WTF Amps El Bad Hombre MK2

After read the thread Push Pull vs OTL vs SET (Tube amps) posted by @gbeast and noticed that I have never try PP headphone amp. Searched on the internet for a while, I only found few such as:
1) Pete Millett's ECC99 SRPP Headphone amp
2) WTF Amps El Bad Hombre
When my wife and kid are temporary away. I really want to build a amp. The second one is obviously easier to me, much lesser components. It takes about 1 month to source parts (with baby!) and another month to build it using the time after work. After this project, really need to rest for a while. I would say, even the circuit is there, it still take a lot of work to build a desirable application.
The internal picture:

Some major components are:
A) @tomchr 's voltage regulator which regulated the B+ to 200. My multimeter shows 0 ac with it. Think it will take oscilloscope to observe the ripple.
B) Phase splitter. it converts single end signal to balanced one. Works like a charm, super symmetry, got a good deal from Ebay.
3) Amplify circuit. it's like the original website showed, a 12AU7 first amplify the signal and pass to ECC99. There is a MK 1 version which only use ECC99 and is easier to build. I think when one is committed to build a amp, it's fairly common to stretch a little more, so I built MK2 as it only add few more parts into the circuit.
4) Constant current source. Well, I never fully figure out how tube amp work, I'll took the WTF Amp's design as granted. It's LM317, it's cheap.
5) Output impedance switcher. This one take me a while to think about. Some output transformers have multiple secondaries, so they can provide different turn ratio. Lundahl's LL2765 is used in this build, and turn ratio are: 12:1 and 6:1 which is suggested by Lundahl to match headphone with 32ohm and 150 ohm impedence. I was pretty naive to think about providing at least 3 kinds of out turn ratio for 32/150/300 ohm headphones. But after read the spec, it's lot of position to switch and the rotary switch will be very expensive. Considered the budget and part's availability, just two will do me good. Even just two turn ratios, it's a lot of wiring, it's nightmare.

At last, the final built looks good to me. Some pictures:



Have not spend sometime with it. But the initial impression is quite matched @gbeast 's impression. The bass is stronger than ZDS (OTL) and WA6 (SET) , the clarity and separation are weaker. It's not like solid state amp such as THX789 which is very analytical but it has a bit of warmth which is very desirable. It's that kind of amp you can put your headphone on for hours. So far, it has been fantastic with this amp. There are still some issues to resolve (ex: little noise on right channel), but should be ok soon!

 

You have made @sodacose proud. Congrats.. dB

 

That WTF looks nice. You're right that P-P headphone amps are quite rare. Here's another option

http://diyaudioprojects.com/Tubes/6DJ8-Tube-Headphone-Amp/

 

Great build with nice transformers!

If you feel like tweaking, add a negative voltage rail to the bottom of the CCSs in place of ground (-12v or so). The extra headroom helps the lm317 out a bit. But if you like what you hear, don't stress!

 

Found the reason of noise on right channel. It's turns out to be bad soldering of a resistor. Re-soldered that, now it's very quiet.