Answer to Why Rectifier has different tone w/Loop On

[boogieslide]

When I recently had my 3ch DR modified by JerryP at FJA Mods I asked him to investigate why there seems to be an affect on tone when you have the Loop engaged in some fashion as opposed to completely bypassed. Many agree that the tone degrades a bit when the Loop is on (I am in this camp). He took a look at it and this was the response.
Quoted from an email:
"There's really nothing that can be done with the loop as far as it
changing tone when it's on. They switch the entire loop circuit in/out with
the loop switching which is why there's a difference in tone. Many other
amps just switch the loop jacks in/out, but leave the loop circuitry in the
circuit and they don't experience that."

Thought I would share for those who notice this and wondered why.

 

[Aramism]

i def experience this. i cant stand the loop being on on my RK



mesa told me thats how it is that putting loops on activates an extra set of tubes and changes the sound. they told me i have to compensate by eqing diffeent and that the eq values and volume values are diff in loop active and bypassed.



i love bypassed mode. sound is more organic and alive. unfortunately when i gig i have to put loops in. sounds worse.

 

[Storm]

Thanks for that piece of information. I find that the very slight tone change on my Roadster doesn't annoy me in the slightest as it's just a great amp.

Ciao ...

 

[parsky1]

Yep, other companies just switch the jacks out of the circuit so you don't get a better tone with the loops disengaged. Mesa disengages the entire loop for the purists who don't like to use fx loops.

Its not a poor design on Mesa's part... its just the physics of the matter.

 

[boogieslide]

I guess I can understand their decision on the design for those who don't want anything to do with an fx loop.
Problem is now there is a baseline on the amp that people hear w/out the loop. Switch it in and its like 'what the hell something is different'.

What I noticed is a little less sustain and harmonic content. The mods that were done to mine have helped overcome that though....most likely the MMOT that is in it now. To be honest though the slight tone difference is not as noticeable at band volume in the full mix.
I find the same thing to be generally true for tube swaps in amps. Playing alone you can hear some difference, but once in the mix not so much. Bad tubes or just absolute crap tubes are another story.

 

[ol4t]

This leads back to a recent post I made. I completely understand what Mesa has done, given me the chance to have better tone without the loop. What I did was make the decision as to which was more important-the better tone of the amp or the loop's added features. 8)

 

[Elpelotero]

the reason for a change in tone is that an extra tube is engaged. that last preamp tube in there is for the EFX loop, or at least one half of the tube is. When you turn on the loop, you engage that tube and all the extra circuitry. The tube creates extra gain. So the more you crank the signal on the back, the moe gain you get.

 

[Aramism]

+1 boogieslide





you "feel" less. less sustain and harmonic content. the breakup of distortion chords and the power that your gut feels when you chug is not the same....

boogieslide also made a good point that at bandlevels or live when things are so loud you cant tell the difference.



what mesa did was the right thing but its like when you see those animals being like abused and stuff in the major farms it exposes you to an ugly truth and its hard to go back (thats why i only eat organic meat [i rarely even do that]) but anyway the point is. all other amp companies (not that i play any other amps) but they just diengage the loop, mesa chose to give a pure tone w/o loop however once you hear it in its pure form its hard to go back. thus makign it hard to gig and stuff and play live if you need effects.


my solution: unless it cvan be modded or something for now when i practice and just play by myself then i have loops off. iwth band i have loops on cuz im just practicing my playing really and bands playing its not a record. for recording i add all effects after so i will record the guitar dry with loops off and for live i will have to have them on but what can you do but try your best to compensate? you gotta sacrifice sometimes. but def for recording i will record with loops off and add delay and stuff after.

 

[ol4t]

my solution: unless it cvan be modded or something for now when i practice and just play by myself then i have loops off. iwth band i have loops on cuz im just practicing my playing really and bands playing its not a record. for recording i add all effects after so i will record the guitar dry with loops off and for live i will have to have them on but what can you do but try your best to compensate? you gotta sacrifice sometimes. but def for recording i will record with loops off and add delay and stuff after.

This is what I'm going to do.

 

[Vigo1999]

do you guys also notice a huge drop on volume?? i experience that on my Stiletto Deuce. it's weird (not to say a **** s$%T). :x

 

[LordOVchaoS]

do you guys also notice a huge drop on volume?? i experience that on my Stiletto Deuce. it's weird (not to say a **** s$%T). :x

When your loop is engaged your Loop Send knob acts like a channel volume and the output knob on front is a master volume. You need to crank the output knob up almost, if not all the way and adjust the mix knob on the cack till it's not clipping your effects and use the channel volumes to match the channels of the amps. There should be no reason at all for a volume drop if you use these knobs correctly.

I'm from the minority I like the way it sounds with the loop on. I don't use any effects as of now but I leave my loop engaged all the time because I like the extra control and the way it alters the tone.

 

[blindsirens]

You're tone is only so good as the weakest component in your chain. If you go from a hi dollar killer sounding head to a cheap efx box or rack and then back into your head,your tone is going to suffer. Whatever the frequency response/noise issue of that rack unit is,is your new limit. To verify how much is the head and how much is the efx your using just plug a cable straight from the send to the return and then compare this with all your efx in the loop. On the Dual Rec V4 the fourth 12ax in is your loop tube. You can experiment with this make and yes,you must find the right settings for your loop active control,send and mix control. You want to send as much signal as possible without overloading your efx. If you don't use the loop you can even take out the fourth 12ax all together. Or simply use it as a spare if any of your others go at a gig.

 

[mrdylan]

Interesting I had never thought of placing just a patch cable in there before to hear the difference in sound. I am going to have to try this because I have had a horrible time trying to get a decent sound out of my Line6 XTL. WIll be interesting to see if it actually is my loop because there are alot of happy people using the XTL or even a Pod XT in a Marshall Fx loop.

 

[Vigo1999]

do you guys also notice a huge drop on volume?? i experience that on my Stiletto Deuce. it's weird (not to say a **** s$%T). :x

When your loop is engaged your Loop Send knob acts like a channel volume and the output knob on front is a master volume. You need to crank the output knob up almost, if not all the way and adjust the mix knob on the cack till it's not clipping your effects and use the channel volumes to match the channels of the amps. There should be no reason at all for a volume drop if you use these knobs correctly.

hummm, but Lord, dont you think this is somewhat strange?? i notice that i really have to crank the output on the front, but it's somewhat stragne to me, sicne will be lil room to the Solo function to work . . .

plus, if i also crank the mix volume on the back, the final 10% of its course dont just bring volume but also a annoying top end . . . :?

 

[Vigo1999]

Interesting I had never thought of placing just a patch cable in there before to hear the difference in sound.

actually this is exactly what i do . . . i really dont go trough any effects, i just engage the loop for the solo function, but i still think the tone w/o the loop is WAY better . . .

 

[CudBucket]

At least Mesa gives you a way to completely bypass the loop. Other amp circuits always keep the tone-sucking loop in line.

 

[Boogiebabies]

The reason is simply more circuitry in the signal path and the lowered value of the cathode caps on the loop. Generally, I am sure we can all agree that they notice th bottom end dissapear when the loop is engaged.
The use of 2.2uf or lower value cathode caps is the culprit. The RK I and Dual Rectifier use a 2.2uf and I hated the loop for killing my bottom end. The RK II has been revised and uses a 10uf cap to add the bottom back. The higher value cap, the more lower frequencies you will hear. The same theory is a common issue with parallel loops as well.

Older Boogie return designs basically saw a 120pf cap for some edge and 15uf cathode cap. To me it seemed like a pretty decent serial loop with minimal coloration.

 

[Boogiebabies]

The loop returns are V4B on the RK Series I and V4A on the Dual Rectifier.

Peace !!!

 

[mbmesa]

mrdylan, you are not the only one having trouble with your XTL. I just can't get a good tone either with mine in the FX loop. I just want to use it for FX with the amp sims off but the tone is all squashed and middy. I tried playing with the different levels , pads etc but was not able to get a satisfactory tone. I decided to F-it and get outboard effects. DD-20 is first on my list.

I use the XTL for those days where I don't feel like lugging my T-Verb combo to the jam and just plug the XTL right into the PA. Bummer coz its a great unit. The Mesa loop and the XTL just seem incompatible.

 

[cant play pool with a rop]

Foe me I had to make a realistic decision, with the effects I use can I run em straight in? Cause in my opinion with the loop engaged it feels like the amp is holding back its true capabilities.Leads are definately more organic and have more sustain.I like the distortion feel much better also.It depends on whats more important : the amps full potential with effects in front or effects in loop and amp tone secondary. Whatever works for you and your band mix.