Effects loop and stomp boxes

GoeieGenugtig

I know there has been threads on instrument level effects which does not work within most effects loop, but I want to make sure on the following.

For example a boss stomp box like the DD-7 has a nominal input of -20dBu which is 0.0775Vrms if 1dBu is 0.775Vrms.

A amp like the Peavey classic 30 nominal ouput is -6dBV which is 0.5Vrms i.e -4dBu which is a 16dB difference.

I have seen DD-7 used in Peavey classic effects loop, but is seems dangerous. I assume I should not do the same?

http://www.guitarforum.co.za/effects/effects-loop/

AlanRatcliffe

You should not try run them in a line level loop. I've seen quite a few toasted RV-3s, DD3's and DD-5's from line level. Things can work fine at lower levels, but the moment the amp is cranked...

GoeieGenugtig

Thanx for the confirmation. Unfortunately the answer I expected ?

Should probably posted this in effects section.

What good alternatives are there if I want to use my effects loop without destroying my pocket?

Note to self - stop believing everything the sales guys say ?

AlanRatcliffe

I'll move it to effects.

Well, you obviously have an understanding of decibels, which implies a firm grounding in the theory. So you can probably already do all the "reading between the lines" needed to decipher specs and that means there is no reason you should have to rely on salesguys for your info - beyond them pointing you in a direction and giving you some subjective opinion.

Gearhead

You could of course put a voltage divider in the lead from send to first pedal - choosing the right resistance would depend on output impedance, voltage drop and input impedance. List the specs and we can work out what you need.

AlanRatcliffe

You'd still have to get it back up to line level for the return.

If you look in the classifieds, Zark was selling an Ebtech Line level shifter fairly cheaply, which would be perfect to run in a loop to change the level down and then back up again. A passive transformer device too.

GoeieGenugtig

Alan Ratcliffe wrote Well, you obviously have an understanding of decibels, which implies a firm grounding in the theory. So you can probably already do all the "reading between the lines" needed to decipher specs and that means there is no reason you should have to rely on salesguys for your info - beyond them pointing you in a direction and giving you some subjective opinion.

True, just surprised with my own neglect to check it myself as I have the necessary background. Was just too lazy :-[. I see many people using it that way. Luckily I have checked before doing something "not so clever"

Gearhead wrote You could of course put a voltage divider in the lead from send to first pedal - choosing the right resistance would depend on output impedance, voltage drop and input impedance. List the specs and we can work out what you need.

Just curious if someone has done something like this. Is this a series resistor to the input of the first pedal? Pedal input impedance is 1M, Peavey output impedance is not specced, that -6dbV is applicable to loads > 1k. Do you further assume the pedal as black box? Would the input resistance not affect any filters, or would there be a buffer stage? Been a very long time since I looked at any schematics. Ignoring the fact now that the line level must be returned to.

Alan Ratcliffe wrote You'd still have to get it back up to line level for the return.

If you look in the classifieds, Zark was selling an Ebtech Line level shifter fairly cheaply, which would be perfect to run in a loop to change the level down and then back up again. A passive transformer device too.

Too bad I didn't know things like this can be a problem and that a solution like this exist. I may have been a customer.

Are there any retailers that would have units like these?

The transformer idea seems interesting. Probably a stupid question, but I cannot help to wonder where the energy go? I as understand power should be dissipated to the input of the first pedal (some parallel resistor). Returning to line level does this only imply voltage as it is a passive device?

Another thing I was wondering about is my BOSS NS-2 and LS-2. I don't see any input specs in the manual. Would they also be on instrument level devices? Does anyone know?

I would probably have a look into this ebtech thing

Gearhead

The voltage divider consists of two resistors in series. You tie the send to the top of the top one and the bottom of the bottom one to ground. The middle ties to the pedal in. The sum of the resistors must be big enough for the send impedance (take between 2-47k) and the ratio bottom/top is you attenuation factor. The bottom one should be lower resistance than the input impedance of your pedal, but not by more than, say, 10x.

Power before and after a transformer is more or less the same, the difference being losses to heat and stray magnetics. This means that voltage times current before equals voltage times current after. If you want to increase the level (in volts) your tranny needs more current on the input. If your pedal has low enough output impedance, it will deliver that current. Meaning that you can, like on the input, calculate with the specs whether a passive device will work. The alternative is buffering before the step-up transformer, something the line level shifter probably does as well.

Are you sure Zark has already sold the Ebtech?

AlanRatcliffe

AdriaanJB wrote Probably a stupid question, but I cannot help to wonder where the energy go?

As Gearhead explained, it does not really go anywhere (other than some losses), it just changes state. Voltage goes down and current goes up, the net result is the same. Same concept as a DI box (which converts lower voltage to higher current to drive cables better).

Another thing I was wondering about is my BOSS NS-2 and LS-2. I don't see any input specs in the manual. Would they also be on instrument level devices? Does anyone know?

All the Boss pedals run at instrument level. The same is true of most pedal format effects. One or two have switchable levels (e.g. Eventides, which have both a switchable input and output), but for the most part, line level gear is rack (or sometimes desktop) format.

Amp manufacturers have started making switchable level loops too, because so many guys want to run stomps in their loops.

Gearhead wrote Are you sure Zark has already sold the Ebtech?

He relisted it on Gumtree a few days ago:
http://capetown-westerncape.gumtree.co.za/c-Stuff-for-Sale-musical-instruments-Ebtech-LLS2-Hum-Eliminator-Line-Level-Shifter-Brand-New-W0QQAdIdZ355889031

I'm also fairly sure that Radial will have something similar. The good stuff can be expensive though - good transformers don't come cheap).

GoeieGenugtig

Gearhead wrote Are you sure Zark has already sold the Ebtech?

No actually he has not. Got it from him yesteday ?

Quite a small box, had a bit of noise trouble but then I changed to a different cable and it works fine. Now the real test is tonight with stage lights.

I have actually no clue as why the last cable I used removed the noise. I just wonder how I would know in future if I have the right cable. Trial and error?

Norman86

yelloooooo ?

Sorry to bring this topic up, but how would one go about setting a tc hall of fame or corona chorus and the like to work in a serial effects loop?
Would the Kill dry be set to on or off? or should one just use the normal buffered bypass setting?

The serial effects loop in my albion has a gain setting of low and high; Low is a loop level of -10dBV, and High is 0dbV.

Thinking for the future ?

ta

AlanRatcliffe

Just normal will be fine (no killdry) - with a series loop the pedal must pass the original sound too. Loop set to low level.

Norman86

kewlness!!
Thanks Alan! ?