Single Rectifier 50 Head with ISP Decimator Issues

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metalms
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Single Rectifier 50 Head with ISP Decimator Issues

Post by metalms » Wed Aug 21, 2019 2:15 pm

Thank you for the add to the forum. I recently purchased a used Mesa Single Rectifier Solo 50 head. The effects loop has been converted to series prior to my purchase. I started running through some tests and found that if I have my ISP Decimator II in the loop and the channel master is pushed to noon and gain is noon or better, I get very distorted/clipping/popping thru the cab.

Decimator out of the loop no problems

No pedals in loop no problems

Decimator in the loop and channel master is less than noon no problems

Decimator in the loop and channel master at noon but gain less than noon no problems

BBE Sonic Maximizer in the loop with MXR Reverb no problems

My pedals are not that old and I did clean the input/output jacks after discovering the problem. It made no difference.

If I put a jumper cable from send to return no problems. So loop jacks should be good

I performed multiple tests per my amp tech and given the results was told that the Mesa loop is tube driven and it could be the ISP decimator cannot handle the preamp setting at noon. I have ran the ISP Decimator II in the loop on other heads such as Mesa Mark V, EVH 5150 iii, Peavey 6505+, ENGL Ironball, ENGL Powerball 2, and Randall Satan. Never any problems regardless of where the preamp channel master was. Wondering if anyone else has experienced this?

I tried 3 different Decimator II's . I have multiple Decimators due to running stereo heads . I run one on the front and one in the loop. This is the first time I have seen this. I contacted Mesa and they never have heard of this.

With all that being said, I usually run with a Fortin 33 boost on the front end.
Typical settings I run :
Channel 2 modern
Gain noon
Channel Master 9 o'clock
Output Master 9 o'clock

So I would not experience the undesired clip/ popping due to low setting of the channel master. The only reason I found it was because I was putting a used head through some tests to see if there were any failure points with my setup. The head is awesome and really is a beast. More or less was making sure there wasn't an underlying issue with the head.

Thank you in advance on anyone's thoughts.

It is worth noting, I ordered a Fortin Zuul to try out in place of the Decimator II. It may have the same problem on the same settings however, it is an awesome pedal so why not. I will post my results of the Zuul this weekend once I receive it in .

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Re: Single Rectifier 50 Head with ISP Decimator Issues

Post by domct203 » Thu Aug 22, 2019 5:24 pm

The signal from the Rectifier FX loop is super hot.

I’ve had good luck using the Ebtech Line Leveler.

+4dB on the amp side, -10dB on the loop side.

Dom
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metalms
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Re: Single Rectifier 50 Head with ISP Decimator Issues

Post by metalms » Thu Aug 22, 2019 9:16 pm

Thanks Dom,

My amp tech thought the same about being hot. First thing out of preamp section is loop. I will look into the line levelers. Would I need to add dB to the amp side? Already using Fortin 33 boost on front end. The head sounds super killer as long as I keep the preamp below 10 o clock. Which I do most times anyway. Just bring up the master output to taste. I thought about taking the head into my amp tech and having him check all the current and voltage that is coming into the loop to make sure it is within what mesa specs. Piece of mind the head is operating properly. Sounds like it is from your comments. Thanks again for your time

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Re: Single Rectifier 50 Head with ISP Decimator Issues

Post by domct203 » Fri Aug 23, 2019 8:18 am

metalms wrote:
Thu Aug 22, 2019 9:16 pm
Thanks Dom,

My amp tech thought the same about being hot. First thing out of preamp section is loop. I will look into the line levelers. Would I need to add dB to the amp side? Already using Fortin 33 boost on front end. The head sounds super killer as long as I keep the preamp below 10 o clock. Which I do most times anyway. Just bring up the master output to taste. I thought about taking the head into my amp tech and having him check all the current and voltage that is coming into the loop to make sure it is within what mesa specs. Piece of mind the head is operating properly. Sounds like it is from your comments. Thanks again for your time
Not sure what you mean by ‘adding dB to the amp side’.

Connect the +4 dB jacks on the level shifter to the amp’s FX send and returns, and use the -10dB jacks as the new send and return connections. The amp’s loop level will remain the same as it will be seeing the same levels, but the effects on the other side of the level shifter will be working at -10dB.
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Re: Single Rectifier 50 Head with ISP Decimator Issues

Post by domct203 » Fri Aug 23, 2019 11:17 am

I tried to reply to your PM, but the forum tells me 'page not found' when I submitt my message.

Yes, the Ebtech unit (the one you linked in the PM) goes between the amp and pedals. You would use both side of the unit.

The LLS-2 is a two channel level converter. Each channel has a +4dB jack, and a -10dB jack and is bidirectional, meaning it will convert from +4dB to -10dB and vice-versa.

For your setup, run a patch cable from the amp's FX Loop Send to the LLS-2 Channel 1 +4dB jack. Run another cable from the LLS-2 Channel 1 -10dB jack to the input of your pedal (or effects chain).

Now run a cable from the output of your pedal (or effects chain) to the LSS-2 Channel 2 -10dB jack. Run a patch cable from the LSS-6 Channel 2 +4dB jack to the FX Loop Return on the amp.

What you are doing is taking the +4dB signal of the FX loop, dropping it to -10dB for the pedal, then bringing it back up to +4dB for the return to the amp.

The Rectifiers are known for their ability to create crazy amounts of gain in the preamp circuit, and make mention of it in many of their amp's manuals. Add in the Modern Mode settings and you are pushing a lot of signal through the amp. All normal behavior.

I use the LLS-2 to stop from clipping the FX return on my TC G-System.
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Re: Single Rectifier 50 Head with ISP Decimator Issues

Post by metalms » Fri Aug 23, 2019 12:55 pm

Thank you for the information. Much appreciated. I did take another look through the manual and now see a statement

NOTE: Because the MASTER Control creates the send to the Effects Loop, extreme settings will cause
a large signal to be sent to the Loop for that Channel. Not only may this cause possible overloading of the
processors Input stage

I will check out a line leveler. I normally do not need it on channel 2 modern because I keep the preamp down around 9 with power output at 9. So do not see the loop clipping the ISP. Although on Channel 1 clean and pushed modes I could see needing it more due to the need for more higher preamp level to achieve a higher level of sound. Channel 1 is where I first found this. So definitely will benefit use on that channel.

Do you notice any tone difference or any other differences in performance when using the line leveler other than no more clipping pedals? Thank you again for your time.

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Re: Single Rectifier 50 Head with ISP Decimator Issues

Post by domct203 » Fri Aug 23, 2019 2:12 pm

I don’t even know it’s there, except that I no longer clip the digital converter in my G-System which actually makes the rig sound better.

Are you playing the rig at band / gig volume?
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Re: Single Rectifier 50 Head with ISP Decimator Issues

Post by metalms » Fri Aug 23, 2019 9:42 pm

I play it anywhere from bedroom to as loud as my cabs can handle. I run it through a 412 and 212. With that said I rotate in other heads in stereo with it. Evh 5150 iii 6L6 , EVH 5150 iii EL34 , and Peavey 6505+ heads. Those run a separate 412 and 212 cab. It sounds crushing! Regardless of the combination I use. The Mesa is the only one I have experienced the issue with. But good news. Line leveler on the way and be here Monday 🤘. Will provide feedback once I try it out. Thanks again

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Re: Single Rectifier 50 Head with ISP Decimator Issues

Post by metalms » Sat Aug 24, 2019 1:32 pm

So I received the Fortin Zuul today and experienced way better results than the Decimator II. I dropped the Zuul in the loop of the single rectifier and it performed quite nicely. I still ran a Decimator on the front end of the amp to clear any guitar noise. I was able to get the Zuul to clip if I ran the preamp channel volume at noon on channel 1 with gain 3 o'clock. So as expected the hot signal is still there, the Zuul just handles it much better than the Decimator II.

With that being said, my Ebtech line leveler will be here Monday. I think I definitely could get away without having it however, why run the loop pedals so hot if you do not have too. See what results or changes I see once the leveler is in place Monday. The Zuul was well worth it!

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Re: Single Rectifier 50 Head with ISP Decimator Issues

Post by metalms » Tue Aug 27, 2019 4:52 am

Tried the Ebtech line leveler Shifter and while it did solve the clipping of the isp decimator, it did have a bad side effect. The tone was thin and heavy on midrange vs not using it. If I engaged the BBE Sonic Maximizer, the signal would drop further and have to compensate with power amp section. I don’t have clipping or popping problems with the fortin Zuul gate in the loop unless I really push the gain and channel preamp master to where I don’t normally play it, so I am sending the Ebtech back and sticking to the Zuul. The Ebtech would have been great if it did not take all the meat away from the tone.

Signal chain
send to channel 1 Ebtech +4
Channel 1 Ebtech -10 to Isp decimator II to BBE Sonic Maximizer
BBE Sonic Maximizer to -10 on Ebtech
Ebtech channel 2 +4 to return

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Re: Single Rectifier 50 Head with ISP Decimator Issues

Post by domct203 » Tue Aug 27, 2019 5:23 pm

I’m surprised to hear of the tone issues. When I first got the LLS-2 I did have to tweak the FX send level (on the rear) to get unity gain in the G-System, but no tone loss at all. I used my master ‘All Bypass’ patch and switched the loop in and out, there was hardly any difference in core tone and response, especially at band level.

Always best to keep the signal chain simple, if I was in your position I would go with the Zuul as well as ditch the LLS-2.
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