Ever try 5 SPAX7-A tubes in a Mark IV at once?

[MarkIVwidebody]

What happened?

 

[Restless Rocks]

Ten minutes later I removed them.

 

[tetsubin]

It totally exploded.

 

[Fxrs]

My DC-5 had 6 from the factory.

 

[stokes]

An SPAX7 is just a 12AX7 that is supposedly selected to be low noise.FYI,I just finished checking about 50 NOS tubes for noise since my new tube tester has a noise test feature,and havent found a noisy one yet,maybe I'll get one in the next batch.I dont understand the practice of charging extra for a "low noise" tube,does this mean if you choose to save a couple of bucks they are going to sell you a noisy tube?Just my opinion,but to me its just tube dealer voodoo to get you to spend a few more bucks.

 

[MarkIVwidebody]

I only ordered one so it's no biggie. Gonna put it in V-3. Also DO NOT buy Ruby 6L6 GMSTR or whatever they are. They sap the gain and make a Mark IV not a Mark IV anymore. Huge difference in tone. The Sovteks are good but the ones Mesa is selling are still best to me.

 

[stokes]

The idea of using an SPAX7 is that it is supposed to be quieter,and if so would be most beneficial in V1 which is the first stage of gain,even the slightest noise here gets amplified thru each following stage.I am guesing the Ruby 6L6 you tried isnt in the correct bias range for your amp,if I am not mistaken Ruby is a Chinese tube and is likely the same as the Chinese STR-440 Mesa sells.

 

[Restless Rocks]

For you guys who play with extreme gain settings at high output volume, especially using the mid gain switch the spax7 may help you with the microphonic screetch associated with those settings. I have a few of the original Sp's from the early 80's and (IMO) sound a lot better than the current Sp's available. When using them in all positions at once I found the tone a bit "grainy" and a little loss of gain. I like an Sp in V1 with a combination of NOS in other positions but I use more traditional gain settings and rarely set the output above 2.5. I'm not a tube dealer so I have no problem saying that I really like the current production chinese 12ax7 mesa's and have been using the STR 440's with very good results. Of course the russian tubes don't fair very well in tweed power settings or in the cathode follower positions of the dual rec and RK series amps. However the Sovtec LPS X7 sounds fantastic in the PI position in my mark amps. But my cup of tea may not be yours 8)

 

[MarkIVwidebody]

The idea of using an SPAX7 is that it is supposed to be quieter,and if so would be most beneficial in V1 which is the first stage of gain,even the slightest noise here gets amplified thru each following stage.I am guesing the Ruby 6L6 you tried isnt in the correct bias range for your amp,if I am not mistaken Ruby is a Chinese tube and is likely the same as the Chinese STR-440 Mesa sells.

No. wrong. they are the ones recommended for use in Mesas but they are not as tight or ballsy. They're not bad, just not as good as the Mesas or Sovtek and you can tell a difference.

 

[stokes]

"No. wrong. they are the ones recommended for use in Mesas but they are not as tight or ballsy. They're not bad, just not as good as the Mesas or Sovtek and you can tell a difference.[/quote]"
Recommended by who?If they were selected for the correct bias range,who selected them.When you buy tubes "selected" by suppliers other than Mesa you can get tubes that vary quite a bit from what Mesa considers "correct".If the Ruby's are indeed Chinese manufacture,thats the part I'm not 100% on, they are the same factory Mesa gets their Chinese crap from.Compare the bias point on both tubes and I am willing to bet the ones you say arent as tight or ballsy are drawing less current.