Looking for high power warming sounding tube amps

Quicksilver Q4 monoblocks

My Quicksilver Mono 120s with KT120s (midrange) or KT150s (linear/transparency) fit the bill for the same reasons you are looking for. 100wpc.  I also have a Soderberg (recently) modded and upgraded Pass/Forte' now true Class-A 50wpc just to give you an idea.  Enjoy both for different reasons, but gotta say my tube amps are my fav when Im ready to really sit and listen to music and want that extra 15% of magic.  The upgraded Pass/Forte' Class-A not far behind. 

My QS have a bit more body, bigger transformers (4 of them, 2 per amp), with a bit more depth, layering, 3D sound than my Class-A Pass/Forte. Just to see what they could really do, on the QS M120s I upgraded the coupling caps to even better Mundorfs and upgraded the four main power caps to even better Nichicons. The amps really came into their own. My speakers enjoy the added bit of current.  They sound their best when driven by a nice tube preamp, I'm using a dual triode 6SN7 preamp. Add really good interconnects for source, and pre-to-amp, and ur there. Play with input tubes on the preamp and the mono amps for fine tuning.   

https://forum.audiogon.com/discussions/mcinlosh-lol

Mono blocks up to 150W per channel

Found the v4 monos right here: https://www.usaudiomart.com/details/649873599-quicksilver-v4-balanced-monoblocks/

Unfortunately many high power tube amps use KT120 and KT150 which are tough to get.    

V4 is a great amp.  It can use a few different tubes which helps when it’s time to re-tube.   You can not go wrong with a Quicksilver.   Huge bang for the buck 

+4 Quicksilver!

Mike

+5 Quicksilver. I have the Mono 60's and they're delightful in the midrange.

That said, I also have the Pass XA25 and its mids are luscious and intimate. Close your eyes and you might swear you're listening to a tube amp. 

I was a long time owner of a Pass x350. I now have Audio Research Reference 160m monoblocks. The moment I heard the ARC 160 that was the end of my love affair with solid state amps. It is because they sound like real music and in particular the bass.

Most likely what you like about the X350 is the slap you get because of the really fast bass… the slam. You’re not going to get that with tubes. Also, that is not real. I spent over ten years going to hundreds of concerts and that bass slap doesn’t happen in the real world. I used to crave it as well… then realized that when you switch to a Conrad Johnson, Audio Research, or other high quality tube amp you get much more. You get highly detailed natural sounding bass and fully fleshed out midrange smoothly transitioning to bass. The very fast powerful solid state generated bass tends to be monolithic and accentuated by a leaner than real lower midrange/ upper bass. There are great detail in the bass of a good tube amp.

So, when I swapped in a ARC 160 for a test (leaving it nearby so I could swap it in and out), I thought, “what happened to the bass?… the Pass is never going back in.” It never did. In fact that I quickly switched from the 140 watts per channel linear mode to the 70 wpc in triode mode… no difference in loudness, but more musical.

I recommend spending some time with one of these great tube amps and really listen carefully weighing what you get / what you loose. At least for me, there is no contest. Tubes win. Your decision may be different.

Now having been pursuing high end audio for 50 years I realize the most important transition I made was that in the last fifteen years i changing from looking for simply what “sounded good” to me, to pursuing true high fidelity audio reproduction. This ended the problem that a change would improve one genera of music and negatively impact five other genera that liked. A huge step forward for me was getting a high quality tube amp… and letting the pursuit of slam go by the wayside.

@ghdprentice interesting description. What preamp are you using with the ARC 160 monos?

• Check out his main system page: Audio Research Reference 6SE Preamp

@ghdprentice 

Most likely what you like about the X350 is the slap you get because of the really fast bass… the slam. You’re not going to get that with tubes. Also, that is not real. I spent over ten years going to hundreds of concerts and that bass slap doesn’t happen in the real world. I used to crave it as well… then realized that when you switch to a Conrad Johnson, Audio Research, or other high quality tube amp you get much more. You get highly detailed natural sounding bass and fully fleshed out midrange smoothly transitioning to bass. The very fast powerful solid state generated bass tends to be monolithic and accentuated by a leaner than real lower midrange/ upper bass. There are great detail

Terrific observation!

I do believe that the higher damping factor (DF) is appealing and its effect on bass is desirable for many. In my experience it adds a “tightness “ to bass frequencies that I just do not hear when listening to actual live acoustic lower range instruments. So I clearly understand your point. Nonetheless, the DF tightening is sought after.

Charles

@ghdprentice ya I am already convinced by tube amps thats why I am pursuing this. I am skeptical about ARC as i had a ref 5se (as you might remember from my other thread) that got beaten in many respects by my bottlehead moreplay pre. The ref5se had a ss sorta sound where the moreplay brought the warmth, colour and fullness and holographic depth the ARC just did not have.

CJ monoblocks also did the same thing. So I am trying to move in that direction.

re: X350

@charles1dad I do believe that the higher damping factor (DF) is appealing and its effect on bass is desirable for many. In my experience it adds a “tightness “ to bass frequencies that I just do not hear when listening to actual live acoustic lower range instruments.

Speaking of damping factor and comparing - quite a wide range with familiar amps many here listen to. Its kind of interesting studying damping factor in different type amp designs.

With Pass’ different designs and comparing, the older X350 and newer X30.8, both have a damping factor of 150.

The lower power Firstwatt SIT3 is a lower damping factor of 30, and Firstwatt F8 is 40. Then we compare to the venerable class A Pass XA-25 bounces up to damping factor of 500.

While I look for some of that lower midrange bloom and upper mid-bass bloom myself hoping for a more realistic sound,

Noting my own QS Mono 120s, have a damping factor of 15.

The latest Quicksilver KT Mono amps have a damping factor of 20.

The ARC 160S Reference Stereo amp has a damping factor of 14.

The Deware SE34I.5 into 8 ohms has a reported damping factor of about 5.7

Decware ZMA is probably about the best you'll find in "high power".

Jerry

+1ghdprentice

I'm using Bob Carver Raven 350 mono blocks. 350 WPC for a little under $10K. These replaced Pass Labs X350.5. X350.8 and Atmasphere M60 3.3, Krell.

You might be able to find used in your price range,

ozzy

@decooney

That is a nice representative amplifier list and reinforces @ghdprentice listening impressions and the distinctions he heard. I realize that it depends on what type of sound performance or sonic character one is seeking.

Ramp up the utilization of NFB and the amplifier’s output impedance is lowered while inversely the DF increases. So again, what is the individual listener trying to obtain/achieve?
Charles

+6 Quicksilver. I have the M135’s. They have driven everything I’ve thrown at them with authority.

@charles1dad So again, what is the individual listener trying to obtain/achieve?

Exactly. Your post about the "snap" got me thinking about this more. I guess some like that unnatural ultra-fast snap of snare or kick drums or fast ping of a piano key. Not for me. While I’m not into sluggish playback either, finding that sweet spot matching the amp with the speakers in the right way, sure can make it enjoyable.

Individual-who, likes what:

• Listeners: I tend to look for posts and feedback on these audio forums by those who’ve played instruments and/or grew up listening in/around live music. Their brain has been shaped, knows what good sound is and can recognize it without even having to think about it :)
• Engineers: some focus primarily on signal-to-noise and flat lines on graphs, I digress - they usually don’t get it, and think they do.
• Hyrbrids: Individuals with a background in music who can also design and engineer amplifiers and speakers is a rare breed to look for.

Truly appreciate those who understand this balance and can design it and produce it for normal consumers to purchase. This community can help save/protect them by paying a little more for their products and services to keep them in business. 

Are the quick silver amps more fast and neutral and linear? Or more romantic, bloomy and warm ?

@smodtactical Are the quick silver amps more fast and neutral and linear? Or more romantic, bloomy and warm ?

It depends on which output tubes you want to run and size of amps/transformers. The older version amps have changed some if you are looking at 20 year old amps.  

Changes with EL34/KT88 tubes with smaller amps and smaller opt transformers (Mid Monos) having more of that Classic sound like you get with CJ "Classic" amps.  The older (vintage type) collectible (MX-190s) run multiple EL34s, larger amps.  

As you move towards the newer generation amps (Mono 60s, KT88s) or running more KT88s (like V4s), adding more power, similar sound.  Split the difference some with KT120s in the Mono 120s if you can find a pair.  Kinda has the EL34 sound with more power with KT120s, sort of. Not exactly, each opt is different.  

Now similar to CJ new "Art Series" The transition to more linear/neutral sound you ask about comes in when running tubes like newer KT150s. More power, neutral, more bass. Less of the classic sound. If you truly need 100w, the larger amps with the bigger transformers can get you there if you are willing to go with more output tubes (V4s) or the larger KT120s, KT150s.

In 2022/2023 The new "KT Mono" amps from QS allows you to run a wider range of the opt tubes now.  The older gen amps tend to only run 1 or 2 opt tubes types, specifically. i.e. I can only run KT150s/KT120s (higher plate voltage) in Mono 120s, cannot run KT88s.  However, the new gen "KT Mono" amps quote ("accepts KT66, KT77, KT88, KT90, KT99, KT120, KT150, and KT170 power tubes and when ordered  with KT150s will produce 100 watts".) Gives a bit more variation for the type of sound you might want.  At QS, lots of other amps existed between over the years, with different sounds (8417 / 6C33C triodes).,  Seems the closing chapter is winding down to the "Mid Mono" or  the all new "KT Mono". Many others shows "DISCONTINUED" if you click on each on the site, as TBD coming out of th pandemic.  Hopefully some of those come back, we'll see.  Some nice used stuff out there too. 

I can't say enough about my 300b's and 6c Triodes

It pains me to think where they might end up!

Had his products since 1980 with no issues.

@smodtactical 

Does the amp have to be tubes if it has the same good character as a good tube amplifier?

@atmasphere  Id love something like that although im skeptical an SS amp can bring the tube magic the way real tubes can. The pass does have some tube character but when I heard the CJ monos I heard the true mid range magic.

But ya I am open to an SS if you think it can match tube sound.

@smodtactical "but when I heard the CJ monos I heard the true mid range magic."

Hook, line, and sinker!   When your buddy let you demo them, knew exactly what was going to happen. :) 

Id love something like that although im skeptical an SS amp can bring the tube magic the way real tubes can.

I know of at least one such amp.

;)

Get into a VTA M-125 monoblock pair.   120 watts each.  You can enjoy the immense satisfaction of building them as a kit  ($2000/pair - no tubes), or just buying them fully assembled and tested ($2800 - no tubes)(tube sets available for $750).

@atmasphere  And, which amp would that be?

And, which amp would that be?

An amplifier that has the same distortion profile as a tube amp of course.

In case this is mysterious to anyone, the ’sonic signature’ of any amplifier is the distortion it makes.

Tube amps sound the way they do because they have either a fairly prodigious 2nd harmonic (as in the case of SETs in particular), 3rd harmonic (as will be the case with a fully differential push-pull amplifier) or both. These harmonics mask the higher ordered harmonics which has two effects: it makes the amp nice and smooth and tends to bring out a sense of ’presence’ of images; ’musicians in the room’, that sort of thing.

In most solid state amps while there is always some 2nd and 3rd, they are usually suppressed by feedback enough that the higher orders are not masked- and so cause the amp to sound harsh and bright (that is how the ear interprets higher ordered harmonics).

One of the problems of traditional amplifier design has been how feedback is applied to the amplifier. In tube amps this tends to be the cathode of the input tube; in solid state amps usually the input of a transistor that is part of a differential pair at the input of the amplifier. The problem with either approach is that feedback node isn’t linear. So the feedback is distorted before it can really do its job. The feedback node in tube amps is more linear than seen in solid state amps so the feedback tends to be distorted less, but this still causes higher ordered harmonic generation that would not be there if the feedback node was linear.

There was a highly respected engineer named Baxandall who proposed that the non-linearity of the feedback node could be overcome with greater amounts of feedback.

Its been this issue why there was the hunt for greater amounts of feedback in the late 1970s. The problem that so many solid state designers didn’t realize is that the input of the amplifier was outside of the feedback loop, in addition to the distortion always added by the feedback node. This is what caused TIM (transient intermodulation); remember those days?? Really low distortion amps that sounded bad.

So feedback got a bad rap and this was the tip of the iceberg.

Another problem that was never overcome by tube and solid state designers until very recently is the phenomena of distortion rising with frequency.

The significance of this is that the THD number can sweep the actual distortion of the amplifier under the carpet, at the frequencies that are most important to the human ear!

This problem is caused by a lack of gain and bandwidth in the amplifier. Together they form a value known as ’Gain Bandwidth Product’ to engineers. This is the frequency at which, when the amplifier is run with no feedback, that its gain has fallen to a value of 1.

Obviously a gain of 1 is impractical- usually you need 25-30dB. 30dB is a gain of 1000. That’s not trivial. If the amplifier has a gain of 1 at 1MHz, what you do is divide 1 MHz by 1000 (if your gain is 30dB). You get a value of 1KHz; above this frequency the feedback will decrease on a 6dB (or more) per octave slope and so distortion will increase on that same slope.

THD is usually measured at a lower frequency- 100Hz is common. You can see where this is going! At 5KHz the distortion can by much higher than the THD suggests, and this is right in the middle of the ear’s most sensitive range (the Fletcher Munson curve, also known as the loudness curve). So an amplifier with this problem can sound bright!

This is why we didn’t use feedback in our tube amplifiers- we wanted a nice straight line across the audio band when graphing distortion vs frequency. This results in smoother sound!

You can do this with solid state and feedback, but you have to jump through some hoops. Class D offers a way to do this because its very easy to get insanely high Gain Bandwidth Product values- in excess of 20MHz. This allows the feedback to be supported across the audio band; distortion vs frequency is a ruler flat line. This makes the amplifier sound smoother.

I can't speak for all class D amplifiers, but in some I’ve heard, the non-linearities that cause distortion in the amp tend to make lower ordered harmonics (the 2nd and 3rd) and so can sound just like a tube amp.

If you’ve gotten this far through this post, the take away is that there is a direct line between what we can measure and what we hear. That old trope about hearing things we can’t measure was true in the 1980s but it isn’t true now. If you got thru this whole thing, now you have knowledge about exactly why amps sound they way they do. There’s no magic; its all engineering. Whether designers know all this stuff is a different story...

@russbutton have you heard them? Are they warmer and richer sounding or more neutral ss ?

@atmasphere  But what actual amp has those characteristics ?

@smodtactical I run a VTA preamp I’m thrilled with. I’ve heard one of their ST-70 amps. Were I in the market for a big tube amp, the M125 pair would be what I’d go for. The designer, Bob Latino has a very good rep. These are well built and engineered amps. Well supported after sale as well.

Here’s a clue for you. They’ve sold hundreds of these M125 amps and you very rarely see them on the used market. There are none for sale at this time so far as I know.

Here’s an article comparing the VTA ST-120 vs a Mac 275. All of the VTA amps sound pretty much the same, with the bigger amps simply having more headroom.

@smodtactical 

But what actual amp has those characteristics ?

Our class D does. I think the AGD Audion does too.

@mijostyn Wrote:

 @atmasphere  And, which amp would that be?

Whichever amp or amp class that the manufacturer or designer promotes at the time as the Holy Grail, will be the best sounding amp of all time. LOL 😎

Mike

Whichever amp or amp class that the manufacturer or designer promotes at the time as the Holy Grail, will be the best sounding amp of all time.

There is also the possibility that engineering was applied- the same sort of things that make airplanes fly and the like...

Used Vacuum Tube Logic (VTL) 750 monoblocks for $7K. 750 watts per channel.

https://youtu.be/_7ZGLrOpCQo

https://youtu.be/xUMDlpVu98w

I have VAC signature 200 IQ monoblocks with KT150's.  It can be run in stereo with 100 wpc. This should be close to your price point.  When I purchased these 5-6 years ago, I did a side by side comparison with what I recall was a Pass 350.   With the KT 120's, they were close.  The VAC with the KT 150's have it all and blew the Pass away by a long shot.  Now this is to my tastes.   Big bass, sweet mids and great soundstage.  More lush than analytical with no ear fatigue.  Plus, if you decide to go bigger, just add another as a monoblock.  They drive my Magico S7's wonderfully.  Happy hunting.

Bob Carver Silver Seven 900 mono blocks.

Thanks guys especially @orthomead 

@orthomead  I didn't know that one could just drop in a KT150 quartet in at all or with modification.  The amp is rated 100 watts per side with a quartet of KT88s (which VAC claims they achieve tapping 3 tube elements instead of just the plate and filaments)

KT150 should provide at least 100 watts per side and probably much more with VACs 3 sided tube power.  

Do VAC amps tubes burn up quicker using getting max power out of them?

I just read the Audioshark forum.  No difference in power per KT tube, interchangeable as well.  Preference apparently for the stock KT88 over other types and most NOS tubes except for V1 6SN7s

@fleschler I checked with Kevin (owner and president) at VAC before doing even demoing the KT 150's.  Kevin, by the way is awesome to deal with -enthusiastic, engaging, and available.  No problem at all according to him. No modification necessary.  I can't directly comment on tube life, because I have only run the KT 150s.  When I auditioned the amps, I didn't care for the KT 88s at all.  Best for chamber music I think.  I listen to rock, jazz, and blues which need a little more umph.  The KT 120's were better to my taste but the amps really started to sing with the KT 150's.  Bass in particular.  I have had the amps for 6 years and had to change tubes only recently.  I've checked the expected tube life of KT 150's and my tube life is in the ball park.  Hope that's helpful.

@orthomead Thanks for the tube life at 6 years.  I listen a minimum of 2 hours nightly, more than 800 hours annually. 

I have 2 EAR 890 amps but they sound great with classical chamber/orchestral, vocal/opera/pop, jazz (traditional to post bop) and 50's to Led Zep rock-so every type.  They run rather warm (2=4 degrees room temp rise after an hour).  A pair of VAC 200IQ have more power.  I have not  compared the two sonically and have not read of a direct comparison either.  

@fleschler I'm not as fortunate as you in terms of listening time per week, probably on the lines of 6-8 hours weekly, so your tube life is likely to be less than mine in terms of time.  Like your system, my room does get a little toasty after a few hours. But that's when all the magic starts!

I spoke to Mike at quicksilver and he told me his amps are tonally neutral and that if I wanted a warm sound I should look elsewhere. 

I think i should be ok with at least 50 watts. I am trying the CJlp70S and R800i right now, both drive my speakers quite well. The CJ is warm and HUGE sounding. The r800i is smaller but more clear and resolving.

@smodtactical consider Manley either snapper 100w or mahi 40w both use EL34 that easy to find and have smooth sound in the mid range .

Thanks honeyooi