Headphone impedance and Bottlehead Kits

[Doc B.]

1/9/12 - This thread is outdated.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.htm

With 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 Kit

Crack 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 Kit

What 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 ohms
HD595 - 50 ohms
HD 590 - 120ohms
HD280 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 ohms
iGi - 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 ohms
DT-880 32 - 32 ohms
DT-48 -  200 Ohms

Sony
MDR-SA5000 - 70 ohms

AKG
K702 - 62 ohms
K701 - 62 ohms
K240 M  - 600 ohms
K240 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 ohms
K280 - 75 ohms
K271 - 55 ohms
K270 studio - 75 ohms
K260 - 600 ohms
K241 - 600 ohms
K240 Studio - 55 0hms
K240DF - 600 ohms
K240 Sextett - 600 ohms
K200 - 90 ohms
K180 - 600 ohms
K171 Studio - 55 ohms
K160 - 600 ohms
K150 - 600 ohms
K145 - 200 ohms
K141 Studio - 55 ohms
K141 Monitor - 600 ohms
K140 - 600 ohms
K134 - 150 ohms
K120 - 600 ohms
K101 - 19 ohms
K100 - 100 ohms
K71 - 19 ohms
K70 - 100 ohms
K66 - 32 ohms
K60 - 600 ohms
K55 - 32 ohms
K45 - 200 ohms
K40 - 200 ohms
K27i - 32 ohms
K20 - 600 ohms
K14P - 17 ohms
K12P - 17 ohms
K4 - 400 ohms
K2 - 200 ohms

Koss
Pro 4AA - 250 ohms
Pro 4AAT - 250 ohms

It 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/

[Paully]

Sennheiser HD 590 - 120ohms

(added, thanks! - Doc B.)

[Paul Birkeland]

AKG K501 - 120 ohms
AKG K500 - 120 ohms
AKG K401 - 120 ohms
AKG K400 - 120 ohms
AKG K340 - 400 ohms
AKG K301 - 120 ohms
AKG K300 - 150 ohms
AKG K280 - 75 ohms
AKG K271 - 55 ohms
AKG K270 studio - 75 ohms
AKG K260 - 600 ohms
AKG K241 - 600 ohms

AKG K240 Studio - 55 0hms
AKG K240DF - 600 ohms
AKG K240 Sextett - 600 ohms
AKG K200 - 90 ohms
AKG K180 - 600 ohms
AKG K171 Studio - 55 ohms
AKG K160 - 600 ohms
AKG K150 - 600 ohms
AKG K145 - 200 ohms
AKG K141 Studio - 55 ohms
AKG K141 Monitor - 600 ohms
AKG K140 - 600 ohms
AKG K134 - 150 ohms
AKG K120 - 600 ohms
AKG K101 - 19 ohms
AKG K100 - 100 ohms
AKG K71 - 19 ohms
AKG K70 - 100 ohms
AKG K66 - 32 ohms
AKG K60 - 600 ohms
AKG K55 - 32 ohms
AKG K45 - 200 ohms
AKG K40 - 200 ohms
AKG K27i - 32 ohms
AKG K20 - 600 ohms
AKG K14P - 17 ohms
AKG K12P - 17 ohms
AKG K4 - 400 ohms
AKG K2 - 200 ohms

(added, thanks! - Doc B.)

[JC]

You've covered so many, but here is one of my favorites:

Beyerdynamic DT-48     200 Ohms

(added, thanks! - Doc B.)

[xcortes]

And there's, of course, The King:

Sony MDR-R10 at 40 ohms

[autobayer]

Guys.
There

[Armaegis]

A note about the Beyer DT48; there have been many versions released over the years. Most are *not* high impedance... in fact, most of them are rather low, around 25, and I think there's a few rare ones even down to 8.

[hasafraker]

to go with my Crack my wife got me a pair of Audio-technica QuietPoint ATH-ANC7b's I have nothing to compare them to but they sound good enough connected to the Crack to give me goose bumps. These are 300ohm cans.

The noise cancellation is really quite good. I took them to work and without any music turned them on and put them on and it was akin to stepping into a sound proof room. It's pretty insane how loud my office is.

[Jim R.]

Dan,r the ones that are alsu suitable for the Crack?   Also wonder why the AKG 601 isn't listed.

-- Jim


Could you do something like put a * afte

[Doc B.]

As a general rule of thumb anything from 120 ohms up should be OK with the Crack. However there may be subjective qualities that will make some listeners like cans that have lower impedance with Crack, and qualities that may make some folks dislike a higher impedance headphone with Crack. I have not listened to all of the headphones myself so I can't really make a definitive recommendation beyond the impedance.

[Laudanum]

Some more Hi-Z phones for Crack.

The following list from both manufacturers are only the models I am aware of.


German Maestro

GMP 400 - 300 ohms
GMP 450 PRO - 300 ohms
GMP 800.3 D - 300 ohms
GMP 250 - 100 ohms
GMP 240 - 100 ohms

They also have some lower impedance models.

MB Quart

QP 220 - 100 ohms
QP 400 - 300 ohms
QP 805HS - 300 ohms

These MB Quart phones are NOS.  Quart isnt making phones any longer.  Some of the German Maestro models are reprotedly equivalent or based on/similiar to Quart models.

[Doc B.]

In light of the upcoming Smack amp that has switchable output impedance settings creating yet a third headphone amp choice in the Bottlehead stable, I have created a short article about Bottlehead amp choices for various headphones and listening setups. This has what I consider to be the most current info with respect to the community's experience. Note that I have shifted the suggested minimum impedance headphone to use with Crack up from 120 ohms to 200 ohms. This is not cast in stone, it is simply an adjustment based upon the aforementioned community feedback, and it also takes into consideration the ability of the new Smack to be set as high as 128 ohms output impedance.

http://www.bottlehead.com/et/whichheadphoneamp.htm

[xcortes]

You're missing the mighty Quickie. It's battery power supply make it a very good component for battery powered sources (iPod anyone?).

Of course with the Specos gone one needs to source other options. Hmmm, how about the Schmack (OK, just checked and the spelling is wrong but goes well with Schmalle) opt for a Crack?

[Doc B.]

One can certainly do these kinds of mods. I have to say that I think the Quickie is a killer preamp stock and a just OK headphone amp with the Specos added. With respect to putting an output transformer on the Crack, to my mind it's not really optimal to put a transformer on a cathode follower. I think both CFs and transformers are compromises and one or the other is a necessary evil. But I am not that big on making both compromises together to get the output impedance down. That's why we are doing the Smack, it's really the best circuit design we have found to use with a purpose-built transformer. Both the Smack and the Crack do what they do very well with the type of headphones they are designed to run (Smack below 200 ohms, Crack above 200 ohms), and neither is quite as good as the other with headphones outside their designed impedance range.

[xcortes]

Stoopid me. I meant a Smack OPT for a Quickie?