NGD: JP2C and a potential problem

Discussion in 'Gear & Equipment' started by efx1138, Aug 16, 2019.

  1. HeHasTheJazzHands

    HeHasTheJazzHands SS.org Regular

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    I will say it pissed me off because one of the reasons I sold off my Mark III was because I thought it was fucked up because of the noise issue. It wasn't until my Mark IV started having issues AND I did more reading about the Mark-series squealy issues that I realized it's unfortunately by design.
     
  2. protest

    protest SS.org Regular

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    Yep my Studio Preamp does the same thing. The IV I had was quieter though. I dropped a 5751 into V1 and it helped a little, probably need another one though.
     
  3. oneblackened

    oneblackened Tube Amp Dork

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    There's definitely something oscillating there... It's not normal. It could be a microphonic preamp tube, tap them lightly with a pencil or a chopstick or something - if one rings through the amp and sustains some, that tube is microphonic. However I don't think it's a tube problem, more likely some circuit thing.
     
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  4. c7spheres

    c7spheres GuitArtist

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    It sounds like a microphonic tube but that's normal for this amp depending on settings. This is what to try first
    - Per Boogie manual, turn amp channel treble below 2 o'clock when using upper gain settings. I interpret that as above noon which is the upper range of the dial. This could apply to any channel potentially, though moreso with the shred mode.
    - Plug guitar into amp, turn guitar volume down
    - Plug amp into load box using an actual speaker cable, not a guitar cable, make sure ohm setting is correct and matches both amp and load box.
    - Plug load box into monitors using proper unbalanced or balanced cable
    - Literally triple check connections. Actually make sure they are right, don't assume or glance over them. It happens to everyone even after triple checking sometimes.
    - Turn on load box, turn on amp in standby mode, turn on monitors
    - Make sure guitar volume is down again.
    - Select amp channel and turn it's gain, treble, and master down
    - Turn standby on amp off
    - Start with gain, master, then treble up to about 9pm, adjust to taste. When you hear it squeal, back off treble control before master or gain settings to try to eleminate squeal, but first see if squeal goes away at all by physically moving away from the amp
    - when playing move away from amp about 15-20 feet
    - When near amp turn the guitars volume down.
    - Normally if you have this amp turned up that loud and you're sitting right next to it then it will feedback or squeal, but Mesa talks about it in the manual and to back off treble knob. The load box, power source etc probably have nothing to do with this noise. Most likely everything is operating as normal, probably the worst case scenario you're looking at, which I doubt, is a micro-phonic tube that needs replacing. The sound you're hearing is very likely a micro-phonic tube, but the tube is probably good still, it's just being pushed into that micro-phonic territory by the settings / setup etc. Mesa manual talks about it too.
    - Drain is from Stockholm. They were awesome. I saw them several times back in the 90's . If you see them around town, say hi from Arizona : )
     
    Last edited: Aug 17, 2019
  5. mnemonic

    mnemonic Custom User Title

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    Ground is often still connected even when a unit is turned off.

    I see the SRLIR does not have a ground lift. Does your interface have a ground lift button? If so, click it.

    Another option is to use a cable between the SRLIR and your interface that is only for that purpose, unscrew the jack, and clip off the ground on just one side.

    That way the units aren’t connected via the ground in the cable (eliminating the loop). Only clip it on one side. If you clip both sides the ground won’t provide any shielding, and you’ll add noise.

    This diagram gives an idea of what I think is happening, but imagine it’s your amp/load on the left, and your interface on the right.

    60507449-03BF-49D3-893D-78590DA9A62F.jpeg
     
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  6. c7spheres

    c7spheres GuitArtist

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    Yep, probably this. I completely ignored you said that and was still focused on the squeal, not the hum. Sorry.
     
  7. mnemonic

    mnemonic Custom User Title

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    The squeal is weird since it’s not what I would expect from a ground loop. But I guess if seperating the ground works, it works.
     
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  8. laxu

    laxu SS.org Regular

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    I had issues like this when using my Bogner with a Fryette Power Station 2. Never noticed it unless I was cranking the amp. It was a microphonic phase inverter tube. Replacing that cured the problem just fine.

    Only time when I had ground loop issues with this setup was when using the Fryette fx loop in 4 cable mode. It did not like that at all and would have required several ground lifts to solve.

    The first thing I would do is take the setup to the bare minimum of amp and reactive load, then swap the phase inverter tube or if you don't have any spares, shuffle the ones in the amp around. Just make sure that you don't swap a reverb driver tube for a 12AX7 if it expects a 12AT7 or something.
     
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  9. Guitarjon

    Guitarjon SS.org Regular

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    Didn't read all the answers but I had similar issues with my tube amps and loadbox setup.
    For me it turned out to be a ground loop and what solved the issue completely was to press the ground switch on my Fractal LB-2 loadbox.
     
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  10. c7spheres

    c7spheres GuitArtist

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    I use a Sequis Motherload Pro load setup. I never got a squeal or ground issue. It's passive though so maybe active load have something to do with it? I wouldn't think so though cause I think the load are still passive in the Fryette and Suhr. I think the power supply is for the internal amp on the Fryette and the IR's thing on the Suhr, but I'm not sure. I still think the squeal may still just be how the Mesa manual describes it when the controls are set that way. Tracking these issues is usually solved easily or a pain and you go through hell chasing ground gremlins. I do love a good load box though. It's been a godsend for me.
     
  11. efx1138

    efx1138 SS.org Regular

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    @mnemonic This advice looked good so I tried it but what happened then is that then the SRLIR's output doesn't include the onboard IR nor does the DI level on the Suhr have any effect on the signal which does get very loud into the interface. This is an unbalanced cable that I tried this on. The inputs on the RME audio interface are balanced, would that make any difference?
     
  12. c7spheres

    c7spheres GuitArtist

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    - The unbalanced normally doesn't make a big difference if the cable run isn't too long like under 25 ft.
    - I'm more surprised the Suhr Di level isn't working. According to the block diagram on pg 15 of their manual it says that it is connected to the unfiltered output. If you're still connected into the IR output with no power then it wouldn't work, but it should work passively from what the manuals block diagram indicates on pg15 from the unfiltered output. If that isn't working then either their block diagram could be wrong or something might be wrong with your SUHR. Also, did you follow all the power on/ off cycles the manuals talk about? That could cause issues possibly.
     
  13. mnemonic

    mnemonic Custom User Title

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    So using the IR output but no IR? That’s odd, I’m not sure why that would happen. Or why the DI level wouldn’t work now.

    I suppose you could try a stereo cable so that the balanced signal is retained, and desolder the sleeve on one end of the cable, but it might end up in the same situation as I thought the mono cable would work...

    For what it’s worth it looks like the SRLIR would need power even for using the unfiltered output, on the block diagram in the manual, it shows the symbol for a powered buffer on both outputs (the triangle shape).

    You could try emailing Suhr and asking if they have a solution to ground loops, as I’m sure it’s not uncommon. I think their support is supposed to be pretty good.
     
  14. efx1138

    efx1138 SS.org Regular

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    @c7spheres and @mnemonic thank you guys for chiming in again. I tried switching back to the cable I used before and the DI level could be set again. AFAIK, the DI light didn't even light up when I used the altered cable so something was obviously off. I did the same thing to another cable and got the same result.

    A couple of things, I will take the SRLIR back to the store and see if I can try another unit tomorrow. But barring that, would something like this accomplish the ground fix? https://www.radialeng.com/product/stagebug-sb6 seems like it would be good since it has two outputs and my idea was to capture both outputs of the SLRIR at the same time. But I thought I'd ask here before I spend even more money :) Thanks again, I've learned a lot from this thread so far and hopefully I can find a solution soon.
     
  15. 4Eyes

    4Eyes SS.org Regular

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    So ground loop...

    Just bear in mind, as someone mentioned before, you got noise at levels that would equal to attempting a suicide when playing through actual cab, at so high levels of output even coils inside the reactive load may start to resonate and create weird noises
     
  16. efx1138

    efx1138 SS.org Regular

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    That's a fair point but the strange thing is that this only happens within the actual amp once I use the line level outputs from the Suhr. Actually having those volumes set and not having those cables hooked up and it's dead silent. Had this been an issue with just the speaker cable hooked up I would have written it off as what you wrote but if the difference is just a line level cable going to a turned off audio interface I'm thinking the groundloop could be the more likely culprit.
     
  17. mnemonic

    mnemonic Custom User Title

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    The little schematic picture on the unit shows it is transformer isolated so that would eliminate any ground loops. AC signals are able to pass though the transformer but DC is blocked.

    Word of warning, passive transformer isolation tends to alter the sound a bit, as it can be pretty hard to make a small and cheap transformer that can handle 20hz to 20khz without some level of rolloff in the highs and lows. Unless manufacturing has improved in the last few years (entirely possible).

    I believe the non-IR Suhr load uses a transformer on the output, from memory.
     
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  18. c7spheres

    c7spheres GuitArtist

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    Hard to say if the buffer is powered by the Power supply or by the speaker voltage or not. My Sequis has this but it's all passive and gets it's power from the speaker out of the amp signal voltage. It shouldn't matter though either way with this setup.

    - According to the Suhr block diagram you should be able to use either balanced or unbalance cables on either jack. They can both accept either type so it shouldn't matter really. The panel wirting makes it look like one is balanaced and one is not, but they can both accept either.
    - I'm guessing the problem is probably further down the line in the interface, computer, or monitors somewhere.
    - Trying mnemonic's method might work by disconnecting the ground from a cable on one end too.
    - I would next try to just connect directly to one speaker/monitor with the levels all the way down at first just to eliminate the interface and computer from the equation as the problem. If you haven't tried it as mentioned yet, try flipping the ground lift on your interface first too before moving on to this step.
    - Is it a really bad / loud hum? Amps usually have a really loud hum when turning them up loud and also being in close proximity to other gear too.
    - If you try the direct to monitor approach I suggested make sure everything is on the same
    outlet. Don't use any power strips either unless it's a pro rack unit like a Furman or something.
     
  19. efx1138

    efx1138 SS.org Regular

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    Well, I have actually isolated the issue to some degree since I have done the following.
    Shut down and unplugged the entire computer/audio interface rig so that nothing is connected. The only thing plugged into anything in the room (and I have done this test in several rooms as well) is the Suhr and the amp. With only the speaker cable connected between the two there is no squeal at all coming from the amp. The second I connect anything from the line outs of the Suhr the squeal comes from the actual amp itself. Of course, the sound isn't as loud as when it then gets amplified through the monitors but it's that line out connection that causes it to happen.

    I should also note that this happens when I plug it into the audio interface even if the actual interface is not plugged in at all (meaning not even the power cable is connected to it)

    Clipping the cable worked as far as the squeal going away but it introduced all the issues in my above post like the IR section not outputting and the DI level on the Suhr not reacting at all.
     
  20. c7spheres

    c7spheres GuitArtist

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    It unfortunately does sound like something wrong with the Suhr. Clipping that wire fixed the problem, but the other issues are a different problem than a ground issue it sounds like to me at least. If there is still some type of ground issue going on I still think there's something wrong with the Suhr.
     

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