Sennheiser headphones, Bottleheadphone cable and one of a kind headphone storage rack not included
Proof that S.E.X. never goes out of style
In late 1994 a small group of experimenters from a Puget Sound area vacuum tube audio club known as VALVE, among them Dan "Dr. Bottlehead" Schmalle, Paul "Brainiac" Joppa, and Dave "Full Track" Dintenfass, spent a Sunday afternoon building a simple one tube single ended amplifier, the original "spud amp" (being a one-tuber, you see). Expectations were not high for the sound quality, the intention was to build as simple an amplifier as possible and see if it made sound. The result was absolutely confounding. The guys in the listening room/lab who threw the circuit together in 45 minutes couldn't believe that it not only made sound, but it made great single ended triode sound!
At the time single ended triode tube amps were considered a screwball cult thing by most conservative mainstream audiophiles. But there were those adventurous souls who wanted to try the SET sound for themselves and see what all the buzz was about. The few commercial SE amps available were expensive. Doc looked at the parts count, figured a large part of the cost was going into machined aluminum front panels, rare and expensive vacuum tubes and boutique electronic parts. He decided he could put together a simple kit based on the "spud" experiment, that was reasonably priced yet captured the lifelike essence of the single ended triode. And the original Single Ended eXperimenter's amplifier kit was born. Within a few months the biggest problem of the new business was keeping up with orders made by audio experimenters eager to learn about the single ended triode sound. The success of the original S.E.X. kit led to the development of a full line of tube electronic kits and the growth of the innovative and influential Bottlehead Corp. over the next decade.
Fast forward ten years
Having worked together on successful designs for everyone from novice kit builders to Grammy award winning mastering engineers, Doc and PJ are reminiscing about the now retired S.E.X. amp over cocktails. The discussion runs to how much the two have learned about tube audio design over the years. The natural progression of the conversation leads to ideas about what a 2004 version of the S.E.X. amp would be like. Before the evening is over the new S.E.X. amp project is agreed upon in earnest.
The new S.E.X. amp
The new S.E.X. kit is a stereo integrated single ended triode (SET) amplifier of 2 watts per channel output.
The two stage zero feedback RC coupled circuit uses parallel feed (a.k.a. parafeed) output, a topology championed for use in modern single ended amplifiers by Bottlehead and MagneQuest. Parafeed output assures articulate, musical bass, great high frequency extension and minimizes the influence of the power supply on the sound.
A split rail bias scheme derived from classic Western Electric designs of 70 years ago allows the use of cathode coupling with an output autoformer grounded for safety.
The dual mono power supply uses dual high voltage secondaries on a single power transformer for separate yet economical power to each channel.
A Schottky rectified DC heater supply and careful high voltage power supply design using custom Bottlehead power transformer and plate loading chokes assures an exceedingly low noise floor, around 83dB S/N - with zero feedback!
The combination of low noise and ample transformer coupled output drive means the S.E.X. amp is perfect for use both as a loudspeaker amp and as a headphone amp, It works great with high efficiency (97 dB or higher) speakers for listening room systems that work well with similarly powered 45 amps, and practically begs to be plugged into computer sound cards and smaller speakers for desktop audio systems. An IHF standard output configuration on the headphone jack means exceptional low noise performance with headphones of virtually any impedance. The integral level control makes a very simple system possible. Only the addition of a source (CD player, portable disc player, Ipod, sound card, phono preamp, tuner, etc.) and speakers or headphones is needed to get the three dimensional, highly resolved sound of single ended triodes.
And remember that the "X" stands for eXperimenter! The kit comes with 6DN7 dual triode tubes, but can be modified easily to work with others, like the popular 6EM7/6EA7. While designed as an integrated amplifier the kit could be converted to use as a low output impedance line stage, a 4 watt parallel single ended monoblock amplifier, a 2watt single channel monoblock amplifier with shunt regulated power, and the hardcore eXperimenter might even convert it into a 10 watt push pull class AB monoblock amplifier! The Bottlehead community is composed of highly creative individuals and we expect to see a smorgasbord of mod ideas for this kit on the Bottlehead Forum. We also hope to have some of our own upgrade options available in the future, making the S.E.X. kit one of the most versatile SE amp kits in existence.
The kit assembles on a 10"X8"x.080" brushed aluminum chassis plate and comes with a beautiful Pacific Northwest alder wood base kit that you can assemble and finish to taste. RCA jacks are high quality gold plated, and the binding posts are durable color coded dual units. The 1/4" stereo headphone jack is by Neutrik. This kit also employs a fused power entry module that allows the use of IEC terminated power cords. A standard IEC type cord is included and you can try out boutique cords and your own experimental power cords as well. Wiring is point to point.
The amplifier's power output is approximately 2 watts RMS per channel at 10% THD at 500Hz, similar to a single ended 45 tube amplifier. Frequency response at 1V output is -3dB at 27Hz and 22kHz. The amplifier has an input sensitivity of .62V RMS and a gain of approximately 15 dB at 1 kHz and can be wired for 8 ohm or 4 ohm speakers. 16 ohm speakers will run well on the 8 ohm tap at slightly reduced power levels. Input impedance is 100Kohms.
Assembly is a one or two evening affair, designed for the builder with little or no kit assembly experience. A very thorough assembly manual (the S.E.X. Manual) is included in Adobe PDF format on a CD ROM, containing step by step printed instructions you check off as you work, detailed photos of the chassis underside and components, and a thorough checkout procedure. You will need a copy of the free Adobe Reader software to use the manual.
All the builder needs to supply is solder. As with our other kits the Bottlehead Forum serves as the builder's online tech support resource, with dozens of experienced builders participating to help you with your questions.
Recommended speakers for listening rooms
NEW! a S.E.X.y DIY speaker system to go with your S.E.X. kit!
The S.E.X. kit should work well with speakers of sensitivity in the 95dB range or higher. Here are a few other higher efficiency speakers that we've heard and liked -
Cain & Cain Abbys - Terry Cain ordered 6 S.E.X. kits to go with his outrageously successful Abby tapered pipes when he found out about them. Need we say more?
Lowther America Alerion - Jon VerHalen's Alerion is a delightful surprise, a small Lowther speaker design that sounds really good. The Medallion and Big Fun designs should work very well too.
Vivaldi Audio Academy - Lew Hardy's 101 dB efficient two driver Lowther based speakers can fill a huge room with sound when used with the S.E.X. amp. The second driver does a nice job of filling in the bass, and the cabinets are stunning.
BD design Oris horns - a superb sounding Lowther based speaker
Of course the big horn based Altec systems will work well too, from the classic A7s and Valencias to John Tucker's awesome 21st century adaptation, the Exemplar Horn
Klipsch speakers like the Heresy, Cornwall, LaScala and Klipschorn should work very well.
The Bottlehead Climax speaker project is alive and kicking. Watch for progress reports of the new 96dB Bottlehead speaker kit.
And DIYers should be sure to check out Fullrangedriver.com for some great project speakers
Recommended speakers for near field listening
When the listening distance is close, like in a computer sound setup, you can use just about any speaker. Even lower sensitivity mini monitors will sound great up close.
Most any headphones will work with the S.E.X. amp. Here's a few we've found to work very well:
Sennheiser HD600 and HD650 - 300 ohms - truly great headphones, especially when upgraded with our Bottleheadphone Cable
Sennheiser HD497 - 32 ohms - a super headphone for the money. If you need some sub $100, heck, sub $75 headphones look no further.
Sennheiser PX200 - 32 ohms - this is a controversial closed back headphone, because the small pads don't always seal well on everyone's ear. Try before you buy, leaving the headphone band a bit "loose" so the pad's weight helps them seal - if they fit well and you want small cans that can also service your portable Mp3 or CD rig they are nice for the money.
AKG 240 - these 600ohm phones are the least sensitive we've tried. You will want a source with an output level around the CD player standard of 2V to get the 240s to play loud.
Koss SportaPro - 32 ohms - great bang for the buck. Not the most open or extended sound, but those sins of omission and the decent bass make these super for knockabout use and less than stellar digital sources. The Portapro, KSC50 and KSC55 supposedly use the same drivers.
Some cans we haven't tried with the S.E.X. amp yet, but we have heard on other gear and liked:
Sennheiser HD202 - 32 ohms - these are super bang for the buck
Sennheiser PX100 - 32 ohms - the open back version of the PX200, with bass adjusted up to compensate. These don't have quite the clarity of the PX200, but will work with more ear shapes and sound very good.
Single Ended eXperimenter's amplifier kit $469 plus shipping. Delivery averages four to five weeks.
Your pre-order will be charged the day the kit is ordered. We do this to allow cash in advance payment to our vendors to keep the price you pay as low as possible.
Before ordering, please read:
S.E.X. amp kit shipped UPS ($25) to US address
S.E.X. amp kit shipped Priority Air ($40) to Canadian address
S.E.X amp kit shipped Priority Air ($60) Worldwide (see note below about ordering a 240V version)
Notes for Our Customers Outside the U.S. - S.E.X. kit is now available in a 240V mains version for an additional $25. Email Eileen to adjust your order to the 240V version.
or call us at 360-697-1936 M-F 9-5 PT
Tools you will need:
Soldering iron - at least 40watts. You can buy an inexpensive iron from Radio Shack like 64-2071, but an entry level soldering station like 64-2185 or a Weller or Hakko can be one of the best investments in DIY audio that one can make.
Solder - good old 60/40 or 62/38 tin/lead solder works fine. Silver solder will tempt you, but understand that silver solder has a higher melting point that requires more iron wattage, and it's more difficult to get a good looking solder joint with. Don't go higher than 2% silver content. The boutique eutectic solders like Cardas are very nice, though more expensive.
Multimeter - once again Radio Shack has inexpensive gear to get you started, like 22-218. Digital meters can be a bit easier to decipher, and the investment in a quality meter like a Fluke will not be regretted.
Diagonal cutters - the most used hand tool. Once again Radio Shack can supply something to get you started for a few bucks. Higher quality cutters will last longer.
Wire stripper - for the teflon insulated wire included in the kit. Once again Radio Shack will have a functional and inexpensive solution. Be warned that the fancier strippers can have trouble grabbing the slippery teflon insulation. The simple combination stripper/cutters work fine with a little practice.
Needle nose pliers - great for handling small parts and anchoring wires to terminals
Slotted screwdriver - for mounting hardware
Iron Supplement for enhanced S.E.X.
Link to Iron Supplement installation instructions
Mike LaFevre of MagneQuest has worked with us to design some custom by MagneQuest for Bottlehead output transformers and plate chokes specifically intended for the S.E.X. kit. Bass punch, treble smoothness and resolution are all improved by the upgrade. We have worked out a new system of ordering the parts necessary for this upgrade that should save the builder a lot of wait time. You now order the fabulous MagneQuest/Bottlehead BH-1 output transformers and BH-2 plate chokes used in this upgrade directly from Mike Lefevre at MagneQuest. Call 215-288-4816 (up to midnight ET) or e-mail email@example.com to order. We offer a kit of C4S load boards and supporting parts and hardware for $45, that you can use with you own choice of capacitors to complete the installation. The instructions for installing the MagneQuest iron are linked above and you can figure out the additional parts you need if you decide to order them yourself from the parts list at that link. The Bottlehead Forum is available for tech support on this installation.
Enhanced S.E.X.prototype (right) performing with a restored Ampex 934 transport and custom Seduction tape head preamp at Rocky Mountain Audiofest 2004
Sonic improvements? Here's what S.E.X. kit designer Paul Joppa says about the MQ iron -
"The output autoformer inductance will be much higher, so bass at low levels should be much more solid. The nickel in the center of the lamination stack will improve low level detail too, and the better materials and construction should give a sweeter treble, as well as being more extended. You can probably gain an extra octave on each end - approximately - as well as reaping the sonic benefits of better construction."
And the upgraded capacitors and C4S loads will improve power supply ripple rejection, lower distortion, and increase resolution.
Is the improvement worthwhile? Well, we took the prototype to the AES convention in 2005 and came back with requests for upgraded S.E.X. amps from Paul Stubblebine Mastering and Air Studios. If it's good enough for those folks...
Before ordering, please read:
order Iron Supplement "C4S and hardware kit" for S.E.X. kit, shipped UPS to US address
order Iron Supplement "C4S and hardware kit" for S.E.X. kit shipped Air Parcel to Canadian address
Posted by jtkarma on November 10, 2007 at 10:47:03
I was eating breakfast this morning and listening to the opera Carmen on the
radio through my Bottlehead amp. Suddenly one of the characters who had been
lurking in the background moved to the front and surprised the woman singing
which scared the crap out of me. It was as if he was in the room belting it out.
I literally jumped in my chair. Great stuff!
It's been about a year with the amp and I still love this little beast. In fact I've listened to some push pull amps as a possible replacement but they never seem to do classical music as well as my Bottlehead amp.
An insanely great product. If you're sitting on the fence about getting one, just do it, get your name on the list. Your ears and brain will thank you! BTW my amp is bone stock and I doubt I'll change it as I'm so in love with the sound.
Have a great weekend lads....
Posted by Valvefan on September 20, 2007 at 13:37:54
This is my first post. I just discovered Bottlehead online.
I'm looking for a headphone amp with SET magic. I'm currently using Senn 600 'phones and a Headroom Home solid state headphone amp. I'm going to need to do more of my listening on 'phones in the future (family situation changing) so I want a luxury headphone amp. The associated gear will be a Linn Ikemi CDP, BelCanto DAC2 and Blue Circle BC3 (tube) Preamp.
I would appreciate any advice that SEX owners could provide.
Do you think that the SEX is the right choice for this system?
Thanks for your help!
RE: Newbie - SEX as dedicated headphone amp?
I have loved mine with Sennheisers. Not as a good a Sennheisers as you have but I can only tell you that the sound is marvelous and it is a really good headphone amp. I think you would be quite happy.
RE: Newbie - SEX as dedicated headphone amp?
Highly recommended for the Senn600.
I have an Enhanced SEX which I use with Senn600's. Modded with a Goldpoint stereo attenuator and silver Vcaps (which I like better over the Clarity or MusicCaps I tried). I run a Benchmark DAC-1 and vinyl through a modified C4S'd Seduction and Jupiter caps.
Much to my surprise, the biggest improvement was upgrading the Senn cable to the Bottleheadphone cable. I'm not a big cable tweaker, but the change was a significant improvement over the stock cable.
SEX + Senns = eargasm
The Senns seem to be a perfect match for the SEX amp. The Bottle headphone cable is a nice upgrade - as I've mentioned many a time, though my ears are not good enough to appreciate the difference, the extra body (stiffness) of the bottleheadphone cable helps to keep it from getting wrapped around the axles of my desk chair wheels, which was a definite problem with the very flexible (flaccid might be going too far) stock Senn cable.
I have the Enhanced SEX, bottleheadphone cable, and Senn 600's - my front end components are very pedestrian, but the SEX seems to relieve their limitations.
RE: Newbie - SEX as dedicated headphone amp?
I use my 6DN7 amp as a headphone amp and integrated amp. It has to be the best bargain in all of audio. I've run mine just about everyday since I built it at the end of last year. Takes about two nights to build and the instructions are fantastic. I will never give away or sell this amp.
Your equipment is much better than mine so I'm sure you'll have an even better experience.
Good luck with your decision.
SEX amp is a good choice.
The Sennheiser HD600 with a SEX amp is excellent.
We share the same situation young children.
My HD600ís have a couple thousand hours on them now. I have heard and owned many of the Head-Fi ďflavors of the monthĒ amps IMO the SEX amp betters most of them. Simple fact, for the money the SEX amp is in a league of its own.
The MagneQuest iron with the C4S load boards takes the kit to another level, a very worthwhile addition.
Upgrading to Bottlehead cables is a significant improvement as the stock HD600 cables are the weak link. I bought the Stefan Audioart Equinox cables in 2002. When Doc offered his cables we compared the two. I was unable to distinguish any difference.
Just a quick note of thanks to
Doc, Paul, Eileen, and the Bottlehead community. I have recently completed the
SEX kit, playing now through SEXy speakers, my first foray into the world of
tubes. Beautiful kit you've pulled together, and if I can tear myself away from
my listening room here, I may even get to work on the FPIII still in the box
But for now, I'm hearing all sorts of things I never realized were there, be it in the bongos of Jaco Pastorius' Donna Lee, the bowing of Janos Starker's Bach Cello Suites, Peggy Lee's voice on Black Coffee, or the jaw-dropping percussion on Wynton Marsalis' Flight of the Bumblebee.
The only issue seems to be physiological; it can be a bit difficult when listening to things that are at the same time heart-stopping and breath-taking.
Again thanks, and looking forward to many hours of happy listening.
Posted by tsingle999 on November 14, 2006 at 20:53:59
I just completed the upgrade in a couple stages and WOW! I can't believe how
good it sounds! I put in the new iron and large cap and then played the amp
while i took my time building the c4s boards. the amp had much more ooomph with
just the iron & cap upgrade. i compared it to a decware zen amp which i had
previously liked better than the sex amp (it does go for twice the price tho)
and the sex amp was as good as the decware amp. i was very happy!
Then i put the c4s boards in with the resistors and caps and couldn't believe what i heard! Very full sound with lots of bass which made the zen amp sound like it had no bass. and the clarity of things like drums was amazing. It was like all my music was rereleased and remastered or something. and totally non fatiguing. i have a cd that is really fatiguing - i mean i can hardly listen to the whole thing in the car as some of the synth is screeching. but this amp totally smoothed it out. The other thing i found was i really like my speakers now... the klipsch forte ii's really sound good and i cant even turn up the sex amp to 3/4 without it being way too loud (in my small room albeit). Anyway i'm a very happy camper with my sex amp!
My question is
what is the next best upgrade to perform on the sex amp?? i'm having fun with my
new soldering skills!
Thanx Doc and PJ for a great kit! I am looking forward to the climax speaker kit!
Re: Enhanced Sex Amp Instructions
Posted by Dyna Saur (A) on September 06, 2006 at 07:56:05
In Reply to: Re: Enhanced Sex Amp Instructions posted by Doc B. on September 6, 2006 at 06:57:08:
With the "typical" rained-out New England long weekend, I was able to (finally) get around to installing the SEX amp upgrades. I used the "on-line" instructions, printed out, and everything went smoothly, with no problems encountered.
I did it in two stages, first, change to the MQ iron, and the new 2 uF output coupling caps, give it a trial run, and then after trying that out, I next installed the C4S boards and the interstage coupling caps. The iron and cap change was quite noticeable, and the C4S kicked it up another notch or two!
Sound source is a medium-cheap, but fairly good sounding Sony CD player of unknown vintage, and I used Sennheiser 600S to listen.
It was always a great-sounding amp, and the upgrades make it even greater! My "test" CD is the "Big Bad Voodoo Daddy" (modern big-band / swing) which really gives everything a real workout. At this point, I'm totally "blown away" by the sound quality, and this is without a good long "burn-in" period yet.
Thanks to Doc and PJ for another great sounding design!
/ed B in NH
OH MY GOD! - Yes, I'm Yelling
Posted by motorbruce (A) on July 08, 2006 at 21:05:50
OH MY GOD!
After triple-checking, quadruple-checking, and more, I finally determined that my S.E.X. amp is A.-O.K. and ready to play.
Literally, in the first 10 seconds of a recording I know well, I heard astounding things that I had never heard before. Unbelievable!
I'm listening to my S.E.X. amp with Sennheiser HD580s, and music sourced through an iPod (O.K., so I'm going through the longest move in history and I don't have access to my speakers, CD player, or CD collection). The sounding is still astounding.
This little amp is not just impressive as a little amp, but as an amp. I couldn't be more pleased.
I went overboard toward the end of the build. Almost all of the resistors are Tantalum resistors. I splurged. I can hardly wait for my Enhanced S.E.X. upgrade that is on order.
For those who saw my threads (pleas for help actually) regarding resistance checks, fuses, and voltage readings, it turns out there there really weren't any problems, although the readings were different than those in the manual. The only real problem with my build was a misplaced resistor that I caught and corrected during the first round of resistance checks.
This amp rocks, and I had an absolute blast building it.
I hope that all of you are having at least 1/10th the fun and listening pleasure that I am having.
Posted by scott_m (A) on July 09, 2006 at 08:30:33
In Reply to: OH MY GOD! - Yes, I'm Yelling posted by motorbruce on July 8, 2006 at 21:05:50:
Good job! I remember after installing the iron upgrade, listening to Gil Evans + 10 SACD (through HD 580 headphones as well), and being floored by the sound quality. Absolutely floored.
via e-mail, October 19, 2005
Hi Doc, Hi Eileen,
I thought you might be interested in seeing, what system your kits ends up in. I just finished the S.E.X. amp that I got from you a couple of months ago. It is the first "major" soldering kit I ever attempted and it worked right from the start; no problems at all. I am driving a pair of Cain Abby and you can see the finished amp at
The S.E.X sounds wonderful on the Abby's; I could not have imagined what 2W can do for the Abby's. And it does play reasonable loud with maybe a little headroom missing. I hardly notice the power limit though. The bass with the S.E.X. is much tighter and balanced compared to my EL34 based Jolida amp; there is much more detail, instruments and singers are more well defined and sound much more real with the S.E.X. amp. Even more important, I can' believe how much life you managed to pack into this little amp. It has better timing and, within its power limits, has much better dynamics as well.
Anyway, thanks for designing and putting together such a great little amp.
Posted by rmryan on January 18, 2005 at 20:10:34
I'm not much on describing sonic experiences or waxing poetic, so I'll just state a handful of quick and easy facts.
First of all, everyone who has built the new S.E.X. amp has said it and we've all read it ten times, but now that I've experienced it, it bears repeating again. This thing is unbelievably quiet. With my source paused, with either my Koss KSC-35's or my Senn HD-600's, and the volume cranked all the way up, there is absolutely no sound. No hiss. No buzz. Nothing. Turn the volume down to a reasonable level and hit play and the music simply appears out of a dead quiet background.
Second, detail. Two of the selections I listened to were Dire Straits' "Love Over Gold" and Cassandra Wilson's "Glamoured." In "Private Investigations" there's some reverb and echo added to Mark Knopfler's voice that I've never noticed was there, and I've literally been listening to this album since I was about 15. Cassandra Wilson's covers of Dylan's "Lay Lady Lay" and of "If Loving You Is Wrong" absolutely blew me away. Overall, I'm extremely happy. And I haven't even hooked up a CD player or a pair of speakers yet.
Third and last point, and I know most of you are going to say "Duh." The S.E.X. kit completely blows away my Creek OBH-11 headphone amp. The S.E.X. power transformer alone weighs considerably more than the whole Creek unit.
Bottlehead S.E.X. Amplifier: My experiences, and a mini-review!
Posted by Mikey on January 10, 2005 at 09:29:30
Bottlehead S.E.X. Integrated Amplifier: (the construction)
Since several other builders have touched upon all of the noteworthy electrical issues and assembly manual misprints, I will not mention them here. However, two items I have noted during construction are summarized below.
Wow, a new and improved chassis plate! This is great! The thicker chassis plate really gives the kit a higher quality feel than the previous version of the chassis plate. Also, the fit of each component onto (or into) the chassis plate is improved. It is readily apparent that more time went into the design / layout / fabrication of these plates.
Mechanical Assembly Notes:
The mechanical assembly was very straight forward, with the exception of the assembly of the tube socket area. The first issue was loose fitting O-rings, which was easily cured by cutting about 3/16Ē from the O-ring, and re-gluing it with some super glue. The glue does not really like to adhere to the silicone rings, but with some patience it will work. Now the O-rings stay in place on the tube socket, which is what I believe Doc B. intended. I'm fairly certain this issue has been addressed, and smaller diameter O-rings will be included in future kits (yup - Ed.).
I deviated from the manual when mounting the socket / terminal strip assembly. One of the really neat features of those octal socket hold-down brackets is the ability to hold a #4-40 nut captive, so I had to exploit that feature! In place of the nut that would normally get sandwiched between the hold-down bracket and the chassis plate, I used a stack of washers (four SAE washers to be exact Ė a similar height spacer would be better) to keep the hold-down bracket spaced away from the chassis plate. This allowed me to tighten the tube socket mounting hardware by the screw head, rather than try to get those little nuts to turn inside of the hold-down brackets.
Assembly the second time was much less complicated, as I built it both ways!
All in all, the build was very straightforward. Once the typos in the manual are corrected, this kit shouldnít pose any problem to a builder with some previous soldering experience.
All resistance checks and voltage checks were spot on, so...
Bottlehead S.E.X. Integrated Amplifier: (the sonics)
The speakers I used for testing were my JBL 2446 / Gauss 4583 combo. They are roughly 97 dB efficient, with a 16 ohm compression driver, and a 8 ohm 15Ē woofer.
The source I used was a modified Pioneer PD-65 CD player.
I hooked up the system, fired everything up and...what the f$%k? I didnít hear a peep from the loudspeakers. OK...goof around with the volume control, recheck the interconnects, the tubes are glowing...so what the hell is going on? Everything looked in order, so I hit play on the CD player and music poured forth!
Lesson one: This is one quiet amp! I mean really friggin' quiet!
Every amp I have ever tried with these speakers has had audible hum or buzz, but not this one...even with the volume control wide open I couldnít hear anything with my head right up next to either of the speakers.
Lesson two: This amp sounds very good!
I observed a very natural, neutral sound, with what seemed like a very even frequency response. The amp is very musical and involving, with good coherence from top to bottom. The bass response is taut and tuneful, and extends extremely low. The midrange is glorious, very real and palpable. The top end is extended and smooth, with a surprising lack of glare and harshness. All this without any break in!
Lesson three: A couple of watts can get pretty loud!
I kept inching up the volume control, and ended up at the point where it was getting fairly loud. If there had been anyone else in my listening room, they would have had to really raise their voice to be heard over the music! Further attempts at more volume brought on some audible distortion, and some loss of woofer control, but what did you expect with a giant 15Ē prosound woofer?
I havenít yet auditioned any headphones, but I have a set of Sennheiser HD 580ís on order. I canít wait to try them.
Thatís all for now...
S.E.X. Integrated Amplifier (part two, headphone listening notes):
Posted by Mikey (A) on March 16, 2005 at 10:00:32
So...Iíve been working like a madman lately, putting in really long hours at the office. Listening to some tunes while plugging away at the CAD system is a nice way to get creative, so I brought my Bottlehead S.E.X. amp to the office, along with my Sennheiser HD-580ís. Sure, the big headphones and funny Ďtube-ampí generate a few chuckles from co-workers, but one listen and theyíre not laughing any more...but I digress!
Before we go any further, read about my assembly notes and initial impressions at:
At the office, the S.E.X. amp is fronted by a bone stock Rega Planet CD player.
- On to the sound:
As I wrote previously, this is one very quiet amp. The music pours forth from an absolutely black background, and what frigginí *exceptional* music it is! Iím no audio magazine reviewer, so I canít spout off colorful paragraphs of worthless prose trying to convey what I hear with this amp; but I can list a few of the terms that come to mind when Iíve got some tunes playing!
It seems funny to be writing the following sentence...but here goes:
I am hearing things on my CDís that I didnít hear before! There, I said it. I can hear so deep into the mix that it is freaky at times, like Iím actually at the recording studioÖ.no doubt helped in part by the eerily silent background. Sure, soundstaging and imaging are lacking while listening through headphones, but I donít place a high priority on those items anyway. The tonality of voices, guitars and drum kits is truly amazing!
Quite simply, the S.E.X. amp with headphones is in some ways a new reference for me. Above all else, this amp-headphone combo has allowed me to connect with the MUSIC in a way that I didnít know was possible before now!
Thanks Doc B. and Paul Joppa for another fantastic product!
HOLY CRAP!!!! S.E.X. AMP !!!!!!!!
Posted by John EH on January 07, 2005 at 17:31:19
Just finished my SEX amp. Completed it and gave it a once over. Good to Go!
Resistance checks = Spot on!
Voltage checks = Damn near what the book says for every one!
Note: The manual calls out -17vdc on tag strip 7 and 27.....nothing is hooked to these.
Scratched my head for a moment then decided it was a goof, or a misprint or something.
Decided to go for it......
Hooked it to a stock CD deck and my Fostex FE-103 Back Load Horns........
Volume down......CD starting......gently easing up the volume and I'm greeted with 2 perfect channels of sound.
A Tony Rice CD is spinning now and it sounds FREAKING AMAZING right out of the gate....100% stock.
HOLY CRAP doesn't begin to explain it. I swear it has more ooomphhh with the Fostex horns than my Paramours do.
If you don't have one.......You need one.
Build quality is exceptional.....I did some good work on this one as well. Took me probably 6 or 7 sittings and I just relaxed and did it slow. Did about 3 hours today to finish up.
Pictures after the base is done and everything cleaned up.
Comment about Sex Amp Hum and Buzz.......
Posted by John EH (A) on January 07, 2005 at 18:04:24
There is NONE! Nothing. Nada.
Quietest tube amp I've ever heard.
I pressed my ear to the speaker and there is no difference at all between on and off.
This is one SILENT amp.
Another SEX amp joins the family!!!
Posted by cary on January 07, 2005 at 20:24:06
Just finished my SEX amp. All I can say is FANTASTIC. It was a lot of fun to build. I did most of the work between Xmas and New Year. I want to thank Doc for answering all my questions. I promised him to post what I learned from the process. One of the most important lessons learned was to read and re-read the assembly manual. Follow it word for word! Also to TAKE YOUR TIME! Never be in a hurry, that's how mistakes are made! I spent a few hours every day on the assembly. I took a very conservative approach in the construction. when soldering any part I always used a heat sink. Also used a continuity checker on every connection. Checked, double checked and triple checked every connection to make sure no mistakes were made. I work at a nuclear weapons National Lab, so being precise and careful is second nature
On the voltage test the fuse blew. I double checked all wiring, everything was correct. Replaced fuse with a 2 amp, slow-blow. (Editor's note - Cary got a kit from the first production run with a 1A fast-blo fuse. We now supply the proper 1A slo-blo fuse) Did the voltage check, everything within spec. Amp is now connected to a pair of Pi 1 speakers-95db and a Sony ES, CD player.
Again thank you Doc, this amp was well worth the wait!
Posted by MarkER on December 19, 2004 at 16:06:59
I've been listening to the new stock S.E.X. rig all day through both Sennheiser HD-600s and Straight 8 speakers. In the headphones it is dead quiet and has plenty of bass. Plenty of power to run the Straight 8s, if not with the force and volume from 300Bs. Running vinyl through a C4Sed Seduction into it gives great sound. Highly recommend listening to the opening chimes of Santana's Abraxis (not to mention all the great percussion) and the Beatle's Sgt. Peppers to really hear the detail available. And I am not a very good builder.
Posted by Rich vSB on December 11, 2004 at 17:24:12
I completed my S.E.X. amp tonight and it's breaking in. It's sounding very good right from the start. The amp is very quiet when there is no signal -- absolutely no hum! I'm currently listening with my Sennheiser 570's with a DVD player source. The assembly went very well, resistances checked out fine and voltages were pretty close. The instructions were very good and the pictures in the manual are fantastic. Another great Bottlehead product! Thanks!
Posted by Caucasian Blackplate on November 27, 2004
I really like this new manual Doc! It's sooo much easier to have the reference pictures every couple of steps, definitely leaves less to the imagination. I am very impressed at how much you pack into this kit for the price. I see 3 pieces of custom iron and quite a well thought out layout...nice going!
Got the S.E.X. up and running stock.
Definitely way better than I expected...way better than it should be for that price. How do you get so much bass out of such a tiny little amp (on
300 ohm HD-600's none the less)? I am loving it Doc, I'll have to work on PP mods and order another set soon.
Posted by JellyRoll Mozart on August 20, 2004 at 06:58:47
I spent an afternoon with Doc this week listening to the SEX amp using my Lowther Academy speakers. The Academies are about 101 db efficient and we found that the SEX amp performed wonderfully with them. Very quiet--which is problematic with super efficient horns--and very good sound.
Sex Amp with headphones
Posted by Mossback on June 10, 2004 at 18:01:19
Docís prototype Sex amp sounds very nice with cans! I own the Pete Millet kit amp as well as a one off from Gary Dahl with MQ iron. Iíve owned several other head amps both tube and SS. The Sex Amp Doc has coming out soon is one of the best I have heard.
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