[shinewu]

I have the Littledot LD-Y2 300B headphone amp. And the pre-amp tubes are 6SH7, normally with metal shells. They are not expensive, about $5-$10 for a single and $10-$20 for a matched pair. Recently, I have dropped the metal shell tubes a few times to my desk while handling them. Though I can't hear any difference in audio quality, I am curious in general how robust these metal shell tubes are. I have seen folks storing a whole bin of metal shell tubes loosely, so seems like they are pretty sturdy in terms normal shock and collision.

Also if I shake the metal shell, I can hear some metal wires loose in the shell. But they seem to work fine. Hopefully they will last.

Lastly, even though I purchased these pentode driven amps, I highly recommend folks stay away from them. The main challenge is that there are no current productions of these tubes. And based on my experience, about 50% of them are noisy/humming for headphone amp usage. I have been searching far and wide for good quality 6SH7 tubes. I think the later productions (196x to 197x) seem to be better for hifi. But if I can choose now, I will go with 6SL7 and 6SN7 driven ones.

 

[lumdicks]

I have the Littledot LD-Y2 300B headphone amp. And the pre-amp tubes are 6SH7, normally with metal shells. They are not expensive, about $5-$10 for a single and $10-$20 for a matched pair. Recently, I have dropped the metal shell tubes a few times to my desk while handling them. Though I can't hear any difference in audio quality, I am curious in general how robust these metal shell tubes are. I have seen folks storing a whole bin of metal shell tubes loosely, so seems like they are pretty sturdy in terms normal shock and collision.

Also if I shake the metal shell, I can hear some metal wires loose in the shell. But they seem to work fine. Hopefully they will last.

Lastly, even though I purchased these pentode driven amps, I highly recommend folks stay away from them. The main challenge is that there are no current productions of these tubes. And based on my experience, about 50% of them are noisy/humming for headphone amp usage. I have been searching far and wide for good quality 6SH7 tubes. I think the later productions (196x to 197x) seem to be better for hifi. But if I can choose now, I will go with 6SL7 and 6SN7 driven ones.

You can try finding a pair of Western Electric 717a as replacement. I found it sounded very well when I still owned my LD-Y2 and it is not expensive and not difficult to get.