Hi All,

Do not have the style or experience of writing a review, following is the best i can manage:

**All mods for headphones, DACs, Amps were done by Gurubhai**

Recently replaced my EHHA Rev A amp with a DIY tube amp. This tube amp has topolgy similar to Apex Teton. The amp is designed/assembled by the forum member Gurubhai.
I have tried it with lots of tube combinations and the amount of quality variation is really surprising. The sound can range from good to amazing depending upon the tubes.



Before i go ahead with the sound description of the new amp i'd like to mention what i think of other amps i've heard in the past so that a reference can be set:

1) Asus Xonar STX sound card - Bad sounding. Both DAC and amp sections were very rough

2) NWAVGUY O2 amp - Compressed dynamics, clean, blackground, coarse mids and treble. It's listenable with mid fi headphones but with resolving headphones it sounds dead.

3) Beta 22 - Almost like a mature O2 sound. Very similar issues as that of the O2. Unresolving treble, dry mids, flat dynamics. Bass is good. Background is clean and black. Listenable with LCD2 caliber headphones but lifeless sounding with better resolving headphones.

4) EHHA Rev A - I have owned 2 of them. The first one was based on a toroidal transformer and the second one had R Core transformer instead. Tubes used were Telefunken and mullard. Mullards were just bad. Thick, fart like bass. Telefunkens were really good though.
R Core version was much better than the toroidal. Bass had better authority, overall more dynamic and the background was much cleaner in the R Core version. The toroidal version had this sense of looseness throughout the range. The R core version was a good amp by all means. It did nothing bad although nothing extraordinary either. Still much better than a Beta 22 and was on par with my expectations of a good sound.

Now onto the new DIY tube amp, description as per tube combination used.
Gear - SPDIF header from desktop motherboard to BNC input of Assemblage DAC 2.0 and Adcom GDA 600 (both modded) + Yamaha HP1 aniso/YH100/HP1 sintered/LCD 2

1) OSRAM rectifier tube + TUNGSOL output tube - Easily the best sounding pair. Superbly dynamic and lots of texture. Extended solid bass. Least rounded tube bass that i've ever heard. This was one configuration that was really effortless, endless resolution, hint of brightness but supremely controlled even when the volume was maxed. I thought the qualities were limited only by the DAC used.
**The above tube config is really in a league of its own. The below descriptions are relative only to what all tubes are left**
2) Mullard rectifier tube + Kenrad output tube - Great bass texture, slightly dry mids yet very clear, not very extended treble. Overall a very enjoyable, neutral and resolving config.
3) Mullard rectifier tube + RCA output tube - Rich & Un-naturally smooth sounding overall. Silky treble but the bass is bit slow and loose. Not my cup of tea.
4) Mullard rectifier tube + TUNGSOL output tube - Very nice sounding ,better texture & treble extension than Kenrad. Although the TUNGSOL really shines in conjunction with OSRAM rectifier tube only.

I understand there can be lots of better amps out there, but for my threshold i can easily live with it. It's easily better than the EHHA i had earlier and is miles ahead than the likes of B22.
To sum up the differences, i am finding really easy to identify the track quality. Compressed and non dynamic sounds are much easier to spot.



Thoughts on some headphones that i've been listening or have listened to for extended time:

1) HE400 - Hated it with pleather pads. Sold it when heard it with velour pads. Extremely lo-fi sound for $400 i paid at that time. Razor sharp unresolving grainy highs, mid range was a joke, dynamics were barely available, the whole spectrum sounded so compressed, bass was tolerable but was soft and not much extension.
I could listen to it with O2 for few weeks but with EHHA the shortcomings were so much evident that i never wished to hear it again. Even my 100$ modded HP50A was in another league.

2) Denon D2000 - Mud, mud+mud,mud+mud+mud, ..................

3) ATH M50x - Better than D2k but too much lack of details and grainy sound make the listensing tiresome for the ears and brain.

4) LCD2 rev.1- Think of the Genie from Alladin cartoon series. Thick and thin at the same time. Voluminous and bit loose mid bass, thin and slightly grainy treble, usually absent upper mids. Good for easy listening but ultimately lacking lots of details.Sub bass is present and is clean but the mid bass dominates the sub bass just too much.

5) Yamaha YH100 (modded) - Very similar to LCD2 be it the bass explosiveness, thick nature of notes. The difference is that the treble doesnt sound thin and is more linear/extended. There is slight darkness in the mids,not as much as the LCD2 yet higher than my threshold.

6) HP1 Aniso (modded) - I have heard 2 pairs over the past few years. Both belong to Gurubhai. The first pair is my reference for the most effortless sound i've heard whether it be from speakers, headphones, alarm clocks... etc. and am yet to find any hairsplitting flaw with it let alone major ones.
Resolution, speed, dynamics , delicacy, imaging, linearity, clarity...you just name it.
The second HP1 pair is second only to the first pair in terms of technical caabilities. Most notable differences are that the second pair has less extension at both ends, is smoother at the expense of texture and the mids are less lively.

These HP1 are the only pairs that i found to be equally enjoyable with any kind of music -electronic, classical, acoustic or whatever there is available.

7) HD800 - Heard it only once for couple of hours with EHHA R Core version and Assemblage DAC 2.0 (Modded) and had compared directly to the second HP1 pair and LCD2. Grand soundstage, good deatil, upper treble is very extended and quite linear.
The HD800 is easily technically better than LCD2 in all regards except for sub bass clarity & extension.

Compared to the second HP1 pair the HD800 had fuzzy imaging, sub bass either absent or only present in traces,elevated upper bass, better upper treble extension, sometimes the female vocals appeared bit too recessed, sharp in the sibilance area, other than bass the overall details were comparable but the HP1 had little faster tranients. The HD800 is really something in the upper treble. While the bass, mids and most of the treble had this layer of grain , the upper treble is very clean. I plan to revisit the HD800 on my new amp as i still cannot figure the reason for grain despite good resolution. The new amp being more resolving than the EHHA should explain things better.

HP1 sintered (modded) - Some things such as mids resolution and tranient response is next only to the two HP1 aniso pairs. However, the treble is somewhat grainy, and similar to the HD800 grain layer there is a sense of unrefinement throughout the spectrum. Bass Dynamics are quite inferior to either of the aniso HP1 , maybe even the LCD2 and HD800.

9) Fischer Audio DBA2 MKII - Tiny looking, tiny sounding, clean background , loose bass, certain midrange section is sharp and grainy, smooth treble. Do not have much experience with IEMs, but no more than 50$ for these. 

Thank you all.