/products/roadtest/b/blog/posts/rohde-schwarz-mxo4-scope-meets-thermionic-valve-pre-ampMXO4 Road Test and an Audio Amplifier A recent thread on E14 discussed a simple valve pre-amplifier. /technologies/experts/f/forum/52476/i-have-a-small-audio-amplifier-project-i-am-working-on The thread starter, /members/rcayot , had some issues abouten-USTelligent Community 12https://community.element14.com/products/roadtest/b/blog/posts/rohde-schwarz-mxo4-scope-meets-thermionic-valve-pre-ampFri, 03 Mar 2023 14:52:57 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:fef98c90-f5b3-4e89-bdce-9d5a3fd69942dougw0<p>Interesting choice of test devices.</p><img src="https://community.element14.com/aggbug?PostID=25292&AppID=14&AppType=Weblog&ContentType=0" width="1" height="1">https://community.element14.com/products/roadtest/b/blog/posts/rohde-schwarz-mxo4-scope-meets-thermionic-valve-pre-ampFri, 03 Mar 2023 13:37:53 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:fef98c90-f5b3-4e89-bdce-9d5a3fd69942jc20480<p>That was a nice, entertaining test.</p> <p>I don&#39;t know very much valve stuff. It&#39;s new to me that you can even operate one on 56V (I can just about remember portable valve radios that had 90V valves in them). Presumably, this gets them under all the LV regulations.</p> <p>Does the fact that the heaters are sitting at different voltages make a difference? The cathodes shield them from the rest, but mightn&#39;t the different potentials still affect the supply of electrons to replenish the cathodes?</p><img src="https://community.element14.com/aggbug?PostID=25292&AppID=14&AppType=Weblog&ContentType=0" width="1" height="1">