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Svetlana SED "Winged C" 6550C


Product Description

These have been quite possibly the best 6550C/KT88 tube type in production.  But impossible to find in first-quality grade because the bulk of them were being bought by guitar-amp manufacturers.  This left naughty-boy tube sellers offering "B" grade tubes which may work OK, may not, may have a shorter life, or go knows what.  These tubes have been a personal favorite of Uncle Kevin for years.  But the people responsible for getting them into the U.S. have been less than stellar in my opinion.  So we bring them in direct from Russia.  They are perfect as perfect can be.  Leave it to Upscale Audio to get you these tubes in a way to make it safe and get you first quality.  Such a harmonious and perfect tube.  Happy days are here again. 

Pricing above includes a 72 hours burn-in, and custom matching in any quantity you need at no extra charge.

All power tubes are Platinum Screened & Tested to the highest standards, including a 72-hour burn in process, and testing at real-world voltages.

Every power tube is different. This applies especially to power tubes like EL34, 6550, KT88’s, etc. Two tubes can be brand new in the original box, with one testing at [as an example] 6500 micromhos, the next one at 8600 micromhos. Both tubes would be considered "new" by the factory, and not defective. While the weaker tube isn’t "defective," it will certainly have a shorter life. So if you pay 10% less, you might get a tube with a significantly shorter life. The big lie from manufacturers of tube equipment and tube dealers themselves is that they “reject” these tubes. It’s not true. You can imagine the nightmare that would create for the tube factory if people are sending back 50% - 80% of the tubes that get shipped, coming back in all kinds of condition.

As the owner of Upscale Audio, a company that has supplied tubes into over 50,000 components, and someone obsessed with treating your amp like it’s my amp, I can tell you in no uncertain terms the factory doesn’t take them back. The only tubes they will take back are tubes that have shorts, gas, or measure BELOW the minimum number they assign for that tube type (it varies from type to type, so don’t bother trying to figure that out).

I’ve overcome that issue for you. I can say with calm assurance that we pay the factories more for our tubes than any other tube seller, and we ensure that we receive the absolute cream of the crop. This flies against the logic of how to run a business: The way you make money is to pay less for the goods you sell! That’s what most ANY business owner will tell you. We also don’t sell certain brands of tubes because while they might be cheap and sometimes good, they can be more trouble than they're worth. We pass on a lot of money as a result.

Upscale Audio is the only dealer that does what we do on a grand scale, and have a deep understanding of high end tube electronics. We’re the only dealer that manufacturers give a thumbs-up to, and recommend to their customers. And I promise you only the best.

- Kevin Deal

Warranty Information

Vacuum tubes are warranted for 90 days against defects, except in cases of abuse, and replaced with like-item only.

Vacuum tubes are warranted for 90 days against defects, except in cases of abuse, and replaced with like-item only.

  • Tubes being sent in for warranty must have a return authorization number from Upscale Audio. This RA number must be written on the outside of the box. Please also include a note in the box that has your name and telephone number, and please explain the issues with the tube. If this information is missing it will delay the shipment of your replacement tube.
  • Vacuum tubes being sent to Upscale Audio for warranty replacement must be shipped in a box with appropriate packaging to keep them from being damaged. Vacuum tubes returned to Upscale Audio using inadequate packing will have a voided warranty and will be refused at the customer's expense.

Exceptions to our warranty policy are as follows:

  • Upscale Audio reserves the right to refuse warranty at our disgretion based on the equipment being re-tubed. You will be notified of any change prior to your order being processed.
  • Using a tube in an application in which it was not meant to be used. If your amp calls for a 6550, and you decide you want to plug in a 6V6GT, Upscale Audio is not liable if the tube fails, and will not honor any warranty in such a situation.

Upscale Audio is not liable for any damage or injury caused by the improper use of its tubes or the use of an incorrect/incompatible tube type. If you are unsure of what tube or tubes your equipment uses, consult the manufacturer before making a purchase. Using an incompatible tube type may cause severe damage to your equipment and will void your tube's warranty.

vacuum tube returns for refund:

Vacuum tubes are electronic parts and are not refundable under any circumstances.

Product Reviews

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Showing reviews 1-10 of 13 | Next

  1. Impressive!

    Posted by Todd Levitt on 24th Apr 2015

    I really like these power tubes in my Primaluna Dialogue Premium HP power amp (8 6550s). I've used the stock EL-34's and Tungsol KT-150's. In comparison, these (now NOS) SED 6550C Winged =C='s offer an incredible combination of the great qualities of the smooth and lush EL-34s and the powerful and dynamic KT-150s. These 6550's are like dynamic EL-34's and give my amp the best "live music" tone and depth that I have ever heard. They are very musical and light up very nicely at night :) compared to other power tubes. Highly recommended but save some for me!!!

  2. SED 6550C's are Terrific!

    Posted by Barry on 2nd Oct 2014

    I use these in a high-end ARC preamp and they are the best - they sound much better than the Sovteks the factory currently supplies. It's a very natural sounding tube with very good extension into bass and highs and beautiful tone with just a touch of warmth. I've test 11 pairs of these with an Amplitrex AT-1000 and Upscale's matching service is as advertised. Kevin and team are terrific to "deal" with too!


    Posted by Victor Emanoel on 12th Jan 2014

    Wow!!! What an upgrade!!! Took two months to receive down here in Sao Paulo, but it was worth it. Magical tube!

  4. Best Christmas present in a long time!

    Posted by Steve Morris on 25th Dec 2013

    These tubes sound wonderful in my Cary SLI 80 and Harbeth 7ES-3. Kevin was a great help. I found out what was worse than not having a High End Audio system. That is having one and it is not working. Back to the music. Great tubes and great service thanks Upscale Audio.

  5. Svetlana SED "Winged C" 6550C

    Posted by Mark Hatley on 26th Sep 2013

    I replaced my third-hand Shuguang KT-88s with these Russian power tubes. Immediately I noticed the soundstage was much deeper, and the in-your-lap immediacy of the KT88s was replaced with a lush and detailed midrange that wrapped the sweet spot in nuance and musicality. Also of note, the bass retained its tight, controlled presentation, but also extended up into the frequency range, integrating with the midrange to create a live sound that I have never heard in any of my amps. Kevin’s matching was good, and I am hoping or a long run with these well-made valves.

  6. Wonderful Bottom End

    Posted by Unknown on 28th Jun 2013

    Purchased these tubes with the hope of improving the warmth of my system vs. that previoisly provided by Gold Lion reissue KT88s on my McIntosh MC275. And I was not disappointed! My system is now much warmer sounding with 4 SED 6550 Winged Cs, exhibiting the beautiful lower midrange & bass I'd always hoped for from a tube amplifier.

  7. Svetlana SED Winged C

    Posted by steven c mills on 19th Jun 2013

    These are the best tubes for this amp bar none. The ARC REF. 110. The amp now sounds like its supposed to. The detail is amazing! Thanks again Kevin!

  8. Winged Cs fly.

    Posted by Mark on 14th May 2013

    These may be the best 6550s I've ever heard in my Leslie speakers, including NOS. Power, headroom, balance, harmonics, presence -- it's all there. Yes, not cheap, but very much worth the cost. To fully appreciate them, use a good 12au7 tube (probably NOS) like Mullard, Telefunken, or Amperex.

  9. prologue 7 monoblocks

    Posted by Sheldon on 5th Mar 2013

    I recently purchased the prologue 7 monoblocks by primaluna from Kevin here at Upscale.Amazing-I will take these amps over any other tubed product I have heard---incredible sound--build quality-and most important the guidance and support from Kevin & Jarod at upscale are second to none-----thank you Guys!!!

  10. Buy from Upscale

    Posted by Brad Farnsworth on 2nd Feb 2013

    I love these tubes. I had ought some from another vendor, and thankfully had my technician test them and install them. He said two of the drew excessive G2 which is a problem. I don't even know what that means. Upscale tests for that and the tubes are perfect.

    Like anything in life there are all kind of scources.Upscale is my new scource.

Showing reviews 1-10 of 13 | Next