Smash Microphonics

[Brent]

Just wanted to report that I've had good results with the vinyl coated flask rings Doc identified above. I got a pair of them from Amazon for about 40 USD shipped. The Smash sits on 0.5 inch ID, 1.5 inch OD, 0.5 inch, thick 30 duro washers, also from Amazon, sandwiched between similar sized steel washers of normal thickness.  I also have a few random heavy things sitting on the top plate, but I'm not sure that this is doing anything. Also also, the top plate is screwed to the base, and everything is on a rigid, wall-mounted shelf.

With this isolation and damping setup, ringing is a non issue with music playing and is much reduced in level and duration when handling controls or otherwise touching the Smash itself. Before, I would occasionally hear ringing after big orchestra hits & other loud-silent sequences.

The Smash connects to Paramounts with 300Bs driving 90dB Fostex FE103-SOL speakers with a Fix in between, so results might vary with more sensitive downstream components.

[dpwoos]

Our Smash is microphonic to the point of being unusable. Honestly, disappointed that Bottlehead would offer a kit like this. How much of the preamp is useful in some other design that uses different tubes?

[Paul Birkeland]

Our Smash is microphonic to the point of being unusable. Honestly, disappointed that Bottlehead would offer a kit like this. How much of the preamp is useful in some other design that uses different tubes?

What amplifier and speakers are you using?  Too much gain after the Smash can make the microphonics unbearable, but this issue can be addressed as well. 

[dpwoos]

The amp is a Bottlehead Seductor, and the speakers are ADS L420. Our house is on a street with a lot of traffic, and the (simply awful) microphonics seems to be related to that. BTW, my son and I have built a bunch of amps and preamps - both kits and from scratch - and never experienced anything like this!

https://www.hifiengine.com/manual_library/ads/l420.shtml

[oguinn]

I also have a Smash. I get some light ringing with heavy footfalls but nothing noticeable when music is playing. I have it sitting on a marble tile and some rubber padding. I think it’s a pretty incredible preamp.

[Doc B.]

You didn't mention whether you have tried the isolation techniques mentioned in this thread. If not, you might try isolating the preamp from the vibrations from the passing traffic. Something as simple as a few layers of bubble wrap between preamp base and the item it sits on can be tried to see if this kind of isolation will help. If it does you can switch it up to some sorbothane pucks or similar isolation devices.

[dpwoos]

We have tried to isolate the preamp case (on a wall-mounted shelf inside what had been a closet), but without much benefit. We have also wrapped the tubes with teflon tape, which maybe helps a bit. What seems to stop the microphonics is to push down hard on the top of the tube with a finger, and we have been thinking about how best to accomplish that. Maybe we need to look harder at the tube sockets, and use rubber washers to separate them from the top plate? Also, we haven't secured the top plate to the base so that is something we can try.

Bottom line - we will work on this more over the next few weeks. We have been hugely distracted and captivated by our first moving coil cartridge (DL-103 + Cinemag CMQEE-3440A transformers) and it is hard not to play another record, and another ...

[Doc B.]

Your ideas are definitely on the right track. In my experience the most effective approaches have been isolating the wood base from the shelf and putting mass on the tube (like when you press on the tube). Silicone o-rings under the tube can help too, but they are usually not as effective. Mass on the chassis can create a small improvement, but not as effective as mass right on the tube. You might try something like bendable lead fishing weight wire coiled to sit on top of the tube. Maybe like this -

https://www.walmart.com/ip/Bullet-Weights-Solid-Core-Lead-Wire-1-lb/16928066?wmlspartner=wlpa&selectedSellerId=0&wl13=2317&adid=22222222227000000000&wl0=&wl1=g&wl2=c&wl3=42423897272&wl4=pla-51320962143&wl5=9033458&wl6=&wl7=&wl8=&wl9=pla&wl10=8175035&wl11=local&wl12=16928066&veh=sem&gclid=Cj0KCQiAjfvwBRCkARIsAIqSWlMbAZKigLU2whcUaOHOPdPRUCEIIqj6I-7nMwO4YAaPEJyqk8H6zOYaAq6FEALw_wcB