MKIV FX Loop & 12at7's I need some help

[Lights Out]

Hi
I have finally rack mounted my MKIV
with a Replifex in the FX loop .

It sounds a little unclear & muddy at times
I have replaced my Valves with a JJ Tesla "High gain" set.
6L6's & all 12ax7's

Being a MKIV A should I be using a 12at7 in the position marked "12at7"
Im assuming its the phase inverter ?

Does the type of valve used in this position make a big difference to the FX Loop & general tone ?

 

[Bullen]

The 12at7 is the reverb tube. I´m not sure if it has another function on the A version. I believe the phase inverter is the tube that is positioned on it´s own.

Does it sound muddy when the loop isn´t used?

 

[Boogiebabies]

Ahh, another person takes the high gain JJ tour.
Just because the gain rating is 115 does not mean it will necessarily give you more overdrive. The JJ's are notrious for being the blanket over your speaker tube. The loop runs through the V2 A and B. The Verb runs through the V3 A and B.

 

[Shep]

I run JJ and they are dark but that does very much so suite the mk IV 's tone..they that harsh pierce out and smooth it out as well..

 

[GLydian]

Ahh, another person takes the high gain JJ tour.
Just because the gain rating is 115 does not mean it will necessarily give you more overdrive. The JJ's are notrious for being the blanket over your speaker tube. The loop runs through the V2 A and B. The Verb runs through the V3 A and B.

The reverb runs thru V4 A and B in Mark IV A version, I have have 12AT7 on this position.

 

[Lights Out]

Ok thanks for that , so that position dosen't effect the Loop then.

I sometimes find that FX units can sound not as good through the MKIV FX loop
Even though I keep the masters below 3.
has anyone else noticed this.

I still have to play around with levels etc
Im getting close

 

[t0aj15]

I sometimes find that FX units can sound not as good through the MKIV FX loop even though I keep the masters below 3 has anyone else noticed this. I still have to play around with levels etc Im getting close

IMO the efx loop is the one weakness in the Mark IV, that's why I don't use it. I instead use the Slave (D.I.) output to drive the stereo efx which then feed a Boogie 50/50 poweramp. This way I have a W/D/W setup that sounds great.

 

[GLydian]

Hi
I have finally rack mounted my MKIV
with a Replifex in the FX loop .

It sounds a little unclear & muddy at times
I have replaced my Valves with a JJ Tesla "High gain" set.
6L6's & all 12ax7's

Being a MKIV A should I be using a 12at7 in the position marked "12at7"
Im assuming its the phase inverter ?

Does the type of valve used in this position make a big difference to the FX Loop & general tone ?

Ok here is some things I found out about my Mark IV series A amp and tubes.

Obviously V1 is the most important tube and affect all the channels. And I got a hi-gain Tung-Sol marked 110/110 and it maid big difference to what I had before JJ EC83 marked 111/114.
V2 tubes A/B controls the effect loop in and out, I had old tube and I always had to max out G-Majors out level and still had weired problems so I changed it to JJ EC83 and now G-Major is at unity gain and loop in or out doesn't make any level changes.
V3 tube is the lead stage and I have that JJ EC83 marked 111/114 on this.
V4 is the reverb tube and I have Mesa 12AT7.
V5 is the phase inverter tube and I got Shuguang 12AX7 balanced tube 105/105 in this place, previously I had some unknown gain GT 12AX7.

And I have changed all power tubes to Winged =C= SED 6L6GC and I feel now my amp is really responsive and I can emulate some of the sounds in the manual.
After power tube change I can here very specific differences between tweed/full, classA/simul and Penta/Triode modes, presence controls became very responsive too.

I have played with V1 position using a Chines Ruby tube/GT Rusian/Mesa SPAX7-A/JJ EC83 and last Tung-Sol and I wold say the Tung-Sol made a big difference in my clean sound of my JS1000 neck/single coil mode.
I don't know how to explain those sounds, and don't like to use very subjective terms like three dimensional and such. Basically I wanted some non uniform but bright with subtle variations in harmonics clean sound that shines when added little delay and/or reverb some times Vai's old songs have this kind of tone and then again Eric Johnson has it always.

As per everyones recommendations of the net forums I bought the tubes from Dougstube.com and he was very helpful and very fast service too.

 

[Boogiebabies]

Ahh, another person takes the high gain JJ tour.
Just because the gain rating is 115 does not mean it will necessarily give you more overdrive. The JJ's are notrious for being the blanket over your speaker tube. The loop runs through the V2 A and B. The Verb runs through the V3 A and B.

The reverb runs thru V4 A and B in Mark IV A version, I have have 12AT7 on this position.

Yup, I was obviously looking at the reverb but quoted the Lead stages.
**** happens. 8)

 

[Restless Rocks]

In the Mark IVa and Mark IVb one must also consider that V2a is the tube stage being overdriven for the Rythm 2 mode. This tube, at least the A side, will have a drastic affect on the quality of your R2 sound. That's why the three channel masters are next in the signal chain so that you can control the signal level going out your effects send so as to not over load the input of your effects processor. The effects return signal goes directly to the grid on V2b and can easily be overloaded by excessive signal coming from your effects processor. By the same token sending an unusually low signal back to the effects return will cause you to have to raise the setting of the output level control to compensate and your signal to noise ratio will suffer as well as the overall dynamic range . The key is to use processors which you can set up to have a "unity gain": that is getting the same level signal out of the device as you put in it. Most of the better processors have a seperate input level and output level. If your processor has seperate in and out meters try this: set the input gain (on the processor) at 12:00 then use your channel masters (these could be called fx send levels) to adjust the input meter on the processor for 0db or just before clipping. Then leave them alone. Now unplug the processor from the fx loop and set your amps output level to the volume you wish to play the amp. Leave it alone. Now plug your processor back into the loop and use the processor's output level to adjust the amps volume back to what you heard when you had nothing in the fx loop.

OK here's another scenario: suppose all you want to run in your fx loop is your trusty ole DD or Chorus stomp boxes. No in or out level controls. A similar procedure works for this. Put your stomp boxes in the loop and adjust your channel masters as high as you can get them to make the sound full but when you hit distortion back off half a notch. Use the amps output level to set your overall playing loudness. Others may use different methods each of which has it's merits but this one was always easy and it works for me.

 

[Lights Out]

Yeah I have played around with the FX levels.
The unit I use (Replifex) has different DB levels
So I have matched the levels .

Reading through some other threads .
They got me thinking of changing the
Filter caps , since there original ones so there about 16 yrs old

Though my tech tells me the filter caps have no influence on tone
Im sure they must have some influence ??