hours added to already used tubes, imho, you are due for a tube change. How are you currently running your system I.e fully balanced, as that will dictate which tubes need replacing. 

As as an aside, have you swapped out the horrible JJ rectifier tube in the power supply. 
mikey8811 OP
259 posts
 
OK so do you suggest I try another set of tubes?

I am running fully balanced and so will need to change 6 tubes.

I have swapped out the rectifier to a Mullard 5AR4.
mikey8811 OP
259 posts
 
My memory is hazy. Which tubes do I match?

1&2 - left & right channel positive phase gain (1st 2 tubes on front row from left to right)

4&5 - left & right channel negative phase gain (1st 2 tubes on back row from left to right)

3&6 - left & right channel balanced input buffer (3rd column, 2 tubes from front to back)

Correct?

joey_v
669 posts
 
I believe that is correct. 
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