Pre/Post high pitch noises in Fx loop

[Skeith00]

Hi,

I bought an H9 max which I’d like to love, but there is one big problem, that can be seen only at “drummer volume”.

Using it alone in the Input and alone in the Fx loop (at least in mono only with IN1-OUT1, not using stereo) works flawlessly in any setting or combination. The used amp are a Koch twintone II and a Koch Multitone II, which, imo, have the best quieter fx loop I’ve ever heard, which can be chosen as serial or parallel with a level control.

Due to the fact that I’d like to use the H9 as a Wah and as a Delay, I set it with the pre/post option, using the amp’s distortion. Notice that it couldn’t be a hardware issue regarding cables/tubes/amp/guitar/power supply. It’s all perfect and I’ve tried every efficient combination of hardware and setting (different cables, different amps, different guitars with lace sensor noiseless pickups, different isolated power supply; gain input settings and gain output settings on H9 or any combination of Killdry on/off,Bypass options, …) and I updated it 2 weeks ago.

So: H9PRE(Wah)—>Amp input with distortion; H9POST (DigitalDelay). This is done by setting the Killdry is set ON, Relay set true bypass (with dsp noises get worse) and using the Fxloop in Parallel with volume on unity (but the same applies with the Fx loop in serires without the killdry)

Well, while the amp is in the clean channel I only notice that the sounds got worse, the volumes and equalizations are different and I have to set again every parameter and volume, which is annoying, mostly on the delay (e.g. the first preset of digital delay in the h9 control app) and, in general, on the Post algorhitm in the Fx loop.  But that’s not a big problem, I can work around it modifying the preset and saving it.

The big problems arises when I activate the distortion of the amp. The delay make an high pitch uncontrollable whistle/Feedback, and the quality is bad: totally not usable. Using other algorithms may be quieter, but there’s a noticeable drop on quality, clarity, volume…something isn’t working correctly.

Oh, I’ve tried a ground loop killer too,  which didn’t improve nothing.

Furthermore the Sculpt/Crushstation can’t be used in the Fx loop, but I think they still aren’t much usable live for guitar…so not a big deal. 

Hoping for your help, I’d like to keep the H9 and don’t send it back to the shop.

Regards,

Fabio

 

[baron58]

And you have it set up correctly as shown here. https://www.eventideaudio.com/support/downloads/setting-prepost-routing-options-h9

Also for everyone else, the H9 is designed for -10dB input levels. Which is guitar levels. Most amps especially tube amps are +4 to +6 dB and will overload the H9 input. Now if the loop has adjustable gain. Settings you are good to go.

[Skeith00]

baron58 wrote:

And you have it set up correctly as shown here. https://www.eventideaudio.com/support/downloads/setting-prepost-routing-options-h9 Also for everyone else, the H9 is designed for -10dB input levels. Which is guitar levels. Most amps especially tube amps are +4 to +6 dB and will overload the H9 input. Now if the loop has adjustable gain. Settings you are good to go.

Thanks, but I’ve already read it 10 times.

I know the line level issue, but Koch designed their amp for -10dB input so that it could handle guitar pedals. Yes, they’re smart 🙂

I repeat that without using the pre/post function, the h9 alone in the fx loop works perfectly.

[nickrose]

I'm afraid I don't really understand your description, but:

1) Mr baron58 is correct on the H9 levels – some effect loops are too hot and will overdrive it. The H9 is designed to be used at guitar level.

2) If you (as you imply) are using a parallel effect loop, you should usually have KILLDRY on to avoid the sort of feedback you describe. But, this will cause problems if you have more that one pedal in the loop. No solution to this – it is the nature of parallel loops.

 

[Skeith00]

nickrose wrote:

I’m afraid I don’t really understand your description, but:

1) Mr baron58 is correct on the H9 levels – some effect loops are too hot and will overdrive it. The H9 is designed to be used at guitar level.

2) If you (as you imply) are using a parallel effect loop, you should usually have KILLDRY on to avoid the sort of feedback you describe. But, this will cause problems if you have more that one pedal in the loop. No solution to this – it is the nature of parallel loops.

1) I’ve already answered to baron58 🙂

2) Let’s put it like this: The H9 is set in Pre/Post and it’s the only pedal in all the chain. My signal is: guitar— h9(in1-out1)—amp input; Amp Fxloop–h9(in2-out2)–Amp Fxloop. Now: I want to use the amp distortion and use the digital delay on amp’s distorted signal in Fx loop, thus I need the delay set in Post in the fx loop. Sometimes I want to use the Sculpt alogirthm, which goes in Pre in the input of the amp. The problem is that when I use the delay on the distortion of the amp I get the noises. 

This happens even if I set the fx loop in serial  (So without a line control) with the killdry OFF, and even if I set the fx loop as parallel with the killdry ON, as it should be to avoid feedbacks. 

 

[nickrose]

I regret that I am not going to be able to diagnose your problem without being there, especially as you seem to know what you are doing. My guess is that it is one of the following:

1) Something at your end, probably cabling or ground related, or maybe a peculiarity of your amp. This is most likely, as the nature of PRE/POST is that if almost anything goes wrong, you get mains hum or feedback.

2) A hardware problem in the unit. I've not heard of anything that will do as you describe, but there is always a first. If you think that this is the case you should send it in for service ( support@eventide.com or your dealer ).

3) It could be a software problem, but none of the many many people using this feature have reported it.

 

[Skeith00]

nickrose wrote:

I regret that I am not going to be able to diagnose your problem without being there, especially as you seem to know what you are doing. My guess is that it is one of the following:

1) Something at your end, probably cabling or ground related, or maybe a peculiarity of your amp. This is most likely, as the nature of PRE/POST is that if almost anything goes wrong, you get mains hum or feedback.

2) A hardware problem in the unit. I’ve not heard of anything that will do as you describe, but there is always a first. If you think that this is the case you should send it in for service ( support@eventide.com or your dealer ).

3) It could be a software problem, but none of the many many people using this feature have reported it.

I’ll give you more infos: 

 I tried to use the pre/post without the FX loop of the amp. It means something like: guitar-H9Pre-effect pedals-H9Post–Amp input … and it works great (using Hi gain distortion pedal too!). 

Next thing that I’ll do is going to a friend of mine and try with another amp with different Fx loop.

By the way, I’ve noticed a peculiarity on the feedback/hum that I hear: in the Fx loop set on Post, the bad sounding delays (or any other fx) got a metallic “flanger” sound… it’s like a faulty EHX Electric Mistress attached to it. 

I’ll post here what Koch writes on the Fx loop: 

” A good Effects Loop has to include an electronic circuit that:

1)     brings the high signal level of the tube amp back to the low signal level of the effects unit which goes to the Send input on         the amplifier

 

2)     brings the low signal level of the Return jack back to the high signal level of the tube amp

 

3)     matches the impedances of the tube amp to those of the effects unit.

 

4)     does not affect the sound of the amp (!!!)

….. All our Effect Loops operate on a signal level of -10dBV which perfectly matches the signal level of all battery operated effects units. I always use a “buffer” circuit to drive the Send output. This buffer circuit brings the high impedance of the tube amp down to a very low output impedance. Therefore, our Send outputs will drive any effects unit on the market with minimum signal loss due to cable influences. “

 

So…since the problem appears only in the Fx loop I think the problem lies in some ground problems…uff. If, on the other hand, the problem is hardware but it appears only when I use the H9 both in input and Fxloop,  the problem must lie in something that checks the signal level and changes some parameters…e.g. :from the link I read:”Warning: Set up your H9 for Pre/Post routing mode (“Changing routing modes” below) before making cable connections. Otherwise you risk feedback or clipping of your signal.”

…does the pedal adapt to the tension like it does for the expression pedal?

and 

“Note:  When hooking up your gear in this manner, you may encounter a ground loop which could introduce a low frequency hum in your signal. This is not a fault of the H9 or your other gear, it is a grounding issue. Please see the EventideAudio.com website for a discussion and tips on ground loops.”

What do you mean for low frequency? a 60Hz hum? Because the noise I hear is surely over thousands Hz…

I hope now you can tell me something more!

 

[nickrose]

I'm hoping that trying a different amp will tell you something. In the meantime, it would be good to double-check your cables.

 

[Skeith00]

I made another chek with cables and power supplies, nothing has changed, but at least I understood part of the noise problem.  Using the loop fx in serial brings noise due too feedbacks (and we know it), but in parallel, since the volumes are differents I have to blend the signal and, boosting the wet signal in parallel, there’s an evident flanging metallic sound coming, filled with high frequencies. This metallic sound, with the high gain of the amp, turns into my hated high pitch feedback. 

Now I have to understand if is a peculiarity of the amp, or of the pedal. Waiting to test on another amp then, since my amps have an identical fx loop.

In the meantime, thanks for the help, I’ll update you.

[nickrose]

The flanging sound probably means that somehow you are mixing the dry output with the input. Don't know how, but it is pretty recognizeable.

 

.

[Skeith00]

nickrose wrote:

The flanging sound probably means that somehow you are mixing the dry output with the input. Don’t know how, but it is pretty recognizeable.

.

Ehm, can you explain me this thing better? If it’s pretty recognizeable maybe I can solve it..

[nickrose]

nickrose wrote:

The flanging sound probably means that somehow you are mixing the dry output with the input. Don't know how, but it is pretty recognizeable.

.

Skeith00 wrote:

Ehm, can you explain me this thing better? If it's pretty recognizeable maybe I can solve it..

Not sure that I can, but I'll try. In Pre/Post, one output channel carries the effect, the other carries a dry signal (unless KILLDRY). This signal will be delayed about a millisecond from its input (due to A/D and D/A transition times).

If this delayed "dry" signal is mixed with either input, you will get a "comb-filtered" sound, much like a flanger (this is how a flanger works). You can tell whether it is the effect input or the through input by seeing whether it has the effect on it. If you mix it with the through input you may get some feedback, as you describe.

Now over to you to see how they are getting mixed.

 

 

[Skeith00]

nickrose wrote:

Not sure that I can, but I’ll try. In Pre/Post, one output channel carries the effect, the other carries a dry signal (unless KILLDRY). This signal will be delayed about a millisecond from its input (due to A/D and D/A transition times).

If this delayed “dry” signal is mixed with either input, you will get a “comb-filtered” sound, much like a flanger (this is how a flanger works). You can tell whether it is the effect input or the through input by seeing whether it has the effect on it. If you mix it with the through input you may get some feedback, as you describe.

Now over to you to see how they are getting mixed.

Thanks, now I understand. Well, we found the problem finally!

So: first of all the pedal must be in Relay bypass. The Dsp buffer keeps the flanging always on.

 

Then: if I use the h9 in Pre with the parallel FXloop turned off the flanging disappears (and the feedback noise with it 🙂 ), while if I keep the parallel fx loop active the dry signal from output 2 goes into the fxloop and gives the flanging sound, as you mentioned. So I need to keep always the killdry On…

This way I have 2 solutions,which I don’t like.

1) turn the fx loop on only when I use the h9 in Post with the killdry activated (but it’s boring and I need tap dancing )

2) keep the killdry On when using any algorithm in Pre ( so Bye Bye blending wet and dry for any fx in the Input of the amp) and some algorithms sound strange..

Honestly I don’t like any of these 2 possibilities…

If you could make an option to set the killdry off/on  for any of the 2 IN/OUT I think the problem could be solved!

Uh, and a “master Pre/post” for any kind of fx could be useful… buy I already read this request from another user!

[Author]

Posts