Mesa Mark IV A fx loop problem

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Discordantsystem86
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Joined: Wed Jul 20, 2016 12:33 pm

Mesa Mark IV A fx loop problem

Post by Discordantsystem86 » Thu Oct 10, 2019 7:35 am

Hi guys, I'm having some problems with the fx loop of my Mark IV A, especially on the clean channel. If I have no fx connected in the loop the amp sounds awesome. If I connect for example a delay, even with short cables, the clean channel distorts, and I have a sort of volume drop. I've tried to change preamp tubes but nothing. I've had this problem when I bought the amp, after retubing the problem was solved, today I'm having the same problem. I have 4 Ruby 6L6s in the power section and in the preamp section a Tung Sol 12AX7 in v1, Ruby 12AX7AC5 HG V2, Electro Harmonix 12AX7 V3, Tung Sol 12AT7 V4 and a Sovtek 12AX7 LPS in V5. Please tell me what you think, if you have had the same problem. Thanks a lot

Discordantsystem86
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Posts: 3
Joined: Wed Jul 20, 2016 12:33 pm

Re: Mesa Mark IV A fx loop problem

Post by Discordantsystem86 » Thu Oct 10, 2019 7:53 am

If I connect a patch cable between the send and the return the amp works great again, so a friend of mine told me that could be a flip flop transistor of the delay that is gone and distort the signal.

stephen sawall
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Joined: Tue Nov 20, 2007 9:58 pm
Location: seattle wa usa

Re: Mesa Mark IV A fx loop problem

Post by stephen sawall » Fri Oct 11, 2019 8:09 pm

You might be sending too hot of a signal to the delay.... Read the manual to properly set levels.

R1 Master / R2 Master / Lead Master these control the send level in the effects loop. If you set them too high for your pedal it is going to distort.
The fact that Stephen appears from nowhere, is sentenced to death in an emotional public trial without anyone interfering at all and is then altogether forgotten as if nothing happened, is already suspicious.

Discordantsystem86
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Posts: 3
Joined: Wed Jul 20, 2016 12:33 pm

Re: Mesa Mark IV A fx loop problem

Post by Discordantsystem86 » Sat Oct 12, 2019 8:52 am

Hi Stephen, we have tried with a Boss DD7 and with the same settings we had no problem, so it's a pedal problem for sure. Thanks a lot

stephen sawall
Single Recto
Posts: 1354
Joined: Tue Nov 20, 2007 9:58 pm
Location: seattle wa usa

Re: Mesa Mark IV A fx loop problem

Post by stephen sawall » Mon Oct 14, 2019 7:36 am

Every pedal has different input levels....you need to adjust your amp different for every pedal.
The fact that Stephen appears from nowhere, is sentenced to death in an emotional public trial without anyone interfering at all and is then altogether forgotten as if nothing happened, is already suspicious.

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