Original Cary 300B Monos Reliability?


Anyone have long-term experience with the original Cary 300B monos (with the single 6SL7 tube)? I'm looking for feedback regarding reliability. I've read that the engineering choices made in the design should have the amps failing on a regular basis, along with eating tubes. 

Outside of a few DIY complaint/discussions, I haven't really seen this brought up as an issue.

I'm not concerned about the sound qualities or speaker compatibility as I have heard the combination before. Just looking to see if any of you have experiences to share regarding technical issues. I realize that these amps are now 28 years old, but they are point to point with basic parts. If the chosen values have worked for years, replacing defective caps/resistors should be straightforward.

Thanks for sharing!

128x128leahy

@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.

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