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It was the output tubes all along...

I think I finally reached the balanced sound I have been seeking for years.  I've had my VAC 200 IQ's monos for about 7 years.  When auditioning the amps I was comparing these to a similar priced Pass solid state amp.  I liked the bass of the Pass, but really liked the tube sound of the VACs.  The VAC's come stock with KT 88's which seemed a little tame to me at the time.  Mike at Suncoast Audio was incredibly generous with his time during this process and rolled some KT-120's and then finally the new KT-150's over the course of a couple of hours.  The KT-150s added the bass slam that was equal to the Pass but had the nice warmth of the tubes to boot.  Sold!  Kevin Hayes was great-switching out the KT-88's for the KT-150s when my units were manufactured.  This was my first big boy purchase-a move up from an older MacIntosh unit.  We moved a few times and 5years ago I was able to build a listening room with optimal dimensions in what will be our last house.  By this time Mike had been able to secure lightly used Magico S7 speakers for me and things sounded pretty good. I've sequentially added rugs to the wood floor, first reflection point GIK art work, and other acoustic treatmens.  The bass was a little prominent, so I added bass traps as well as The Swarm subwoofers.  Things sounded great.  Then I added the secret sauce-VAC Master preamp with phono.  I was stunned at the sound I was hearing.  I added Valhalla 2 interconnects and speaker cabling with further improvements.  However, I started to notice the bass had become somewhat intrusive on about 30% of my records (mostly classic rock, jazz, blues).  I paid extra attention at live events to see what proportion the bass occupied in a variety of musical events.  About this time I found several excellent discussions on tube rolling here on Audiogon.  I paid extra attention to the posts of @Mulveling as he has owned most of my current equipment and has lots of experience with different tube combinations.  I played with some NOS input tubes which further improved the sound stage and overall timbre, but the pesky bass persisted.  It got in my head big time.   I stopped listening to the music, rather focusing on where and when the bass would vie for sonic dominance.  I reread some of the tube articles where @Mulveling stated he didn't care for the sound of KT-150s and found the best sound was achieved with KT-120s. I talked to Kevin Hayes who prefers the KT-88s.  What to do?  At this time I was sure I needed a tube change, but not sure where to go. I spoke with Mike from Suncoast, who actually had come previously just for a listen.  He liked the bass, but suggested I try the KT-170's.  He said it was the best sounding and tight bass he had heard and a has a set up featuring them in his shop.  I polled this group, but there was no one with an opinion on the virtues of the KT-170 over the KT-150 tubes.  Sooo. I am now 400 hours in with the KT-170's.   The bass is spectacular! Fast and full and but balanced. Didn't lose the slam.  No more subterranean rumbles, either.  The sound stage is broad with good depth and instrument placement. The mids and highs are great.  I had one audiophile friend over for a 3 hour listen.  He had heard the system before the tube switch and had commented after prompting that he didn't like the bass sound at all and it wasn't 5 minutes in that he exclaimed that the sound "was perfect".  I am now hearing only music. Using the retrospectuscope, as my system incrementally became more revealing, the faults of the KT-150 slowly emerged.  I see no detriment to any aspect of my sound after making the switch to the 170s, only a much much better bass.  Hopefully this post can help inform others as to what to expect with the KT-170 tube, especially if they are running KT-150s. I did check with Kevin at VAC who indicated there was no conflict with this tube, as the parameters were similar to the KT-150, but this may not hold true for other systems-so please check if you decide to try the KT-170's.  However, it's still not clear what tube is actually the best for this system...

orthomead
mijostyn's avatar
mijostyn
8,570 posts
 

@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. 

orthomead OP
134 posts
 

@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.  

orthomead OP
134 posts
 

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.

 

mulveling's avatar
mulveling
1,895 posts
 

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 :)

orthomead OP
134 posts
 

@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!

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