Line to Instrument level question

[Gary75]

Q: Will line level inputs into the POD destroy it? The manual says the POD is built for guitar level inputs, but can you run line level inputs from keyboards into the POD without messing it up?

A: You won't destroy it, but the overall sound quality may leave something to be desired. You might want to try a buffer/direct box between your keyboard and the Pod to lower the level back down to instrument level settings.

 

I'm wanting to run my Dunlop wah with the Scarbee Clavinet. However it dawned on me last night why it sounded not that great before when I tried. I had been using the amp sim of VKFX pre my wah, hence I was not only filtering the clav but also the whole amp sim. So I tried just having the scarbee plug in and the filter pick up fx, then ran into my wah. Big difference for me. But I'm left without a speaker sim. So I'm needing a pod device for the post wah. However as they are all instrument level and the receptor is line, I need somebody to recommend what Line 6 recommends above to match up them both.

 

Any ideas?

[bloodyMary]

Oh, this is an issue for me too. I've tried to run my synth into a wah pedal a couple of days ago, and as you said, it doesn't sound too good. My guess is that impedance/capasitance mismatch sucks out the high freq's). Nothing will get ruined by plugging a keyboard into the Pod, but my guess is that the sound will be 'dull'.

 

There are converters out there, cost few tens of dollar, I think. A DI will probably make things worse as it has a mic level output.

 

I'm thinking of building an adapter circuit next time I have a vacation...

[Gary75]

To be fair, I'm not clued up on that front. Surely there is a do it all box with variable attenuation?. No idea what a buffer is though?

[TJ Cornish]

A keyboard line out is VERY stout - you're not going to suck anything out of this like is possible with a guitar. Impedance should have very little to do with it. Output voltage yes, impedance no.

 

The first place I would start is by turning your volume knob down. That would help a lot. If that's not enough, you need a pad in your line, like a direct box. You may have to make an XLR to 1/4" cable to go from the XLR output of the direct box to your pedal, but that is easy to do.

[J. Dan]

I've run my Moog Opus 3 into the POD with very good results. You do have to keep the volume down a bit, though. I'd probably target around 25% on the keyboard and then play with the gain on the POD for the right amount of overdrive.

[Gary75]

Ill try that, just bidding on a Pocket Pod, nothing too extravagant. The only concern is that I have tried it into a guitar amp, and there was digital stepping noise coming from Receptor into the amp. Clean as a whistle when ran into Mackie SRM350 set to line input. No matter how low I set the volume on the Receptor, the digital stepping was still in proportion. This is not the case, as I say when ran line level into Mackie.

[TJ Cornish]

This is EMI - electromagnetic interference. This is the same thing that often happens when you plug a laptop directly into a sound board without using a direct box or other type of isolation transformer.

 

Get a DI and adapt the XLR output cable to 1/4" if you're having this problem. For another suggestion, you can take two direct boxes - note they must be passive direct boxes - nothing with active electronics inside, and place them back to back with a female to female XLR adapter. This will give you 1/4" connections on both ends and several different options for the amount of pad to use. The Rolls Matchbox DI is like $25, so getting two of these wouldn't break the bank.

[Gary75]

Thanks for the helpful input, I have a passive Behringer DI lying around I could try, but as you say, having two back to back would'nt hurt the budget.

[J. Dan]

I don't think what you describe is EMI, but in fact, digital stepping as you describe. But it would be generated by the amp, as evident by the fact that you don't get it running into the Mackie.

 

We had this problem in my old band running a Digital EQ on our main mixer output. The problem is we ran main out into the EQ. Well, we usually ran fairly low, meaing the signal to the EQ was low, so we were using the lowest few bits of sampling resolution, thus the stepping. We switched the EQ to the Main Out INSERTS, so that it was line level to the EQ, and volume control AFTER that. Problem solved.

 

In your case, the only way that would happen is if you are running a LOW level signal into the POD. The problem you are concerned with is the opposite - OVER driving the pod.

 

You'll want to closely match the range of an instrument level and you'll be fine.

 

One other thing to consider is that the DYNAMIC RANGE of your keyboard output may be greater than that of a guitar. So even if you get a good average level, it may be the case that you can still occasionally overdrive it undesireably. The answer would be an analog (VCA or Optical) compressor/Limitor before the POD.

 

In either case, just try it without anything first and add tools required to fix if not good.

[Moog_Man]

I remember seeing a reverse DI box on analoghaven.com that changed a balanced signal into a instrument level signal, which would be ideal for a POD or wah. I briefly looked but I can't remember the name, I just remember it being a red box. It was around $200 however, which seems a bit steep for what it does.

[bloodyMary]

it's called Reamp, and yes, it's around $200, which for me is a deal breaker (I don't like overpriced products). It's essentially a transformer + maybe some resistors.

 

Anybody happens to know the parameters of guitar output? (impedance, voltage range)

[MoodyBluesKeys]

The classic Fender guitars impedance was somewhere between 10,000 and 50,000 ohms, determined largely by just how many turns of wire were on the pickups and the size of the wire; with a voltage output up to about 10 or 15 volts is a big chord was played hard. That was back in the tube amp days. A lot of the replacement pickups had higher output (for more overdrive to the amp). Now, normal output voltage when played say picking a single note at a moderate strength was one or so volts.

 

[Moog_Man]

it's called Reamp, and yes, it's around $200, which for me is a deal breaker (I don't like overpriced products). It's essentially a transformer + maybe some resistors.

 

Yeah, that's the one. I agree, way overpriced but maybe they can get away with it because its the only product I know of like that.

[BillWelcome Home Studios]

Guitars output mV, not V. somewhere under 20mV. Mic level is similar, but the impedance is different. You might try running a DI backwards and wiring an XLR to 1/4" mono adapter. won't fix the impedance, but might get the voltage level close enough for rock and roll.

[bloodyMary]

Why backwards? DI's input accepts line voltage and outputs mic level (lower) voltage. So if I wanna use a line-level device into a guitar amp, I plug it straight, no?

[BillWelcome Home Studios]

Why backwards? ...

 

Because sometimes I type faster than I THINK? That's probably it. You are entirely correct.

[JeffLearman]

No, I think he's entirely wrong.

 

There is more than one kind of DI. The kind BM refers to is a line-to-mic DI. Line is medium impedance (10-50 KOms).

 

A mic is low impedance: 150 - 600 Ohms.

 

A passive guitar pickup is high impedance: about 250 KOhms.

 

Try to use a line-mic DI and you're going the wrong way.

 

In any case, active guitar pickups are pretty damn near line level devices, but with nominal -10dBV levels. They work fine into a typical guitar amp. Ditto with most stomp boxes: essentially line outputs. (Try it: plug one into your mixer's line input some time. Works great.)

 

However, many synths output nominal +4dBu levels, which is 4 times the voltage.

 

So, just turn the sucker down. However, some keyboards do their volume control digitally, which sux, because you'd be lopping off two bits of your A/D converter. If this is the case, just get an audio 10dB or 20dB pad, available in various configurations, last I checked.

 

What about matching impedance? IT DOESN'T MATTER in this case. You match impedance in order to get the maxiumum signal transferred across an interface. In the case of a mic, where signals are very weak and must be treasured, this is very important. For beefy electric guitar pups, it's less so. For active line outputs, it's totally no problem. You just need high enough load impedance so that your divers don't burn out. And low enough so the damn thing works at all.

 

Oh, there is one more thing: protecting the line outputs. They used to be spec'd with a minimum load impedance (or maximum load impedance, meaning the same thing, for reasons I won't go into). If you went under that level, it would draw too much current and damage the driver. We don't see that spec any more, so they must be more robust (i.e., self-current-limiting).

[JeffLearman]

Oh -- we've all played synths through guitar amps, haven't we?

 

Again, works great -- just don't turn it up too high. Unless that distortion is what you want.

[bloodyMary]

learjeff, the other problem I've encountered was that plugging synth into a guitar pedal (a Dunlop wah, to be specific) killed the high freqs, even on bypass. Is this the wah filter not fully opening up, or impedance issues?

 

What you were talking about was matching impedances to achieve minimal signal loss, so only the resistance part of the impedance is relevant. But what about the capasitance/inductance part? I guess mismathed impedances could create unwanted frequency response (like low pass filtering). It's just a wild guess, since I never saw synth's output stage circuits or wah pedal input stage circuits. I probably won't want to get the circuits and calculate stuff, so I'm looking for a quick answer from somebody who knows here..

[J. Dan]

A Wah pedal is a bandpass filter. Most bypasses are not true bypasses.

 

With other pedals designed for guitar, they don't need to operate over as wide of a frequency range. Reducing the high frequency response reduces hiss without noticable impact on guitar. Keyboards - another story.

[BillWelcome Home Studios]

I agree that turning down solves the problem (though S/N could suffer) but I've yet to encounter any keyboard player whos various patches match in level. That could be a problem. Padding down the output level is simple enough, and undoubtedly there are several pad circuits on the net.

 

I was talking about plugging the output of the synth into the input of the DI and using the mic level output, which is closer to what most guitars output in level, to drive the pedal. Not ideal, but cheap. (by the way, not many guitar players run active pickups.)

 

and indeed, I have used a pedal as an instrument to line level converter many times... I used to carry an eq pedal with my BB passive acoustic guitar pickup system, to convert up before hitting a DI/house PA.

 

In spite of being correct levels, guitar pedals inserted into a PA usually sounds like dog balls, unless either your PA already bites or you were looking for that interesting and unique sound.

 

 

[J. Dan]

I guitar pedals inserted into a PA usually sounds like dog balls

 

That's EXACTLY the sound I've been searching for! I tried sampling some dog balls, but he bit me. I'm going to try this tonight, thanks!

[bloodyMary]

I guess that guitar pedals sound best when plugged into a guitar amp/cab, or a speaker sim at least (or a line6 POD).

 

 

I've got a Boss pedal lying around, and it's supposed to have a buffered bypass, so it might do the 'line->instrument' trick for me.

 

b3boy, why don't you use a software solution, for wah and speaker sim? Something like NI Guitar Rig has a lot of diff. amps, pedals, whatever. There are solutions from IK Multimedia, too.

 

Regarding the wah-wah, after reading what Dan wrote, I guess I'm better off with the expression pedal and my synth.

But the pedal feels so cheap.. I suppose I could get an Ernie Ball for expression, but it's too much money.

[Gary75]

I won the Pocket Pod last night si I'll give it a go next week. Im using it on Receptor you see where routing is not as comprehensive. I have stereo out and stereo in on the Receptor. I'd have to go back in through the line in then select a channel to load VKFX up then output it again through the other side of the stereo out to desk. It's a long winded way of doing it, and would tie up my channels unless I had an ADAT Lightpipe to expand my channels. It gets rather confusing! I'll just try a simple insert with the POD post wah.

[BillWelcome Home Studios]

That's EXACTLY the sound I've been searching for!...

 

Lets not forget that John Lord plugged his B3 into a Marshall guitar amp and made history. Wouldn't have been my first choice... but it sure did work out for Deep Purple!

[Gary75]

Funny, someone just came last night to buy a console stool as John Lord was using his split C3 for a gig and he didn't have one. Apparently the chap I bought the POD off just now has used it with his Juno and said it was fine. Not at home until tomorrow so hopefully it will be good to go.

[JeffLearman]

Really, you don't need anything.

 

Oh, I forgot earlier, but I had an OB3 "hammond emulator" (and a very bad one). I used it for a little while until I puked. Anyway, I plugged it into my Genesis3 to get the Leslie effect, and that part sounded great. Unfortunately, their imitation of tonewheels suffered a lot. (I actually bought it to use the drawbars as MIDI controllers for NIB4, but I got the wrong model, which only had MIDI in.)

 

Bottom line: you probably don't need anything between the keyboard and the POD. However, if your keyboard is +4 dBu levels, you'll need something to tone it down. Hopefully, the master volume on the keyboard will do the trick.

[JeffLearman]

learjeff, the other problem I've encountered was that plugging synth into a guitar pedal (a Dunlop wah, to be specific) killed the high freqs, even on bypass. Is this the wah filter not fully opening up, or impedance issues?

Personally, I think most keyboards sound like crap through most stomp boxes, but not for electrical reasons, but because of what the stomp boxes do. They sound great on a guitar, but not on most keyboard sounds.

 

What you were talking about was matching impedances to achieve minimal signal loss, so only the resistance part of the impedance is relevant.

Not at all true, for mic level signals: the impedance is what matters, whether it's due to reluctance or resistance. Impedance is just the total force against the current, with two components: a static part (resistance) and a dynamic part that's a function of the current (reluctance).

 

In any case, the impedance in stomp boxes is mostly resistance. Have you ever seen any coils in the input stages of a stomp box?

 

Capacitors, yes, but they'd have the same effect on a guitar. Their effect depends on the frequency but not the current and not the upstream impedance, as I hazily understand it.

[BillWelcome Home Studios]

uote=learjeff] ...I think most keyboards sound like crap through most stomp boxes, but not for electrical reasons, but because of what the stomp boxes do. .....

 

I think so too. Much more limited frequency response, and much less fidelity expected. After I started working with the studio compressors an eqs and stuff, dumped all my stomp boxes. I've only more recently picked up some boutique models because they sound so much better than the typical Roland/Boss/MXR/EH pedals, and don't suck all the life out of my vintage guitar/boutique amp rigs. But I still wouldn't use them on PA (or, probably, keyboards...) except as a special effect.