BobTFM35

Just about anything can be going on. I assume you have alot of confidence in the repair facility. Have you contacted them for some guidance and or suggestions? I would do one of two things. Work my way backwards removing a component and testing to see if the hum or hissing has gone away. Or unhook everything then add an item one at a time. This is in no particular order, so..... I remember from your previous post you were trying to bi- amp some speakers and at the end you had everything "singing". So things worked then. Something has changed from then to now, is anything new? 1. I would plug the bluos into the CD input and then test. 2. Next I would remove the sub from the bluos then test. 3. I assume the same speakers. What make and model? 4. Was the new non inverting amp tested before and worked fine so we can rule it out for now? Still bi-amping? 5. Tubes were replaced. Who sourced the tubes? What were they? Matched sets and tested? Line board and or phono board tubes? 6. Any other parts replaced on the preamp 7. Any new cables? Just look at one thing at a time and something will pop up.

Welcome to the Carver site!! Should be an interesting pairing. I use a 6cb in one of my systems. What's the candidate for the preamp? As for the music side, records or cd's?

If you don't see what you need in the Manuals and Specsheets section, maybe one of these three offerings on eBay might be of interest. https://www.ebay.com/sch/i.html?_nkw=carver+klw+audio+service+manual&_sacat=293&_from=R40&_trksid=m570.l1313&_odkw=carver+klw+service+manual&_osacat=293

Welcome to the Carver site!!

Welcome to the Carver Site!! Tell us a little bit more about the system using the PM175.

Welcome to the Carver Site!!

https://www.turntableneedles.com/round_rubber_drive_belt_medium

@MattB @gwolford A few places I have in my saved folder, Listed in no particular order https://lptunes.com/collections/vpi-turntable-belts https://www.lpgear.com/category/V1.html https://www.turntableneedles.com/Rubber_Drive_Belts-Tape_Decks_Turntables Was able to source a tt belt from Amazon based on knowing the size and cross section information. For mine I used this to start the search; Turntable Belt for Record Player 20.7" Replacement Flat Medium

Welcome back!!

Welcome to the Carver site!!

Welcome to the Carver Site!! Tell us more about yourself and your equipment. Download the file in this link to find belt size information. And for good measure look at this

Welcome to the Carver site!! I previously owned a IV. Question, Is the unit still operational and not experiencing any problems, and you just want to get it refreshed due to age? Or it is experiencing problems? At one time I owned a IV and it gave me many years of GREAT pleasure. I had a recap done and the unit completely went dead after one year. Nothing related to the recap just the processor failure it was determined. I really loved the unit but not enough to try fixing it again nor purchase another replacement. I put that money into a new Marantz AV unit that had a 5 year warranty. Its not exactly the same, but I have improved several items around it that more than makes up for the loss of the Sunfire. I also was able to incorporate all my older Carver equipment and add new modern day equipment so it was, for me, a big plus.

Welcome to the Carver site!!

Welcome to the Carver site!! Tell us what's in your collection.

I will also go along with @Sk1Bum for the C-4000t because of the addition of the Digital Time Lens function.