Members Crunchtime Posted September 30, 2012 Members Share Posted September 30, 2012 I've had a lot of amps with and without the aluminum preamp tube shields. What is the general consensus on these? My Rivera has the shields and inside the top interior of the shields is a wool looking material that helps the spring hold the tube firmly. I'm wondering if I should be concerned about heat buildup in the shield. Are 12ax7's susceptible to decreased life under such an environment? Link to comment Share on other sites More sharing options...
Members sled Posted September 30, 2012 Members Share Posted September 30, 2012 Preamp stages are generally High-gain Hi-impedance and are thus susceptible to stray electromagnetic fields. The shield is just added protection. Link to comment Share on other sites More sharing options...
Members syscrusher Posted September 30, 2012 Members Share Posted September 30, 2012 I've had a lot of amps with and without the aluminum preamp tube shields. What is the general consensus on these?My Rivera has the shields and inside the top interior of the shields is a wool looking material that helps the spring hold the tube firmly. I'm wondering if I should be concerned about heat buildup in the shield.Are 12ax7's susceptible to decreased life under such an environment? They don't get all that hot, so it shouldn't be much of a concern. There usually a hole at the top of the shield to keep it ventilated. Link to comment Share on other sites More sharing options...
Members Crunchtime Posted September 30, 2012 Author Members Share Posted September 30, 2012 They don't get all that hot, so it shouldn't be much of a concern. There usually a hole at the top of the shield to keep it ventilated. The wool looking material I mentioned covers the hole. Looking in the hole you see the wool not the tube. Link to comment Share on other sites More sharing options...
Members syscrusher Posted September 30, 2012 Members Share Posted September 30, 2012 The wool looking material I mentioned covers the hole. Looking in the hole you see the wool not the tube. It really shouldn't be a problem. I have no idea why they put that wool in there unless they were trying to cut out any chassis vibration getting into the tube as microphonics (sp?). Link to comment Share on other sites More sharing options...
Members hcprimerib Posted September 30, 2012 Members Share Posted September 30, 2012 I cover mine in wool during the winter months. it's the right thing to do Link to comment Share on other sites More sharing options...
Members diocide Posted September 30, 2012 Members Share Posted September 30, 2012 Hmmmm. I've never seen ones with wool in them, just the springs. Anyway, I can't imagine they make a big difference either way... Link to comment Share on other sites More sharing options...
Members chromatica17 Posted September 30, 2012 Members Share Posted September 30, 2012 Just take em off. I always take mine off. Makes no difference unless the tube is already bad/microphonic, in which case should be changed anyway. Link to comment Share on other sites More sharing options...
Members shane159 Posted September 30, 2012 Members Share Posted September 30, 2012 They help lower noise like shielding guitar cavity's. It is not noticeable on all amps ,but they are put there for a reason. Link to comment Share on other sites More sharing options...
Members mbarn3065 Posted September 30, 2012 Members Share Posted September 30, 2012 They're intended to block RF noise.. they also extend the life of the tube by keeping them protected from excessive vibrations caused by loud volume/low freq's.. and prevent that microphonic thing from happenin.. I leave mine on. Link to comment Share on other sites More sharing options...
Members Zozobra Posted September 30, 2012 Members Share Posted September 30, 2012 preamp tubes are run well under their max plate dissipation limits so they don't really get all that hot as they aren't delivering any power. In any case the max dissipation for a 12ax7 is 1W per triode anyway Link to comment Share on other sites More sharing options...
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