Original Cary 300B Monos Reliability?

Charles - I found the information regarding concerns with the Carys running the 300Bs near their limits. It came from the EML web page. They suggested the XLS as a best option for Cary. Those tubes may draw more amperage, so I would check with Cary to confirm that the power supply will have no issue. Might also be a question about the base fitting into the tube cutout (a little on the lean side). I know the WE will fit and be a great tube, but I wouldn't mind paying a bit less.

Current preamp is a Croft 25 w/ phono. It's quite good without complaints, but other options might bump things up another notch.

Two-Left - thanks for taking the time to reply. I won't go wrong if I get the WE, especially based on your experience. If they last 10-15 years, it will be a great investment!

@leahy Hopefully you won't have issues with the Cary monoblocks, While I can't speak to those exact amps, I did run SLM 100 monoblocks back in the day. The Jentzen coupling caps Dennis was using at the time were known to leak, sure that's been addressed in yours. I applied diy repair here. I also had issues with bias circuit, don't recall the exact issue as I sent in for repairs.

As far as running power tubes hard, not all that unusual. Between running higher voltages in the amps and lesser quality of many new tubes, failures happen. I'd stick with the EML XLS or Western Electric 300B's in more difficult amps.

Thanks SNS. I need to look into biasing the monos.

I’m listening to "3 tube" Cary monobocks as I type. I run WE 300Bs and they are stunning. The WE tube was what Cary originally supplied in the amps. Your concern about XLS fitment is well taken. I had a pair of KR 300BXLS and they would not physically fit into the chassis; the openings are too small.

The KR 300B XLS was offered by Cary as a separate model monoblock in the day, not as an optional tube. I suspect there is a reason and I strongly suggest you check with Steve at Cary before you run XLS tubes based on other’s opinions. As my amps are auto bias, I am more than happy to run Western Electrics since they were OEM.

As far as reliability, these are 1999 vintage, had the original tubes until last year and have had no service. Eventually caps will dry out, but I suspect alleged reliability issues may come from people suggesting the use of tubes Cary did not recommend. Equipment can be fussy about which 300B tubes are used. I have a preamp whose maker told me to use Electro Harmonix as supplied, no exceptions and no warranty otherwise. Another integrated of mine with auto bias tried to red plate a set of WE 300Bs, but is perfectly happy with KR tubes. My point is no one cares about the price of a signal tube, but if you are paying $750 per tube, you may want to ask the people who designed, built and service your equipment rather than people who tell you their tube will work "just fine."

I’d certainly agree that it’s wise to check with the manufacturer regarding approved and compatible tubes for use in their amplifiers. If for Cary the W.E. 300b is the recommended or safer choice then so be it. By many indications it’s an excellent current production 300b.

The EML XLS has been nothing short of truly brilliant in my Coincident SET mono blocks. But surely better safe than sorry.

Charles