Bottlehead S.E.X.

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by batriq, Dec 1, 2015.

  1. batriq

    batriq Probably has made you smarter

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    Does anyone here use it? Any impressions of it?

    I have one, but I'm currently using it in a small speaker setup. I don't have a reference point to compare it against besides the O2 which sounds sterile.
     
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  2. fraggler

    fraggler A Happy & Busy Life

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    I have had a v2.1 with "upgraded" capacitors and pot running balanced for headphones only for several years now. It has made it to several meets and I'd say it holds up quite well to most amps that I have heard. If you have the impedance boards, it performs very nicely with both orthos and dynamics. Only clearly surpassed by upper tier amps. I am sure there are amps in the range that do certain things better, but for me, I haven't heard anything except for the Ragnarok and possibly the DNA Sonnet when I still had HD800's that would make me want anything better. That said, I haven't heard this generation of Schiit amps, so those may have surpassed it by now. Sadly, I have a hum now that I haven't been able to trace the source of. Can't hear it while music is playing, but pretty clear during pauses and really quiet passages.
     
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  3. batriq

    batriq Probably has made you smarter

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    Thanks! I don't have much to compare it with, so this is very good to know. I have also changed/upgraded some capacitors, but haven't updated the pot. Which pot are you using?

    I got rid of the hum by implementing the "filament supply resistor mod". Some more info is here with a picture I took at the end of the thread:
    http://bottlehead.com/smf/index.php?topic=7695.msg74418#msg74418
     
  4. fraggler

    fraggler A Happy & Busy Life

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    I got my hands on an old RK40 from Alps. I don't know if it made a difference, but it was rare, big, and satisfied my ego :)

    Hmm. Interesting mod. I might have a go at it if I get some time. Thanks.
     
  5. JoshMorr

    JoshMorr Friend

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    Any one still use this amp? Curious how it compares to the crack sound wise, or if it is just a more versatile amp where it works with multiple headphones / speaker output.

    Interested in this as a beginners SET amp with Pete Millet's Jonokuchi being the other contender that piques my interest.
     
  6. fraggler

    fraggler A Happy & Busy Life

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    I have only heard the Crack at meets, so hard to really say at this point. I want to say it was a bit more neutral in presentation, with better resolution. I built mine because at the time I had an LCD-2.2 and some HE-500s and the SEX made them sound better than anything else I had heard sub $1000 at the time. Did beautifully with my HD800's, too. I ran balanced out exclusively. In my poor recollection, I would say it is a better amp (taking out its added versatility), but I don't think it is as euphonic or as easily tweakable since its tube selection is pretty limited.
     
  7. Scubadude

    Scubadude Almost "Made"

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  8. Sherm

    Sherm Acquaintance

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    Since Bottlehead had a great sale going on the S.E.X. 3.0 + C4S upgrade at the beginning of July, I finally jumped on one. I've been looking to get into tube amps for a long time now, and since I love soldering and building stuff, Bottlehead looked like a great avenue to pursue. Initially I wanted to get something more along the lines of a Crack or Crack-a-two-a to pair with my HD650, but knowing how much money I'd end up dropping rolling tubes I decided against that--there's not much point in tube rolling with the S.E.X., so I can put the rest of my budget towards eventually obtaining a better DAC instead of surrounding myself with a bunch of tubes that I'll never use again once I settle on what I like. The versatility of an OPT amp was a little more appealing to me, anyway.

    I've had my S.E.X. running for a little over a week now. My initial reaction after getting to know this thing was "why the HELL didn't I get into tubes sooner?!" Granted, I've only had the opportunity to hear a couple different solid state amps, but I'm still thoroughly impressed by what I'm hearing. I've been using an upgraded HeadRoom Desktop Amp along with HeadRoom's Desktop Power Supply for the last 7 years, and in just a week's time this S.E.X. amp has left me wishing I would have been listening through tubes from the beginning!

    As compared to my HeadRoom amp, sound stage and imaging is greatly improved. With the HeadRoom amp, the sound stage is focused mostly right in front of my eyes, with only the hard-panned sounds going far left or right. With the S.E.X. the stage seems like it stretches from ear-to-ear. Instruments are easier to separate and seem to have more 'air' around them. I've seen several people around here describe tube amps as having a holographic sound stage and I can finally say I get what they were saying. Going back to my HeadRoom amp I realize how much flatter everything seems--I can still pick out everything that is going on, but it just seems like it is compressed by comparison. HeadRoom amps were known for their implementation of a crossfeed circuit which does help to alleviate the narrow stage, but I never really found it to be as enjoyable to listen to even with the "brightness" filter engaged to counteract the extra bass the crossfeed adds.

    One other area that I saw a noticeable improvement was in dynamics. On a few different occasions now I've nearly had the shit scared out of me when I turn up the volume on a song that starts out gently and quietly only to get blasted when the beat drops or the chorus starts up. I've even had this happen to me with songs that I was quite familiar with. It seems to me like the better stage and imaging of this amp is making the presentation seem more dynamic. I've also heard it said that tube amps are more adept at highlighting the difference between quiet and loud passages in a track, so maybe that is what is going on? In any case, I'm having a great time with the livelier effect this is imparting.

    All of this said, my trusty ol' HeadRoom amp is still good in it's own regard--it just doesn't seem to be a presentation that I'm as enamored with now that I've gotten a taste of SET sound. The basshead in me likes the harder hitting nature of the HeadRoom amp's bass, but the S.E.X. has made me realize that this tends to color the music a bit. I once thought my LCD-2 rev. 1 was a little muddy in the bass and low mids, but after plugging it into the S.E.X. and being met with a headphone that sounds leaner than my HD650 I'm rethinking that.

    So far the only mods I've done to this amp have been adding an Alps RK27 pot and configuring it for balanced output to a 4 pin XLR. Not sure if I'll pursue any capacitor upgrades or not--for now I'm too happy with the sound to much care about changing it!

    Still trying to decide what to finish the wood base with. For now it'll just have to be naked.

    [​IMG]
     
    Last edited: Sep 5, 2017
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  9. Elnrik

    Elnrik Super Friendly

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    Alder blotches with most stains and dyes, so get a little can of this to seal it. It's a spray on dewaxed Shellac. (Shellac sticks to everything, and everything sticks to Shellac.) A thin coat will do. Sand with 400 grit paper to knock bumps down. Then get a good stain, wipe on, wipe excess off, and then you can use the Shellac as a varnish to seal it/finish it (with about 3 coats) to a nice shine, lightly sanding between coats. If you want a dull finish, get some furniture paste wax or beeswax, apply the wax to some 000 steel wool, and give it a gentle buffing on the final coat. Might cost about $20-$30 to do this. It's the cheapest and fastest way I've found to finish these nicely. Shellac dries in just a few minutes, so you can easily do this in an afternoon.

    Or, just apply TruOil to the wood directly to give it a slightly darker color and to seal it in one step. 4 coats should do, 24 hours between coats. First coat should be generous, as the wood will drink that stuff up. (Google how to apply it, you'll see what I mean.) Light coats for the rest. Watch for drips! Don't let anything impact the finish for 1 week, it needs that time to cure.

    Don't forget to use the SBAF affiliate link if you order the stuff from Amazon. :)
     
    Last edited: Sep 5, 2017
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  10. Sherm

    Sherm Acquaintance

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    Thanks for the tips, @Elnrik! I was considering something like boiled linseed oil since I've had great results with it restoring old rifle stocks, but I honestly don't think I'd have the patience to spend a week rubbing oil into the wood base and not have anywhere to set the amp for use in the interim. That shellac finish sounds like just the ticket!
     
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  11. Elnrik

    Elnrik Super Friendly

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    Glad to help.

    If you prefer brushed on Shellac, Zinsser makes this. The problem is that applying a new coat dissolves the previous coat, so you have to be very careful. Easier to use the spray can imo.
     
  12. slankoe

    slankoe Tongue tastes of LH butthole

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  13. Ice-man

    Ice-man Friend

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    Nice review! The SEX with the upgrade is just outstanding and flies under the radar for the most part. It does some impressive things with the hd800 as well as planars. Great kit!
     
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  14. winterfog

    winterfog Almost "Made"

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    Finished a Bottlehead S3X build about three weeks ago. I took my time with the build, and it paid off when my resistance and voltage checks all passed on the first try... with one exception. All of the nuts & bolts that serve as grounding points had to be re-tightened in order to get a correct reading (i.e. < 1 ohm) for ground resistance. If I was doing it again, I would put a drop of Loc-tite on those bolts during initial assembly and really crank them down tight the first time.

    The finish on the wood was achieved with about 8 coats of Tru-Oil, with each followed by a light fine-grain sanding and a buff with a steel-wool alternative. The top-plate was sprayed with several coats of Rustoleum Hammered Forged in chestnut; the chokes and power transformer bell cap got Rustoleum Hammered in black. Unfortunately, due to the nice-looking winding caps on the chokes, the assembled top plate is too wide to fit into the wood frame upside-down like earlier versions of the SEX did. This meant that the plate had to sit upside-down on my workbench with all of its weight sitting on the chokes and transformer bell cap while I installed the internals, and the finish got dented and marred in the process. I will have to go back and refinish the top of the chokes and bell cap at some point; luckily Rustoleum sells the Hammered black paint in a pint-size brush-on can, so I won't have to deal with overspray.

    The initial sound of the base S3X kit (tested using HD-6XX and LCD-2.2 pre-fazor) was really very nice, with lots of body and nice bass presence. Tons of power for headphone use, with normal listening range being somewhere around 9 o'clock on the volume knob. Resolution was clearly a weak point, and the presence region could be a little shouty with high (headphone) volumes, but treble extension and clarity surprised me. Tonal balance much more neutral than I had anticipated. Plus, because this was my first taste of tubes, it had AMAZING SOUNDSTAGE compared to any other amp I've used.

    Next step was upgrades, which I did all in one pass. I ordered a Alps 100k pot from Parts Express ($14.58), as well as Jantzen Superior output coupling caps (800v 1.8uF, $19.29 each) and interstage caps (1200v 0.1uF, $10.28 each). And while I was installing those, I also installed the C4S upgrade. Unfortunately, the particular Alps pot I got was made for circuit-board mounting, so it had pin outs instead of lugs. It turns out that trying to solder loose wires to bare pins is incredibly frustrating, so I would suggest avoiding that if you can. In addition, this Alps pot had a much longer 25mm (1 inch) shaft, meaning that the stock volume knob didn't nearly cover its length. I ended up ordering a 30mm rose-colored aluminum replacement knob.

    Pictures:
    [​IMG]
    A better view of the finish on the top-plate:
    [​IMG]
    The guts:
    [​IMG]
    That tube glow:
    [​IMG]

    The upside of doing all of the upgrades in one pass was that it was much easier and quicker. All of these parts—C4S, caps, pot—are intertwined in a very small amount of space, and it would have been a huge headache to do them separately. The downside is that I couldn't listen to the effect of each upgrade separately. I can only offer impressions on the whole package deal.

    That being said, the upgrades really took the amp to another level. Bass extends deeper and is tighter, even outdoing my solid state amps in some ways. Big, obvious improvement in resolution, refinement, and microdynamics. Tonal balance, macrodynamics, and soundstage haven't really changed, which is just fine by me. Both my test headphones gave me the "realism chills" on the test track I like to use to check for that. ("Man Of Constant Sorrow" by Jerry Garcia, David Grisman, and Tony Rice, from "The Pizza Tapes" album; specifically the between-verse improvisation from ~0:54-1:40, which should sound like the guitar is right next to your left ear, such that the transients can be felt viscerally.) The remaining weak point of the amp, IMO, is that it's not an amp that encourages low-volume listening; it's one that begs to be turned up. And when you do turn it up, the upper midrange "presence" range can still get a bit shouty, though less now than before the upgrades.

    I'm definitely going to be keeping this one around as my main amp for the foreseeable future. Tube soundstage is really some spooky magic. I'm looking forward to trying hooking up some speakers to it. I used the 4 ohm taps, as Bottlehead recommended for those who would primarily be using the amp with headphones, but my understanding is that using the amp with higher-impedance speakers won't cause anything to blow up.
     
  15. restrav3

    restrav3 Likes Audio-GD

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    wow that's a beauty. well done.
     
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  16. winterfog

    winterfog Almost "Made"

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    Some thoughts on 6FJ7 tubes:

    To start, what everyone says is mostly true: tube rolling on the S3X does NOT make very much difference in the sound. You can get away with using an unmatched pair from different brands, and if you didn't see the tubes you'd never notice a difference. The exception to this rule for me is GE tubes, discussed further below.

    I have now collected 8 6FJ7 tubes: 2 RCA, 3 GE, 2 Zenith, and 1 Sylvania. The pair of RCA tubes were provided by Bottlehead. They work great but are obviously from different batches / manufacturing plants, as the internal construction is very different. The rest were bought off eBay as cheaply as possible, most as NOS/untested. It turns out that it's quite difficult to find matching pairs of 6FJ7 tubes with the same brand & construction, since almost nobody is selling these as "audiophile" tubes and matching them up. In addition to my mismatched RCA pair, my Zenith pair has different internal construction as well.

    GE tubes... One of my GE tubes is extremely noisy with static hash; not sure if it needs more warm-up time or is just trash. The other two GE tubes were initially my primary tubes, as they appeared to have matching construction. However, I now think they were largely responsible for my nitpick about a sometimes-"shouty" presence region. Switching to other brands undeniably tames the upper midrange and enhances bass quantity & quality. Although I have to mix and match right now and can't practically compare single tubes very well, it seems to me that any mixture of the RCA, Zenith, and Sylvania tubes results in a less shouty, more engaging sound than the GE tubes. I'm currently using an RCA/Sylvania combo that appears to have near-identical internal construction, and I'm pretty happy with it.

    There's definitely an audible noise floor with every tube tested. But this is only audible on headphones when the amp's volume is past 12 o'clock (i.e., unusably loud), so it doesn't bother me at all in practice. What noise does exist is far more audible in the right channel than the left for some reason; this appears to be a function of circuit topology rather than tube selection, as the increased noise floor in the right channel persists through a tube switch. Very strange, considering that the volume of the actual signal is channel-matched well enough. People who care a lot about noise floor probably shouldn't buy this amp. [EDIT: The right-channel noise floor issue actually turned out to be a product of my source, not the S3X. So nevermind--the noise floor is really quite low.]
     
    Last edited: Jun 18, 2019
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  17. batriq

    batriq Probably has made you smarter

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    It's been on my todo list for a while, but I finally got a chance to upgrade the power filter caps in the SEX (this is 2.1 so may not be relevant to everyone). I upgraded the Panasonic 100uF 450v caps to Nichicon GW 150uF 450v caps (rated at 1.3A ripple!). Any hiss that I noticed before when the pot was at 10 o'clock or above is gone. I don't listen at these levels but with no signal, that high volume helps in hearing the background noise. What this translated to is better instrument separation and better decays.

    In the spirit of picture or it didn't happen:

    [​IMG]
     
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  18. fraggler

    fraggler A Happy & Busy Life

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    Of all of my cycling through gear, I probably regret selling my S.E.X. the most. Kind of had to be done at the time, but I still regret it.
     
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  19. bobboxbody

    bobboxbody Wow, I made it this far without being a friend?

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    I just crammed some Jantzen Superior 0.1uf 1200V interstage and Jupiter Copper 1uf 600V coupling caps into my sex today. The big Jupiter caps were actually easier to install than the interstage caps. I was concerned about the size which is why I went with 1uf instead of 1.5, but they probably would've fit fine. Also switched out the stock volume pot for a Pec carbon 100k.
    [​IMG]
     
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