ARC Ref 3: Tung-Sol 6550 in power supply?

My ARC Ref 3 approached 2000 hours. I obtained a 6550 tube from ARC. Upon replacement, it was alarming to find that the Sovtek 6550 WE could not produce the ambience of the original SED Winged C 6550. The soundstage shrank notably and the new tube sounded sterile. I reckoned that burn in was unlikely to change the character much and removed the Sovtek and put the SED back. I ordered a Winged C 6550 from Kevin Deal. He was credible and advised that his batch was suitable for Primaluna, not the more demanding ARC. I decided not to chance it even for a regulator. Not satisfied with the remaining options of the allegedly unreliable JJ 6550 and the pricy and sonically unproven Black Sable SED 6550, I turned to Vintage Tube Service to try an NOS Tungsol 6550 but found it unavailable.

I noted a buzz in various forums about the nice qualities of Shuguang's black Treasure KT88Z and in particular the improved Psvane gray KT88T Mk II. I spoke with Kalvin Dahl of ARC concerning rolling tubes. He was most supportive and believed that KT 88 could be a substitute but the warmer sound might differ from the original Winged C and the larger size would be a tight fit. I ordered the gray Psvane KT88T from an eBay seller ListeningChina recommended by Michael Samra on Tube Asylum. The tubes in a thorough package arrived in about a week. I have been listening to the new tube since last evening. Even brand new, the quiet Psvane KT88 clearly produced a tightly woven, wider stage and more layered depth plane along with exquisite high frequencies and bigger, rounder bass. I go through familiar disks successively to confirm the qualities and am continuously impressed with the rich tones. Instruments and voices have more bodies and string tones are lovely. This tube is about as extended at both ends as the Winged C and surpasses it in musicality. The trade off might be that the Winged C has more dryer low end impact. Unlike the Sovtek which I impatiently removed in 4 hours, the Psvane sounds both more powerful and delicate than the Winged C. I realize that the Winged C will not go back in any more. I have done some tweaks lately including a decent power conditioner, Stillpoint and Townshend footers, this single Psvane tube surprisingly produced the most pleasing improvement. The result is musical aside from hifi qualities. I have been tentatively in the market for a replacement of the Ref 3 with 5 SE. My previous audition of the 5SE did not impress me as much as this tube change. I am sharing the experience with those who are also dissatisfied with the current choices of the Ref 3/5 regulator. I was nervous as ARC was adamant before about not rolling with a KT88. I am happy to report the recent ARC change and my encouraging findings.

Now there are some shortcomings. This particular KT88 is wider and longer. The length requires slight bending of a small capacitor behind the display such that it does not touch the tube. Ref 5 owners with a horizontal board may not have the same issue. Further, one of the matched pair arrived with the getter flash largely vanishing and turning milky. ListeningChina communicated promptly and sent out a matched replacement today. So the Psvane QC may not be as solid as the Russian crowd yet. Given the remarkable sound quality, I will not hesitate to continue using Psvane tubes especially if I can monitor the conditions with a tester.

In Ref 3, the SED Winged C 6550 from ARC takes almost 500 hours to break in fully... Sonic evolution is very significant during this period. What I herd from a brand new tube was not indicative of its capabilities post break-in. G.

Forgot to come back with comments. But I'm back.

Ok, I swapped the ARC 6550 WE tube into my PH-8 and pulled the Tung Sol 6550. Maybe the 6550 isn't as critical in the PH-8 because I am not hearing a world of difference.

I have 3 ARC components that use the 6550 as a regulator tube in the power supply. Hopefully, Kevin will source a more reliable batch of SED Winged Cs when I am ready for a retube.

@Guido -- 500 hours seems kind of a long time for break-in. Can't say that I have had such an experience.

@Elberoth -- gotta say I am a believer about ARC sourced KT-120s. Maybe it's just bad luck, but for some reason, some of Kevin's KT-120s just don't bias as closely in my Ref 150 as those sourced from ARC. Can't say why.

Most interesting Ptcl99 , my regards for your spirit in pursuing your experimentation, especially with your utilization of non NOS valves.

I have an ARC Ref 3 and also a Ref 6, which is the one I use in my main system. I recently bought a NOS Tung-sol grey plate and tried it my Ref 6. (I presume the comparison would be the same in the Ref 3, although I did not try it in this unit.) The original Sovtek had a nice coherent quality—a sweet, rich midrange with an all around natural quality. The NOS Tung-sol had a deeper, tighter bass, more extended highs and was more dynamic. However, the midrange was utter crap—bright and edgy. The original Sovtek was so much better, so I would agree with the people who advise to stay with the original 6550 used. One person mentioned that tubes are biased differently and that may be the reason why some tubes work better in some systems than others; I am not really tech savvy, so I can only wonder if this is the case here. I got this NOS Tung-sol from Andy of Vintage Tubes who assured me that the midrange was outstanding in this tube. Giving him the benefit of the doubt, I wonder if he was referring to how it works in equipment other than the ARC Ref 6. (He probably never heard it used in the Ref 6 and never mentined a caveat on how it might not be compatible with my preamp.) Another person mentioned that the Tung-sols need 200 hours break in time. That sounds excessive; I did a break in for 50 hours and there was some improvement, but not really that significant. Anyway, from someone who has done the comparison of the original Sovtek 6550 and the much more expensive Tung-sol, I would advise to leave well enough alone and stick with the original.

I think my comments on the 6550 tube replacement for the Ref 3 would be relevant to my failed experiment with this in my Ref 6.  I tried the Tung Sol NOS grey plate that was recommended by Andy at Vintage Tubes.  He assured me that it had a great mid-range.  He was dead wrong.  This tube was dynamic, tight, deep bass and extended highs--but the mid-range was utter crap--not musical at all.  I went back to the original Sovtek and this has a rich, sweet mid-range.  The expensive Tung Sol gives you listening fatigue in a very short time.  Stick with the original tubes used by ARC.