What do defective phono tubes sound like?

The one easy thing about trouble-shooting tube gear, is the ease to swap out tubes as a first check for a problem. What you describe is very much what I recently observed with a phono stage (ARC MCP-33) power supply tube. There were loud pops and other times it was an oscillating upper-bass tone. When it happens it can really make you race out of your chair! A quick tube swap and it was gone. A day or so later I put the suspicious tube in and the problem was back which confirmed this was indeed the problem and in the trash that tube went.

Another thing to consider here: since this is a new tonearm, there may now be an intermittent connection. Is the cable attached or the same you used before? Removing these can result in weakening the connection, especially at the din. If the level is high and the connection is intermittent this could cause any link in the chain to cause a "spike" but generally more of a hum.

John

I can tell you for a fact that just becuase they are NOS tubes ,does not always make them NOS..Ocassionally you can receive a tube that tests well at the supplier,but for some reason the tube does not survive the ageing process and you will get Spitting or Sharp distortion noises etc..I recently had to send back a nice pair of NOS Tungsram 12ax7 due to this same situation..I am not in anyway saying this is your problem..Only saying its possible it is..Trying flip,flopping tubes and see if you noise travels with positioning...Also sounds like it may be a Static Electricity problem ..Good Luck

yes to the above posts, but also, get the tubes out and clean the sockets and tube pins. I had an Audio Research unit whose sockets and tube pins had to be cleaned, and the spitting noise was no more.