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[Gordon Waugh]

My keyboard player has a Hartke KM60 keyboard amp. The keyboard is the only thing plugged into her amp. The only way she hears the vocals and other instruments is from the nearby vocal wedge monitor which is about 6 feet to fer left. And it is not quite loud enough for her.

Hartke manual:
http://www.samsontech.com/site_media/legacy_docs/KM60100_OM_5L_v1.2.pdf

I am thinking of plugging an aux send into her amp. However, the amp has only unbalanced line-level inputs and one balanced mic-level input. The aux send is, obviously, balanced line level. I could also connect the (balanced) output from the active vocal monitor wedge to an amp input. That would give me one fewer monitor mixes to adjust.

What's the best way to hook them up? Can I just put a DI box before the unbalanced amp input. I think that would covert the balanced signal to an unbalanced signal but would the impedance or level be way off?

[Jordan Wolf]

My keyboard player has a Hartke KM60 keyboard amp. The keyboard is the only thing plugged into her amp.

That's good.

The only way she hears the vocals and other instruments is from the nearby vocal wedge monitor which is about 6 feet to fer left. And it is not quite loud enough for her.

Are there any limitations, other than budget, that stop you from supplying another monitor mix & wedge just for the keyboard?  Not enough Aux Sends, need another power amp or monitor wedge, etc. - just so we know what we've got to work with.

If you're stuck with using the keyboard amp, I would do a couple of things:
1. The manual states that the nominal input level for both channels 2 and 3 is -20dBu.  If your Aux Sends are referenced to +4dBu, then a 25dB pad would match levels nicely.  You could then use the P/AFL function on the mixer to make sure you're not sending too hot of a signal.

2. Run the Aux Send up to the amp balanced and unbalance it at the input using an adapter that taps the Tip and Sleeve but not the Ring from the TRS connector.  Or, try keeping it balanced and see what it sounds like through the amp.  If it sounds thin or distorted, use the adapter; if it sounds "normal", then you'll probably be fine.  Also realize that when you only take the Tip instead of both it AND the Ring, you'll lose 6dB of level since you're only tapping half the voltage.  Just keep that in mind when adjusting levels.

[Brad Weber]

My keyboard player has a Hartke KM60 keyboard amp. The keyboard is the only thing plugged into her amp. The only way she hears the vocals and other instruments is from the nearby vocal wedge monitor which is about 6 feet to fer left. And it is not quite loud enough for her.

Hartke manual:
http://www.samsontech.com/site_media/legacy_docs/KM60100_OM_5L_v1.2.pdf

I am thinking of plugging an aux send into her amp.

Are they using the KM60 as a monitor or as an amp and if the latter is it mic'ed into the system or is it the reinforcement for the keyboard?  My concern is that this seems to be giving the keyboard player control on stage over their monitor position, level and EQ and doing so with a speaker that may be adjusted based on other usage, which seems like it could potentially turn into a nightmare for feedback, bleed into other mics, etc. 

[Sidney.Pilien]

Are they using the KM60 as a monitor or as an amp and if the latter is it mic'ed into the system or is it the reinforcement for the keyboard?  My concern is that this seems to be giving the keyboard player control on stage over their monitor position, level and EQ and doing so with a speaker that may be adjusted based on other usage, which seems like it could potentially turn into a nightmare for feedback, bleed into other mics, etc.

I tried it before and major feedback problems. Can't you mover her closer to a wedge? If not, get her a Rolls PM w/ a good earbuds. This worked perfectly w/ our keyboarder.

[Bob L. Wilson]

My keyboard player has a Hartke KM60 keyboard amp. The keyboard is the only thing plugged into her amp. The only way she hears the vocals and other instruments is from the nearby vocal wedge monitor which is about 6 feet to fer left. And it is not quite loud enough for her.

Hartke manual:
http://www.samsontech.com/site_media/legacy_docs/KM60100_OM_5L_v1.2.pdf

I am thinking of plugging an aux send into her amp. However, the amp has only unbalanced line-level inputs and one balanced mic-level input. The aux send is, obviously, balanced line level. I could also connect the (balanced) output from the active vocal monitor wedge to an amp input. That would give me one fewer monitor mixes to adjust.

What's the best way to hook them up? Can I just put a DI box before the unbalanced amp input. I think that would covert the balanced signal to an unbalanced signal but would the impedance or level be way off?

Woe to him that ever gives a player a stage monitor they can control the volume on. As soon as that amp gets turned up the first time you will have other players asking for more me and the volume war will have started.

[g'bye, Dick Rees]

Woe to him that ever gives a player a stage monitor they can control the volume on. As soon as that amp gets turned up the first time you will have other players asking for more me and the volume war will have started.

I like the 16 ohm passive monitors like the HotSpot.  They can only be turned down........

[Gordon Waugh]

Are there any limitations, other than budget, that stop you from supplying another monitor mix & wedge just for the keyboard?  Not enough Aux Sends, need another power amp or monitor wedge, etc. - just so we know what we've got to work with.

The keyboard amp is not miked. It is used only as a monitor for the keyboardist. It is placed facing toward the back of the stage and away from the audience. The purchase of the keyboard amp was against my better judgment. The keyboardist wanted it because:
- She wanted to control its volume,
- Its sound quality is much better than our (active) Harbinger wedges (which, I believe, are a house brand at Guitar Center), and
- Our music director wants to minimize the number of monitor mixes. That's a whole other story. We currently have two mixes: vocals and guitar/bass. We have only 30 minutes to set up all of our equipment (in a school gym) and do sound checks. We have an analog mixer. I would like to set aside an hour to get the mixes just right, but have not done so yet.
- One of our two keyboardists says that no earphones fit her. The latest she tried were the Shure SE215s which have six different pairs of sleeves (i.e., the part that goes in the ear).

By the way, I do have an unused Harbinger active wedge. The keyboardist used to use it with her own mix from the Aux send.

Jordan, if I understand you correctly, it looks like neither of your two suggestions give me a balanced line. I am concerned that the unbalanced signal down a 100' snake will be too noisy.

[g'bye, Dick Rees]

Jordan, if I understand you correctly, it looks like neither of your two suggestions give me a balanced line. I am concerned that the unbalanced signal down a 100' snake will be too noisy.

Re-read his point #2.  If you un-balance the signal at the far end of the run, it will in effect be balanced all the way there, so it is balanced for the length of the run, then converted at the far end.  You'll be OK and there should be no extra noise.

[Gordon Waugh]

Re-read his point #2.  If you un-balance the signal at the far end of the run, it will in effect be balanced all the way there, so it is balanced for the length of the run, then converted at the far end.  You'll be OK and there should be no extra noise.

I guess I don't fully understand balanced signals. I thought that a device at the end of the signal path has to subtract the voltage on the neutral-negative pair of wires from the neutral-positive pair of wires. That's where the noise gets eliminated. So, if you don't have a device at the end to subtract the voltages then the subtraction does not occur. What am I missing?

[John Roberts {JR}]

I guess I don't fully understand balanced signals. I thought that a device at the end of the signal path has to subtract the voltage on the neutral-negative pair of wires from the neutral-positive pair of wires. That's where the noise gets eliminated. So, if you don't have a device at the end to subtract the voltages then the subtraction does not occur. What am I missing?

me too...

It depends on the definition of the rather vague "adapter" at the far end...

If you take a strong balanced signal or balanced line (they're two different things) to span the distance, then at the Keyboard amp, pad it down with a "H" pad  or similar, to feed into the "balanced" mic input... it should work fine.

Note: the OM calls that a mic/line input, so you might plug right in.

Connecting a balanced line to an unbalanced input, will unbalance it. About the only "adapter" that wouldn't unbalance it is a transformer. 

Note: again looking at the OM the line inputs call for using musical instrument cables (T-S) so are clearly not balanced or differential.

While a pad at the far end of a long balanced feed may isolate the line from being impedance unbalanced, if the pad resistors are relatively large, but this is largely unimportant if the receiver is not differential. About the only merit to this would have is if that one balanced feed is sent to multiple other balanced inputs to preserve the balanced termination.

Whether this is a problem or not probably depends on quality of the grounds between FOH and the stage, more than distance, but given enough distance pretty much guarantees the grounds will be different.

I'd plug it balanced into the mic/line input and see how it goes.

If you must plug into the T-S input, consider using an isolation transformer.

JR

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