Crack/Speedball sounds better on metal stand?

[xmas_one]

Hello,

I recently bought an assembled Crack with the Speedball mod and have been listening to a bunch of records on it. I got an IKEA Kallax 2x2 bookshelf (fiber/particle board) as an upgrade to the metal 1960s TV stand I had originally had my setup on. I immediately noticed that my setup on the Kallax sounded flat and “unmusical”. Once I swapped back out to the metal TV stand, the dynamic, musical sound was back. Any ideas?

Rega P3, Nagaoka MP200, Ifi Audio Zen phono, and HD600

[Paul Birkeland]

Well, you won't find much resistance here to hating on particle board, that's for sure!

Maybe take a cake pan and put it on the Kallax to see if that makes any difference?

[Mucker]

Some of the 6AS7G / TS5998 tubes I use in the Crack cause a very high rate of vibration which translates to hum in my headphones. If I push the plate down hard on the wood base, the hum is killed off, but we're talking extreme pressure. I've been looking for a way to clamp the plate to the base without destroying the look of the unit. Tube dampeners did not work. I would like to keep the gravity mount for easy removal and would like to avoid drilling the plate and screwing it down but that could be the only option to kill the resonance.

I have also read of negative effects of tube dampening and killing off dynamics.

I believe what you are experiencing is entirely possible. If something is working I say stick with your own recipe. Whether it's doing the sub crawl to place a sub-woofer, moving transformers and cables around to eliminate noise and ground loops, etc., etc.. Go with what works for you, it's going to be system dependent.

[Paul Birkeland]

I've been looking for a way to clamp the plate to the base without destroying the look of the unit.

Shoot me an e-mail at pb(at)bottlehead(dot)com and I can share a strategy that isn't too difficult.

[Deluk]

Bed the plate to the base with some Blu Tak.

[Doc B.]

I don't think clamping the plate to the base will do much. What is happening in these cases is the amp is peforming better dumping vibrational energy into a mass. In the first case the mass of the metal stand draws the energy off better than the light and hollow Ikea stuff, in the second case the mass of your hand pushing on the chassis absorbs the energy.

Try putting some weights on the tubes and/or the chassis. And/or try putting something massive under the amp like a granite tile.

[Mucker]

Thanks PB, Doc, and Deluk. I appreciate the suggestions. For me, it only happens with certain tubes. With the right set of tubes, the amp is quiet.

My S3X amp also has a slight noticeable hum when I placed on my wood kitchen table. When I lift it off the table, the hum disappears. I like the idea of a heavy piece of granite to absorb the vibration. Thank you!

Greg

[xmas_one]

Thank for all the replies!

I think Mucker may be on to something with overdamping possibly causing detriment to the dynamics, as the amp sounds better on the more resonant stand (the metal TV stand).  I’m also thinking that the metal shelf under the amp might be having an inductive effect on the choke mod, the way the amp was built the choke is very close to the bottom of the amp and consequently the metal shelf. I’ll mess around with it tonight if I have time and see if I can eliminate some variables.