Which amp should I buy for my headphones?
The Single Ended eXperimenter’s amp (S.E.X. amp) V 2.1 is a two gain stage transformer output amp with 2 watts per channel output that can be configured to run speakers and headphones. It can be set up for 4, 8, 16 or 32 ohms output impedance. If you plan to use the amp for both speakers and headphones, match the impedance of your speakers. When the headphone plug is inserted into the jack on the S.E.X. v2.1 the speakers will be cut off, making it easy to switch between the two by simply plugging and unplugging your headphones. If you’re using headphones now but plan to use efficient speakers or regular speakers in a near field setup like a computer in the future this is a great way to go. The low output impedance of the S.E.X. amp will work with virtually any standard dynamic headphone of any impedance. It’s a great match with AKG K1000s and Audeze LCD-2s.
The Crack amp is an output transformerless amp of about 300mW output power designed specifically for high impedance headphones (best above 120 ohms). It’s a favorite of Sennheiser HD585/HD600/HD650 and HD800 users. Other great matchups would include:
K141M (600 ohms), K240, K240M, K240DF (600 ohms), K241 (600 ohms), K250 (600 ohms), K260, K260 pro (600 ohms), K340 (360 ohms)
DT 100 (400 ohms), DT 150 (250 ohms), DT 250-250 (250 ohms), DT 411 (250 ohms), DT 511 (250 ohms), DT 531 (250 ohms), DT 550 (600 ohms), DT 660 MKII (600 ohms), DT 770 (250 ohms), DT 770 (600 ohms), DT 770 pro (250 ohms), DT 801 (250 ohms), DT 811 (250 ohms), DT 831 (250 ohms), DT 880 (250 ohms), DT 880M (600 ohms), DT 880 Pro (250 ohms), DT 880 S (600 ohms), DT 901 (250 ohms), DT 911 (250 ohms), DT 931 (250 ohms), DT 990 (250 ohms), DT 990 Pro (250 ohms) Tesla T1 (600 ohms)
Pro 4AA (250 ohms) Pro 4AAT (250 ohms)
HD 222 (600 ohms), HD 230 (600 ohms), HD 250 II (300 ohms), HD 420 (600 ohms), HD 420SL (600 ohms), HD 425 (600 ohms), HD 430 (600 ohms), HD 540 (600 ohms), HD 560 II (300 ohms), HD 580 (300 ohms), HD 600 (300 ohms), HD 650 (300 ohms), HD 800 (300 ohms) , HDC 451 (250 ohms), PXC 150 (300 ohms), PXC 250 (300 ohms), PXC 300 (300 ohms)
QP400 (300 ohms)
The Mainline amp is a single gain stage transformer output headphone amp with about 600mW output power and switch settings for output impedance of 32 and 64 ohms. The switch allows for using headphones of different impedances and for trying different output impedances with a given headphone. The amp has a standard stereo TRS type 1/4″ jack and also a 4 pin XLR jack that allows for balanced headphone cable operation. This is the dedicated headphone amp for almost all of the dynamic headphones that are available (why almost? see the AKG K1000 comments below).The general rule of thumb is that one will set the output impedance switches to match or be slightly lower than the impedance of the headphone you are using. For Grados one would use the low impedance setting. For Sennheiser HD800s one would use the high impedance setting. If you are using something near the high setting like the K701 (62 ohms), one could try both settings and choose whichever sounds best.
This amp is Doc’s favorite for any headphone with normal power requirements. And it’s excellent with high end cans like HD800, Beyer T-1, Sony R10, etc.
So, S.E.X. and Mainline both work with low impedance headphones? Why make both?
The Mainline circuit has a single gain stage and a more sophisticated regulated power supply. It also has a stepped attenuator of very high resolution. It puts out less power than the S.E.X. and can’t run a speaker, but it edges out the S.E.X. in terms of resolution in a dedicated headphone setup.
If S.E.X. and Mainline also work with high impedance headphones, why make the Crack?
Simple, while all three amps work great with high impedance headphones, Crack is less expensive – an excellent choice if you are on a budget. Pair it up with some used HD600s and upgraded cable or our Bottleheadphone and you have a killer setup for less than a pair of top dog headphones alone.
What about AKG K1000s?
We use these as one of our reference headphones. They are extremely inefficient and AKG recommended at least 7 watts of regular speaker type power to run them. Our Paramount 300B amps turned out to be a wonderful combination, and if you are lucky enough to have a pair of these no longer in production ear speakers you owe it to yourself to try them with Paramounts. If that is beyond your budget the S.E.X. 2.1 set up for 32 ohms output is a great amp with the K1000s too.