High level unbalanced output to balanced input

[5016]

Hi -

I have a Nord C1 organ, which I connect directly to an EV sxa360
active speaker.

The speaker has one input only (Neutrik combo input, 1/4"/XLR) with
very little control over the volume. I have been taking the unbalanced
line level output of the Nord and plugging it directly into the
speaker.

This doesn't give me a great deal of volume. In the past, with other
keyboards, I used an active direct box to boost the line level, and
connected the output of the direct box (on XLR) to the XLR input of
the speaker. This greatly increased the volume available to me.

However, the C1 also has something called a "high level" output, which
the documentation claims is 14V RMS. This is for Leslie speakers and
other related products.

I don't like carrying the active direct box because it is just another
thing to go wrong which needs to be plugged in at gigs. So, I was
wondering if I could connect the high level output to a passive direct
box that obviously wouldn't need any power, and take the XLR output of
the direct box to speaker, which would presumably give me a lot more
signal.

In fact, I think that I would get so much signal that I would blow up
my speaker, so presmably I have to throw a few resistors together to
knock the voltage down and put this in before the signal hits the
direct box.

I have a couple of problems:
1. I don't know how much to knock the signal down in order to get a
full range +4dBu output. I don't know how the mathematics works.
2. I don't know if I am doing something stupid here which is going to
damage something.

My rough guess, based on very little knowledge, is that I should step
the voltage down by a factor 5, which I come up with by
- a vague recollection that +4bDU is 1.3V (factor of 10)
- a vague recolllection that signal loss when using a passive DI is
around 6db (factor of 2)

resulting in 10/2 = 5.

Am I wrong? Missing something?

Thanks for any help you can give and grateful for any help.

[Mike Rivers]

5016 wrote:

> I have a Nord C1 organ, which I connect directly to an EV sxa360
> active speaker.

> The speaker has one input only (Neutrik combo input, 1/4"/XLR) with
> very little control over the volume. I have been taking the unbalanced
> line level output of the Nord and plugging it directly into the
> speaker.

That doesn't seem to be an unreasonable thing to do. What do you mean
by "little control over the volume?" You can't turn it up loud enough? Or
you can't turn it all the way down? The specs on the web site don't give
the input sensitivity, but it does say that the level control has a range of
30 dB. That's quite a bit.

> This doesn't give me a great deal of volume. In the past, with other
> keyboards, I used an active direct box to boost the line level, and
> connected the output of the direct box (on XLR) to the XLR input of
> the speaker. This greatly increased the volume available to me.

Now that's unusual. A direct box reduces the level, it doesn't boost it.
Perhaps the output level of this synth is low. Do you have its volume
control turned up all the way? How about internal levels in the patches?

> However, the C1 also has something called a "high level" output, which
> the documentation claims is 14V RMS. This is for Leslie speakers and
> other related products.

> wondering if I could connect the high level output to a passive direct
> box that obviously wouldn't need any power, and take the XLR output of
> the direct box to speaker

Why not connect the "High level" output directly to the powered speaker?
You shouldn't need the direct box.

> In fact, I think that I would get so much signal that I would blow up
> my speaker, so presmably I have to throw a few resistors together to
> knock the voltage down and put this in before the signal hits the
> direct box.

You're working too hard on this, at least until you perform some more
experiments. I suppose it would be asking too much for you to take some
actual measurements.

> 1. I don't know how much to knock the signal down in order to get a
> full range +4dBu output. I don't know how the mathematics works.

The mathematics is easy. What you don't know is what the actual level
of the synth is when playing whatever patch you're using.

> 2. I don't know if I am doing something stupid here which is going to
> damage something.

It would help if you knew more about your synth. Is this "high level" output
controlled by the synth's volume control? If so, you can start with the
synth
volume all the way down, the speaker input level control at 0, and just
turn
the synth volume up until it's loud enough for you. You won't blow anything
up. I promise.



--
If you e-mail me and it bounces, use your secret decoder ring and reach
me here:
double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers
)

[Scott Dorsey]

5016 > wrote:
>I have a Nord C1 organ, which I connect directly to an EV sxa360
>active speaker.
>
>The speaker has one input only (Neutrik combo input, 1/4"/XLR) with
>very little control over the volume. I have been taking the unbalanced
>line level output of the Nord and plugging it directly into the
>speaker.

This is fine.

>This doesn't give me a great deal of volume. In the past, with other
>keyboards, I used an active direct box to boost the line level, and
>connected the output of the direct box (on XLR) to the XLR input of
>the speaker. This greatly increased the volume available to me.

The direct box is actually _dropping_ the level, and you're plugging
it into a mike-level input on the speaker, which has more gain, I
suspect.

>However, the C1 also has something called a "high level" output, which
>the documentation claims is 14V RMS. This is for Leslie speakers and
>other related products.

Well, try it, then.

>I don't like carrying the active direct box because it is just another
>thing to go wrong which needs to be plugged in at gigs. So, I was
>wondering if I could connect the high level output to a passive direct
>box that obviously wouldn't need any power, and take the XLR output of
>the direct box to speaker, which would presumably give me a lot more
>signal.

Why not connect the high level output directly to the speaker line input?

>In fact, I think that I would get so much signal that I would blow up
>my speaker, so presmably I have to throw a few resistors together to
>knock the voltage down and put this in before the signal hits the
>direct box.

Don't turn it up that high, then. 14V isn't a lot... it's still lower
than the old +8 broadcast line standard. The volume control goes down
as well as up.

>I have a couple of problems:
>1. I don't know how much to knock the signal down in order to get a
>full range +4dBu output. I don't know how the mathematics works.

It's in the FAQ for this newsgroup. Or look at the section on attenuators
in the Audio Cyclopedia.

>2. I don't know if I am doing something stupid here which is going to
>damage something.

I don't know why you have the DI box in there at all.

>My rough guess, based on very little knowledge, is that I should step
>the voltage down by a factor 5, which I come up with by
> - a vague recollection that +4bDU is 1.3V (factor of 10)
> - a vague recolllection that signal loss when using a passive DI is
>around 6db (factor of 2)

Maybe. try it without any attenuation. If the levels are too high,
make a pad with two resistors. If the shunt and series resistors are
the same, you are dropping 6 dB. if the shunt resistor is half the
series resistor, you are dropping 12 dB, and so on.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[5016]

On Aug 2, 1:44*pm, Mike Rivers > wrote:
> 5016 wrote:
> > I have a Nord C1 organ, which I connect directly to an EV sxa360
> > active speaker.
> > The speaker has one input only (Neutrik combo input, 1/4"/XLR) with
> > very little control over the volume. I have been taking the unbalanced
> > line level output of the Nord and plugging it directly into the
> > speaker.
>
> That doesn't seem to be an unreasonable thing to do. What do you mean
> by "little control over the volume?" You can't turn it up loud enough? Or
> you can't turn it all the way down? The specs on the web site don't give
> the input sensitivity, but it does say that the level control has a range of
> 30 dB. That's quite a bit.

This particular powered speaker does not the same control over the
input level as some of them (eg the Mackie) do. I don't think that you
can boost the input signal by 30db, for instance. Maybe 6db.


>
> * > This doesn't give me a great deal of volume. In the past, with other
>
> > keyboards, I used an active direct box to boost the line level, and
> > connected the output of the direct box (on XLR) to the XLR input of
> > the speaker. This greatly increased the volume available to me.
>
> Now that's unusual. A direct box reduces the level, it doesn't boost it.

I have an active DI that does boost the level. It has a preamp circuit
built in (but of course it requires a power source as a result). I
would prefer not to use it because it is just another thing to have to
plug in at a gig. A passive DI would be simpler.

> Perhaps the output level of this synth is low. Do you have its volume
> control turned up all the way? How about internal levels in the patches?

The output level of Nord keyboards is quite low. This is well-known
problem with the Electro. I've tried raising all the internal
settings. But even with other keyboards, if I feed their -10dBV
outputs directly into this speaker, max out the volume, I don't have
nearly as much available volume as I do if I put the keyboards into a
mixer and connect the +4dbu output of the mixer to the speaker.

>
> > However, the C1 also has something called a "high level" output, which
> > the documentation claims is 14V RMS. This is for Leslie speakers and
> > other related products.
> > wondering if I could connect the high level output to a passive direct
> > box that obviously wouldn't need any power, and take the XLR output of
> > the direct box to speaker
>
> Why not connect the "High level" output directly to the powered speaker?
> You shouldn't need the direct box.

My concern was that 14V into a standard audio input would have the
potential to damage the equipment.

>
> > In fact, I think that I would get so much signal that I would blow up
> > my speaker, so presmably I have to throw a few resistors together to
> > knock the voltage down and put this in before the signal hits the
> > direct box.
>
> You're working too hard on this, at least until you perform some more
> experiments. I suppose it would be asking too much for you to take some
> actual measurements.

Not sure what you want me to measure. The output maxes at 14V.

>
> > 1. I don't know how much to knock the signal down in order to get a
> > full range +4dBu output. I don't know how the mathematics works.
>
> The mathematics is easy.

I'm sure that I can handle the mathematics. But I don't know the
equations.

> What you don't know is what the actual level
> of the synth is when playing whatever patch you're using.

14V RMS from the high level output.

>
> > 2. I don't know if I am doing something stupid here which is going to
> > damage something.
>
> It would help if you knew more about your synth. Is this "high level" output
> controlled by the synth's volume control?

yes

> If so, you can start with the
> synth
> volume all the way down, the speaker input level control at 0, and just
> turn
> the synth volume up until it's loud enough for you. You won't blow anything
> up. I promise.

I wasn't sure whether this could cause damage or not. Nord says that
it could, but that could well be CYA. To be honest, even if it worked
with the volume control set at 10%, I would still want to pad the
input down so that I could use the range of the volume control during
the gig, instead of using the first 10% of it.

I also like the idea of running a very short unbalanced line to the
DI, and then long XLR from DI to speaker thereafter just to minimize
hum on stage. Though this isn't normally a problem with keyboard level
outputs as opposed to guitars.

>
> --
> If you e-mail me and it bounces, use your secret decoder ring and reach
> me here:
> double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers
> )

[Mike Rivers]

5016 wrote:

> This particular powered speaker does not the same control over the
> input level as some of them (eg the Mackie) do. I don't think that you
> can boost the input signal by 30db, for instance. Maybe 6db.

If you gave the correct model number, I looked up the correct spec sheet
from the EV web site. It has 6 dB of gain and 24 dB of cut. But what it
doesn't
say is what the reference level for 0 on the control (neither boost nor
cut) is.
I suspect that it's +4 dBu and that makes the speaker play about 20 dB below
its maximum level to allow headroom for peaks.

> I have an active DI that does boost the level. It has a preamp circuit
> built in (but of course it requires a power source as a result).

That's not what we call a DI, then, but I suspect that it doesn't have more
than about 10 dB of gain, because you don't usually need any gain with
an instrument pickup, you just need a higher impedance to plug it into,
something that your keyboard doesn't need.

If you tell me what this DI with a preamp circuit is, I'll try to look it up
and maybe I can clarify what it is.

> The output level of Nord keyboards is quite low. This is well-known
> problem with the Electro. I've tried raising all the internal
> settings. But even with other keyboards, if I feed their -10dBV
> outputs directly into this speaker, max out the volume, I don't have
> nearly as much available volume as I do if I put the keyboards into a
> mixer and connect the +4dbu output of the mixer to the speaker.

If the keyboard's nominal output level is indeed -10 dBV, then you probably
don't really have enough level to get full output from the speaker. You can
easily get 20 dB of gain out of a mixer from line input to main output.

> My concern was that 14V into a standard audio input would have the
> potential to damage the equipment.

Not even close. Just do it.

> Not sure what you want me to measure. The output maxes at 14V.

14 real volts is pretty high, particularly for a device that has a nominal
-10 dBV output. I'll bet that's 14V peak-to-peak which, for a sine wave,
would be about +16 dBu. Your speaker's input level control has adequate
range to handle that.

>> What you don't know is what the actual level
>> of the synth is when playing whatever patch you're using.
>
> 14V RMS from the high level output.

Well, you see, that, by itself, is not very meaningful because you
don't know the conditions under which it was measured. But even
if that's the absolute maximum that the synth can put out when going
downhill and pedaling as fast as you can, it's still well below what
could cause damage to the speaker.

> I wasn't sure whether this could cause damage or not. Nord says that
> it could, but that could well be CYA.

It's probably what their lawyers told them.

> To be honest, even if it worked
> with the volume control set at 10%, I would still want to pad the
> input down so that I could use the range of the volume control during
> the gig, instead of using the first 10% of it.

I think it'll work fine with the volume control at 100%. Turn down the
input level control on the speaker. It goes down (or "pads" in your
terminology) by up to 24 dB. I doubt you'll need more than 6 dB, or
maybe 10 at the most.

> I also like the idea of running a very short unbalanced line to the
> DI, and then long XLR from DI to speaker thereafter just to minimize
> hum on stage. Though this isn't normally a problem with keyboard level
> outputs as opposed to guitars.

That's true. But a passive DI will drop the level. Maybe the combination
of a passive DI and the high level output of the synth will work out. But
without absolute, MEASURED numbers, the best you can do is try it
out and find a comfortable working combination of settings of the synth
volume control and speaker input level control. You're not in any
danger of damaging anything as long as you start with the settings low
so you don't damage your ears.



--
If you e-mail me and it bounces, use your secret decoder ring and reach
me here:
double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers
)

[5016]

On Aug 2, 4:55*pm, Mike Rivers > wrote:
> 5016 wrote:
> > This particular powered speaker does not the same control over the
> > input level as some of them (eg the Mackie) do. I don't think that you
> > can boost the input signal by 30db, for instance. Maybe 6db.
>
> If you gave the correct model number, I looked up the correct spec sheet
> from the EV web site. It has 6 dB of gain and 24 dB of cut. But what it
> doesn't
> say is what the reference level for 0 on the control (neither boost nor
> cut) is.
> I suspect that it's +4 dBu and that makes the speaker play about 20 dB below
> its maximum level to allow headroom for peaks.
>
> > I have an active DI that does boost the level. It has a preamp circuit
> > built in (but of course it requires a power source as a result).
>
> That's not what we call a DI, then, but I suspect that it doesn't have more
> than about 10 dB of gain, because you don't usually need any gain with
> an instrument pickup, you just need a higher impedance to plug it into,
> something that your keyboard doesn't need.
>
> If you tell me what this DI with a preamp circuit is, I'll try to look it up
> and maybe I can clarify what it is.
>
> > The output level of Nord keyboards is quite low. This is well-known
> > problem with the Electro. I've tried raising all the internal
> > settings. But even with other keyboards, if I feed their -10dBV
> > outputs directly into this speaker, max out the volume, I don't have
> > nearly as much available volume as I do if I put the keyboards into a
> > mixer and connect the +4dbu output of the mixer to the speaker.
>
> If the keyboard's nominal output level is indeed -10 dBV, then you probably
> don't really have enough level to get full output from the speaker. You can
> easily get 20 dB of gain out of a mixer from line input to main output.
>
> > My concern was that 14V into a standard audio input would have the
> > potential to damage the equipment.
>
> Not even close. Just do it.
>
> > Not sure what you want me to measure. The output maxes at 14V.
>
> 14 real volts is pretty high, particularly for a device that has a nominal
> -10 dBV output. I'll bet that's 14V peak-to-peak which, for a sine wave,
> would be about +16 dBu. Your speaker's input level control has adequate
> range to handle that.
>
> >> What you don't know is what the actual level
> >> of the synth is when playing whatever patch you're using.
>
> > 14V RMS from the high level output.
>
> Well, you see, that, by itself, is not very meaningful because you
> don't know the conditions under which it was measured. But even
> if that's the absolute maximum that the synth can put out when going
> downhill and pedaling as fast as you can, it's still well below what
> could cause damage to the speaker.
>
> > I wasn't sure whether this could cause damage or not. Nord says that
> > it could, but that could well be CYA.
>
> It's probably what their lawyers told them.
>
> > To be honest, even if it worked
> > with the volume control set at 10%, I would still want to pad the
> > input down so that I could use the range of the volume control during
> > the gig, instead of using the first 10% of it.
>
> I think it'll work fine with the volume control at 100%. Turn down the
> input level control on the speaker. It goes down (or "pads" in your
> terminology) by up to 24 dB. I doubt you'll need more than 6 dB, or
> maybe 10 at the most.
>
> > I also like the idea of running a very short unbalanced line to the
> > DI, and then long XLR from DI to speaker thereafter just to minimize
> > hum on stage. Though this isn't normally a problem with keyboard level
> > outputs as opposed to guitars.
>
> That's true. But a passive DI will drop the level. Maybe the combination
> of a passive DI and the high level output of the synth will work out. But
> without absolute, MEASURED numbers, the best you can do is try it
> out and find a comfortable working combination of settings of the synth
> volume control and speaker input level control. You're not in any
> danger of damaging anything as long as you start with the settings low
> so you don't damage your ears.
>
> --
> If you e-mail me and it bounces, use your secret decoder ring and reach
> me here:
> double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers
> )

Thanks. I will try this out. Appreciate the advice.

[Peter Larsen[_3_]]

5016 wrote:

> I have a Nord C1 organ, which I connect directly to an EV sxa360
> active speaker.

I'll skip the googling for manuals ...

> The speaker has one input only (Neutrik combo input, 1/4"/XLR) with
> very little control over the volume. I have been taking the unbalanced
> line level output of the Nord and plugging it directly into the
> speaker.

> This doesn't give me a great deal of volume. In the past, with other
> keyboards, I used an active direct box to boost the line level, and
> connected the output of the direct box (on XLR) to the XLR input of
> the speaker. This greatly increased the volume available to me.

The simplest solution that puts controls where you are: Get the smallest
Behringer mixer and use it to control the signal you send to the active
speaker. Actual brand is suggested because it has some really small stuff
that will do the job, otherwise there are two other brands I'd look into,
some would also like to look into Mackie, but I'm not compatible with their
ergonomics. If neatness is what you want, then it is the Soundcraft
catalogue you go browse .... but is is Behringer that has the small cheapie
that fits the job at lowest cost and physical footprint.

Kind regards

Peter Larsen