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marvar

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Everything posted by marvar

  1. Myles-A question that I have been wondering about. If the PI isn't part of the tone generating stage of an amp, then it would seem that any specified tube would sound just like any other tube, (balanced of course!) but changing the PI from, say, a 12ax7C to a 12AX7M or, short plate to long plate, the tone seems to change- is this an aural illusion, or does the PI indeed have an effect on overall tone? or is about how a certain tube passes current? or, am I way off base here?
  2. Myles- Haven't heard alot about the GT EL34M, whats the scoop? are they in production, how has the response been to them? Generally, how do they sound, say compared to the GT EL34Ls? Thanks-
  3. Myles: I just replaced my EL34Ls tubes in my JCM600- the B+ voltage is 491, as I understand these tubes are 30 watt, and I should set them for around 55% (33.8ma?)- they are the GT matched set, but one pulls more than the other, at idle, I realize that it's due to being dynamically matched vs statically- Do I try to set the bias with the one that pulls more current, or the lower value one? or do I do a comprimise and set them in the middle of the two? currently they read 34.8 ma and 29.9ma. Wish I had access to a 'scope.
  4. Hi Myles! I have bugged you in the past, and you have been very helpful - Thank you! My amp is a Marshall JCM600 & 4x12 w/H30's and Greenbacks. Currently my on hand tube stock is: GT 12ax7M (2) GT 12ax7C GT 12ax7R GT 12ax7R2 Jan Philips 12ax7wa (2) GT Ecc83 GT 12ax7MPI GT EL34LS #7 power tubes I'm currently using a Philips JAN 12ax7 in V1,and I'm pretty happy with that. V2 is for the overdrive channel, I'm using a 12ax7M in that position. V3 is a toss-up, and V4- the PI I'm using is the R2-just a regular one-not matched. one of my questions is why does the R2 sound better, at least to my ears in V4 than the MPI? and yes, the bias is set right. Second question- do the 12ax7M have more compression than most of the other 12ax7's? again to my ear it sounds that way- that's why I'm using it in V2 to help smooth some of the clipping in the OD channel- and, third- without going into alot of detail-what exactly does V3 do?(cathode follower/tone stack) and out of what is listed above - which would you recommend for V3- or feel free to give your own personal recommendations (if you have any experience with the JCM600) as to which tubes you would use in any of the positions. I play mostly 70's and 80's rock w/ a Les Paul w/Alnico5 pups. Thanks again!
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