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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

Showing 4 responses by mikey8811

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?

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
mikey8811 OP
259 posts
 
I’ll be darned. I swapped back the old tubes and guess what, it wasn’t the tubes after all. Eveything sounded OK again even with the old tubes so I’ll continue using them for now.

So to everyone who said it wasn’t the tubes - you are right!

This is a crazy hobby - I didn’t think that power cord, USB/ SPDIF reclocker break in would have such an effect especially since the power cords were used and I have been running them in for slightly more than a month, albeit with only 20 hours of play in all. It's just weird that things just "clicked" after the tube swap.

Thanks again everyone and apologies for the false alarm...


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