How important is the Phase Inverter

[Spotted Dog]

Admittedly, I am a dummy when it comes to valves.
I found this link http://www.guitaramplifierblueprinting. ... verter.pdf on the Dr. Z-Forum, and thought some of you might have an interest or a comment.

Here is the full discussion:
(http://ztalk.proboards.com/index.cgi?bo ... read=39881)

[slowpokerhino]

Very interesting.
Currently my Super Reverb is back to stock tube configuration (thought I was going to have to sell it, but it has been saved in the eleventh hour), but I like it best with the 12AX7 pulled from V1 (disables the normal channel and adds a bit of gain to the vibrato channel) and the 12AT7 replaced with a 12AX7 in the phase inverter position. I also like KT66s in place of the 6L6s (Gold Lions fit, albeit snuggly, into the bear trap holders BTW).
With these simple substitutions and the amp cranked (6-8) it sounds amazing. Beatiful breakup and very touch sensitive.

[Spotted Dog]

Very interesting.
Currently my Super Reverb is back to stock tube configuration (thought I was going to have to sell it, but it has been saved in the eleventh hour), but I like it best with the 12AX7 pulled from V1 (disables the normal channel and adds a bit of gain to the vibrato channel) and the 12AT7 replaced with a 12AX7 in the phase inverter position. I also like KT66s in place of the 6L6s (Gold Lions fit, albeit snuggly, into the bear trap holders BTW).
With these simple substitutions and the amp cranked (6-8) it sounds amazing. Beatiful breakup and very touch sensitive.

I'm with you on that, I'm set up the same with mine, except for the Gold Lions where I have JJ' 66s in there. I changed the tubes, changed the speakers, and upped the bias, so I'm not sure how much the PI tube altered the tone. (Still need to change out the JJ reverb tube, there's no range -- its either off or INTENSE.)

Makes me wonder about the VM's PI.

Then again, if it ain't broke don't fix it.

[slowpokerhino]

Did you have to modify it at all to get the JJ KT66s to fit? I love the Gold Lions but man they're expensive.

Let me know what you come up with for the reverb. I have the same issue. I've tried a couple different tubes in there (don't remember what tubes now) but it didn't really help so I went back to stock.

[Spotted Dog]

Did you have to modify it at all to get the JJ KT66s to fit?

They fit fine with different retainers, you know those kind with the springs that run up the sides of the tubes and connect to a ring? Don't remember what there called.

Let me know what you come up with for the reverb. I have the same issue.

Ya, been to lazy to change out and experiment, but I'll let ya know if I find anything.

[inca_roads]

Regarding the Fenders, maybe try a 12AU7 or AY7 in the reverb driver (V3) slot for more range (less springiness), or a quality NOS AT7, like a Mullard (these can be found for $25!).

I like older Mullard AT7s in the Fender PI position (not the 1980's CV4024, which is somewhat linear by comparison). The older ones seem to add some midrange grunt if that's your thing. A 5751 is nice here too. Don't overlook V4 either; this tube can greatly affect tone.

You'll hear debate about whether the PI tube should be balanced or not; my advice is to use your ears as a guide. If you can get a tube that is known to be balanced, use it a a basis for comparison to other tubes.

Regarding the VM, I find that a balanced PI does seem to add clarity. If I use new production tubes (JJs), I change the PI with each power tube change. NOS will last longer.

These links here may be helpful.... good luck!
http://www.kcanostubes.com/resources

[Onza_Jk]

Wow i always overlooked the Phase inverter. It was an interesting read. Thanks

[Spotted Dog]

Tube swaps, for experimentation, is an area I have not explored too much. I'll get some gas every once in a while to go down that road, only to give up when I try to digest the info, opinions and hype. Then I cross reference what seems like a good idea, check pricing and availability and say "WTF, well maybe tomorrow."

Anyway, IR I appreciate you sharing the info and thanks for that link, it was helpful.