12AT7 phase inverter in Marshall TSL? And another question.

[ken361]

Re: 12AT7 phase inverter in Marshall TSL? And another question.

would lower the gain and sound thin and like crap!

[dystrust]

Re: 12AT7 phase inverter in Marshall TSL? And another question.

I’d also suggest the Mullard in V1 however I don’t think putting it in he PI is a waste of a tube. I have one in my Quickrod’s PI slot and I love it there. Although, it is typically used in the V1 slot.
I can’t explain on a technical level what the PI does but I know it somehow splits the signal to the power section in a push/pull type amplifier, like the Marshall. I don’t feel as if it makes a huge difference to the tone of the amp, rather it affects the feel of it. It seems to make my amp a bit more syrupy and feels great when you dig in to it....if that makes sense. It’s tough to describe.
I generally like a long plate tube in the PI as well.

Also:
If you are happy with what you hear from your amp....don’t go messing with a good thing.

I've noticed changes in frequency response from switching PI tubes. For example I like the Sovtek 12AX7LPS due to how full it sounds; it can be a huge help in lower wattage amps like my Marshall Mini Jubilee.

[HyBr1d]

Re: 12AT7 phase inverter in Marshall TSL? And another question.

I tried switching things around and putting the 12DF7 in different spots, but(to my ears) it’s absolutely to die for in v1! I just tried a new mix and took the Mullard out of the tsl and put it into the jvm1c as it’s v1...Now, it’s too late to be rally jamming at this time of night, but (super low volume) first impressions are very good with the Mullard Blackburn in the v1 slot of the lil 1 watt....I’m really bummed because I wanted to put in a set of the 6085’s for the “power tube” section, but there isn’t enough clearance for one of the two tubes because of the speaker(though I don’t know if it could have fit w/the 8incher I replaced ) But I’m not going to get rid of the g10 greenback because of 1 tube...Adding the 10 was a huge improvement in tone, so gotta look for a different 12au7 matched pair!! Oh, so v1 is the nos Mullard Blackburn 58-59 longplate, nos Mullard CV4004/12ax7 in v2, a pair of RCA Cleartop 12au7’s for the power tubes(thinking about upgrading them just to see if it’ll make any kind of difference) and a GE Pewter Plate 12ax7 for the “v3”(I’m guessing phase inverter spot...) Hoping it sounds as good at higher volume as it does right now, the Mullard really seemed to bring up the gain and smoothness of the lead channel, but there’s still enough “sizzle” to the top end tha I really like!

Then that means I’ll also have to see what the tsl60 sounds like with the 12DF7 in v1 and the other 3 sockets being filled w/Mazda France tubes! Anyways, thanks for the info, I’m going to not do a 12at7 in v4...Either going to put the Mullard back in, or get another vintage Mullard tube and keep the Blackburn Longplate in the JVM1...I’m going for a classic to hard rock to “light metal” kind of tone...And the nos tubes are giving me that, but with a depth I couldn’t even imagine before I started “rolling” tubes! I’d like both amps to have a treble And harmonically rich lead channel distortion, but also want the clean channels to be able to take pedals, as I have like 7-8 different fuzzes to throw at it! Hoping the Wample Dracarys That’s on the way can take care of the hard rock/metal side of things when I’m not using the amp’s distortion...The 12df7 takes Fuzz like a champ, I’m very happy with how it’s responding to what is thrown at it! Have definitely experienced the most noticeable difference in to since putting that into v1, almost as much of a difference as when I put my first nos tube in there! With the amount of $ shelled out for guitars and pedals, it just makes sense to me to go for the big guns when it comes to tubes and to just go nos...I’m sure many may have differing opinions regarding preamp tubes, but to each his own! That’s y it’s so awesome to me that there are all sorts of 12ax7’s(and comps) out there that can be experimented with...And no matter what l, even if it’s not giving you the sound you’re looking for in a particular amp, it could do just that in another! And I just realized that with the Xotic Stereo X Blender that I can run the Supro, Jvm1c and the tsl60 at the same time! I have the jvm in the center, with the Supro to the left and tsl to the right! Sounds really cool to have a fuzz going through then all, as the variations in tone between the amps just adds up to a more complex and “richer sounding” tone! Also it’s really fun to have the jvm as a center channel that bypasses the Empress Echosystem, as I can have delays running on both the tsl and Supro, but the jvm stays without the effect...So it’s almost like what the “mix” function does, allowing you to hear the unaffected tone through the center and the delays in stereo bouncing of your ears from the left and right!!

Can’t wait for my 59RI to be finished so I can try out the new setup!(Seymour Duncan 59 Custom Hybrid in the bridge, with a Custom Shop Duncan hybrid in the neck, a 78 model screw coil and a Pearly Gates slug coil with rough cast, degaussing Alnico 5 got the mag! Plus a Doyle Coils full vintage harness....And hopefully something else I wanted to try, the Duncan Triple Shot system for both pickup rings...Hoping it’ll turn the 59 into a “do everything” kind of guitar with the coil splitting, series and in and out of phase stuff, all while keeping the benefits of the tone of the vintage style harness!!(mad sure to order 4 conductor wire so it could be something to attempt! Ok, will keep on this as the rig changes, but here’s a few vids!

https://youtu.be/aQV1XA43hBc

https://youtu.be/YtrRoz69T_E

https://youtu.be/gmZuVH3qsdY

A couple different vids w/different fuzzes, different guitars, etc...I’d recommend nos tubes any day! And am waiting to put in a matched pair of Mullard Xf1 EL34’s, just have to wait to take it to the shop for a quick bias check after switching out the new production Genalex Gold Lion KT77’s!(wish I could find a pair of actual nos, REAL Genalex KT77’s, just too rare and costly!!) Hopefully my experimenting will inspire others to try out some nos tubes, though I’d recommend starting small(like a v1 change) instead of a full, down the rabbit hole approach I’ve taken...The tsl60 is a much better sounding amp than I thought would be possible! Don’t write off your tired amp just yet!!;I only started playing with tubes over the last 3/4 months, I’ve had the amp since 2000! Merry Christmas, and everyone have a great New Years!!

[Gtrjunior]

12AT7 phase inverter in Marshall TSL? And another question.

Just a word of caution about the V3 (cathode follower) in the JVM amps. I’m not 100% sure about your particular amp but I used to have a JVM 210H. The V3 slot has a slightly higher voltage than the other preamp positions. Iirc, it has about 105v (?). In any case it’s pretty particular about what tubes will work there. I blew out a couple of tubes before I learned about the higher voltage. The JVM forum has a lot of info about it. Just be sure to check the spec sheet on whatever tube you run there. It seems that the spiral filament type tubes are especially prone to failure.
As always, ymmv. I ended up using a TAD 12ax7 as it can handle 180v.

[Darg1911]

Re: 12AT7 phase inverter in Marshall TSL? And another question.

I think the issue is mainly with the New Sensor made tubes with spiral filaments. 12AX7 spec for heater to cathode voltage is around 200V. The Sovtek made tubes with spiral filaments don't handle the higher cathode to filament voltages in cathode follower circuits despite meeting the spec on paper. Either that or it's a QC issue. But a techie can correct me if I'm wrong.

[JMP/HBE]

Re: 12AT7 phase inverter in Marshall TSL? And another question.

AT7 in the PI will lower your gain and reduce performance/dynamics. You really need a 12AX7.

[Joey Voltage]

Re: 12AT7 phase inverter in Marshall TSL? And another question.

AT7 in the PI will lower your gain and reduce performance/dynamics. You really need a 12AX7.

Not by much at all. A 12AT7 will put out a gain nearly comparable to a 12ax7 in practice. The much larger internal plate resistance of the AX7 (rp) will ensure that it will never nearly reach it's potential MU of 100 in most applications. about the most you will ever get out of a 12ax7 in most configurations is a gain of about 60-70, and it's not even pushing that in the PI spot, where it also has to drive a somewhat heavier load presented by the often 100K-220K gridloads of the power tubes (often mis categorized as bias feeders). high Z tubes like the AX7, are not great at this.

on the other hand , an AT7 has a much lower rp, and will be able to drive output tubes a little harder as well as heavier loads, and a offer bit more headroom as there slightly lower input sensitivity will allow them to swing more. You should however set the amp to more effectively use them though if you want to gain the performance.