*1/9/12 - This thread is outdated. Please click the link below for the latest info on matching Bottlehead amps to headphones.*http://www.bottlehead.com/et/whichheadphoneamp.htmWith two different kits capable of driving headphones we have no doubt created a bit of confusion for folks considering buying one. The two kits - the S.E.X. kit and the Crack kit, are rather different animals.

The S.E.X. kit is a more traditional single ended tube amplifier of 2 watts output that can run very sensitive speakers (like 99dB or better) and headphones ranging from 4 ohms impedance on up to several hundred ohms. In its newest V2.1 livery it even works well with the very inefficient AKG K1000 (which happens to sound marvelous with our Paramount 300B monoblocks) and the Audeze LCD-2. If you need a very versatile amp for a wide range of headphones and also occasional speaker use, S.E.X. is the right choice.

Single Ended eXperimenter's KitCrack is an output transformerless amp that is designed specifically for higher impedance headphones. The output impedance in stock form is about 120 ohms, and thus

*headphones of 120 ohms impedance or higher are the best choice to go with Crack.* It will play music through lower impedance headphones, but it will not be an optimal match. Sennheiser, AKG and Beyerdynamic are three of the most well known manufacturers of higher impedance headphones and those models are usually very highly regarded. If you run 5998 tubes in your Crack instead of 6080s you can probably go as low as 70 ohm headphones.

Crack OTL Headphone Amplifier KitWhat I would like to start in this thread is a list of headphones and their impedance, so folks can decide which amp might be the best fit with their favorite cans. All of the headphones listed should work great with S.E.X. I have highlighted

in orange any headphones of 120 ohms or higher that would also be suitable for use with Crack.

Here's some for starters:

**Sennheiser** HD 600 - 300 ohms

HD 650 - 300 ohms

HD 800 - 300 ohmsHD595 - 50 ohms

HD 590 - 120ohmsHD280 Pro - 64 ohms

**Ultrasone** Edition 8 - 30 ohms

Pro 900 - 40 ohms

Pro 650 - 75 ohms

**Denon** AH-D7000 - 25 ohms

AH-D5000 - 25 ohms

AH-D2000 - 25 ohms

AHD1001K - 32 ohms

**Grado**SR60i - 32 ohms

PS1000 - 32 ohms

GS 1000i - 32 ohms

RS1i - 32 ohms

RS2i - 32 ohms

SR325is - 32 ohms

SR225i - 32 ohms

SR125i - 32 ohms

SR80i - 32 ohms

iGrado - 32 ohms

GR8 - 120 ohmsiGi - 24 ohms

**Audio Technika** ATH-W5000 - 40 ohms

**Beyerdynamic** Tesla T1 - 600 ohms

DT 990 - 250 ohms

DT-880 600 - 600 ohms

DT-880 250 - 250 ohmsDT-880 32 - 32 ohms

DT-48 - 200 Ohms**Sony **MDR-SA5000 - 70 ohms

**AKG** K702 - 62 ohms

K701 - 62 ohms

K240 M - 600 ohmsK240 S - 55 ohms

K240 MK II - 55 ohms

K501 - 120 ohms

K500 - 120 ohms

K401 - 120 ohms

K400 - 120 ohms

K340 - 400 ohms

K301 - 120 ohms

K300 - 150 ohmsK280 - 75 ohms

K271 - 55 ohms

K270 studio - 75 ohms

K260 - 600 ohms

K241 - 600 ohmsK240 Studio - 55 0hms

K240DF - 600 ohms

K240 Sextett - 600 ohms

K200 - 90 ohms

K180 - 600 ohmsK171 Studio - 55 ohms

K160 - 600 ohms

K150 - 600 ohms

K145 - 200 ohmsK141 Studio - 55 ohms

K141 Monitor - 600 ohms

K140 - 600 ohms

K134 - 150 ohms

K120 - 600 ohmsK101 - 19 ohms

K100 - 100 ohms

K71 - 19 ohms

K70 - 100 ohms

K66 - 32 ohms

K60 - 600 ohmsK55 - 32 ohms

K45 - 200 ohms

K40 - 200 ohmsK27i - 32 ohms

K20 - 600 ohmsK14P - 17 ohms

K12P - 17 ohms

K4 - 400 ohms

K2 - 200 ohms**Koss**Pro 4AA - 250 ohms

Pro 4AAT - 250 ohmsIt would be great for the community to add to this list to build a more comprehensive resource.

Here is a link to a good resource, though it may be a bit dated. You will have to pull up individual specs, but it looks pretty comprehensive:

http://headphones.warzone.org/