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Bottlehead Amplifier Discussion / Comparison Thread: Crack, SEX & Mainline

Discussion in 'Headphone Amps (full-size)' started by loquah, Sep 24, 2013.
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  1. adydula
    OK all done except for the missing 49.9 ojm resistors, should be here on Tuesday!

    The resistance checks looked ok...so (2) more days for the real "smoke" test!!

    I removed one side of the springs and ball bearing to make the vol adjusts smother to my liking.
    Also after (4) applications of Formby's High Gloss Tung Oil it looks great to me, smooth and solid.


    Last edited: Mar 25, 2018
    JamieMcC likes this.
  2. adydula
    Well its finally complete and functioning and functioning very well!

    Voltage checks were spot on biased the 6c45pis to145volts....regulated voltages ok.

    Never heard my T1's and T90's sound so good....

    I was able to use the two inputs to set up two differnt dacs with 2 different pcs and play the same song at the same time and the same level and compare dacs..,..now I know how an ODAC compares to a Schitt Bimby MB!!

    Highly recommeded amp..

    timind and slankoe like this.
  3. timind
    Beautiful build Alex. Assuming you've owned both the Crack and S.E.X amps, where does the Mainline rate? I ask as I've built the Crack and the S.E.X. and the S.E.X. is head and shoulders better than the Crack. Curious how you rate the three amps?
  4. adydula

    Unfortunately I have not heard a S.E.X. amp, only my Crack w/Speedball. I have a Schitt Vahalla 2, Asgard, Lyr, and several other SS DIY amps..some very, very good.

    The mainline IMO after just a few hours of listening and doing some quick comparisons is really on the top of the pile for real musicality....with great songs is absolutley astonishing.

    The one thing that steps out (and I hate using those glittering adjectives)...is the resolving "power" or "ability, some say "micro-details".

    With the T1's on the high impdeance unbalanced setting, its really uncanny in being able to hear all thats there even at low amplitude.

    It seems so "stable, solid, doesnt loose its composure....the 6C45PI is a great tube, ultra linear, and doenst cost an arm and leg for greatness.

    The mainline even with 600mw seems to be able to drive the T1's more easliy than the crack. With the crack you have to turn the volume control a lot to get to the higher
    amplitudes..seems like the Mainline has more power but its about the same rating as the Crack.

    The mids are superlative, voicing is very nice, and the bass is solid, really stable, again depending on your source it will be almost as perfect as you can get, depending on how the bass or ecording was authored in the first place.

    I have a wonderful supply of great recordings from a few friends and play some of these "reference" recordings its a mind blower.

    If I had to do it again I would most likely just buy a Mainline and be very content,,,but you dont know that unless you try other stuff...reading about stuff is great but we all are different
    and hear things abit differently....

    You dont hear much about this amp out there in the audio wild, but its definitely a TOTL for me.

    Last edited: Mar 29, 2018
    DavidA and timind like this.
  5. adydula
    On the micro-details stuff....listening to an old "The Doors" recording with "Riders on the Storm" cut.....with lesser amps, cans you strain to hear the rain and thunder in the background
    in the oppening of the tune, as well as trying to discern it while the main part of the song is playing...with this amp and the T1's its just "there" like it was meant to be...no straining, its just "there"....simply amazing resolution ability.

    slankoe likes this.
  6. timind
    Thanks for the comprehensive answer.

    I was a Senn HD650 devotee for years until a friend loaned me his Beyer T1s a couple years ago. They really opened my eyes/ears to how much more there was to hear with headphones. The T1s set me on a search which eventually ended with Beyerdynamic DT990 (not pro version). I find them to be a perfect match of natural sound and detail.

    I had built a couple Cracks for the Senns and had one with the DT990s. That amp seemed a bit lifeless compared to my old Nuforce HDP so I built a S.E.X. That amp was amazing, but had more gain than the 990s needed. I found I was listening with the volume control on "1" instead of 3 or 4 like most amps.
  7. JamieMcC
    Congrats on the getting your Mainline up and running its a superb amp.

    Sex + T1 is very good by the way even more so with some high quality caps like the Mundorf Silver oils which bring nice gains in soundstage and resolution.
    Stock Mainline is another level up again.
    gab840 likes this.
  8. Doc B.
    That would be 600mW, not 60mW. Crack puts out more like 300mW into a 300 ohm load. None of this has to do with how much you turn the volume knob of one amp relative to the other for the same level. That has to do with the gain of the amp, not the power output.
  9. adydula
    Thanks for the correction Doc....
  10. Doc B.
    I'll backpedal just a bit here - the output power will indeed be lower into 300 ohms, and your 60mW number is probably in the ballpark. The Mainline should put 600mW into a 64 ohm load from the 64 ohm tap. However I would not necessarily use this as the only yardstick by which to measure the relative performance vs. another amp. For one thing these numbers don't have a distortion figure associated with them. We typically use about 5%-10% THD, which freaks out the SS guys who use amps with tons of negative feedback to kill the more prevalent odd order harmonics their amps produce. The Crack has a little higher distortion at low levels than the Mainline does at similar levels simply because of the circuit differences - cathode follower vs. transformer output. FWIW this notion that the power level is reduced into higher impedance loads is also true with SS amps and the S.E.X. amp, since it is also using a transformer with a relatively low output impedance compared to the impedance of high impedance cans. It's a fairly moot point when you consider the power output of the S.E.X. amp is way more than necessary for most headphones.

    The notion of when impedance matching is important seems not that well understood in the community. There is nothing wrong with connecting a higher impedance load to the lower impedance output of a zero negative feedback amp. It may sound better or worse (particularly in terms of perceived bass performance), but it does no harm. And in some cases the improved S/N and the tighter bass gained from using a lower impedance output tap might be the overriding factor in deciding which tap to use.
  11. adydula
    Thanks for the update...I am finding that the Mainline with 250 ohm and 600 ohm Beyers there is more than enough "power" to drive these headphones to a very
    high level, way to high for safe listening.

    With these cans, the high impedance setting and unbalanced output to me seems the best in providing an overall sound that IMO works wonderfully with all kinds of music.

    The tonality of a bass violin, male and female voices just sound very natural and musical to me....lifelike etc.

    Depending on how well the recording was done originally and mixed, this amp and my T1's produce a bass with organ music (27hz) that just astonishes me. Yeah not as great
    as a really good 2 ch loudspeaker setup, but really awesome when you consider the size of the transducers.

    Most of my SS amps THD's is measured extremelu low in comparison, and they do sound different, but the Mainline and Crack just sound so "musical"...its the only word that I know of that describes the beautiful presentation these tube amps provide.

    Every headphone enthusiast should take a listen with one of these amps.....theres no turning back!! Ha!

  12. gab840
    Congrats Adydula & welcome to the Party!!!
  13. adydula

    I listen to this via this amp almost daily...being retired.

    I have a BH Crack modded with Speedball and a dozen other assorted SS and tube amps.

  14. rayhe19
    Hey Guys,

    I have a pair of HD800 with a Schiit Lyr2. However I am thinking about getting a bottlehead amp to build as a hobby and as an upgrade to the Lyr2. Compared to the Lyr2 I would like more bass extension and soundstage. I am wondering what would be the best bottlehead amp to go. I've been looking at the crack, crackatowa, and mainline. From what I've read so far, the crack seems to be a sidegrade while the mainline is overall a pretty good upgrade in terms of both soundstage, extension of highs and lows, as well as details.

    I was also wondering if the stereomour II could be modified to run headphones?

    Thanks, Ray
  15. adydula
    I have both the Crack and Mainline...if you can afford the Mainline...just do it and be done with it...its that good...

    deserat likes this.
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