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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
 
The best tube compliment/combination will vary based on the mode of operation.

If single ended from input to single ended output, you only need to concern yourself with tube positions #1 and #2.

If you are running single ended inputs to balanced output, you need to concern yourself with tube position #1, 2, 4 and 5

If you are running balanced inputs to single ended output, you need to concern yourself with tube positions #1,2,3,6

Balanced in to Balanced output you need to concern yourself with tube positions #1,2,3,4,5,and 6

Tube positions 7 and 8 are for the headphones.

jond's avatar
jond
5,845 posts
 
So just for fun maybe before you start changing out all your tubes try removing the new power cords and USB/Spdif reclocker and see what happens? You can do this immediately and get results plus it's free. Good luck!
elevick
2,636 posts
 
I would expect 5000 hours.  You need to get them tested.  The rectifier will last even longer.
Blame the sound on the power cord. They do need break in time.
mikey8811 OP
259 posts
 
OK i have swapped the tubes.

So far it seems to be the tubes (I still have to swap the old ones back to reconfirm) but what I was getting was a muddier sound overall with less pitch definition which made the deeper bass from the power cords and the USB/ SPDIF reclockers seem boomy. Everything has tightened up now, soundstaging has improved as well as space between instruments and air.

So if I swap the old tubes back and confirm it is the tubes, I am guessing I will have to change all 6 at the same time? Or can I economise and change the ones that need changing by swapping out pairs at a time and replacing only those that are weak and causing the problem? I realise if I have a tube tester it would be easier but unfortunately I do not.

Also, when do I need to change the rectifier tube? What are symptoms of its end of life?

Thanks
brf
1,715 posts
 
Assuming you are running fully balanced, you can change out the tubes in 2 steps. 1,2,4,5 as a matched quad and 3 and 6 as a matched pair. 
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