yorkville 200KB line out level

[guitardad]

Customer has problem saying line out level is too low for most house boards. Some cranking input gain to max and still not having enough to really mix the line sound.

Spec is .2v according to manual, and send on the amp is 1v (5x greater)

I know most of these should be +4db and if I guess right that is about .885v 0db for most units. So .2v seems rather low.

Customer says sound guys will have to mic his cab (which he hates doing).

Question is would you suggest or should I modify the FB loop of the line out circuit to enable at least "send level" signal amt.

I have not seen too many units with a line out level as low, and the Owners manual does not suggest adding a preamp when in use.
People at KB forums seem to recall this being a problem as well, but most just bought something else.

I compared this to a Roland 350 KB amp and the line level on that unit is almost 8x as high a signal on the scope.

yorkville 200kb.pdf

[Chuck H]

200mV does seem low for a line out. Especially if the driving signal isn't adjusted appropriately, which is eminently likely with musicians that have no concept of headroom and noise floor.

Try bumping R38 to 470R (or even 1K) and see if that solves the problem. I know it's a mod but the stock circuit doesn't seem to be working for your man.

[g1]

They are using the xlr line out into a mic input and can't get enough level?
Why not use the FX send?

[Chuck H]

They are using the xlr line out into a mic input and can't get enough level?
Why not use the FX send?

Because they are musicians and club stage sound men

For the repair guy to substitute an equipment lesson for a circuit correction negates the whole reason for going to him in the first place! They don't get it. They want it set up so THEY can use it the way they want to.

[The Dude]

That's what I was thinking. I suspect they are attempting to connect to a line input on the board using the 1/4" balanced output. Otherwise you should be able to drive a mic input easily with 200mv using the XLR out.

[The Dude]

Because they are musicians and club stage sound men

And that's why colored electrical tape was invented.

[Chuck H]

Dude! You responded ahead of my edit They want to be handed a solution, not schooled on how to mark cables

[g1]

All I know is: they don't put xlr connectors where they want to run line levels. I've never seen an xlr "line input" on any kind of board. Poor choice of wording on the jack, maybe Direct out would have better served.

[The Dude]

Belittling the electronically illiterate aside, this circuit does make some sense. Maybe deceptively called a "Line Out", one could assume that most will be plugging the XLR jack into a snake which will be fed to a mic input on a mixer. You wouldn't want line level there for fear of clipping and possibly destroying a mic preamp in the board. Modifying the circuit may cause worse problems if one were to connect to the mic input of a console without padding. IMO, rather thank modifying the circuit, some customer education is best in this instance.

[Chuck H]

Belittling the electronically illiterate aside, this circuit does make some sense. Maybe deceptively called a "Line Out", one could assume that most will be plugging the XLR jack into a snake which will be fed to a mic input on a mixer. You wouldn't want line level there for fear of clipping and possibly destroying a mic preamp in the board. Modifying the circuit may cause worse problems if one were to connect to the mic input of a console without padding. IMO, rather thank modifying the circuit, some customer education is best in this instance.

Agreed! Separating the jacks and re-labeling for independent function would probably be the best solution. Also probably more than the OP signed up for.

[J M Fahey]

I had to mentally trace signal paths and gain 4 or 5 times because I couldn't believe they made such design choices.
Not actually bad, but across the grain or poorly labelled.

1) as Dude says, that XLR out expects going through a snake to a faraway mixer , using a standard XLR-XLR mic cable, available everywhere, into an XLR Mic input, which is also available everywhere, doubly so in small box mixers which often have nothing else, go figure.

Of course, this is too complex for that operator who must be certain that "Line in" means using that 1/4"jack in his mixer, because it's so labelled, so he also must use the 1/4"Line Out.

Even so, 200mV is ample for ANY decent Line In, capisce?.

In a real small Club, no snake involved, it will go straight to the simplest mixer with its own microphone cable .... I guess that's the idea.

And sound level is ample ... in fact even too much for the cheapest mixers, if you go to the microphone input.

So the real solution should be to grab a piece of paper tape and Sharpie and relabel, in big bold letters:

Microphone Level Out

and when they come with that microphone they are menacing with, you just say "thanks" , unplug the XLR connector and plug it in your amp.

2) that said, Yorkville is cheating, that is notb a true balanced out by any means.

Pin 2 XLR and 1/4" Tip get 200mV ; Pin3 and Ring get nothing.

Don't mess with R38 and R215, they are there only to ensure that the not-so-balanced cable gets properly terminated and "sees" 250 ohms on each wire or 500 ohms end to end.
They do not affect signal level.

So problem answer is to plug the proper XLR microphone cable into the mixer Mic In, and the other end in the relabelled "Line Out" .

Level is ample if used like that.

[Chuck H]

Isn't R215 a series resistor and R38 a load resistor? That's a voltage divider in my universe

I humbly default to the higher minds about their relevance though. For all my ignorance WRT anything but toob schtuff I'm probably missing an important aspect. I'll reiterate that I might be inclined to flip the 1/4 jack upside down (if it's board mounted) and do a simple mod to separate the XLR and 1/4 plugs with different outputs. Easy peezy, everyone wins.

[The Dude]

True 'nuff Chuck. If they do want an actual line out without modification, they can use the effects send as g1 (the new guy ) pointed out.

[J M Fahey]

Isn't R215 a series resistor and R38 a load resistor?

You can call them that.
In this particular application, they mean the same, you'll see.

That's a voltage divider in my universe

Well, if the cable and the mixer input are properly wired they are not connected in series or to each other, so the voltage divider action does not happen.

The idea is this , it's a cheat which reasonably works.

Balanced inputs as God wants them, receive the exact same signal, out of phase, and from same source/generator impedances.
Which happens naturally if they come from a dynamic Microphone capsule (your old trusty Shure SM58) or the secondary of a line transformer, both of which have true balanced and floating windings.

Problem is, transformers are expensive and hum catchers.

But the requirements can easily be met from cheap yet incredible quality Op Amps.

To guarantee that, look at modern active balanced line out circuits, generally pin 2 is fed from the output of an Op Amp, pin 3 from the output of another OpAmp which is connected to the first output as unity gain (so both are same) inverting amp (so we get out of phase).
Typical feedback resistors are 10k/10k .
To ensure that both have same internal impedance, each one gets its own series resistor.

Here you have the line out of an Ampeg B200:



U2b is the real Line out Op Amp, it drives pin 2 (Hot) through C47 and R81 .
U2a is an inverting, unity gain (22k/22k=1) slave driving pin 3 (Cold) through C49 and R83 .

The mixer at the other end of a looooong XLR cable (up to 200 meters) does not know who or what is driving it, just that it sends balanced signals and "looking" into that cable, it "sees" 270 ohms to ground (Op Amp internal impedance is nil) ... it's

By the way, Ampeg is not shy, they send up to 1.9V RMS

How come?
Real pro mixers do not have an XLR Line In, true, but with their wide range (50 to 60dB) gain adjustments plus typical -20dB input pads, they can handle anything.

And will always use the XLR cables, no Pro will send a stage to mixer unbalanced signal beyond, say, 10 or 20 yards (very small Club with mixer to a side of the stage)

Now to the even cheaper minded guys.
WHAT ?????? A 50 cents Op Amp ?????? Do you wantb to see me HOMELESS???

Enter the FAKE Balanced line out:



Here U204 is a true driver, to Pin 2 through R215 (notice similarity to Ampeg circuit)
But Pin3 is NOT driven by anything

Now if we simply ground it, there will still "exist a voltage difference between pin 2 and pin 3 and the other end should still work" (most do, and that's their bet) ... but the mixer input sees a series resistor of 250 ohms yet pin 3 sees ground, or 0 ohms, so external interference does not cancel, not surprising because this is not a balanced circuit.

Somebody discovered that if you insert a dummy 250 ohms resistor, in this case between pin 3 and ground, hum is canceled ... sort of.

You can pull this stunt if there's really not strong interference, cables are reasonable quality and distances are short.

Clearly that Yorkville was designed with small Clubs or Churches or Weddings in mind, and for that use it's perfectly adequate.

[guitardad]

To top this off, I got an email from their sound guy. He says they use a standard Mic input on the board, but the run from the stage to the console is 165'. Primarily used in a Sanctuary.

That 200mv Line Out is really going to get loaded. Now I can see why Ampeg, and the Peavey I compared this to was so much higher. Maybe Yorkville is thinking ....meh they'll just a use a 20' mic cable.

It was the sound tech for the church (which can mean anyone most of the time) that requested the Amp get looked at for possible modding. Perhaps I can goose the signal level and add a pot for them to adjust. I'm not really a fan of re engineering for these situations, but it seems a way to possibly help this guy out.

I'm thinking of adding a pot of 25k for R39. That should not upset the balanced line out pins.

Or what about changing R228 to about 10k or 15k pot?

I could just dilly dally with a res sub box, but I figured I'd ask around first.

Thanks for the replies