Tube Rolling Help for Wheatfield Audio HA-1, thinking Mullard

The Mullards tend to be a warmer tube and from your description that is what you are trying to avoid. Secondly, are they worth the money? Not to me .... I suggest you try a 5814/A from Raytheon or Hytron .... the black plate 2 mica D getter tubes are very good. The RCA 12AU7/5814A is also very good but this tube is a richer, fuller sounding tube. If your amp can handle the additional heater current, check to make sure, a 12BH7 would drop right in. The Sylvania or GE 12BH7 would brighten up the sound .... and 12BH7s are just better sounding tubes vs 12AU7s, IMO.

Having used 7044s the GE 7044 is quite dark like you describe (Penta didnt make tubes so the 7044 could be a GE) unless the tube is balanced with something more neutral .... tube, interconnect, headphone etc... The Sylvania 7044 vs the GE 7044 is a tube with a brighter treble that sounds harsh and unrefined but with the same muddy low end. I cant stand the Sylvania 7044 n my SP amps.

Fortunately, you can use the much less microphonic and wonderful sounding 5687 as a drop in replacement for the 7044. I recommend the Sylvania 5687 if you want to get a cleaner more transparent sound. The Amperex 7119 is another tube you can sub and this one is a very fast, clean and clear sounding tube. The TS D getter 5687 is a great tube but I dont know if the TS is what you would like from your description; the Sylvania sounds more like what you are looking for. The TS has a nice rich sound with good speed and lots of dynamic punch.

Once you get a good 5687 or 7119 in the amp your 12AU7s may sound much better to you. Still, the 12BH7> 5687 combination is one of my very favorite if you can use the 12BH7 ... and a good nos 12AU7/5814A in most cases will easily trump the 12AU7s you have been using.

Try some 5687/ 7119s first and then see what type of sound you are getting. Once you know then describe the sound you are getting and ask for some 12AU7 recommendations.

I've done a lot of tube rolling in my Wheatfield HA-1. Of course I'm using AKG k501 phones, so I'm less likely to want to tighten the bass. I have a Mullard 12AU7 and it is a worthy combination. I bought one since the amp requires only one, not two of these. I've also picked up some RCA cleartops, which it more the direction I'd point you in. Since you're in Chicago, you may want to drop in a Triode Electronics and rummage through their loose 12AU7s. I've never even considered changing power tubes, which I might do for fun. I met creator Pete Millett at last year's CANJAM when it came through town. He's quite a nice fellow and has a lot of affection for this design.