Community: Message List - HD500 FX Loop ... level drop or not?

Re: HD500 FX Loop ... level drop or not?

support@line6.com — Thu, 03 Jan 2013 01:07:03 GMT

I came to very similar results and found a solution for this problem

see my thread here (in particular point 2):

http://line6.com/support/thread/90441

bye

Lore

Re: HD500 FX Loop ... level drop or not?

support@line6.com — Sun, 25 Nov 2012 10:02:15 GMT

Done with this disaster of time and money, I am out so much money on this thing. $500 HD 500, $130 Mission expression pedal, $200 high ohm headphones. Oh how I wish I would have dropped all that on more pedals and just stayed with my board.

There is a level drop on the main out as well. If you boost to compensate the noise floor hiss gets terrible, unuseable for me, obviously they know this and obviously they hope no one tries to use external better effects and stays w the 4CM amp hook up. With the 4CM you just compensate the amp level, same with recording you do not notice anything. Try to drive an external pedal from the loop or the main out and it does not work.

I gave up on the loop and redid a bunch of my board pedals. Since I have a great amp I do not need amp models with it. I wanted to try just using a wah matrix and a few filters front of my chain and run the POD into my line of drives and gains I use. The level at master on full and mixer at "unity" zero, panned to center, is at least 6db off and cannot drive a pedal correctly. I hooked up my chain straight to the amp and hit my Wampler Pinnacle and my god I think I heard it for the first time. The Pod was seriously killing my tone and I was compensating using clean boost. I had been using "guitar" and "aux" with no input on the aux as this is less noisy. Why is that, because using "same" increases the level and more level equals more hiss. It stares you in the face at what is going on here. More level more noise.

Both the effects loop and main outs are NOT unity, somewhere like 6db off. Line 6 is hoping most users do not progress past the 4Cm and internal effects useage. That is why they never respond to requested minor fixes expecially on the effects side of things. They do not care and no doubt believe most guitar players have a house plant IQ and will not notice the real problems. They are simply hiding the noise floor digital hiss of this unit by rolling off the levels and hoping no one ever actually tests it.

I'm done. Back to my pedal board. I just wanted to use some wahs I cannot be guessing at what is unity level, I need unity to be what the unit claims it is. It is NOT.

Re: HD500 FX Loop ... level drop or not?

support@line6.com — Tue, 13 Nov 2012 23:16:14 GMT

A small update with some interresting measurements via USB (adding more to the puzzle):

The experiment did not work. I could not make Studio EQ to really clip as far as I can tell. It causes gradually increasing distortion/compression if its output gets above -6dB or so. Mixer will reduce or up output level as expected and dialed in no matter what the Studio EQ was set at. The mixer's dialed in values seem to exactly match measurements.
Mixer with channel A and B panned hard left and right will produce 6dB less gain than with a setup where both channels are set to center. I checked that this is the mixer's doing by recording a small sample with the looper in pre position to check output and then moved the looper to post position (by passing the mixer) and checked again. I had no effects and no amp configured, i.e., only the mixer is measured.

Started to measure the Studio EQ's real gain knob setting to output level function to find what's going on with the compression/distortion. It can easily get up to 2dB off what you'd expect despite having 0.1 dB steps on the dial. The only real good match is around 0 and +/-18dB. But watch on the +dB side. It seems that everying resulting in an output signal larger than -6dB gets compressed and sounds distorted as if clipping. But the latter may not really what happens because the output level is far from 0dB. Will keep checking till I have some solid data to post.

Would be still interested how Karl set the mixer and the effects loop line/effect switch in his external effects loop test.

Martin

Re: HD500 FX Loop ... level drop or not?

support@line6.com — Tue, 06 Nov 2012 19:58:22 GMT

MartinDorr escribió:

The simplest explanation I could come up with was that
The Input 2 setting of Same causes a -4dB change in the HD internal signal level sent out of the effects loop
The Input 2 setting of None (Variax, Mic, Aux not connected) case a change of -10dB for the above (at least when you come in via Guitar as Input 1).
The Mixer adds +5.7dB even when set at 0dB (at least for the no Amp use case).
The effects loop in or out of the path causes a level change of 0.15dB (I found the same effect with the Studio EQ)
This seems to be the simplest explanation, but that does not make it necessarily right.

I have no time to check anything for a while but thought of doing a little experiment using a Studio EQ in front of the Mixer with gain +4 or +10dB to make up for the suspected drop on the input. If the 0dB Mixer setting really causes +6dB gain on the mixer (or if the input did not get lowered and the Studio EQ gain will exceed 0dB) we should see clipping on the output (or more than 0dB output). Now if the Studio EQ caused the clipping we should see the output to come down -6dB if we pull the mixer down -6dB. On the other hand if the mixer caused the clipping (because it really added 6dB gain on the 0 setting) we should see the output not come down (or not below 0) if we pull the mixer down -6dB because the Studio EQ will drive 0dB to the mixer.

I can't do Karl's experiment setup due to lack of equipment. But I can come in with a Variax on the digital input and check output via USB. From the past I already know that for a specific guitar model I will have -10.7dB out with a pre Mixer Studio EQ and a post Mixer Studio EQ, no amp and mixer set at 0dB. Hope that works out and we can determine whether the 0dB mixer setting is really something else ... or we have more puzzles .

The test you proposed is very interesting. Mainly, due to the fact that the output level through USB is not affected by the master volume knob, as opposed to the 1/4" outputs. That is why it should not be very important the "number" measured at the 1/4" output in Karl's experiments (as it should be affected by the master volume position). But what I have found to be very interesting in Karl and Jimsreynolds experiments is the "tendency".

In fact, I have a question: the stomp level is an instrument level (i. e. -10 dB) and line level is +4 dB for the FX loop send? If so, it will explain the FX loop behaviour we have found here.

Best Regards,

Daf

Re: HD500 FX Loop ... level drop or not?

support@line6.com — Tue, 06 Nov 2012 18:05:57 GMT

I was told there would be none...

Re: HD500 FX Loop ... level drop or not?

support@line6.com — Tue, 06 Nov 2012 18:00:34 GMT

Thanks for that, Phil. I never was good with the maths.

Re: HD500 FX Loop ... level drop or not?

support@line6.com — Tue, 06 Nov 2012 17:30:33 GMT

If the latency introduced by the effects loop block is 40 samples, that works out to be less than 1 ms according to my math. Something doesn't add up here. Another way to look at it - if the sample rate is 48kHz, that means there's 48 samples every millisecond. So 40 samples is less than a millisecond. Even if the sampling rate is 44.1kHz, it would be less than a ms.

Re: HD500 FX Loop ... level drop or not?

support@line6.com — Tue, 06 Nov 2012 17:09:27 GMT

meambobbo wrote:

my tests show the FX Loop created a 40 sample or ~42 ms latency in whatever channel it was placed in.

That sounds awfully high.

Thinking about latency in terms that we can quantify: Latency via distance from an amplifier:

Speed of sound in air at roughly 72F = 1131.29 ft/s

If I'm 10 feet from my amp, that translates to 8.8 ms latency. Negligible, probably not able to feel that. Typical use case, right?

What you're saying is that the latency of the effects loop is the equivalent of me being 47.5 feet from my amp??? That's definitely audible, and annoying I might add. You couldn't play that way. And I definitely play using the effects loop 100% wet, so something seems a little off about that result.

Re: HD500 FX Loop ... level drop or not?

support@line6.com — Tue, 06 Nov 2012 16:55:07 GMT

meambobbo escribió:

my tests show the FX Loop created a 40 sample or ~42 ms latency in whatever channel it was placed in.

it's important to note that two audio signals can be out-of-sync, whereas two specific frequencies can be out-of-phase. When two identical, or near identical, signals are out-of-sync, some frequencies will be in phase, while most will be out-of-phase, to varying degrees.

and I have also noticed there is a difference in the way the loop works when before an amp model vs. behind one. I find it adds much more noise in "pre" than "post" regardless of the levels fed into it.

Hi MeamBobbo, thank you very much for your clarification. As you have pointed out, the proper term in this case should be "sycn" rather than "phase", as we have a group of waves rather than a single one. In fact, what you have described is the explanation of the "comb filtering" effect. Anyway, what I said should still apply, because when input 2 is set to "same", you have exactly the same group of waves going for the two inputs in the performed experiment.

I have to say that I am not an audio engineer and I am not familiarized with the "sample rate" concept for example (but I would like to!!! ), everything that I said is based on physics, so I might be missing something. I would expect always some degree of latency unless we have unlimited power processing capabilities. Of course, my words are not God's words, and I could be wrong!!!!

Best Regards,

Daf

Re: HD500 FX Loop ... level drop or not?

support@line6.com — Tue, 06 Nov 2012 14:50:32 GMT

The simplest explanation I could come up with was that

The Input 2 setting of Same causes a -4dB change in the HD internal signal level sent out of the effects loop
The Input 2 setting of None (Variax, Mic, Aux not connected) case a change of -10dB for the above (at least when you come in via Guitar as Input 1).
The Mixer adds +5.7dB even when set at 0dB (at least for the no Amp use case).
The effects loop in or out of the path causes a level change of 0.15dB (I found the same effect with the Studio EQ)

This seems to be the simplest explanation, but that does not make it necessarily right.

I have no time to check anything for a while but thought of doing a little experiment using a Studio EQ in front of the Mixer with gain +4 or +10dB to make up for the suspected drop on the input. If the 0dB Mixer setting really causes +6dB gain on the mixer (or if the input did not get lowered and the Studio EQ gain will exceed 0dB) we should see clipping on the output (or more than 0dB output). Now if the Studio EQ caused the clipping we should see the output to come down -6dB if we pull the mixer down -6dB. On the other hand if the mixer caused the clipping (because it really added 6dB gain on the 0 setting) we should see the output not come down (or not below 0) if we pull the mixer down -6dB because the Studio EQ will drive 0dB to the mixer.

I can't do Karl's experiment setup due to lack of equipment. But I can come in with a Variax on the digital input and check output via USB. From the past I already know that for a specific guitar model I will have -10.7dB out with a pre Mixer Studio EQ and a post Mixer Studio EQ, no amp and mixer set at 0dB. Hope that works out and we can determine whether the 0dB mixer setting is really something else ... or we have more puzzles .