Don said:
The difference between rectifiers is not tonal. It's in the amp's feel and attack.
A 5U4 should feel more spongy and have a softer attack than a GZ34.
This is not entirely true, from my experience. Though I do appreciate you bringing up an important point: the attack/feel is where you would notice the most impact.
Lower frequencies take more energy to produce than higher frequencies. The
sag I've noticed when testing out rectifier tubes effects lower frequencies more, with a delay to powering those power-hungry tones. This results in what I'd say is a definite tonal impact. Note that phase-cancellation relationships will occur anytime you alter the power parameters over time.
For example, I vastly prefer my Ken-Rad 5U4G to RCA 5U4G, because the Ken-Rad provides a more powerful low-end punch, and has greater clarity to the highs. In comparison, the RCA is more compressed, and has reduced high-frequency information (more rolled-off). This effect is even more pronounced when comparing RCA 5V4G to Ken-Rad 5V4G.
For 5U4GB, I much prefer NOS Tung-Sol to, say, Sylvania. This is for much the same reasons as the Ken-Rad/RCA referenced above. One may choose the opposite of me, for the same reasons (but with different taste).
And if you don't hear it, or feel it, no sweat! I still highly recommend NOS rectifiers for their durability. You'd definitely notice if it stopped working :wink:
- Thom
