[analog97]

I thought it better to start a new thread on this because the earlier posts were buried.  Briefly, I had experienced repeated tube squeel thru the multiple (about an even dozen!) of 12 au7's I had inserted in my Clarinet.  Based on the recommendations here, I followed TubesForever's advice and bought a few JJ Tesla's.  I have logged at least 50 hours with a JJ in the second position (nearest the rectifier) and VOILA!!!!  No squeel!!   

Now the bad news.  The first JJ I inserted caused the WORST explosive-type noise I ever experienced, forcing a quick amplifier shut-down.   The second and third JJ's were fine, so I must have just gotten a bad tube.  I chalk this up to my bad luck with tubes.

What I find most curious is that, shortly after my "success", my amp broke down!!  When it did, and when powered off, some "squeel" was still being sent to the speakers.  This really screwed my head around.  I substituted my back-up amp, an old 100W Parasound and all has been fine since.  No, I have not put back in to the Clarinet any of the tubes that squeeled just to see if I could reproduce that squeel (what the heck kinda scientist am I?)

Anyway, thanks to Tubes and others who made 12au7 suggestions.  I think I am golden now!  I simply can not believe how good the Clarinet/Cornet2 combo is.  My noise floor is in the basement.  This stuff designed by Herr Hagerman is really too good to be believed.  Many thanks to the engineer and all those who helped.  Happy listening!

[analog97]

I must report that I appear to have made an error.   I re-inserted what I previously reported as faulty 12 au7's and have not been able to reproduce the "squeel".  It seems that the amplifier most likely was the cause.  I have no idea what problem in an amp could cause such a sound, but it just goes to show how problems reported to occur in one component are not always caused by that particular component.  Any thoughts appreciated on what tips I can pass along to a repairman are appreciated.   

[schwarcw]

Larry, this is great news!  First, the tubes you thought were bad you can now roll back in and taste them again.  Second, how many times do you get a legitimate reason to buy a new amp??   Let me suggest a pair of Parasound Halo A21's, or one big Krell KSA-250?  The Krell will be great just in time for Winter aa

Carl

[tubesforever]

Great news about the squeel and sorry to hear about the broken amp....

I hope that Jim Hagerman will review my information and correct anything I state that's incorrect.  The Clarinet is phase inverted.  However its not a pure 180 out of phase where you can just flip flop the speaker connections at the amp.

He called it a slight J on one post. 

He also stated that the Clarinet would also be affected by the transfer function of the amplifier, so if you take the Clarinet's slight J and add it to a slight or hard J transfer funtion at the amp you might hear some phase interactions.  With my Bedini 150MKII solid state amp I had to put my speakers back to a pure 8 ohms to cure the phase irregularities I was hearing.

In my line of thinking the squeel is a different issue.  Basically if the tube is not working like new it will bleed high frequencies because of the circuit Jim employs. 

Interestingly, in my situation,  I will put in a 12au7 and it will sound awesome for 2-3 hours and then start squeeling.   I am using Pearl tube coolers on my tubes now and have less squeeling.

Yes indeed, the C2 and Clarinet aound amazing together.  Just pick the passive parts that work best in your system and you are in for a big treat.

The JJ 12au7 tubes are actually a very decent sounding tube.  Thanks for the kind words.  I hope to build an octal version of this circuit if Jim can find his notes and forward them on to me. 

Cheers!

[hagtech]

He called it a slight J on one post

Linearity and phase are two different things.  Yes, the CLARINET inverts phase.  It also has a tiny amount of 2nd order distortion (amplitude linearity) which is the "J" curve shape of the transfer function.  Phase remains at roughly -180 degrees, independent of linearity.  There will be, of course, an additional phase lag due to the high frequency rolloff (-3dB is at ~100kHz).

jh