Tube Lab #26 Rolling 6550 & KT88 in Willsenton R8 Amp

First look at the 6550 & KT88 Power Tubes and a discussion on the differences with the EL34 Power Tube.
Link to my online store: valvesnmore.com/

[@2HatHudders]

Glad videos like these exsist on the internet, this will be my go too when my stock tubes burn out on the R8.

[@MartyFavento]

Awesome stuff Jim! I enjoy your vids so much ! :)

[@freddawkins8868]

Thanks Jim , i want to bild a ( 6 ) 6550 mona Amp and i have learn a lot from you say about these out put tube. Thanks again( Fred .D )

[@harrothepilot]

A great and informative vid, thankyou for posting it. I remember 6 or 7 years ago thinking tubes look interesting. I bought and built an Elekit TU8200 amp, then i was given an old 1993 Silsonic SAP-E50T push pull EL34 amp in great condition. After a couple of thousand hours of use of them, i bought a genuine Line Magnetic LM88ia with KT88's. I love the way both EL34 and KT88 sound, along with 6L6GC, KT77, 6550 etc. Thinking of buying a quad of GL KT88's for the Line Magnetic amp now, but then watched your vid..... hmmm might stick with the ever reliable JJ's.

[@gregj.gotham4402]

Try the EH KT-88 before you go with the JJ KT-88. I have a quad of the EH KT-88 they are liquid sounding, amazing sound stage, very articulate in reproduction of instruments and out last the JJ.

[@harrothepilot]

@@gregj.gotham4402 Good info tks. I have EH6L6GC's in the TU8200, and they have NEVER given cause for alarm. Could be the way to go, not to mention being marginally cheaper than the JJ's here in Aus. 👍

[@AlarusOne]

Love the technical diagrams. Nice detail! :)

[@JohnEricBooth]

I've owned an R8 for about 10 months. I was super excited to get this amp. Quality build for sure! Using the factory KT88's. I was disappointed with the low frequency response sadly, however I'm sure there's a solution for this! I DID take the plunge and purchased NOS Raytheon and RCA for the front end, but this didn't help in that respect (I'm still learning). Just displeased with bass response... and I wanna love this amp! I've wondered about their cap selection as well.

[@tubelab194]

Bass response is tricky in any amp. It depends on your speakers more than anything! But tubes are in general weak in the bottom end and fantastic in the mids and highs. First if you're using stock KT88's that could be a big part of the problem. My stock EL34's were so bad I threw them out! Also your front end tubes could be improved upon as well. Some preamp tubes just are a wee bit bass forward, which helps! Send me a message though the store and I'd be happy to put together a custom tube package to help solve this problem.

[@JohnEricBooth]

@@tubelab194 thanks! I have your site loaded so I'll shoot you a message. Also, I didn't mention I'm running older Cornwall's (recapped of course) :)

[@EsotericArctos]

You may get more change by upgrading/rolling the preamp tubes rather than the power tubes. The pre-amps influence the sound a lot more than the power tubes do in this amp. Another channel did a review just rolling in some PS-Vane tubes, and it made a pretty big difference rolling the pre-amps compared to the power tubes. :)

[@JohnEricBooth]

@@EsotericArctos I rolled in vintage tubes for that as well. Noticeable improvement but nowhere near (and reasonable) what I hoped for. I sold it.

[@dougg1075]

This is great stuff as the R8 is my first tube amp and I’m totally ignorant of tube rolling.

[@tubelab194]

Yes I remember when I went from solid state over to the bright side! I knew absolutely nothing and very little was on the net for beginners, so that is my focus, some episodes will be a challenge for beginners, but if you stick with it you'll enjoy this amazing passion even more!

[@johnanderson8096]

Mines on the way... well almost... its been ordered!!

[@phillipvansant6368]

Reading your comment was like reading my own thoughts. Just got my R8 set up and I'm looking at tube rolling like a foreign language.

[@EskWIRED]

I hit subscribe the moment I heard that you are a Who fan. 😊

[@1968krug]

I’m considering moving away from my ‘vintage’ (20 year old) Rotel transistor hi fi to a Willsenton R8, the reviews I’ve watched are encouraging. I figure if someone like yourself likes the amp... thank you for your informative tune reviews, greatly appreciated. I’m enjoying the learning curve and look forward to getting in touch one day. Thank you

[@tubelab194]

Remember the Willsenton R8 is a "budget" integrated class AB tube amplifier. It makes some compromises to keep the cost down. For anyone who hasn't owned a tube amp before, it will sound wonderful! And for the money it is an absolute steal. However, remember it needs complete re-tubing, to sound it's best, which easily adds 50% to the purchase price. I'd note most new tube gear needs better tubes, post purchase. And as I'll talk about in my next Tube Lab, it benefits greatly from the addition of a nice preamp, again this is not unusual.

[@markmckelvey6515]

@@tubelab194 50 % for tubes is a little excessive IMO. With shipping the amp is 1200 to 1300 (with the KT88 upgrade). I just got a pair of Sylvania 6sl7 and a pair of Electro-harmonix 6sn7 reissues for $140. A definite improvement over the stock preamp tubes.

[@tubelab194]

@@markmckelvey6515 maybe, it will depend on the matched quad of power tubes you buy, Mullard EL34 xf2's run a minimum $800, a nice matched quad of Electro-Harmonix 6550's only about $140. With prices of many quality vintage tubes rising rapidly as new demand for tubes continues to increase, what you pay to retube any amp is going to vary wildly! Typically when a customer orders a complete set of quality vintage tubes + a spare or two, for an amp like the R8, the bill is about $600usd.

[@tubelab194]

@@markmckelvey6515A budget option using Electro-Harmonix 6550 or EL34'S for output tubes and spending your money on the preamp/driver tube - 6sl7 (key tube in the amp) and going budget on the phase inverter 6sn7's, would cost roughly $350usd, maybe with a spare or two thrown in!

[@markmckelvey6515]

@@tubelab194 I guess what I am saying is the amp sounds pretty good even with stock tubes. Not "necessary" to spend a large sum on vintage tubes to make it usable.

[@rasmuskokholm7044]

Hallo Jim, thanks for another great video. I was wondering whether or not you have an opinion on the fact that the R8 have a fixed B+ voltage of 440v, in regards to the usage of the EL34 variants vs KT88 variants in the power tube postition? It seems to me like the EL34 variants are a better match with a typical anode voltage of 420v, vs. the KT88 variants that seems to typically wants around 600v? Kind regards from Denmark.

[@tubelab194]

Yes this is a very good question. I ran out of time to talk about this in today's video, but I did measure my R8's plate voltage at 473vdc, grid bias switch for KT88 -51vdc, EL34 -43vdc, the bias voltages are approximate as they have a range of adjustment. Power output potential comes from design, plate voltage, bias setting and how the tube is configured to the output transformer (triode or ultralinear connected). Turn down the B+ (plate voltage) and you reduce output. However power tubes and most tubes can operate well over a fairly large range of plate voltages. In order to answer this question properly a whole series of experiments would have to take place along with carefully organized critical listening sessions. And we'd only have an answer for the R8, given that another amp is likely to have a different output transformer. My approach has been - let's listen to a variety of tubes and see how the amp performs, given we're not going to be able to increase the B+ or change the output transformer. In general terms I discovered that for intimate acoustic music the EL34 sounds best and for Rock'n'roll or similar "Wall of Sound" types, the 6550/KT88 sounded great.

[@rasmuskokholm7044]

@@tubelab194 Thank you for your thoughts, good to know you don't think the 6550/KT88 is disqualified in the R8 on the ground of specs alone.I guess I'll just have to pick up a quad of each, and see what i like, on my system, in my space.

[@tubelab194]

@@rasmuskokholm7044 Yes so much of what works is going to be personal preference AND the rest of your system, speakers play the most important role in your overall sound and the room itself! My reviews are meant to help guide your choices intelligently! And when I get a spare minute, I'll look at the bias point settings of the R8 and see if they make sense.

[@ALtheDoctorWho]

It's hard to find a KT88 that lives up to the original mullard GEC. I always felt the 3 gutters had something to do with the sound. Teslers sounded Great but they Blew right away. Now I have a set of Gold lions in the Major and it's as close as it gets. Thanks for posting c];-)

[@tubelab194]

I actually have a couple of quads of kt88 Gold Lions in the store, I should roll them in and see how they sound! I'm presuming you're referring to the New Sensor reissue.

[@ALtheDoctorWho]

@@tubelab194 Yes New Sensor Genalex. I haven't pushed the Amp yet but I have the Bias set just enough to crack out some harmonics. When I think about the time when I first bought the amp those GEC tubes were tuff. You got me thinking now about the construction process you were talking about that made them kinkless. perhaps this is what the tubes that followed didn't get right.just a thought. Thanks for the come back. c];-)

[@lemmyliquidcooled7009]

Hi Jim, thanks for the great vid and the lesson! As an R8 owner (came with Willsenton KT88) I decided to buy some reissue EL34 (New sensor Mullard) as I had to hear the difference. As you point out, the mids on the EL's are fantastic, especially with jazz, classical, etc. Overall, I keep the EL34s in place most of the time for most listening, as on average, it fits more of the genres I listen to. However, I also like rock music and find the EL34s lacking where the KT88 has punch. All this to say, I'm wondering how you find better KT88s compared to Willsenton stock KT88, and if you think that grabbing a quad may serve serve solid improvement? Appreciate your thoughts and suggestions. Keep up the good work!

[@tubelab194]

Thanks for the kind comments! Well I can't comment on the stock KT88's, mine arrived with the EL34 option. However if they are anything like my tubes, they will be significantly mismatched. Even the very expensive, well liked vintage GE6550's I tried sounded blah and they were mismatched. A close matched quad of Electro-Harmonix 6550's is going to sound amazing compared to the best vintage KT88 that's not matched. That's what I do everyday for my customers - find and match preamp and power tubes. Note, I often buy matched quads of power tubes and just end up breaking the quad up and rematching them!

[@freddawkins8868]

Thank's Jim for the lesson. Because i want to bild a (6) 6550 Amp

[@William2005Ball]

Hi I have a muzishare X7 tube I’m trying to figure out how to remove the tube ? With breaking it

[@tubelab194]

No problem, just grasp the base with your fingers, GENTLY rock the tube slightly as you pull straight up.

[@jaismohamad1497]

Hello Sir. You're a master of tubes and that makes you the person to go to for advice. I'm saving to buy the Wilsenton R8. What tubes do you suggested and recommended to make it sound better. Where can I get them?

[@tubelab194]

You can check out our complete sets at www.valvesnmore.com

[@bruceferrara3917]

love the info...great job. May I suggest trying to take LESS time? I need the info but 25 minutes is a long time to spend trying to just know what the tubes sound like. keep doing this...but realize people have limited time. I cant spend hours trying to find out about info. You could have done this in 10 mins and given helpful info

[@tubelab194]

I try and keep the vids under 25min, but honestly after making more than 50 of them, anything less would be a rush and no fun. Just skip over my intro and boring stories!

[@raymondtan2917]

Can you ship tubes to the Philippines?

[@tubelab194]

Yes but unfortunately because of the poor mail safety we need to use a much more expensive level of shipping, so a small additional shipping charge would need to be added to the order. For larger orders, just not taking a discount is usually enough to cover the expense. A much better option is to use a USA based mail forwarder, this we can ship to rapidly and safely. This is how all of our customers in difficult to ship to countries like the Philippines handle the shipping.

[@frankgeeraerts6243]

These are made by Tungsol...........GE and RCA were rebranded.

[@tubelab194]

Beat you to it! See the note in the vid description. Often when I'm filming my memory doesn't keep up with my mouth!

[@johnanderson8096]

Dude lost a lot of Credibility when he choose The Who... over The Monkees!!!!

[@satmoka]

Whaaaa?