It was the output tubes all along...

Tube amps with output impedances of over 1 ohm are tone controls that follow the impedance curve of the speakers. No magic here! Evidently you like the tonal qualities of the KT-170’s better!

Congratulation. Thank you for sharing your experience. It is really valuable for folks to see the dedication and work that goes into crafting the perfect system for yourself. I know, I have at times been really close with some aspect that needed tweaking and just pure effort and persistence ultimately triumphs, congrats.

Also, Magico are really sensitive and revealing speakers… getting the input perfect for them is really required. I have heard a lot of bad sounding Magico… not because the speakers are bad, but they reveal nuances many other speakers will not.

Also went from KT88's to KT170's. There's magic in the 170s.

I will need to contact Kevin Hayes and ask whether I can use KT 170 in my phi 200 amplifiers. Can you suggest a good source?

@jasonbourne71 1+

However, the S7 has a very flat 4 ohm impedance curve. You probably still have a lot of room for improvement. A good friend of mine has S7s. I am working with him to get the best out of them. I think you should try KT88's and I would match them even though your amp does not require this. All 8 should match! Small differences in amplitude response will affect imaging. Another approach, the one I take is to measure the system by channel at the listening position, but I have the ability to correct any amplitude problem, you do not. The amount of power your amp makes is totally dependant on the power supply. With KT88s in mono configuration your amps put out 200 watts which with subwoofers is more than enough to do the job.  

The swarm is a great system for bookshelf speakers. It is nowhere near powerful enough for for the S7's. You need at least four 12" drivers. Two Magico S subs or two Martin Logan BF 212s would do the job. My friend has four 13" JL Audio subs which I am not crazy about because of reliability issues. I believe the S sub has a complete crossover in it. The BF 212 only has a low pass filter like your swarm. This is not satisfactory particularly with your amps. You need a complete two way crossover with complete bass management. I would put the subs outside the S7s in corners. This only works if you can correct time and phase. I would cross at 80 Hz. What are your program sources? 

Done correctly, your system will be able to play Vini Vici at 100 dB and blur your vision or the Melos String Quartet at 85 dB and make you cry. 

Tube amps are generally not the best choice for any speaker with a nominal impedance of only 4 ohms. Not only is the impedance a problem but also such speakers tend to be relatively inefficient. However it is not correct to say as a general principle that 1 ohm output Z is some sort of cutoff point. Mate that amplifier with an efficient 16 ohm speaker or even an 8 ohm speaker where the impedance at bass frequencies remains 8 ohms or higher, and the match can be superb.

@orthomead Awesome! Very interesting results, and that makes me interested to try some KT170 down the line. I’ve moved on from the 200iQs to a pair of Master 300 monos in the big system (Tannoy Canterbury GR), and Statement 450S (older, non-iQ) in the smaller system (Tannoy Glenair 10).

The Master 300 monos are 100% perfectly sonically balanced for my system & ears w/ KT88 Gold Lions. Phenomenal sound. Hard to imagine any improvement here. I’ve tried KT120 (sixteen !!), and there are things I like, but the old problem of overwhelming bass energy re-emerges, at least a bit. I briefly tried one 300 in stereo mode (w/ KT88), and it was a bit brighter & leaner in this mode - that might come out really nicely with KT120 (or KT150/KT170) in stereo mode! Haven’t tried that yet. The monos w/ KT88 are PERFECT.

The Statement 450S shows a huge change in sound from KT88 to KT120 - more than these other VAC amps (yes, I re-biased). I vastly prefer KT120 here, because the smaller speakers in this system benefit from the extra bass power. This may change when I upgrade & upsize the speakers here (very soon). That said, I heard this very same 450S (w/ KT88) on the massive Acora VRC’s (in a large room), and noticed a lot of the same things as I do on my "crappy" little Glenairs. The KT120’s add a lot of needed meat-on-the-bones. I’m sure the Acoras would’ve sounded much better this way, too. Incidentally, I really like the smaller Acora floor-standers (both of them). If I wasn't such a lifelong Tannoy fanatic it would probably be either Fynes or Acoras for me (I like Magico S series too!). 

On the technical front, these VAC’s at their max rated powers seem to exceed KT88’s specification of 42 Watts (plate dissipation) per tube. I know the power capabilities are driven more by PSU and output transformers, but there may still be some advantage to the extra headroom of larger KT tubes. I seem to like KT88’s relatively less as they go down in number - e.g. a single 200iQ in Stereo mode, at only 1 push-pull pair per channel.

As to the issue of tubes driving 4 ohms speakers - if anything, these VAC amps are optimized for driving 4 ohms like Magicos. They offer taps down to "2-4 ohms", and IIRC they only achieve full rated power into 4 ohms (my 8 ohm Tannoys are out of luck - e.g. the 200iQ monos only hit ~ 140 Watts here). Unless the impedance and phase curve is something completely ridiculous, it’s no problem for a VAC.

@peter_s I purchased my 170s from Vivatubes.com. and had a good experience. 

@mijostyn I would like to try them again.  My initial audition was with the KT-88s and I found them to be somewhat anemic.  When I talked with Kevin about tube options, he was surprised on my take of the KT-88s and opined that perhaps they were past their prime.  I have a very open mind about trying them at some time.  In terms of the Swarm, I use the Dayton SA 1000 amp and bypass the internal crossover.  I spent a lot of time talking with Duke LeJeune about room placement and settings.  Low end isn't a problem in my estimation or others who have heard the system.  I'm sure there is room for improvement though. My crossover is set at 40.  I listen to vinyl predominately.  Nottingham Space Ace with platter upgrade and Van den Hul Crimson Stradivarius. I think this combo outperforms its weight.  Have order in for MSL ultra eminent x.  

@Lewm  I spoke with Kevin at VAC prior to the Magico purchase and he felt it was a good match.  I agree with him.  

@Mulveling.  I would try the KT 170s before the KT-150's.

@orthomead The KT 88s are more crystalline for lack of a better description. With proper subwoofers they will really sing. You have a fine turntable. Do you listen to any digital sources? By proper subwoofers I mean a subwoofer system that can be crossed at no lower than 80 hz and be able to put out a 20 Hz test tone at +10 dB from your loudest listening level  Duke has a fine system, but I am afraid it is a bit lost under S7s. Your VAC and the S7s will be A LOT happier if they do not have to deal with low bass. Separating the low bass out allows you to add the proper amount of gain to approximate the kind of bass you get at a live performance. Do you listen to any organ music? 

A system that is ruler flat in a residential room sounds awful. It will be way too bright and almost bassless. The right curve for this situation that most of us find ourselves in has 20 Hz at +10 dB over to 40 Hz at +10 dB then down to 0 dB at 100 Hz. I like a little 1 dB dip after that to 150 Hz, but that is personal preference. It makes the bass a little drier. From 100 Hz you go flat to 1000 Hz then start a slow taper to 20 kHz where you should be down between 6 and 12 dB. The louder you listen the more pronounced you want this. Every recording has a "right" volume, the volume it sounds best at. Too loud and it gets harsh. Too soft and it will be dull. 

If you have EQ capability you can force your S7s to do this, but the VAC will not like it at all. This is one of the two main reasons subwoofers are important. They are designed to make low bass and you can push them to the right volume without punishing the rest of your system. Even better is using a two way crossover to remove the low bass from the VAC and S7. The system will cleanly attain a realistic amplitude response at a volume that will make you feel as if you are at a live performance and I do not mean ear shattering either. To give you an idea, my speakers will not go as loud as your S7s. They sound bigger, but not louder. I use eight 12" drivers in four enclosures, each enclosure getting 2500 watts. Using fewer drivers would result in more distortion. Your Swarm has four 10" drivers. Two 10s equals one 12. Under a speaker that is capable of more output than mine you are using a subwoofer system 1/4 the size. 

Finances are an issue for most of us, myself included and Rome was not built in a day. You have a great start in the S7s, VAC amp and turntable. The Ultra Eminent is a super fine cartridge and the sweet spot in MSLs range. They are about to release the Signature Diamond for $15,000!  A good subwoofer system that matches your speakers will improve your sound quality eons more than a new cartridge. 

@mijostyn Thanks for taking the time and effort to help me improve my system.  I don't do any sound measurements, but it's clear that you have mastered the process. I actually believe everything you are saying.  Initially, I was entertaining purchasing the Magico subs until I saw the financial damage that would be incurred! What was presented primarily then by Mike was the Titan series.  The size and pricing for 2 units didn't make sense at that time.  More importantly, my overseer and CFO felt much more strongly than I did on that matter.  The swarm was an attempt to add something at a low level of risk.  I think I got my money's worth out of them, but I suspect you're right about them being underpowered for the S7's.  It would be great to be able to do an in house sub audition, but I don't think that's easily arranged.   We had an art dealer for a while who knew our house and interests verry verry well.  He would occasionally drop by to show us a piece.  He would do a quick walk through, rearrange some art and leave a space for the piece he brought over and told us just to "live with the piece" for a few weeks and see what we thought.   Oh, if I could only do that with subs.  The S series may be the ticket though. 

In answer to your questions, I have an old Sony SACD and Meridien cd player, but they are over 20 years old and don't see much play.  Meridien died and I don't see the benefit of a repair.  I should have Modrighted the Sony.  BTW, I have a TON of cd/sacds.  I don't have any organ music recordings, but I see where you are going with that. Thanks again for your suggestions.  You definitely got the sub gears whirring in my head.

The issue for many audiophiles is digital phobia. They stubbornly want to keep their system pure analog in the belief that it sounds better. In reality the benefits of moving over to a digital preamp/processor are legion. Conversion to and from 24/192 digital is now invisible. Once you are in numbers you can do almost anything without added problems such as subwoofer management, EQ, room control and high resolution steaming (Qobuz). The benefits for outweigh any detriment if there even is any. The best digital preamp for you would be the DEQX Pre 4 which is still in Beta mode, but the prices are still about 1/2 of retail. My friend with the S7s just got one. We have not set it up yet. The best value is the MiniDSP SHD. Down the line you can add a high end DAC for your VAC amp/S7s. The SHD is only 1500 with the best microphone. Add two Martin Logan Balanced Force 212s and you are in business for a total price of just over $10,000. The 212's are handily the best value in subwoofers today. With the SHD you only need a CD/SACD transport like the Bricasti M19. The SHD is set up to stream Qobuz which IMHO is the very best streaming service. It also uses Dirac Live, the easiest room control system to set up. My guess is that this addition will blow you away and you will wind up getting the DEQX which matches the quality of your system. It also has a fine phono section in it designed by Dynavector. It is designed to use a transformer for low output cartridges. I have a Pre 8 which is the identical unit , but with a 4 way digital crossover for people who want to triamp their systems. You can make any loudspeaker fully active. I would leave the S7s alone in this regard. Magico knows what it is doing. You want the Pre 4 which is somewhere around $7000 now and will retail for $10,000 I think. This would make adding subs a total of almost $20,000, but you won't need to buy a better DAC. Financial advisors always think HiFi is a waste of money. I do not bother mine with it avoiding the argument all together.  

When did this shift from rolling output tubes types to digital EQ and sources?

Anyways, I do agree with @mijostyn that a good ADC + DAC conversion process can be extremely transparent. Rather shockingly so. I’ve heard this by playing my vinyl setup through a Meridian 808v5 CD/preamp/DAC (which converts analog inputs to digital). I’ve considered continuing to use it this way for the excellent L/R balance control. Don’t mind the sacrilege. Still vastly prefer many of my vinyl records to their digital versions; it comes down to the mastering.

I’m surprised you find the need for subs at all on S7’s! They’re beasts, and rated down to 20Hz on their own. For music, no more should be needed, unless it’s some massive room? Adding extra energy down there will also add to the challenge of clean vinyl playback. You definitely DON’T want your VAC amps dealing with any subsonic feedback or rumble - it will rob their performance more than extension gains. Have you tried running the S7’s alone lately? Make sure you don't see any woofers flapping during playback. 

@orthomead There are certainly more august minds that have penned well reasoned advice above.

In the KISS realm a pair of subs with (say a pair of REL classic 99's that will run under 4k delivered) settings and placements fiddled with will yield an all enveloping sound even with the terrific Magicos.

Your listening room I imagine has all the treatments bells and whistles.

If you try the KT170's, then please check with the manufacturer first before putting them in. Not sure about how much space there is where the tubes go in your monos but the Kt170's are fatter than the KT88's.

@mulveling That 20 Hz rating is at one meter. They do better than most speakers, but the issue is that you have to boost 20 Hz 10 dBSP to get the right balance. This will push the S7's woofers into their nonlinear zone at rock and roll volume increasing distortion. This will also torture the amp. Breaking out 100 Hz down to a dedicated subwoofer system decreases distortion in the main speakers and allows you to get the proper boost without torturing the main system. 

@mijostyn I don't really have digital phobia at all.  I started with a room and a pair of monoblocks in my new house.  I was ALL digital until about 9 years ago.  Actually most of my vinyl is from my youth, but I swallowed the CD blue pill and didn't listen to vinyl for 3 decades, building my cd/sacd collection. My Meridien cd player opened my eyes to digital, but listening to vinyl again opened my ears.  I have a good friend who has MBL Radiahlstrahlers (the big boys) with top of the line Esoteric digital front end.  Sounds great-but certain vinyl sounds better in my room compared to his digital source.  I know GIGO.  Needless to say, I'm not digital phobic, I've just been wandering down the analog trail.  At some time, I will modernize the digital side of my Rome.  Just not yet. I do appreciate the path that you have illuminated.  Also, I only listen to rock and roll volume at rock venues.  I rarely listen above 90 dB and wear hearing protection while working as my work environment can be noisy. 

@Mulveling.  I have listened to my system with the Swarm off.  Not quite as good as with it on.  My system doesn't suffer from loss of low end.  I'd like to think I'm helping tune the room with the distributed bass array.  My room isn't huge (25x14x10) at all.  I think Mijostyn may have hit the nail on the head with the concept of a stronger bass array.  I spoke with Mike at Suncoast Audio who really knows my system and fully agrees-new sub array with bass DSP makes some sense to me.  

@wsrrsw You are absolutely correct in noting that the KT 170s are wider than the KT-150s.  Fortunately for me, the VAC configuration allows for plenty of space.  I should have mentioned that in my original post-thanks for doing so.

@orthomead My amp had to be modified to use the KT170 tubes. That i should be dotted. If you get ‘em (Do!) please report after they have settled in. 

@wsrrsw I have over 400 hrs in.  I'll refer you back to my original post which details the adventure and results.  I love em.

@orthomead 90 dB is pretty loud! The loudest I listen is 95 dB. The reason to use the bass management I previously discussed is to create the FEELING of a live performance a less than ear shattering volumes. It is, in large part, the visceral component of frequencies below 100 Hz that make live music so exciting. 

I was over a friends house two days ago. He has a wonderful system. Serblin K'tema speakers, CS Port turntable, MSL Signature Platinum cartridge, Bricasti amp, DAC and transport. We were listening to, of all things Vini Vici (disco dance music with heavy synth bass). He pulled his meter out and it read 104 dB! I had no idea it was going that loud. I played the same cut at home and 95 dB blurred my vision. My friend, having had a bad experience in the past, will not use subwoofers and the fundamentals of the synthesizer bass were AWOL. He is beginning to warm up to the idea again. 

Staying on topic, with a proper subwoofer system you can drop back to the KT88's better sonics and still have a much more powerful system than you would with KT170s and what you are presently doing. 

@mijostyn I suspect a stronger sub array is in the near future.  Will need to live with the KT-170s for a while, but agree that I should give the KT-88's another try.  BTW, 90 is the peak for listening, which is permissible by OSHA's standards for up to 8 hours a day of exposure. I monitor loudness during each listening session. I'm no where near this and wear hearing protection at home while vacuuming with VPI (my first step for all vinyl cleaning) and at work where I'm exposed to pneumatic drill and hammer noise.  FWIW, at work I wear the Etymotic 20 ear plugs.  Reduces all sounds by 20dB but allows for conversation. These were designed for concert listening without changing the sound spectrum. I do take my hearing seriously.  

Soo. Back to point. @mulveling, since you've had extensive experience with the 200iq's and the VAC master preamp, what would be your next tube to experiment with if you were in my shoes?  Also, good luck with Helene-hopefully she powers down some by the time she gets to your neck of the woods.

Soo. Back to point. @mulveling, since you’ve had extensive experience with the 200iq’s and the VAC master preamp, what would be your next tube to experiment with if you were in my shoes? Also, good luck with Helene-hopefully she powers down some by the time she gets to your neck of the woods.

@orthomead The power tubes are the biggest difference maker, IMO. You’ll also get a bit of different sonic balance if you switch from mono into stereo, but with the Magico’s need for power, you may lose too much there. On my Tannoys, Stereo mode w/ KT120 had really sweet mids and nicely proportioned bass. Stereo mode w/ KT88 was simply too threadbare. I don’t run a sub, which as noted, will obviously change the equation.

For 6SN7 V1 slots, my favorite is the Tung Sol round plate black glass. Hard to find good ones. I’ve had a few that sound GREAT for a bit, but then their heater gives out - usually on just 1 side (I have PTSD from enjoying a "perfect" session and suddenly hearing the music hard pan to 1 side and stay that way - dead channel from a bad heater). Big, lush, romantic sound on those Tung-Sols. Classic tube sound, and then some. Various 1940s and early 50s Sylvanias are also very good. The brown-base 6SN7WGT (w/ chrome tops) is a nice change of pace if you need a slightly cleaner / leaner / brighter sound. The side-getter Sylvania VT231 is always good - overall neutral with a nice, airy sound. I also like the Hytron - big sonic image. Always found the RCA gray glass tubes kina "meh", but they are OK; they don’t do anything particularly wrong but won’t blow your socks off either. Don’t waste your time with later GTA/GTB types in these V1 slots.

For the V2 slots, I find the new Russian Tung-Sol 6SN7GTB gives the best dynamics and punch (i.e. the stock VAC tube). These slots are driving the power tubes and they NEED to be strong. You measure these Russian tubes. and they will generally clobber any vintage / NOS tubes in transconductance readings. These V2 slots also run at higher voltages which the GTB can handle. Older GT series tubes will possibly be running beyond their spec here - but they will work, if you so choose to try it.

For the Master preamp - man, vintage 6922/6DJ8 types are so frustrating. I’ve had a number of them go noisy on me, or other various gremlins (even pins which fall out, broken glass, the works). Even tested tubes from Brent Jesse. I had some Mazda / France 7308 which sounded great but went noisy. Then the various Amperex Holland 7308 are relaxed sounding - probably a bit too relaxed. The 8416 Amperex USA (12DJ8) are similar, maybe a bit better. Think I also like the USA Amperex 7308 a bit better - the Hollands sound good but just aren’t for me.

The Japanese / Mastushita 7DJ8 sound great and have never given me problems - they’re my go-to these days. Good musical tube, good balance. Recommended.

Siemens E88CC are quite reliable and a good choice if you want a less warm tube, but they still have a nice midrange. Funny story, I accidentally ran a pair of Siemens E88CC for ~ 20 hours on the 12V setting instead of 6V. When I finally noticed this mistake they were glowing like the SUN but still played fine. Transconductance measured ~ 20% lower than before this incident, so it took a toll - but they can certainly take a beating! Don’t forget to check this switch position if you’re rolling between 12V and 6V types.

I also have some Philips early 1960’s E88CC which are super duper if you want to wear your sound like a warm lush blanket on a cold day (lol). I like them.

Last year I had moved my 200iQ’s in my 2nd system, and then replaced with the Statement 450S. That ended up being a great upgrade, though I was at first disappointed with KT88’s in it. The Master preamp synergizes at a much higher level with the Master & Statement level amps. With the 200iQ’s, I’m still not sure if I may have preferred the ARC Reference 6 on them.

Fellow loud listener, here lol. I am aware of the OSHA standards :)

@mulveling - Thanks so much for the info-that post will help me a lot.  I'd like for you to clarify one point if you would be so kind.  I will probably never use the 200iqs in stereo mode.  With Mono use only in mind, what would be your go to tube.  BTW, Mike was telling about the VAC 300's-they sound like they are super sweet.  Lots of tubes to roll though!

Isn't it really tough for tubes to get along with bass drivers? Isn't that the real challenge herein?

Isn’t it really tough for tubes to get along with bass drivers? Isn’t that the real challenge herein?

For the most part, the tubes are fine. If they’re struggling for your power needs, you just throw more parallel push-pull pairs at it (VAC’s Mono mode puts the 2 channels in parallel). The output transformers have the far tougher task, retaining bandwidth at higher power levels. That’s why they’re so big and heavy in VAC’s. A 200iQ is rated 100 Watts x2 and weights over 100 lbs, most of it transformers - it means business, and will outweigh the majority of other brand tubes amps at this power rating. On the extreme other end you had the Carver 275 claiming 75 Watts x2 at just 19 pounds (on par with claims of turning lead into gold).

With Mono use only in mind, what would be your go to tube. BTW, Mike was telling about the VAC 300’s-they sound like they are super sweet. Lots of tubes to roll though!

The KT120’s were still my main choice over KT88 in Mono mode (but it was close). There was a moment in the small system where mono + KT120 was a bit too much bass and KT88 mono was a bit better. But for most configs, KT120 was my favorite. Keeping in mind your system w/ Magicos & subs is quite different from mine!

Now KT120 in a pair of Master 300’s in Mono is again a bit too much bass (stick with KT88's) - but wow, those amps are something else. Highly recommended. 

@mulveling thanks for the clarification

@orthomead  Etymotic makes great products. I have been using their ear buds for decades and always take their attenuators along for every concert. I insist on people using hearing protection in my shop. Having said all this the recommendations of "authorities" are always on the conservative side. The worst hearing exposure and the most likely to do damage are loud impulse sounds such as gunshots. Steady loud noise gives your ears a chance to tighten their ear bones ( stapedius muscle) and provide natures level of hearing protection. I never start out at 95 dB, but turn it up slowly over a song or two. 95 dB is also the peak level. I am 70 years old and can still hear 16 kHz. I've been rocking since the age of 13. I am also an anecdote. There is a genetic sensitivity to noise induced hearing loss.