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HD500/Blackstar AMP 4CM Hiss
by deadleafhotel on 2012-04-21 17:48:21

I've seen a few discussions here, but I don't think any of them address my particular issue: 

When setting my amp and hd500 up using the 4 cable method, I'm getting a lot of hiss (mostly noticeable when using the high gain channel.)  I've tried using the guide here as soon as I set the fx loop switch to "stomp," the problem gets a lot worse.  Also, setting my amp's fx loop switch to -10db as opposed to +4, quiets the signal (I thought the opposite should happen) and brings the signal closer to the noise floor.  Currently, I have the fx switch on the HD500 at "line," and the switch on my amp set to +4db.

Three of the four cables that I'm using are fairly high quality gold-plated cables.  I'm not sure if the mismatched cables would cause any noise...

The other thing I noticed, is that if I introduce a noise gate after the fx loop, the noise goes away completely.  This suggests to me that it isn't a ground loop (please correct me if I'm wrong,) and is more likely a cabling or some kind of mismatch between the fx loop of the HD500 and the circuitry on my HT-60.

Any suggestions or help would be greatly appreciated.

Re: HD500/Blackstar AMP 4CM Hiss
by Line6Don on 2012-06-07 17:42:13

If you still have questions, please know that Line 6 is no longer supplying support via the forums. Instead, you can create a direct support ticket at:

Re: HD500/Blackstar AMP 4CM Hiss
by jimsreynolds on 2012-06-08 01:46:03

Which model of Blackstar are you using?

I put that 4CM guide together.  The reason I use -10dBV throughout the setup is because

if you use the 'line' (+4dBu) setting on the HDs FX Loop level switch:  you are sending a 'hot' input to the amp's input.  This whacks up the input level and can cause noise and unwanted distortion.

From what you describe:  it doesn't really sound like ground loop noise.  All true high gain amps hiss a bit to some degree or other, once you crank up the gain, but it should not be excessively loud.  On the ultra-high gain 'red' modes for my Marshall JVM I use a hard gate directly after the FX Loop block to trim off the high gain hiss.   When setup right it is very effective and not too intrusive..

I think your problem may relate to the levels set within the preset.   Manual troubleshooting may be needed.

Testing the Preamp gain levels

First off, unplug everything and turn the amp loop off.  Now plug a guitar into the front of your amp, select the clean channel and play it hard.  Adjust the gain so that the amp just starts to distort a little when you are plaing hard.Now turn the gain back to just below this level.

Now hook up the first two cables in the 4CM .  Setup for -10dB on the HD FX Level switch  Create a blank patch for troubleshooting, containing nothing but an FX Loop and the studio EQ that corrects for the loop level drop, setup as per my guide.   Again, the amp loop should stay off.

Play hard, again. Is it distorting?  Right, if it is then you have too much gain somewhere on the input stage and you need to back if off until you are clean again.  Suggestions:

  • Use the input pad switch to cool off the input, if you have very hot pickups
  • Try setting Inputs as Input 1 = Guitar, Input 2 = Variax.  This can cool off levers at the Pod's input.
  • Mess with gain level on the Studio EQ

Testing the Power amp levels

Once you are happy that your Input is playing nice:  you can do something similar for your power amp.

Plug in the other two cables for your 4CM and set the 1/4" output switch on the HD to 'Amp'.  Turn the Pod master to full.

Stay on your clean channel.  Turn off the Amp loop initially. 

Turn on the Pod Looper and set it to work in the 'Pre' mode.  Record some hard strumming and set the loop to run.

Now try toggling the amp loop on and off.  The volume level should be the same in either position.  If it is not, adjust the Mixer level in the patch until it is (assumes the mixer is at the end of the chain.

OK., now with all of this done. Change to your high gain channel on the Blackstar.   Now in principle, your levels should all be balanced off and what you are hearing is probably as good as it gets.  if you still have lots of hiss then you may need to use the gate.  If you want to explore the ground loop possibility then try a Behringer HD400 or Ebtech hum eliminator in the loop.

Re: HD500/Blackstar AMP 4CM Hiss
by Delrevo on 2012-06-23 13:08:51

The blackstar amp's hiss is natural in OD2 channel (HT Stage 60). Pretty annoying. I love the natural driven channel from OD2, but there is a lot of hiss. I am using a Boss NS2 noise suppressor. Using a 5th cable (or Patch cable as Im using), plug the patch cable from the Live Out to the input of the NS2. The Output of the NS2 goes to the amp's fx-return. Settings for the NS2 are: Mode: Reduction, Threshold: 60% and Decay about 25%. Hi volumes in between songs or pauses in solos are now bearable.

Re: HD500/Blackstar AMP 4CM Hiss
by jimsreynolds on 2012-06-24 01:08:58

Out of interest have you tried the NS2 in the middle of Cable 3 - between the Amp FX Send and the Pod FX Return?   That may be better because you are gating the noise directly after it comes out of the power amp but before it hi's the 'post' effects.  Therefore the gate is not fighting with those and it might be easier to set the threshold.

I use the hard gate from the POD directly after the 'FX Loop' block as this achieves the same thing.

Re: HD500/Blackstar AMP 4CM Hiss
by Delrevo on 2012-09-21 09:52:25

Been a while Jim since I have seen this, but yes, Coming from the fx send works as well. Everything works great with the exception of punching in on solos. At higher volume levels the boost function doesnt work too well in this sceanario, since the compressor boost function is set to go through the front of the amp. Wish you could move it within the fx loop grouping

Re: HD500/Blackstar AMP 4CM Hiss
by stumblinman on 2012-09-21 17:23:22

I had a Blackstar Club 40 before I got my DT25 for my HD500, and what I did was go guitar->NS2 in->NS2 Loop Out->Pod HD500 guitar in->Pod FX Send->Amp Input->Amp FX Send->Pod FX Return->Pod Output-> NS2 Loop Return->NS2 output->Amp FX Loop return.  It adds a few extra cables, but eliminates all the buzz, because the NS2 is designed to use it's built in loop to isolate the guitar signal from all the excess noise, and shut the gate when the actual guitar strings aren't making noise.  That's the proper way to use the NS2 if you want to get every bit of noise out.  If you do this, your hum/hiss will disappear completely.  Like I said, it's a few extra cables, but I never regretted running it this way.  Good luck!

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