Community: Message List - What every POD HD 500 owner REALLY needs to know!

Re: What every POD HD 500 owner REALLY needs to know!

support@line6.com — Wed, 06 Mar 2013 23:24:46 GMT

You are welcome. Just keep in mind this is a very crude approach :-).

Re: What every POD HD 500 owner REALLY needs to know!

support@line6.com — Wed, 06 Mar 2013 14:13:18 GMT

wow!

thanks man,

I saved a text file with your steps to measure impedance, I'm shure it will be helpful to me sometimes

but for now I'm done testing with the pod... now I'm playing it!

thanks again

Lore

Re: What every POD HD 500 owner REALLY needs to know!

support@line6.com — Wed, 06 Mar 2013 14:12:23 GMT

drewfx wrote:

that is what the labelling implies. Bit naughty of them to label it up like that if they're not switching the impedance though - imho.

I think it's definitely not mislabeled and these are the manuals descriptions of the fx loop switch:

"Use the LINE-STOMP switch on the back of POD HD500 to choose between levels for Rack FX versus Pedals"

p. 5.4 of the advanced guide (v.2.10 rev A)

"Set the FX LOOP LEVEL switch to LINE to operate at higher peak-to-peak voltage, making it optimal for line level devices. The loop can also be used with stomp boxes by setting the FX LOOP LEVEL switch to STOMP."

p. 0.7 of the quick guide (rev D)

drewfx wrote:
Do you have the tube comp as the first effect in the chain, or as the first effect after the FX-Loop?

being the send that loses 5dB, the comp is the last block before the send,

but if you are testing the input-to-send route against a true-bypassed signal it should be the ONLY block between input and send,

that's the setup I had in mind:

Re: What every POD HD 500 owner REALLY needs to know!

support@line6.com — Wed, 06 Mar 2013 13:13:12 GMT

perapera wrote:

I really don't know if the impedance is changing with the switches, but I think you don't know either: we are just guessing here.

So my guess is: "No, it's just a -12dB pad on the amp or stomp position of the switches", and that's why:

Lore,

If you want to determine the output impedance, here's an easy way to get a ballpark:

- Run a 1Khz. tone through the unit and get a usable level at the output you wish to test. Make sure it isn't clipping.

- Measure the level at the output using an AC voltmeter or sound card + software that is known to have a reasonably high input impedance.

- Note the voltage or dB level at the output.

- Connect a 100k pot to the output, with the low side of the pot connected to ground and the wiper to the hot lead.

- Leave the meter connected. Start with the pot all the way "up" (wiper away from ground) and slowly turn it down to decrease the load impedance.

- When the meter indicates 1/2 the original voltage - or -6 dB - relative to where you started, disconnect the pot and measure between the low pin and the wiper with a multi-meter on ohms range. Make sure the output doesn't start clipping from the decreased load. If it does, start over with a lower initial level.

The value of the pot at the point where level falls 6dB (or 1/2 voltage) will be roughly equivalent to the source impedance of the output at 1Khz. (yes, it does vary somewhat with frequency). For a typical op-amp output, the source impedance is likely to be very low. Audio ICs are generally designed to run into non-terminating or "bridging" loads that are much greater than their actual internal impedance.

One common way to implement things like a "stomp/line" switch is to have it change the negative feedback around the final audio stage that drives the output. On "stomp", it increases the feedback to reduce the gain of the amp and bring nominal level down to a point that floor pedals are happy with. You can accomplish the level reduction by putting a pad in front of the output stage, but by leaving the gain "high" you run the risk of introducing noise.

Re: What every POD HD 500 owner REALLY needs to know!

support@line6.com — Wed, 06 Mar 2013 13:04:47 GMT

Yeah man, I don't know if it does switch the impedances. I naively assumed it would though, since that is what the labelling implies. Bit naughty of them to label it up like that if they're not switching the impedance though - imho.

Do you have the tube comp as the first effect in the chain, or as the first effect after the FX-Loop?

I may just pick one up and see how it sounds with my JVM410JS - which has a fully serial loop, versus the regular JVM's paralell loop.

Re: What every POD HD 500 owner REALLY needs to know!

support@line6.com — Wed, 06 Mar 2013 10:44:18 GMT

Hi there Drew

yeah I know... I always write the message on a text editor and then copy it to the form...

I really don't know if the impedance is changing with the switches, but I think you don't know either: we are just guessing here.

So my guess is: "No, it's just a -12dB pad on the amp or stomp position of the switches", and that's why:

1) if line 6 spent time and money to design and create two impedance changing circuits they would have advertize it IN CAPITALS just like they did vith the pod input impedance switching system

2) in the 4CM the output of the pod is going to the amp return (or power amp in) wich is a LOW impedance input, so the pod output being hi-z would be a problem actually

3) impedance, in the guitar-to-amp connection, is something that makes the pickups interact with the input circuit in a dynamic and frequency dependant way

so if you put A/D and D/A converters between them it's all lost anyway

the guitar is going to interact only with the pod's input circuit, so converting the D/A output to Hi-Z at the send or output jack wouldn't make sense

(example: ALL Boss pedals have LOW impedance outputs)

---

I'm sorry for you bad story with the pod hd,

if you decide to try it again, and you want to test the input-to-send route bypassing it with a true bypass box, don't forget you have to put in a tube comp (thr 100, level 17) fx block if you want at least the level to be equal to the bypassed signal

[note: I didn't like the Studio Eq in this role, firstly because its gain pot is labeled in dB's but the values are wrong (I found that to have a real 5dB boost you need to see "7,4dB" on that pot), but mainly because, because of its design, it's clipping the signal so you loose peaks; the tube comp is clipping too but in a way that, with my preamp, works better]

I tested the pod for MONTHS before implementing it in my (rather complex) pedalboard

and in the end I went for it for the functionality and not for the sound quality... let me clarify:

the point is that the ability to build infinite strange effects of HIGH QUALITY and to switch easily between them overtakes the fact that I'm loosing something in some of the sounds I use

example: a proco rat into a cranked marshall dosen't sound like the modeled versions in the pod even if I use the same marshall power amp and speakers after the pod

but try to go from there to a complete clean sound and then to a synth sound with 4 delays...

I hope line 6 will create a pod HD1000 with better hardware (input stage, converters, switches,...) and more CPU power, I would pay 1000€ for it, but untill then I'll live with the pod hd 500 flaws

that's my experience

bye

Lore

Re: What every POD HD 500 owner REALLY needs to know!

support@line6.com — Wed, 09 Jan 2013 17:51:33 GMT

Hi guys

Last night I found the time to test again the fx loop for the hiss topic that jimsreynolds pointed out (thanks jim!) :-)

...well, he is right !

I'm not going to report all the tests, just some conclusions:

first of all: keep in mind that, if you use the 4-cable method (http://line6.com/support/docs/DOC-2522) to connect to an external preamp you have to be very careful in your choice of settings on the pod or you can get more noise or less gain or even more gain than what should be.

the conclusions of my tests are:

1) the pod itself is adding some noise (e.g. gtr > pod > amp has more noise and hiss that the true-bypassed signal)

2) the 4 cable method adds even more noise because it passes thru the pod 2 times

3) as I said, the fx loop send with the switch on "stomp" does attenuate by -5dB and gives you A LOT LESS gain at your preamp, than if you connected the guitar directly to your preamp (and this is UNACCEPTABLE);

then the level is compensated at the return by a +4dB boost.

4) then comes the "solution" I offered in my original post:

if you use the fx loop with these settings:

switch on "line", send: -7 , return: +8 (these values could be precise only on my Pod HD 500 machine, but the order of magnitude is this)

you get the right gain and level (unity gain)

BUT you get more hiss than what it should be

(getting more gain gives more noise of course, but this is even more)

I tried the stomp and line positions of the fx loop switch, compensating in various ways to their boost/attenuation and the stomp has a little more hum while the line has clearly more hiss

5) I tried a similar solution to the one offered by Jim here http://line6.com/support/docs/DOC-2522 at point 4 of the "Patch Setup - Effects Only"section

[note that the studio eq gain pot is labeled in dB's but the values are wrong (I found that to have a real 6dB boost you need to see "8dB" on that pot)]

anyway I used these settings:

- fx loop switch on "stomp", send: 0dB and return: 0dB

- a tube comp (settings 100% , 17%) giving +5dB before the fx loop

- a fixed volume pedal (at 78%) attenuating by -4dB after the fx loop

I'll call this the "minus two fx-blocks solution", even if it's not an idea of mine, because it's easier to recall

that gave me the correct gain and level (unity gain) but with a lot less hiss than my "line, send: -7 , return: +8" or "line attenuated" solution

of course it's (at least) ridiculous to loose two fx blocks to compensate for a hardware design fault

(I don't think the -5dB send level loss is a fault in my specific unit because many people have found the same problem and because also the output jack switch on "amp" is loosing, oddly enough, -5dB with the master at full)

and of course, depending on your fx-chain into the pod you could:

- use the mixer as a boost OR cut and loose only one fx block

- use other effects (which must include a volume control) that you normally leave always on, as a boost and/or cut

- use an external analog clean boost and attenuation

- compensate with your anp gain and volume controls

but anyway you put it, each of these solutions end up as a workaround that the pod needs to let you do a simple thing

as of me, having to choose a workaround I'm going to stick to my "line attenuated" solution, keeping the hiss and having at my disposal two more fx blocks plus the ability to boost and cut the send and the return

[EDIT: in the end I actually chose this solution even if I loose an fx block (I use the switch on the stomp position and a tube comp with threshold 100 and level 17), BUT I decided NOT to compensate for the +4dB given by the return circuit or I would have to loose another block; so in the end it's a "minus ONE fx-blocks solution"]

oh my god, how much did I write?!?

bye

Lore

Re: What every POD HD 500 owner REALLY needs to know!

support@line6.com — Tue, 05 Mar 2013 22:34:54 GMT

drewfx wrote:

The main outs can be switched from Low-Z (Line) to Hi-Z (Amp) using the 1/4" output switch on the top of the unit. Are you saying that this switch doesn't adjust the impedance, and only adjusts the output level?

I cannot find figures for the output impedances, but it would be easy enough to test with a multi-meter and an exposed patch cable.

Ultimately, as I understand it, there is a difference between output GAIN/LEVEL and output IMPEDANCE. I'd be happy to be shown if I am wrong though.

Even without knowing the circuit, I will almost guarantee that the Line/Amp switch affects only nominal operating level (and indirectly, gain) but not impedance. Impedance is not the same as DC resistance and measuring with a multi-meter is not an accurate way to determine it. For example, it's common to drive an output through a capacitor and this "looks" like an open-circuit (infinite impedance) when checked with an ohm-meter. You can loosely think of impedance as frequency-dependent resistance.

Gain, level and output impedance are all different concepts that I think are getting confused in this discussion.

Re: What every POD HD 500 owner REALLY needs to know!

support@line6.com — Tue, 05 Mar 2013 21:22:58 GMT

Heya Lore,

I just wrote a whole response, and this bloody forum lost it! Garbage interface was also responsible for me misquoting you. I knew it was Phil I was responding to, but for some reason it didn't quote him properly. Don't know why, sorry about that! Anyway...

All of what I'm about to say could be complete balderdash, but here is my take on it:

The main outs can be switched from Low-Z (Line) to Hi-Z (Amp) using the 1/4" output switch on the top of the unit. Are you saying that this switch doesn't adjust the impedance, and only adjusts the output level?

Likewise with the FX loop, it has its own Low-Z (Line) or Hi-Z (Stomp) switch. So logically (if these switches do switch the impedance) you'd set them both to the Hi-Z (Amp and Stomp) setting for a 4CM setup with a guitar amp.

Going from Hi-Z to Low-Z will introduce muffling on the high-end (adjusted frequency response) and will also screw with the signal to noise ratio. This is where the extra hiss and hum comes from in that situation.

Going from Low-Z to Hi-Z should be fine in theory, but not all guitar amps are made equal. The Marshall JVM for instance has a 470kΩ input. The Fryette Sig X has a 1mΩ input. That's a pretty big difference. The PodHD500 has a 1mΩ input impedance too, and AFAIK this wont change when turning the guitar input pad on - although it can be adjusted from within the setup I believe.

I cannot find figures for the output impedances, but it would be easy enough to test with a multi-meter and an exposed patch cable.

Ultimately, as I understand it, there is a difference between output GAIN/LEVEL and output IMPEDANCE. I'd be happy to be shown if I am wrong though.

Quick story: I had a Pod HD500, one of the first ones. At the time I had a Fryette Sig X. No matter what I did, I couldn't get it to stop sucking all my tone - weirdly though, I was losing a ton of low-end, not high-end. Couldn't ever figure it out. Now I use a Marshall Satriani JVM, and I am tempted to try a Pod HD500 out again.

Re: What every POD HD 500 owner REALLY needs to know!

support@line6.com — Tue, 05 Mar 2013 19:12:44 GMT

hi drewfx

1) I see there has been some misunderstanding here

phil_m (not me) wrote the sentence you cited "flip the line/amp switch to line, turn the master volume down, and make up the gain that way"

this could have been confusing because we were talking about the send jack, not the output so there is no "master volume" involved

so, to clarify, the first solution proposed by me (and others) was to use the fx loop switch on the line position and ATTENUATE the sent level with the send parameter of the fx loop block

this solution unfortunately gives back some hiss so of course it isn't ideal

2) you wrote "line is a low impedance signal, and amp is a hi impedance signal"

seems you're still talking about the output stage, right?

where did you get this info?

I don't think the output switch changes the impedance at all;

it could be that the fx loop switch has hi-Z on the stomp position but I can't find any line6 official statement about the send (nor output) jack impedance

anyway as snhirsch stated above, the "low-Z out to hi-Z in" connection in theory shouldn't create the hiss problem

3) the second solution to the 5dB drop of the fx send is to use the stomp position and use an fx block as a boost before the send

this is not ideal too because you loose an fx block

...well I guess we can say that the pod HD itself is not "ideal"

but in the end I actually chose this solution even if I loose an fx block (I use a tube comp with threshold 100 and level 17); and by the way I decided NOT to compensate for the +4dB given by the return circuit or I would have to loose another block

please read this post for a complete explanation of problem and solutions:

http://line6.com/support/message/406077#406077

bye

Lore

Community: Message List - What every POD HD 500 owner *REALLY* needs to know!

Re: What every POD HD 500 owner *REALLY* needs to know!

Re: What every POD HD 500 owner *REALLY* needs to know!

Re: What every POD HD 500 owner *REALLY* needs to know!

Re: What every POD HD 500 owner *REALLY* needs to know!

Re: What every POD HD 500 owner *REALLY* needs to know!

Re: What every POD HD 500 owner *REALLY* needs to know!

Re: What every POD HD 500 owner *REALLY* needs to know!

Re: What every POD HD 500 owner *REALLY* needs to know!

Re: What every POD HD 500 owner *REALLY* needs to know!

Re: What every POD HD 500 owner *REALLY* needs to know!

Community: Message List - What every POD HD 500 owner REALLY needs to know!

Re: What every POD HD 500 owner REALLY needs to know!

Re: What every POD HD 500 owner REALLY needs to know!

Re: What every POD HD 500 owner REALLY needs to know!

Re: What every POD HD 500 owner REALLY needs to know!

Re: What every POD HD 500 owner REALLY needs to know!

Re: What every POD HD 500 owner REALLY needs to know!

Re: What every POD HD 500 owner REALLY needs to know!

Re: What every POD HD 500 owner REALLY needs to know!

Re: What every POD HD 500 owner REALLY needs to know!

Re: What every POD HD 500 owner REALLY needs to know!