Mid-Tier Tube Amp Off

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by Azimuth, Nov 25, 2022.

  1. Azimuth

    Azimuth FKA rtaylor76, Friend

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    Most of us love tubes…the warm glow, the warmth, the grain free smooth sound, the voltage gain we get out of this ancient technology, the harmonics. No matter what, we are addicted to tubes and what they do to audio. And tubes make the most sense almost in headphones where you don’t need megawatts to drive. They also require very few parts, fun to explore new sounds by changing the tubes, and somehow they really get along with high impedance headphones because of that high voltage gain.

    Now there are hybrid designs that use tubes in unique ways to use that voltage gain perhaps to feed the solid state amplification, as in the likes of everything from Vali, Lyr, Liquid Crimson, Little Bear B4, Mjolnir 2, and a whole host of others. Because even if there are few parts to a tube amp, there are other issues and costs, such as output transformers, complicated muli-secondary input transformers, how bias is going to be handled, how high and low gain will be configured for different headphone impedances. Well, you can just get rid of the output transformer altogether (OTL) like a cathode follower (Crack, Valhalla), but then only high impedance headphones will do.

    And yes, the top end headphone amps from the likes of Eddie Current, Donald North Audio, Line Magnetic and others with 300b or 2A3 or other such high output tubes are just way out of the reach of most of us with not huge discretionary income. Pipe dreams. So, there are two paths…DIY, or something off the shelf that is very close. DIY is difficult, and still can be expensive. Ever looked at Elekit prices? And off the shelf…there are so many, how to pick?

    Well…I have three options here that I think all have something to offer. One is the budget pick that many already have that I don’t have to talk much about, but the recent price increase makes it more inclusive to this conversation as I now think the price matches the performance, and still may even be higher. The two are amps that don’t get much mention here or talked about much, and I find that a real shame. One is a bit pricey for the performance, but still an excellent performer. The other is almost an overbuilt design, but well worth the price of performance, even if it is the most expensive in this bunch.



    SW51+ (the affordable sportscar)

    MSRP: $627

    https://www.zampotechna.com/products/shortest-way-51-amplifier

    IMG_1837.jpg


    What to say about this one that already has not been said? Kind of a more forward tube amp, lots of leading edge, air, lots of details, and plenty powerful enough for high impedance headphones, even with just two tubes.

    The thing to love about this amp is the sheer power and performance. It is the most sporty all tube amp I have heard. Not very colored, and maybe a tad on the warmer side if coming from the solid state world, and missing some low end bloom if coming from the tube world. It is certainly not cold at all.

    It has a kind of upfront presentation for a tube amp, especially with HD800’s, and not as noticeable on HD600or 650’s. It is wide enough, just not extremely deep, although deeper than most SS amps. It provides a good center image and it is still more open and airy than most solid state amps including my Black Widow. The bass is also a bit hazy and not quite as forward as the highs. The lows are just not as well defined or have much texture. The bass can even be slightly distorted sounding on pounding tracks, like Daft Punk or The Blue Man Group. However, on jazz and acoustic music, it is absolutely wonderful. And even with upright bass can still be plenty sufficient. On the wrong source the top end might be a bit splashy, and best synergy with warmer and/or fuller sources.

    The thing that mostly impresses me about this amp is transparency. Fairly effortless for only two noval tubes. This is honestly the best part - the closeness where you don’t feel like you are missing any part of the recording and suitable for nearly any genre. Although the soundstage is not huge, it does layer well and have some great bit of micro-dynamic detail. And quite powerful for just two tubes. I will say it is not a slammy amp, but also not one focused on microdynamics.

    At first listen, it may be a little solid state sounding, but after going back to solid state, you realize the smoothness of the amp. And I think that smoothness and uncolored transparency is what makes this a real winner on performance and value. So it’s missing some low end oomph and overall slam, but the tradeoff is smooth performance. Paired with a warm source, it can even satisfy HD800’s fairly well.

    (If this were a car it would be a stock Mustang , 300Z, or Toyota Supra. Very well accepted everyday standard sportscar.)


    Hagerman Tuba (comfortable coupe)

    MSRP: $789

    https://hagerman-audio-labs.myshopify.com/products/tuba-vacuum-tube-headphone-amplifier

    IMG_1839.jpg


    tldr; a light as a butterfly amp that is fair and clean and fatigue free

    Good: fast, lightweight, width, very silky smooth
    Bad: not super powerful and bass is kind of tight

    This one is one that does not get much attention. It is a parafeed dual EL84 amp. It has much in common with the SW51+. Both are about the same size, both are unbalanced with high and low outputs, and both are about the same price. So very ripe for a comparison between the two. This is an interesting comparison for sure.

    This is a very “clean” sounding amp. It has a very wide presentation with even more micro-dynamic or micro-details than the SW51+. The Tuba just has this massive width and space and one of the widest amps I have yet to hear. The quickness and speed are one of it’s great traits. When I first plugged it in, it was slightly reminiscent of the ECP Black Diamond (which was a precursor to the 3F) - lots of microdetails in a very effortless expansive space. Some might attribute this to PRAT or whatever, but the Tuba has loads of it.

    For the overall frequency spectrum, many would say the Tuba is a bit “bass light”. How light you say? I would say the SW51+ is actually a tad bit warmer in the lows. The Tuba not very bloomy in the lows and maybe tighter than SW51+. Plenty of bass textures though. Now this is with the stock Mullard reissue tubes and other tubes can bring back some warmth that I will talk about. But the tradeoff here is where the SW51+ can still sound very transparent, it is kind of missing some layering and immersiveness to me that the Tuba has. Very 3D type of imaging and further back from the stage. This is not an up front amp at all.

    The thing that I keep coming back to is just “light” or “dainty.” It is like a small MX5, it can turn on a dime and give that leading edge without other things stepping on each other or feel congested or claustrophobic. Not meaning that the amp is “fast” as it likely has slightly more softer transients than solid state amps, it just has this very butterfly-like presentation in lightness and clarity. It hardly ever gets harsh to me and just perfect for light acoustic music, jazz, classical, etc. It is that sweet effortless sounds with how silky smooth is very addictive.

    Neither the SW51+ or the Tuba are true powerhouses with lots of push, but the SW51+ having just a bit more power overall. The Tuba is great for medium volume on things like Sennheisers and for the low impedance input are great for Grados or low impedance/high-efficient headphones, like anything with a Foster driver. Will not get extremely loud on either, and volume will be more pushed for comfortable output levels, but don’t let that fool you - the SQ pays off.

    Changing tubes of the Tuba does change the personality, but not by a great degree. It comes stock with the Mullard reissue tubes, which I think suit this amp just fine for the most in detail retrieval. The JJ EL84’s gave it some warmth, but lost some of the detail magic and top end gets somewhat hazy and smeary. Vintage Amperex 6BQ5’s were better and clearer on the low end, but had a more rolled off top end. The Tungsgram EL84’s performed marginally better than the Amperex’s, but at $120 a pair did not think it was THAT much of a difference. There might be some other EL84’s that would work as well - Psvayne, Tung-Sol EL84 or 7189 reissue, Telefunken EL84 reissue….but at the end of the day, I think this amp would be wasting money trying to put megabuck NOS matched tubes in it as I felt the stock Mullard Russian reissues gave the decent balance and performance, and new production tubes would work great.

    With the lower output and lightweight sound of the Tuba, it is better matched with a good powerful source and some darker sounding headphones and/or sources. They still sounded great and smooth with Grado SR80X’s. With the SW51+, the Grado’s seemed a bit congested and flat, but the Tuba gave them lots of space and sweetness.

    (If this were a sportscar, it would be a BMW 30e series or Mazda MX-5. Very fun to drive and cool enough to be a daily driver, corners extremely well, but does not have the power off the line nor the top speed).


    Line Magnetic Mini - (rough riding sportscar)

    MSRP: $1,440; Street:$995


    https://www.line-magnetic.eu/en/pro...eadphone-amplifier-push-pull-el84-2x3w-detail

    IMG_1836.jpg

    This has a tube configuration exactly like the Quicksilver - two 12AX7’s and two EL84’s. However, this is a much smaller chassis, has speaker taps, and a tape out. And again, no high or low gain. Although don’t expect much out of the speaker taps - specs only say “2x3W RMS”...so 3 watts at 8 ohms I presume?

    Initial impressions: With the stock Sovtek’s, the sound is rather clean and detailed, although missing some low end punch. Overall dynamics seems good though as well as some microdyamaic details and air. Speaker outs on my JBL L20T’s was rather flat and harsh. My speakers are 87db efficient and the amplifier seemed under strain and harsh. Headphone out is great though. There is a switch at the front on the left that switches from speakers to headphones. Although, I wish that was the volume since it is so close to the headphone jack, but whatever.

    After listening for a few more hours, there is an overall upper mid-harshness to it that I just can’t get away from. It makes it sound mid-centric and does not have as much width as one would expect with a tube amp. I think it still beats many solid state amps.

    Even with the best tube compliment, music I love is not “coming alive”. Everything is a flat soundstage and dynamics, with smeary highs and not a lot of lows. The biggest sin of omission here is the lack of that last octave. I had to compare it to my Tuba just to make sure I was not losing my mind in saying the low end is kind of missing, but it kind of is. The Tuba is actually warmer sounding.

    On the speaker amp side, sound is just kind of thrown out. Very reminiscent of a bad class D amp or an amp very much under strain. Speaker power is only rated at "2x3W RMS".

    This amp just suffers from too much gain and too much harshness. I never got any kind of tube bloom or any kind of pleasantries. Honestly, a Magni Peity sounded more tube like. I tried all the tubes and there was somewhat improvement, but not nearly enough to satisfy. It looks nice, it is small and compact, but there is not much to like here, especially given the price.

    (if this were a sportscar, it would be a Scion tC or one of those 80's SVO Mustangs with a 4-cylinder engine)

    NOTE: do NOT try to put the 6922 to 12AX7 adapters on this amp. I turned it on and the LED light barely came on, telling me that there was not enough heater current. So I immediately shut it off and only used the 12A*7 tubes.


    Quicksilver Audio Headphone Amplifier (American performance sportscar)

    MSRP: $1,198; Street: $1,050


    http://quicksilveraudio.com/products/headphone-amplifier/

    IMG_1835.jpg

    Tldr; super robust amp with plenty of power and well worth the price tag. Really goes leaps and bounds with some upgraded tubes.

    Good: slammy tube amp with amazing staging
    Bad: stock tubes are hazy and a bit “slow” (easy fix with different tubes)

    This is a headphone amplifier made by Quicksliver Audio and they mostly make 2 channel tube amps and this is their only headphone amplifier and it does not have a model designation. It is just named “Headphone Amplifier.” That is how confident the main guy at Quicksilver is, Mike Sanders, about this amp.

    It has two 12AX7 preamp tubes with two EL84 tubes. It has tons of power capacitance with a super large 1000µf/450V can cap sitting right on top. The output transformers are shielded on top and no overall top lid, just a front facia plate. This gives it a unique kind of look and super easy to change out tubes. You can also clearly see the Alps RK50 volume pot from the top. On the frost is the headphone jack, power switch and volume. No high or low impedance output or switch. And in the back, IEC and RCA connectors, that is it. No hi/lo impedance switch, no gain switch…super simple, super tube, super power. Although not a simple amp as there are small lamps between two of the pins on the preamp tubes? And who knows what else is going on inside - beside some cathode biasing happening. Anyway, to the sound…

    This amp is in another league from the other two amps, and only a few more hundred dollars to do so. And when I say power, I have yet to have this thing above 12 oclock with Sennheisers. My guess is that this tube amp can power higher efficient planars if need be. It sounded just great on Ether CX. But this thing has some slam and authority with barely a push of the gas pedal. Sound is super uncongested. It has a very robust sound that is deep, presents a clear center and very 3D type presentation. But my goodness, it is almost TOO powerful as the volume knob is very touchy and with Sennheisers I am almost in the bottom of the volume pot in the unbalanced area when at low “working through the day” volume.

    As far as the stock sound, I mostly agree with @dematted and @Darkstar1 - excellent big soundstage, although not very grippy or has much finesse and not as detailed. The QS is a very dreamy yet powerhouse amp. It is a very “tuby” sound. Nice clean robust lows, silky smooth mids, sweet highs that are not biting or brittle, although there is not much “air”. It has this effortless like sound where each thing is presented very cleanly. This kind of sums things up with the stock tubes:

    https://www.superbestaudiofriends.org/index.php?members/dematted.8163/

    “Against the Pendant, it has better staging, transient speed, and treble extension, but loses out a bit on things like texture, mid-range and bass detail, and ultimate sense of dynamic slam and resolution. The Pendant also has a better sense of "grip" over the driver, but surprisingly enough, I think the Quicksilver is a bit more refined and nuanced sounding with things like micro-dynamics. The 3F beats it handily in most technical aspects, but it doesn't have the sense of tube bloom, texture, and the stage size of the Quicksilver.”
    The one area I will disagree with dematted here is I actually think the stage size of the QS is quite large. Clear center imaging, with nice width and depth. The stock 12AX7’s might have been pushing things forward, but they quite opened up with different tubes.

    Overall, the amp has a sound that is simultaneously pleasant and engaging at a price-point that is lower than most of the really expensive TotL stuff. Its expansive stage and tube romance, when combined with its sense of speed and rhythm, makes it a fun amp to just listen to and enjoy. Occasionally, though, its lack of resolution as well as its indistinct images lead it to sound somewhat hazy and un-focused, and I wouldn't think it's the best amp for "critical" listening. It is somewhat colored and there is no doubt you are listening to a tube amp.

    The overall sound is very sweet. It very much reminds me of a super powerful Crack with much more refinement and inner details. It is no mistaking that tube sound with full bloomy and punchy lows and romantic mids. However, this amp does have some authority too and super effortless - very congestion free. The low end a bit bleeds into the mids and slightly loose, and the top end seems to be somewhat subdued as I loose that clear top end from the SW51, but it just seems like there I am hearing more and soundstage and instrument separation is incredible.

    It is true as well that this amp can really change personalities with different tubes. The differences in the EL84 tubes I mention above with the Tuba are even more exaggerated on the QS. Preamp tubes almost make more of a difference.

    Mentioned before in an earlier post, I was able to put lower gain factor tubes with very good results. I remember a post from Mike Moffat about how much he did not like 12AX7’s or any most of the 12A*7 family. Those tubes are input tubes for electric guitars with high impedance and low-output. Maybe some good tubes in there, but they were so common, you really have to dig to find some good ones. Anything 12A*7 is a direct plug-in (no adapter needed).

    The RCA 12AT7’s gave the QS more top end air and details and way less cloudiness. I hardly noticed the cloudiness before, but the RCA 12AT7’s were just cleaner and even sweeter. They still almost had too much gain, and with HD800’s could get a bit peaky.

    And yes, you can get an adapter from 6922/E88CC to run in a 12A*7 socket. Of course, with lower pre-amp gain, you have to have more volume and power, but for this amp, it allowed more of the pure amplification to come through. The preamp tubes changed the personality of the amp more than the amp tubes.

    The Russian 6N1P’s gave the low end even more definition and depth, and the control and speed of the amp seemed to increase as now superfiner details were coming through. This reaches way deep and has just a huge expansive quality to it. It is just shy as being as wide as the Tuba, but the details and gorgeous sound of the QS just push it out of orbit.

    I have ever heard a more effortless, powerful, and detailed amp. It is super fun to listen to and clearly has performance to match the price tag and more. I am actually kind of ruined as listening all day and going back to any amp makes it sound like a hot harsh mess.

    (If this were a car, it would be a Corvette. Affordable USA made power that can corner.)

    Conclusion

    IMG_1834.jpg

    So there you have it….the comfortable affordable no-sins of addition fan favorite, the sharp witted butterfly, the nice looking ride that handles rough, and the high end horsepower that corners very well. Of all these, I already purchased the QS, I sold the SW51+, and sent the LM Mini back to the owner. The Tuba I sill have and still debating to keep it or not. I might send it on a loaner tour if we get enough interest. I can also send along the Noise Nuke with it.

    PS - and before I get hate mail, your Eddie Current’s, DNA’s, Elekit, McIntosh, and others, are more like supercars (Porsche, Ferrari, Lamborghini, Bugatti, McLaren, etc.). Those are the TotL and it’s just a fun metaphor.


    Also, as as a bonus, here is tube EL84 breakdown:
    • RCA tubes - bright…like beaming bright
    • JJ - warm in the low-mids, kind of blanketed on top some
    • Mullard EL84 (new production) - really good with LM. Still missing some lows, but sounds cleaner.
    • Gold Lion - Good mid-lows, but not as clean as the Mullard’s on top.
    • Tungsgram - Clean, good lows (not too loose), lush mids, good separation and air. The best on the QS behind the Mullard's.

    PSS - Special thanks to @Ksorota and @Inoculator for their loaner amps. I would not be able to provide this content without their support.
     
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    Last edited: Nov 26, 2022
  2. Darkstar1

    Darkstar1 Facebook Friend

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    Great Review.

    My two issues with the quicksilver are

    Treble splashiness with stuck tubes. I solved by rolling tubes and cap change
    Lastly I agree " Occasionally, though, its lack of resolution as well as its indistinct images lead it to sound somewhat hazy and un-focused," Well said. I think it gets better with some run time and does better with some headphones/tubes.

    HD6xx sounds crazy good with the Quicksilver IMO. Very good match. prefer it to LCDX and Utopia.

    I don't think this amp falls too short of the top tier stuff. It does not quite get there but I think with the HD6XX QS produces a very top tier combo that makes some $$$$ amps sweat. For the price its great and can be tailored quite a bit with tube/headphones. Having trouble letting it go.
     
  3. Azimuth

    Azimuth FKA rtaylor76, Friend

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    Holy smokes, I forgot I even wrote that line. I wrote most of this about 6-weeks ago and then waited on the LM-Mini loaner to compare all 4 and do the YT video.

    It does clear up with details with the 6N1P tubes. Much more so that the 12AT7’s.

    There are also some modifications that can be done to the QS, but that is a different thread.
     
  4. penguins

    penguins Friend, formerly known as fp627

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    Great write up. One minor detail - could you post pricing next to or under the links for each one? Obv google exists but just as a reference.
     
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  5. roughroad

    roughroad formerly mephisto56

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    Don't mean to be that guy, but if you look at QS's site, the listed price for the QS HPA is $1198. I would pay MSRP to get one though (if I had to).:)
     
    Last edited: Nov 25, 2022
  6. Azimuth

    Azimuth FKA rtaylor76, Friend

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  7. ckhirnigs

    ckhirnigs Almost "Made"

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    I’m a big fan of the Quicksilver as well. I also own an SW51+ and like it a lot, but I’ve yet to find a headphone that sounds better on it than the QS. I’ve rolled some really nice tubes in my QS over the last few years and have managed to find some pretty impressive combinations. The amp has been equally adept at driving my Meze Elite as it has my various ZMFs.

    Best thing I can say about the QS is that every time I’ve been tempted to buy a more expensive amp (DNA, DSHA3F, etc) I sit down to one more listening session with the QS and forget about buying something else.
     
  8. roughroad

    roughroad formerly mephisto56

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  9. ChaChaRealSmooth

    ChaChaRealSmooth 2000% biased Planar Hater

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    @Azimuth I'm wondering if you've heard the Woo WA6SE and how you think it compares to the Quicksilver. I personally prefer the Woo (although I think the WA6SE at current retail is a ripoff. Buy a used one and don't pay more than $1100).

    Granted, I have reservations about tube amps nowadays in general due to the skyrocketed tube prices.
     
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  10. Azimuth

    Azimuth FKA rtaylor76, Friend

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    That would probably be a good comparison. I have not heard many Woo amps if any that I can recall. I guess I avoided them as they do get much love over here and I take it they are kind of bass bloated and a bit overpriced, even on the used market.

    PS - There is one on the Gon for $995 RN.

    PSS - If anyone has one and would not mind without it for a couple of weeks, PM me to loan it out. I'll have it on my YT channel. :D
     
    Last edited: Nov 29, 2022
  11. dBel84

    dBel84 Friend

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    I am sure that this wasn't by design... or perhaps it was... but you happen to have chosen amps based on the EL84 pentode (aside from the SW51+). I hadn't appreciated that there were that many headphone amps based on this tube but it also happens to be one of my favorite tubes :) (hence the avatar)

    There are a few ways to configure these amps, I will have to dig deeper into their design to understand their differences which will influence their sound and performance.

    Nicely done review, makes me want to explore more EL84 amps. I built the Baby Huey to feed the desire but so many options

    .. dB
     
  12. penguins

    penguins Friend, formerly known as fp627

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    Sadly this is too true and one of the big reasons I use a Vali2+ and SW51+ over the Stellaris sometimes. Still <$10-15 shipped for a Vali2 tube (yes, I could run better tubes, but IMO should be saved for big boy amps) and matched pairs for the SW51 are still mostly <$35 with one of my favorite matched pairs actually are still currently <$10.

    That or I'm too much of a cheapskate for this hobby or something.
     
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  13. Azimuth

    Azimuth FKA rtaylor76, Friend

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    First off, thank you!

    I love EL84 guitar amps too. Like the Vox AC30, one of the best guitar amps ever built.

    An yeses, EL84's can be run in from pentode to triode to ultra linear I think. I believe the QS and LM-Mini were in ultra linear. LM-Mini had a switcher power supply likely mucking up the sound. The Tuba is of course parafeed, and it had the smooth sound like the ECP T1, but the Tuba had a Hammond output transformer, not a Cinemag like the T1.

    But these amps (except for the SW51+) don't get much mention here, so always glad to discuss.
     
    Last edited: Dec 29, 2022
  14. Aklegal

    Aklegal Almost "Made"

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    I owned a single chassis Woo Audio 6 more than 12 years ago. I remember looking for tubes to replace the stock drivers and not finding really any at all. I think he (Wei Wu) changed the amp design to support 13DE7 driver tubes shortly after I sold the amp, but those tubes seem to be scarce as well. I almost picked up a used Woo Audio 6SE a few months ago but not being able to find tubes scared me off again.

    The Quicksilver has my interest piqued since more sellers carry the tubes it uses.
     
  15. luckybaer

    luckybaer Friend

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    I was pleasantly surprised that I could listen to the Quicksilver with IEMs. The noise floor is very low, and at least with the Thieaudio Oracle MkII, I don't hear any hum, tube noise, or anything else. This is when the QSHA is fed directly from my DAC - without a pre-amp intervening. I don't know if many even bother listening to their big boy amps (i.e. anything not considered "portable") with IEMs, but I sometimes do, and thought this was pretty cool.

    FWIW, the Oracle MkII's sensitivity is 100dB @1kHz, and the impedance is 11Ω. They are one of the least sensitive IEM's in my stable. Will need to try with the Moondrop Kato and Blessing2. Those things seem to be pretty easy to drive at 123dB/32Ω and 117dB/22Ω respectively.

    edit: big fail with the Kato. Lots of "buzz," and not the good buzz. Not room full of bees buzz. Not bees with buzz cuts. Not even swarming Buzz Aldrin. That's a lot of good buzz. I got nothing but bad buzz.

    edit 2: when I say I don’t hear buzz, that’s with the volume knob set at listening level for a particular IEM and no music playing. Oracle MkII, Drop xNuForce EDC - pretty close to silent; Kato - buzz buzz buzz! and 7Hz Timeless, buzz, but not as loud as Kato.

    So, not an option for all IEMs, but maybe for some, less sensitive IEMs.
     
    Last edited: Dec 30, 2022

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