I’ve always found power tubes more important to shaping the sound in ways that are meaningful to me. Small tubes can also be important to be sure, but a lot of times it’s an initial "wow!" impression, then over time I either tire of that variant or just want to hear a different flavor. I listen loud (more strain on power tubes), so perhaps that explains my findings.
With power tubes, my initial impressions tend to stick. The change from a KT88 to KT120 is especially significant in amps where I’ve tried this swap. Anyways, what’s your tube amp that has 16 freaking KT88 slots to replace with a non-existent Siemens 6550? (I know op won’t answer) To be fair, if the Siemens 6550 did exist, I’d prefer it over JJ.
I actually have a pair of VAC Master 300 that use 16 KT88 (plus 8 6SN7), and even with auto bias it’s a kind of a PITA to swap. The KT120 sound great here, too.
Yes I am looking for siemens 6550. It does look elusive. And will have to revisit the source of recommendation whom is very good at what he does. I like to biamp so I'm using MC 901 monos from McIntosh. I like them a lot and they blend tube and solid state very nicely.
I do like VAC quite a bit and still think about it.
I did a lot of rolling on this class tube, kt88, kt66, 6L6, 7581a, 807A, russian tubes I don't remember the number of, and they all sounded different. It seems invariably I liked the new sound (human nature) at first but after going thorugh perhaps a dozen sets of tubes, I ended up back at the tube that the maker (Decware, Steve Deckert) had designed the amp around. Makes sense really.
@emergingsoulI think that you are Hi-Fi hero to go for right-away upgrade before even turning the amp on or defining goals for replacing 16 working tubes.
Are you sure you don't mean Sylvania 6550? Can't say I've ever heard of a Siemens 6550, and I've tried pretty much every NOS KT88/6550 variant out there over time. And some google searches yield zero hits.
Yes, going NOS 6550s will likely make a notable difference in sound (knowing the amp in question will help folks answer), but the question is whether it is worth the cost. If you want to go NOS, the GEC / Genalex have the best reputation (they were fantastic when I used them in an Air Tight ATM-2 - by far my favorite variant), but in the volumes you are looking at are basically unobtanium as NOS (if you need, say, 4 matched quads, you are looking at easily over $10k, and likely over $15k if you want something that is truly NOS and not just "tests as"). So substantial difference, but probably not worth the price.
Of the 6550s, you may be able to scrounge up 16 NOS Tung Sols in the grey plate variation (which are also nice sounding tubes), but you'd likely be looking at >$6k just for the tubes. Again, 16 Tung Sol black plates (the best sounding variation) are also likely unobtanium - TubeDepot is selling singles for $1k per tube).
In the more "reasonable" cost bracket, you are looking at GE or Sylvania 6550s. That will probably "only" run you ~$3-4k. But the question is whether that cost is worth it over something like the current Russian Gold Lion KT88s in your amp (which tube is better than the JJs, but of more reasonable cost than the NOS options). Or you could look at something like the KR KT88s. The EATs are nice but no longer made and also very hard to find. Even the Yugo type ii Ei KT-90s are getting ridiculously expensive - I have seen quads listed at $1700+.
In short, whether NOS power tubes -when you are talking 16 of them for your amps, are at all worth the difference is highly system and wallet dependent - which you haven't told us anything about. In the abstract, I think even moving from the JJs to the Gold Lions would be a nice little upgrade, and depending on how much difference you hear, you can then determine whether it makes sense to spend the serious coin on NOS.
And I was feeling bad because I needed 12 tubes. If you like the way it sounds now, stock tubes might be the best budget replacement. It you want more with great top end extension kT-88 Gold Lions sound very good. Yes, power tubes are everything.
I think you should do this….replace your tube gear with solid state. You’re going to accomplish two major objectives - 1) have less noise in your system and 2) make less noise in the forums
I built an EL84 Single Ended amp. The donor amp camp with some JJ’s. Amp was very much missing something with the JJ’s. Ordered a pair of The Tube Store preferred series 7189’s.
The amp changed completely in its sonic presentation. It now sounds how I hoped it would sound.
But, as a single ended amp, swapping out a tube in this simple a circuit, will showcase tube differences kind of dramatically
I sell tubes full-time for a living and I think you'll be looking for those elusive Siemens' 6550s for a very long time indeed because I don't believe they exist.
I love Siemens tubes and I'll tell you the closest thing to what I imagine a Siemens KT88 or 6550 would be/sound like that you can buy is the modernly made KR Audio KT88. At $400 a pop they aren't cheap and they are about as hard to get your hands on as the fabled Siemens 6550s. They are a nuanced, disciplined tube that is subtle in how great it is such that trained ears might appreciate it far more than ears just looking for "more."
Many say the KR Audio KT88's sound like NOS GEC/Genalex tubes. But I doubt too many of the many that say or have other opinions or claimed knowledge about them have ever actually heard them never mind spent the time to listen to them. I swap my KRs for my GECs on a weekly if not daily basis, and have for years, so I'll tell you that in the I don't think they sound similar at all. In fact, I always tell people if Siemens ever did make one, I expect it would sound like this (the KRs). And now I've told you, do what will with that.
How do you like your VAC gear, specifically your amps? I have a couple MC275s I've run as monoblocks in a bi-amped setup (currently paired with Pass Labs xa160.8s.) that I think I'm ready repurpose and/or upgrade.
I had planned to buy a VAC Master II pre-amp this month but I re-tubed a couple for local clients over the past couple of weeks and didn't know whether to laugh or scream when I pulled the stock tubes out of them. So I've pumped the brakes a bit One had a pair of Golden Dragon 6922s in it along with 6 Shuguang 12AX7B's in the phono stage, the other a pair of garden variety EH 6922s, no phono stage. How they can plug a couple of $5 gumball machine tubes into a $30k pre-amp and think it's okay is simply beyond me. You could socket a grilled cheese in that thing and it would sound better. The Siemens E288CC Red Tips sure did.
I’ve come to the conclusion that emergingsoul has no system at all and just wants us to think he does. No one would be as elusive as he has been. Fairly entertaining though.
Funny they aren’t mentioned yet but the Russian Winged C 6550’s are readily available nos for under $100 each. My favorite power tubes ,and I’ve tried many, are the winged c el34’s and kt88’s.
Those prices are ludicrous. And I buy/sell that stuff everyday. And I feel horrible for charging HALF what those guys charge for that stuff. My god. Everyone thinks the crooks are on eBay when its more often than not the opposite.
TubeDepot's prices are outrageous. Their business practices are even worse. Years ago before I knew anything about anything I bought two pairs of tubes from them. RCA and Ei 12AX7, I still have the receipts. The RCA's that came were a short grey plate and a long-grey plate. The Ei's that came were a nickel plate and a smooth grey plate. I didn't know much then but I knew they looked different enough to warrant a phone call. So I called them asking if there had been a mistake or if I had ordered it wrong. They told me it was absolutely fine, it was intentional on their part, I had in fact ordered two RCA 7025s and technically they were both RCA 7025, and as such they were the same and that there would definitely be no difference in how one sounded from the other. Right, got it. Glad I paid an extra $6 per tube for balanced and matched tubes in addition to the $419.98 I paid for a pair of RCA tubes that weren't even a pair. Same with the Ei tubes. Though, I only paid $155.90 for the Ei tubes, which by way of comparison seems reasonable.
I still have all four of those tubes and the receipts. I use them as training/onboarding materials whenever I bring someone new on to explain which way our moral compass points.
I replaced a quad of E-H KT88 with Gold Lions a while ago along with all my phono and preamp tubes. There was an overall improvement, but it's hard to tell how much was due to the power tubes.
Their contribution was undoubtedly significant. The Gold Lions are a good sounding, generally reliable and long lived tube at a very accessible price point. I ran eight of them for the better part of a decade in my own kit.
The VAC amps are amazing. I also have an older statement 450S (no iQ) for my smaller 2nd system. Of all a system’s components - the big VAC power amps were by far my most fruitful "splurge". For every other component slot, I’ve found cheaper items that yield similar or at least "close" results to my splurge-level items (of course a system’s components must synergize) - this includes the VAC preamp and phono. But I don’t know how to replace the big VAC amps - they’re wonderful. I particularly love them with Tung-Sol KT120.
As for the stock tubes you found - Kevin is not trying to be a broker of NOS tubes. His magic is in the voicing of components. I’ve done the KT120 swap and also prefer some of my old 6SN7 in V1, but for the most part these units sound awesome stock. I’m familiar with his choice of EH 6922 Gold and Shuguang 12AX7B (which are long OOP - he has a large stock). I think these sound very good, despite not being chic or expensive. I’ve got a large collection of NOS, and sometimes still choose Kevin’s 12AX7B for phono slots. Not familiar with the Gold Dragon 6922 (Shuguang?) - I thought it’s been a long time since VAC shipped any Gold Dragons. Of my vintage/NOS 6922, those tubes have been a huge pain in the ass for going noisy and various other gremlins - even sourced from reputable tube dealers. Just had a Brent Jesse Mazda 7308 go noisy on me, and before that an Amperex 7308 had its glass tube crumble out of the blue. I’m about to give the EH 6922 another go. I don’t blame Kevin for no longer supplying NOS. He used to favor Amperex 8416 when they were cheap and easy to find, btw.
Edit: I didn't know the Master has a "II" revision now, neat. Do you happen to know what that entails?
Yes, power tubes are important, and not just for "tone." I recently tested a variety of output tubes in my Williamson amplifiers. Just to give a few examples, the Gold Lion KT66 produced the most power before passing 1% THD, 22 watts. The Chinese TAD KT66 produced only 19 wpc at 1% THD. Vintage 807s also produced only 19 watts before clipping, but at only .19% THD! Dave Gillespie over at Audiokarma is an expert on ARC amps and he says that the Gold Lion KT88 is about as close to the GE 6550 as you can get, in terms of power output and distortion. I've found the same with a number of small signal tubes, including 6SN7s and 12AX7s In general, the NOS tubes perform better than most new manufacture tubes.
Regarding the small tubes, I have an integrated 300B (Elekit with the new Western Electrics) and recently replaced a 5751 (superior substitute for the 12AX7 IMHO) with a Cryotone 5751, the brand which DecWare offers as an upgrade. I also added a pair Cryotone 12AU7s.
After playing it for a couple of days of break-in, I noticed I was losing interest in listening to music. It sounded fine but the emotional engagement was missing.
On a fluke, I switched my previous NOS Sylvania 5751 back in (did not switch the 12AU7s) and Voila! I couldn't stop listening to my rig! The emotion, dynamics and tonal accuracy were back!
I had no idea what a seemingly insignificant tube could do.
@dogearedaudio: I don’t believe you. The 807 uses a top anode cap and a seven pin socket. It is not swappable with octal power tubes. I had some in my tube collection.
I don’t believe you. The 807 uses a top anode cap and a seven pin socket. It is not swappable with octal power tubes. I had some in my tube collection.
I thought that was odd too. Maybe a weird typo?
I’ve used a Williamson amplifier (pair of Heathkit W5) with Gold Lion (Russia) KT66 and it was very "powerful" sounding with strong bass, good "slam", and plump full mids. The same amp, fitted with vintage GE 7581A (near KT66), sounded more airy, spacious and articulate with a gorgeous midrange - but leaner in bass.
Sadly, power tube rolling becomes quite painful in amps using more than a quad. Vintage/NOS is pretty much out of the question. BUT once you get so many push-pull pairs in parallel - that’s where the real magic and beauty of tube power lies for me. On just one push-pull pair per side, I will certainly prefer the tonality of EL34, 6L6GC / KT66 over KT88 - at least until I run out of power,
@carlsbad2: The 807 is a seven pin top cap connector anode tube. It is not swappable with octal power tubes. So how can you compare it to the common octal power tubes as you claim?
@jasonbourne71I’m sorry, what are you talking about? It’s very easy to substitute an 807 for a 6L6 or KT66 with an adapter socket you can buy on eBay. You just have to be careful to observe the lower dissipation rating and keep the plate and screen voltages at 400VDC or below. The 807 is pretty much a 6L6GB with slightly higher max ratings. My amps will accomodate KT66, 6L6GC, 5881 or 807. And the 807 uses a *five* pin socket. The 1625, the 12 volt version of the 807, uses a seven-pin socket.
All…please be very diligent and extremely careful recommending tubes for OP’s system. The tubes must be on a good enough level to not embarrass the amps that will be driving a $50,000 pair of speakers that OP is looking to purchase. Please continue your battle on tube choices, plate voltages, tops, compatibility , requirements and adapters. I’m sure all this information will be extremely helpful to @emergingsoul
And just curious, @emergingsoul, with you being so impressed with Jay’s Audio Lab, are you contacting him for an advice. What did Jay say about your setup and future plans?
The Svetlana Winged 'C' tubes were a very nice tube and I hated to see the company shut down after the St Petersburg plant burned, with all it's equipment.
If you do manage to find any remaining stock; there's a 99% chance, they'll be factory seconds, as all the first quality tubes went years ago.
I went through a few octets of Sylvania's 6550s, until Upscale ran out and I couldn't find any more.
Uncle Kev recommended the Winged 'C' and those were a nice replacement, until the plant burned.
The GE 6550 variants were my next stop and I loved 'em, until they got too salty for my wallet.
I kept a good testing quad, that I've used for comparison against a few other brands and found the Russian Gold Lion KT88s to provide fairly close to the same presentation.
Just to be clear, I was certainly not recommending anything other than the correct tube type for the OP’s amplifier. I was simply pointing out that the quality of the output tubes can make a difference, in terms of both power output and the amount of distortion they produce.
Curious, I read herein that the feedback level related to the amplifier is important to consider for purposes of evaluating whether it really makes much of a difference to tube roll power tubes. Anyone know why that would be?
Further, I am biamping with mc 901 monos and since the solid state part of it handles the bass drivers maybe power tubes are not that important since it appears it impacts the bass area more so.
But since I love spending so much money on everything audio even the slightest change might be worth considering. Maybe power tubes would impact the mid driver.
There are some people posting herein who know a hell of a lot about tubes. It’s actually kind of scary.
I agree, the prices are ludicrous, but that is just what the market is. For example, looking for true NOS Genalex / GEC tubes, I could only find one dealer that appeared to have multiple legitimately "NOS" quads (Gold Monarch) in stock - not the "tests new" stuff you typically see on Ebay. And they wanted $4500 a quad. (Although I do note there is one guy on EBay right now selling what looks to be one legit NOS quad for $2k).
Its a simple issue of supply and demand - there just is no supply. If you can find these tubes in quantity for half that price I'd be forking over the cash pretty quickly.
I agree with you on Tube Depot - they sold me a Mullard EZ81 that wasn't (no date codes, looked to be a Brimar).
I also completely agree with you that anyone says that the KR KT88 sound like the GEC KT88 clearly hasn't listened to them both.
"Curious, I read herein that the feedback level related to the amplifier is important to consider for purposes of evaluating whether it really makes much of a difference to tube roll power tubes. Anyone know why that would be?"
I've seen quite a few people say that tube swapping shouldn't make a difference in a high-feedback amplifier. The theory is that high levels of feedback will pretty much swamp any small sonic differences between tube brands. All I can tell you is that my Williamsons use the standard 20dB of feedback, which is about as much feedback as most vintage push-pull amplifiers employ, but the differences in output tubes are clearly audible to me. Moreover, feedback cannot compensate for poorly-made tubes that produce below-rated wattage, higher distortion, microphonics and other undesirable artifacts.
I use a Denis Had Firebottle SEP "HO" (high output...heh heh) or a Pass XA-25 with very efficient speakers. Swapping between these amps and noting their differences (subtle, and both sound amazingly good) is fun. Also, the Had amp can be used with many different tubes and those differences are also interesting, leading to my drawer full of tubes. All manner of GLs...88s, 77s, 66s...all sounding a bit different...currently KT120s. 2 power tubes in that amp...that's right...2...ha. All my small tubes are NOS GEs because I like 'em...4 in my Freya preamp, 1 in the Had amp, and none in the XA-25 (I suppose I could put a tube in it but it would just rattle around) although when in use it I can look at the tubes in the Had. Another ha...
Curious, I read herein that the feedback level related to the amplifier is important to consider for purposes of evaluating whether it really makes much of a difference to tube roll power tubes. Anyone know why that would be?
Further, I am biamping with mc 901 monos and since the solid state part of it handles the bass drivers maybe power tubes are not that important since it appears it impacts the bass area more so.
But since I love spending so much money on everything audio even the slightest change might be worth considering. Maybe power tubes would impact the mid driver.
Agree with @dogearedaudio - feedback does not free us from the impact of tube rolling on sound. Lessens it some - but never completely gone, in tube land!
Even if those MC 901 push bass frequencies with the SS section (really nice looking amps, btw) - most of the "music" lives in the midrange, and the sonic fingerprints of your components and tube choices will sum up and reveal themselves here. It's not just a matter of raw power; amps each have their own "sound" even when loafing - but they'll certainly strain and sound more colored when pushed hard, so having more headroom is an asset.
It's not just about producing max power IMO. The parallelization smooths out imperfections in each PP pair, and more importantly gives headroom at lower levels. There is an effortless sense of power, finesse and grip with my larger Master / Statement level VAC amps compared to the Signature 200iQ (to be fair there are other improvements too, besides more PP pairs & power). On a good day, the 200iQ sounded wonderful. On other days, the treble seemed a little aggressive. On others, the bass sounded either a bit lean or too loose / bloated. Even on a "bad" day, the Master and Statement amps will outperform the 200iQ's best days.
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