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Unwanted Distrortion From Delay/reverb Effects With A Power Attenuator


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I am gigging now with the Line6 setup DT50/212 - POD HD500 - JTVs since more than one year now. And for me as Cover Rock Musician this rig works fine.

The Master Volume is set at 1 o clock as a standard level for all my presets (no low volume mode). And I am using the Pre Amp Models out of the POD HD500. At 1 o clock all my used amps sounds very good. Especially the Vintage amps like Marshall Plexi Lead 100, PARK-75 are shinning.But this volume level is heavily loud and just doesn't fit to the overall Band level.

As other users I therefore use a power attenuator (Rivera Rockcrusher) to adapt the overall volume level to the specific environment I am playing (rehearsal, club, hall). I had before a SPL reducer which which I was not very impressed on it. The original function of the Master Volume knob is somehow neutralized, because the amp models I am using are reacting pretty much differently sound wise depending on the Master Volume level I am using (12 o clock and above is the good to me).

My sound problem:
What I have realized is that when I am using Delay and/or Reverb effects in my signal chain (post amp) which is configured via the HD500, the sound gets destorted by these 2 effects once I am attenuating to a level of -16db and lower: the tone gets somehow crumbly and scraping (hard to describe for me).

EDIT: I am not 100% shure whether this post amp configuration via a POD HD (as described in Line6 manuals) is really POST AMP: this would mean, that all effects are placed AFTER the power section and BEFORE the speakers, so no distortion irritation will occur in the power section from time/mod-effects( my amps power section are all saturated by setting the DT50 Mastervolume = 1 o clock). Does anyone know, if I can 100% rely on that the line6 "post amp" is really a post amp effect setting in its real sense ?

But this is unfortunately the levels I need to reduce the volume to adapt to the overall band volume.

If I do not use these effects, the sound is pretty good at a level attenuation levels. This unormal distortions increases with the level of attenuation.

As I have tried to modify different parameters in the HD500 like GuitaIn-Z, etc. without a remarkable success, I am wondering if one of you have incountered such a sound behaviour and if anyone of you have some ideas what the root cause is respectively how this can be minimized.

Not shure, if I have described well enough, so you can pick it up from there.

Thanks for your support.

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Your problem is very specific and I don't know the reason, but here are some thoughts:

- i'm always using the DT25 reverb , not the pod reverb, you could try and see

- rather than tweaking GuitarZ , there is a pad switch  on the pod, designed to tame high output / active pickups , try it

- in the end try to lower the preamp volume , or use the mixer to go down a few db, though this might modify your tone a bit


Also after trying a few attenuators, never been convinced, I have bought a reignmaker eminence speaker that has technology to reduce spl by up to -8 dB , and it works great, no tone loss at all.

Only drawback is it didn't fit in my DT25 combo, I had to switch to head + cab stack

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Hi lef38,


thanks for your feedback. Some good thoughts to think about ...


- I will test the DT50-Reverb and look how it behaves. As I am using various presets (with/ without reverb) this might not be a permanent solution to me. But I will check how the sound is going to behave with the DT50-reverb compared to the POD HD.

- The PAD switch in the POD HD is not working using the VARIAX as far as I can see (which I do).

- My pre amp volume is already pretty low: most amps are at 45% (exceptions: JCM800 = 40%; BF Double = 95%). But experimenting could be in idea (will give a try).

What makes me thinking is the POD HD signal chain (see my EDIT-comment): if Time/Mod-Effects are NOT after the power section in the signal chain, then they may generate irritating coloration to the distortion sound coming from the pre amp and/or power section. And at the moment I am not shure whether the Line6 POD HD "POST AMP" signal chain is really POST amp. If not: then this would be very likely the reason.


As far as I am aware several multi effect units (like a POD HD) are not capable to really place effects after the power section and before the speakers.

The design of the POD HD and the DT50 may have this capability. Hope that someone can chime in for specifically that point.

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When you place effects after the amp block in the HD500, they come after what it essentially the preamp of the DT50. So it's not really not any different than how a serial effects loop in an amp works. It's generally not possible to put effects after a power section in an amp, well, because once the signal comes out of the power amp, it's much too hot to send through an effect unit.


I imagine what you're hearing has to do with how the attenuator itself is interacting with the power amp and the speaker. The more you attenuate a signal from a power amp, the more high end you lose. Since delay and reverb depend very much on the high end of the signal to sound the way you want them to sound, it could just be that the attenuator is sucking a lot of your tone.

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Hi phil_m, much appreciated your input.


I wasn't aware that the post amp setting of effects in a HD500 signal chain together with a DT50 (not any other amp) is not after the power section, but after the pre amp section.


What you have described makes now pretty much sense to what I have investigated in the meantime:


- Using the DT50-reverb instead of a HD500 reverb doesn't solve my sound problem.

- I can hear some noticeable reduction of what I consider as a negativ impact by reducing the Master Volume of the DT50 from 1 o clock to 11 o clock.


As long as I see a power attenuator as a must to drive run the DT50 I like, I cannot see that a different attenuator will help that much. I consider the Rockcrusher as pretty much high and end. Also my expercience with another attenuator I had before, speaks for that. May be someone else have similar experience and could solve it with a specific attenuator (greatly appreciated for any reliable tip).


So: as long as I do not see a realistic chance to solve my sound problem with a different attenuator, I will try to minimize me problem just by reducing the overall level of the power section saturation and to reduce as much as possible Reverb and or delay in my presets.


Finally I am just wondering why not any other user have chime in so far with a similar setup (there should be some out there having a DT50 with a power attenuator for good reasons).

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  • 2 weeks later...

I get lots of unpleasant distortion when I crank the attenuator way down, but it goes away at conversation level and above. I think it's mainly due to the speaker being non-linear at very low power levels. This effect could depend greatly on your speakers. I'm using a single 12, if you have a 4x12 you're going to be 12 dB louder when you get your speakers to that sweet spot. 


If you want effects after the power amp, you need an attenuator or load box with a line output to feed your effects, and then send the effects output to a second (preferably clean, solid state) power amp to drive the speakers. Or, something like the Bad Cat Unleash, which is essentially a load box and clean amp with a loop to insert effects between. You'll need to use a separate FX unit(s), I don't think there's any way to use blocks in the Pod for this... unless you were willing to forego L6 Link. Then, you could use a preamp model on the Pod, then the FX loop block, run the send into the DT's effect return, then run the line out of the attenuator into the Pod's return, then add your post-amp effects blocks, then send the Pod's output to the clean power amp.


Given how easy it is to hit the POD's DSP limit, it probably would make more sense to use an M9 or something similar for the post-amp effects, though.

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  • 2 months later...

Like to give an update how my story with a power attenuator has continued in the meantime ...



I have tried in the meantime to minimize all the negative aspects which have come along using a power attenuator sound wise:


I mainly tried not to use effects like Reverb. I have tried different power attenuators (high end). I have tried to lower the Master Volume on the DT50. This all doesn't helped really. After playing more than 1 1/2 years with a power attenuator, I have faced the fact that to my ears:


- Modulation effects

- delay

- reverb

- effects like Harmonizer


very negatively affect the overall tone when at lower levels (I don't talk about bedroom levels; I mean rehearsal volume level in a 5-heads Band).


Other effects like Dist / OD / Compressors do not so much negatively affect the overall tone.


It seems to me that mainly MOD-effects, Reverb and delay are changing the guitar signal in a too "extreme" way so a power attenuators (and may be the speaker interaction as well) can  not handle the signal properly.



2 weeks ago I have reached a point where I was so frustrated with my sound after a gig that I decided to restart from scratch.


I first played the DT50 an the HD500 without a power attenuator and I tell you what: I have forgotten how good it sounds without a power attenuator! This was the point where I started thinking of finding a constellation with my DR playing without a power attenuator.


I then measured the former volume level at rehearsal level with my power attenuator and with a good VU-meter. It ended up with 95 to 102 dBa with Master Volume at 1 o clock depending whether it was for Rhythm or Lead parts.


Next I have identified the lowest Master Volume level where I accept the overall tone for most of my amp models I am playing. This Master volume level is 2,5 (I think this is 8.30 in clock terms).
This is already pretty loud.


As a next step I did some tests to reduce the mixer level in the POD HD presets: I reached the point where a complete MUTING of channel 2 doesn't sound negative to my ears and this lowers the overall volume of course. (The mixer is the one I see less or no impact on sound coloration).


I then measured the overall volume level again with the VU-meter. And this brought me to a overall rehearsal volume level which is similar to the former one when using a power attenuator.


I also tested the LVM mode in the DT50:

at 11.30 clock level the LVM with PRE amp models (I do not want to maintain two type of presets: one with pre amp models and one with full amp models). All in all there is a noticeable tone deterioration, but still acceptable - especially in comparison with my former solution using a power attenuator with mod-effects, delays, etc.

This Master volume level brings even lower dBa-level of 89 - 99 dba.


In both options (standard mode and LVM) I feel the need to adapt parameters depending on the amps I am using. All the amp models where the power section of the DT50 has a significant contribution to the overall tone, needed to be adapted. These are in my case: Plexi Lead, Park-75. On those presets I have modified the Drive-parameter of DIST or OD-Pedals, or compressor parameters, or the Drive-parameter of the amp model itself.

I finally don't come to the overall conclusion that a power attenuator has generally too many negative tone impacts to use it and that this applies to everybody. Without ANY effects (or only with DIST/OD pedals) I completely see the benefit for me. However using MOD-effects, delays, reverb effects quite regularly it turns out, after a long learning curve, that this is not the right thing to do any more for me personally.


Any thoughts?






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Yeah, theres no way to get distortion from the power amp and then have pristine clean reverbs etc after that, with or without an attenuator. Unless you take the line out from your attenuator, run that through you're verb and delays, then send that to another power amp - not overly practical.

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Yeah, theres no way to get distortion from the power amp and then have pristine clean reverbs etc after that, with or without an attenuator. Unless you take the line out from your attenuator, run that through you're verb and delays, then send that to another power amp - not overly practical.

Not sure, whether you got my point ...


WITHOUT a power attenuator I am pretty okay now with the overall tone including effects like reverb, delay etc. This is going to be provided by the DT50 as any other tube amp using its serial effects loop.


And even on Clean presets with the BF DBL (pre amp models) where the power section stays pretty undestorted, the usage of the power attenuator with mod-, delay, reverb effects had generated remarkable negative tone coloration to my ears.


As my technical knowledge is limited I think it is not the power section which causes the tone problems to me. It is the power attenuator which somehow cuts the amplitudes generated by these type effects. And I don't talk about bedroom level. I talk about 95 - 100 dba volume levels.


The MUTING of channel 2 on the POD HD doesn't show negative tone coloration so far to me. In combination with a significant lower Master volume setting AND some parameter-adaptions on specific amps which needs a high Master volume setting to get their power section saturated (to compensate unsaturated power section where needed), I consider the overall tone superior to the former one.



Again: not contra to power attenuators in general. They can help to adapt to the overall volume level you need/want to play. But to me the ones I have used (Rivera Rockcrusher, SPL Reducer) seems to have problems with the type of effects I have mentioned. I consider these ones as high end products.

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