Mark V FX Loop Question

According to the manual, the FX loop on the Mark V is serial, but when I hit the FX button on the footswitch with no FX connected, I still hear some signal (maybe 5%). It's low, but it's there. Is this normal? Will you have the same comb filter effect using multi-FX with the loop as you have with parallel loops?

Anybody?

That's normal, there actually is a touch of bleed-through that occurs.

It's annoying, but normal.
As much as I studied the schematics, I can't figure out how it gets through. It's not a fixed percentage, but rather a fixed level, It seems to be completely independent of the per-channel master settings. It seems to depend only on how much gain is set in that channel, and ch1 doesn't seem to do it at all. So the higher you set the per-channel masters, the better it gets drowned out.

I suspect that it is at least partially responsible for why some effects are reported to sound bad in the FX loop.

Some time maybe I'll get around to calling Mesa.

If I recall, the manual says that even if there is nothing attached, the act of flipping on the FX triggers a bunch of additional circuitry and that the tone will definitely be effected.

Flipping on the FX also activates the FX Mix knob, Mute circuit, Output, and Solo Knobs. If you have any of the knobs completely turned off, you won't hear anything.

lhrocker said:

According to the manual, the FX loop on the Mark V is serial, but when I hit the FX button on the footswitch with no FX connected, I still hear some signal (maybe 5%). It's low, but it's there. Is this normal? Will you have the same comb filter effect using multi-FX with the loop as you have with parallel loops?

Click to expand...

I may have misunderstood the question. It sounds like you are assuming that if there are no pedals plugged in to the FX loop, but it's turned on, that you expect no sound.

I believe the amp detects the situation that there is nothing plugged in, and ignores that part of the circuit.

But it does activate the Output and Solo masters. If they are turned low, you may only hear a little of the original signal. Try turning up the Output master and see if you hear the full deal.

Instead of opening a new 3ad, i thinked it was better to ask here


I put my entire pedalboard in the loop efx..including the tuner...and I've noticed one thing: ( obviously FX engaged on the footswitch ) when using the tuner pedal, I still hear some guitar coming from the speakers....it's just fine or what ?

Mariocò said:

Instead of opening a new 3ad, i thinked it was better to ask here


I put my entire pedalboard in the loop efx..including the tuner...and I've noticed one thing: ( obviously FX engaged on the footswitch ) when using the tuner pedal, I still hear some guitar coming from the speakers....it's just fine or what ?

Click to expand...

Dont know why you still hear signal but dont put your tuner in the loop. Its probably cause your guitar is in the front and and depending how you got the FX knob set then in bleeding through. Only put time based and modulation effects in the loop. Or a EG if really need. Put OD pedals and compressors in front of amp.

Adambomb said:

Mariocò said:

Instead of opening a new 3ad, i thinked it was better to ask here


I put my entire pedalboard in the loop efx..including the tuner...and I've noticed one thing: ( obviously FX engaged on the footswitch ) when using the tuner pedal, I still hear some guitar coming from the speakers....it's just fine or what ?

Click to expand...

Dont know why you still hear signal but dont put your tuner in the loop. Its probably cause your guitar is in the front and and depending how you got the FX knob set then in bleeding through. Only put time based and modulation effects in the loop. Or a EG if really need. Put OD pedals and compressors in front of amp.

Click to expand...

yes I do everything in this way, but it's annoying to put the tuner out of the pedalboard and adding an extra cable to connect everything....my knob is set at noon ( just like the manual suggests )..I just hope it's normal..

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APEMAN said:

Hi,

there is no galvanic connection if you switch the FX on without a FX unit connected, but of course what you have is a electrical influence inside the fx tube - 12AX7 dual triode = one side for send the other side for return. Its the same in any other serial fx loop amp when there is only one fx tube (maybe 99% of all amps). When I built my first tube guitar preamp I had that kind of influence between my clean and dirty channel so I had a very very small dirty sound added to the clean. Took me three days to find out.....

Greetz

APEMAN

Click to expand...

Agreed, sharing the same dual triode for both FX Loop send & return will cause bleed, but it appears that the MKV may only do that with CH3 (assuming the last gain stage of each channel is the FX Loop Driver).

From pg 62 of the MKV manual (tube task chart):
V1A-Input stage
V1B-2nd gain stage CH1/CH3, 3rd gain stage CH2

V2A-2nd gain stage CH2
V2B-N/A

V3A-3rd gain stage CH1/CH3, 4th gain stage CH2
V3B-4th gain stage CH1

V4A-Reverb send
V4B-2nd drive stage CH3

V5A-1st drive stage CH3
V5B-Reverb return

V6A-4th gain stage CH3
V6B-Effects return stage

V7A&B-Phase Inverter

Without the schematic in front of me I can't say for sure, but it seems that the bleed-through should only be noticable in CH3 with high Gain/Master settings.

Dom

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guys, you're just incredible.
Tomorrow I'll check this ch3 thing...in fact when I noticed this, tuner and ch3 were on at the same time...this time I'll try with the ch1 engaged
thank you again !

guys you were totally right about the ch3 thing

everything works very well...what an incredible amp

OP (lhrocker),
I am not sure I understand your question?

My understanding is that you have your MkV set with "effects toggle engaged" in the back of the amp, but with no effects connected to the loop of your amp, and are asking about a "sound difference" when engaging the "effects" button via your footswitch even though no effects are connected in the loop.

Assuming my understanding is correct above........why would anybody ever engage the "effects" button on the footswitch without any effects connected to the loop?

I normally play my MkV without any effects in the loop, but with the effects loop engaged so that the Overall Master Volume and Footswitchable Solo Boost functions are engaged. I would never engage the "effects option on the footswitch" with no effects connected to the loop...so could care less of how the sound might be degraded in this situation.

I may have misunderstood what you are asking, but I am confused with your question. :?

I was looking for a thread on this topic as I discovered today a significant loss of tone (high end) with a few time based boss effects pedals in the loop. I was thinking maybe the V6 tube but I do not know if the effects loop tube(s) affect tone.