clean channel Dual Rectifier 3 channel

[bermuda_]

I was just wondering which V Preamp slot controls the clean channel on the Recto, because I need to replace the preamp tube, because it's gone bad?

I think it's the V1 but I'm not certain.

Also is the V5 preamp the one which controls the third channel on the amp?

 

[94Tremoverb]

Each tube has two halves (A and B).

V1 - A: all channels, B: Channel 1 only
V2 - A: all channels, B: Channels 2 & 3 only
V3 - A & B: Channels 2 & 3 only
V4 - A & B: FX loop/Output Level/Solo (all channels)
V5 - A & B: phase inverter (all channels)

So a problem that *only* occurs on the Clean channel must be V1, unless it's a non-tube fault. Likewise a problem only on channels 2 and 3 must be V2 or V3. Channels 2 and 3 use the same tubes no matter which channel or mode.

 

[bermuda_]

Just out interest, what is the phase inverter used for?

 

[crane]

Just out interest, what is the phase inverter used for?

It's a gain stage and it split the signal into two (180° phase opposition) for the push-pull power section.

 

[Old BF Shred]

Just out interest, what is the phase inverter used for?

Just an "fyi"....it is sometimes referred to as the "driver" tube as it drives the output tubes. The term phase inverter only applies to push-pull designs as crane stated (like the Recto and most Mesa amps). A class A amp would not need a phase inverter, but still has a "driver".
Confused now? :lol:
Good luck!

 

[94Tremoverb]

A Class A push-pull amp still needs a phase inverter.

It's a *single-ended* amp that doesn't. Not the same thing...! All single-ended amps are Class A - or they would be if they were biased to the optimum operating point, which most single-ended guitar amps aren't - but not all Class A amps are single-ended. (Nor is Class A the same as cathode biased, contrary to popular guitar amp myth.)

Confused? You will be if you read a lot of the nonsense about amp classes that's commonly used for marketing purposes!

Anyway, the phase inverter is a critical stage in the tone of an amp, but in most amps - including all Mesas unless the new Transatlantic is different, which it may be - you can't directly control the distortion that comes from it. What it mostly does is affects the clarity and detail in the sound, and to some extent the clean headroom. And contrary to what a lot of tube sellers may tell you, you do *not* need a 'matched' or 'balanced' phase inverter tube. It serves no purpose in the traditional guitar amp phase inverter circuit, since the circuit itself is not balanced... it just costs more.

 

[212Mavguy]

A Class A push-pull amp still needs a phase inverter.

It's a *single-ended* amp that doesn't. Not the same thing...! All single-ended amps are Class A - or they would be if they were biased to the optimum operating point, which most single-ended guitar amps aren't - but not all Class A amps are single-ended. (Nor is Class A the same as cathode biased, contrary to popular guitar amp myth.)

Confused? You will be if you read a lot of the nonsense about amp classes that's commonly used for marketing purposes!

Anyway, the phase inverter is a critical stage in the tone of an amp, but in most amps - including all Mesas unless the new Transatlantic is different, which it may be - you can't directly control the distortion that comes from it. What it mostly does is affects the clarity and detail in the sound, and to some extent the clean headroom. And contrary to what a lot of tube sellers may tell you, you do *not* need a 'matched' or 'balanced' phase inverter tube. It serves no purpose in the traditional guitar amp phase inverter circuit, since the circuit itself is not balanced... it just costs more.

This is an excellent, accurate post. Well done! :wink:

On the balanced PI thang, the point about both sides of the PI circuit not being balanced may be correct, I agree with that assertion, but the amount of balance or imbalance in some cases might be "designed in" to the amp, particularly ones made by some builders who are actually concerned with such a thing. And there are some amps with PI circuits that are not symmetrical in values as well as types of components used! A can of worms for sure! In any case, a balanced PI tube has the possibility to preserve whatever balance/imbalance was intended by the amp designer/builder.

I most definitely concede that most amps are made with parts tolerances that are pretty loose, like 10-20%, not many guys are building amps with +-1% tolerance parts, too spendy in today's market, but a few fanatical ones do concern themselved with that kind of nitpicking. You sure won't see that kind of fanatacism in mass production guitar amps!

FWIW, I still use a PI tube that is well balanced between the triodes, and in more than one of my amps there has been an an improvement in the resulting tone palette as well as the amount of sustain for a given amount of preamp gain and overall volume. Your results may vary from mine for sure. Most of my amps are boutique amps.

Can't hurt to do some tube rolling and listen to what one's ears tell... IMHO that works best rather than to stand rigidly on one side of the fence or the other...if your ears can tell any difference at all, that is! Peace.

 

[bermuda_]

Okay so the phase inverter supplies all the gain to the amp, is that correct.

Also since I'm a 6L6 user, can I use any 6L6 preamp tube I want as the phase inverter example could I use a High Gain JJECC83 as the phase inverter.

 

[Turumbar82]

there is no such thing as a 6L6 preamp tube. You could use a JJECC83 in the phase inverter position but it shouldn't be high gain.

 

[bermuda_]

Right so I'm supposed to use a low gain preamp tube for the phase inverter.

 

[mikey383]

Right so I'm supposed to use a low gain preamp tube for the phase inverter.

You can, but don't expect it to sound great. If the amp is designed around a 12AX7 PI tube, then use a 12AX7 (ECC83).

What turumbar is trying to say is that you don't need a tube graded for high gain in the PI slot. It's not going to help get you any more gain. Those type tubes are best left for the boost or gain stages, which the PI isn't.

Look at the PI as being part of the power amp, and not the preamp.

 

[94Tremoverb]

The phase inverter does not add very much gain compared to the other preamp tubes, but it does add some. You certainly *can* use a lower-gain tube here, if you want a cleaner, clearer sound and/or more headroom - a 12AT7 (as used in this position in Fender Blackface and Silverface amps) will do it. You don't have to modify anything else, it's a straight swap. Because it doesn't add much gain and comes very late in the circuit, so any noise it makes is not then amplified by following stages, you can also use a tube which would otherwise be too microphonic for a preamp stage.

You can equally well use a 12AX7 as the phase inverter if you want a little more gain and a richer sound from your Fender Blackface/Silverface etc amp by the way. But a 12AX7 is the highest gain of the 12A*7 series of preamp tubes, so you can't add more gain to your Mesa like this.

 

[mikey383]

I tried a 12AT7 and a 12AU7 in the PI slot, and the amp sounded like ass. The gain decreased, and the tone got a little thinner. Good if you're going for a rock tone, not good for metal.

Since the amp is designed around a 12AX7 for the PI slot, and is a high gain amp, you're better off sticking with that tube.

The reason 12AT7s work well in the PI slot in Fenders is because they aren't preamp gain based amps...they're more suited toward clean tones or slight breakup of the preamp and power tubes. Not high gain by any means. So you end up not hitting the power section as hard, which makes for more clean headroom.

From your previous posts about the Recto's gain, you definitely don't want to go with a lower gain tube in the PI slot. Stick with the 12AX7.

 

[94Tremoverb]

I should have been clear, I much prefer a 12AT7 in the phase inverter in Mesas exactly because I like lower gain, deeper, clearer and more open sounds that allow the power tubes to get pushed a little more... not tight and focused, or for high-gain metal distortion. For metal you definitely want to stick with the 12AX7. Neither is right or wrong, it just depends on what you want. I also like the 12AX7 in Fender SFs because they're too clean and skinny otherwise... but then I like Marshalls (old ones, anyway) for cleans.

That's why I like the Tremoverb so much - underneath, it's essentially a hot-rodded Marshall with Fender features (reverb, tremolo), but Mesa gain and flexibility - including on the clean channel. The clean channels on the 3-channel Rectifier (and the Rectoverb) are completely different, and while a lot of people prefer them, I don't like them at all.

 

[bermuda_]

Well I'm currently using a Sovtek LP/LPS as the Phase inverter in my amp so I take it that that's a 12AX7 preamp tube I'm using.

Also I was just wondering what Preamp tube position controls 3 channel of the recto is it the V3 Slot preamp slot because on my Recto I'm currently using a High gain JJECC83 for the V2 slot, and a Penta 12AX7 for the V3 slot?

 

[94Tremoverb]

Channel 3 uses V1A, V2B, V3A&B, V4A&B (with loop active) and V5A&B - as does channel 2. There is no one tube that controls channel 3 alone, since channels 2 and 3 use the same tubes. V3 is the only one that does *not* affect channel 1.