I recently bought a bunch of preamp tubes and have been rolling them into various bass and guitar amps. My goal is for my amps to be capable of producing clear/tight lows, articulate mids, soft/smooth high mids, and slightly glassy highs with relatively neutral EQ settings. Rolled 7 new preamp tubes into Trace Elliot V8 Previous tubes (Sovtek 12AX7WA) were all functioning fine but the sound was far from optimal. Additionally, some of the stages seemed to lack drive so it was not possible to push the output tubes to full power without distortion. Speakers are Electro Voice TL405 cabinets that are ported around 27 hz. Bass is Series 1 Yamaha TRB6P. I rolled the tubes in the following order V6, 7, 4, 3, 5, 1, 2. Only one or two tube types were tried in V3-7. Each tube was replaced one at a time with an improvement in clarity and articulation noted. Several tubes were rolled in V1-2. Here’s my final selection and notes on some of the tubes I rolled. The following is IMHO based upon my experience with my amp and the tubes in hand. YMMV. V1 Mullard 12AX7/ECC83 (Russia) This tube is very smooth sounding and emphasizes clear tone and thick, deep bass. Seems to extend the highs and lows, boost the bass and mid bass, and has a dip in the high mids reducing clank and fret noise without gutting the sound. The low end produced with this tube was drastically punchier and tighter than everything else I have tried. The highs tend to be smooth and a bit glassy. Second choice: The Genalex 12AX7/B759 (Russia) has more mid-range content and less lows than the Mullard. This tube provides a lot of clarity and articulation without being overly bright or harsh. Third choice: The Sovtek 12AX7LPS is similar in tonal balance to the Mullard with thick, deep bass, but it is a bit wooly/loose on the bottom and seems to scoop out a bit more of the high mids. With the starting EQ, the Genalex would likely cut through a mix better, but I was totally blown away with the clear fundamental of the Mullard and increased tightness in the bass region. Boosting the mids gets the Mullard pretty close to the Genalex as far as cutting through. Regarding deep bass, boosting the lows gets the Genalex more in the ballpark of the Sovtek than the Mullard. V2 Genalex ECC83 (Sino) The V8’s distortion channel (V2) tends to emphasize highs and rolls of the bass. The Genalex transitions smoothly from clean to distortion and has the most even tone/distortion of all tubes auditioned for this position. The timbre with the Genalex in the circuit was most similar to the bypassed (clean) tone and remained relatively tight with lots of fundamental all the way down to open B. This tube produced the least fizzy/buzzy distortion of tubes auditioned. Second choice: The generic Sino 12AX7B was by far the highest gain of the tubes auditioned in this position. Distortion comes on almost as smoothly as the Genalex but the tone is a bit thinner and the low end washes out earlier. The distortion is a bit brighter. Third choice: The Tung Sol 12AX7 distortion and timbre were very similar to the Sino 12AX7B, but it had about the same amount of gain as other tubes I tried. The Tung Sol’s transition from clean to distortion is a bit less linear than the Sino. Fourth choice: The Electro Harmonix 12AX7 had the leanest/brightest timbre and produced the most uneven fizzy/buzzy distortion. The EH also had the least linear transition from clean to distortion and the break over into distortion varies with frequency. Low notes require a stronger signal to distort than higher notes. All of these tubes can excel with different timbres of high-gain distortion. The Genalex stands out with the best touch sensitivity at low gain settings, and with clearer tone and lows that hold together longer with higher gain settings. V3, 4, 6, 7 JJ ECC803S These stages involve cathode followers or phase inversion. These types of circuits elevate the voltage of the tube’s cathodes which can cause problems if the tube’s heater to cathode voltage limits are exceeded. V3b in the Trace Elliot V8, in particular, has over 200V on its cathode. There is concern that many of the latest Reflektor-built, New Sensor 12AX7 varieties may fail relatively quickly in circuits where there is a significant difference in potential between the tube’s cathode and heater elements. From my understanding, the cathode to heater limit in these tubes is on the order of 100V. The older Sovtek 12AX7 -WA, -WB, and -WC are examples of New Sensor tubes that are reliable in these positions, but they are not generally noted for superior sound. Current production JJ’s and Chinese tubes as well as vintage NOS tubes are also generally considered to be safe in these positions. The JJ ECC803S is a strong tube that typically works well and sounds great in such circuits. It has a tight, articulate, muscular sound and a relatively warm and even response with a bit of mid-range shimmer. V5 Tung Sol AX7 (Russia) This stage provides a bit of amplification and also has a clamper circuit to protect the output from overload. It does not have high cathode voltage, so I didn’t want to use my last ECC803S. I chose the Tung Sol 12AX7 which is also known for a tight even response, although a bit brighter than the ECC803S.