Headphones and amp suggestion (HD650, K712, S.E.X, Crack)

[Joe Garfield]

I have HD650 and K712 headphones. I'm trying to decide between building S.E.X. to work with both, or building Crack to max out the HD650s and keeping the K712 paired with Schiit Vali 2. I just built Crack for my HD650 at another location and am blown away, so I'm wondering if a) the K712s will scale as well with S.E.X, and b) if the HD650 would seem like a compromise with S.E.X. after hearing them on Crack.

[Paul Birkeland]

I would go with the SEX amp over the Crack.  It is far more flexible and I don't believe you'll have any regrets when comparing it to a Crack with the HD650s.

[Joe Garfield]

Thanks Paul. For the heck of it I actually tried the K712 with Crack and realized theOr potential with better amplification, so I just put in a request to the Queen for S.E.X. and a few extra parts.

The purpose will be 64 ohm headphones, secondary purpose is a single 4, 8, or 16 ohm speaker, and third is the HD650. It sounds like there’s no way to combine speaker output power without much modification, so what would be the best impedance/setup?

Edit: I found this (below). Maybe the 4 ohm setting gives the best flexibility to work with a 4 ohm speaker if I end up with one, otherwise no problems with 8-16 ohm speaker or 64 ohm headphones.

The answer to this is multi-faceted, and I'm sure I'll forget a few along the way and others can chime in. 

The Impedance Switch kit took a bunch of these little PC board mount slide switches, and they always seemed to either be out of stock or maybe there would be 3-4 available at a given vendor when we needed to order them.  When we released the kit originally, this part was well stocked at several different vendors by the hundreds.  There's nothing worse than having someone's Steromour packed and ready to ship but the switches for the Impedance Switch kit add on are back ordered for three weeks. 

The manual was another conundrum.  The Impedance Switch kit went with Stereomour I, Sex 2.1, and Smack (not as an option, but rather it came with the Smack).  Making a single manual for an upgrade that goes into multiple kits is pretty difficult, as is supporting this as the products develop.  As anyone who has installed the Impedance Switch kit in a SEX can tell you, the manual was already a bit jumbled just based on the variations of the SEX 2 that were floating around; adding a 3rd would have made the manual even more difficult to follow.  We would have also needed to add instructions for the Steremour II and the Seductor, so now we are up to three variations of the SEX amp (maybe 4 since you can put the iron upgrade in a SEX 2.0), two different Stereomours, and the Seductor.  This is not tenable.

Operator error also seemed to creep up a bit.  I know Doc B. will even admit that we (Doc B would tell you that it was probably me) would accidentally bump those switches underneath when moving gear around for a demo, and it's really embarrassing to have to debug why you have channel imbalance during a demo when an amp permanently wired at 8 ohms would never run into that problem.  If this caught us off guard periodically, how many headaches are we generating for everyone else with this kit?

The issue I would bring up is actual performance.   As I have mentioned on other threads, we actually eliminated instructions for anything other than 4 and 8 ohm operation in the SEX 3 manual to eliminate the repetitive threads of Grado/IEM users wiring their amps at 32 ohms and wondering why they hear hiss and why they can only turn up the volume knob two degrees before the amp is at full volume.  The available power on the 4 and 8 ohm taps is sufficient for 99.9% of the headphones out there and the noise floor is beautifully low in these configurations.

(I would mention that I haven't ever found a use for the 32 ohm setting)

Thank you.

[Paul Birkeland]

Yes, I would start at 4 ohms.  If you have no headphones that are super sensitive, you could also try the 8 ohm setting.  With Grados or IEMs, the 8 ohm setting may not be optimal.