Presonus Bluetube v2 is a 2 channel, pro preamp with a mic and instrument inputs, 48v phantom power, and balanced and single-ended inputs and outputs. The curious part is the inclusion of a 12AX7 vacuum-tube stage with adjustable control allowing all that tube "warmth" to be mixed in variable proportions with the solid-state amplification. While I can run more measurements on this device using Apogee Element24 DAC/ADC and REW, I wanted to see primarily the effect of the Tube Drive on the harmonic content at the output. All connections between Element24 and Bluetube were balanced. Output with the Tube Drive turned off was at 3.6v. With Tube drive at maximum setting the output fell to 3.1v
1. Tube Drive turned off (all solid state). Not awful for a moderately priced preamp:
2. Tube drive turned on, minimum setting. Wow!
3. Tube drive at 10 o'clock:
4. Tube drive at 11 o'clock:
4. Tube drive at 12 o'clock:
5. Tube drive at maximum setting. That warmth should really be easy to feel by now
1. Tube Drive turned off (all solid state). Not awful for a moderately priced preamp:
2. Tube drive turned on, minimum setting. Wow!
3. Tube drive at 10 o'clock:
4. Tube drive at 11 o'clock:
4. Tube drive at 12 o'clock:
5. Tube drive at maximum setting. That warmth should really be easy to feel by now
Last edited: