Tube Dampers

DaveC said:

This is a valid topic and not just snake oil. The reason why is all tubes are microphonic to some degree, so the sound produced by the speaker will vibrate the tubes and the mechanical energy in the sound waves will be converted to electrical energy and sent back to the speaker, forming a feedback loop. You can hear this by gently tapping on a tube. Some may do very little, some may be very audible, it varies by type, use and even sample to sample variance.

The question is whether this is good or bad. If it's bad, then you'd want to isolate the tubes from the speakers. If good, then you can either leave them to their feedback or modify the feedback in hopes of improving or fine-tuning the effect.

Imo feedback via tube microphony can be either good or bad depending on whether the feedback is more or less psychoacoustically correct. If the feedback makes the sound match what your brain expects to hear, it's good. If not, it's bad.

In any case, ideally you're looking at damping tubes... either to eliminate microphony as much as possible, or you're tuning it to achieve the most psychoacoustically correct sound. Or maybe moving the amp out of the listening room. Or deciding it doesn't matter enough to bother with.

What do tube dampers do? Besides damping they are non-linear filters or equalizers. Just from a WAG, Silicone rings are likely to damp high frequencies far more than low frequencies. It's pretty likely from previous experience they will sound worse than no damper because of this non-linear damping behavior. It depends on the tube in question, the system, and personal preference though, so YMMV. Just like footers, YMMV and it's really hard to tell both what the feedback frequency response curve looks like without dampers at all, nevermind what tube dampers are actually doing. It probably varies a lot depending on how the tube is supported too, ceramic vs teflon sockets, PCB vs PtP, etc. So unfortunately like a lot of things we're left with trial and error. The only thing I can offer is that soft materials generally deaden the sound and don't sound subjectively good, this is pretty universal with damping any part of the system with the exception of the speaker/floor interface.

I damp some tubes, but haven't found a solution that I think is a large improvement vs leaving them undamped. I also have not bothered to try a ton of different solutions. The rectifier is often a small improvement, followed by the 6SL7s that are doing all the voltage amplification, but those are ruggedized military versions with a metal base that may be more immune to vibration than other 6SL7s... who knows, lol. Happy New Year.

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treitz3 said:

Gentlemen, our goal is to have a friendly place where everyone shares ideas and information without the level of bickering and angst that other forums tend to create. Let's try to be a little bit more friendly with each other or utilize the ignore feature.

Some unnecessary posts have been cleaned up from this thread.

Tom

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