signal path for QSC K10?

[BluesB3]

I've been rehearing with my new band in a 22x24' garage. Signal path for the Electro 2 is 1/4" mono out >Mini Vent I 1/4" in> IMP DI box in>DI xlr out>QSC channel A xlr line in. Signal path for the CP73 is 1/4" mono out> IMP DI box in>XLR out QSC to channel B xlr line in.  Both A&B gain pots on the K10 are dimed out at +10.

 

QSC K10 is on a standard TS80 speaker tripod about six feet behind me. All patches are maxed out at 127 midi value, with the master volumes dimed on both instruments, it just doesn't sound loud enough for a weekend warrior, cover band average venue. This isn't a Marshall stack band. Guitar player plays thru some sort of Peavey KB2 or 3. The drummer is not a hard hitter and the tasty bass player is playing thru a Hartke KB12.

 

Am I doing something wrong in my signal path? I know the Electro 2 has a low output. I've used a 1/4" TS cable from the headphone out to the QSC before, but I thought the DI box might take care of that. The CP73 is new to me, so I don't have much experience with it.  Should I be trying to run 1/4" TS cables to the QSC instead of the DI boxes?

[mynameisdanno]

For rehearsals I'd suggest you run 1/4" TS from your two instruments into the two channels on the QSC.

 

The Whirlwind IMP 2 will make things quieter, not louder; like most DI's, it puts out a mic level signal (this is because DI boxes are primarily used to feed signals to mixing consoles, and the general expectation of mixing consoles is mic-level signals at the inputs).  If you absolutely need to use DI's between your keyboard and your speaker e.g. to eliminate hum/buzz (which it doesn't sound like is an issue here), you'd want to run into the Channel A input on the QSC, and set the mic/line switch to mic.  This will make that input considerably louder, so turn down the gain on the QSC input first and slowly bring it up; you may also need to turn down your keyboard output volumes.  Unfortunately Channel B input doesn't have a mic level input mode, so you won't be able to use the K10 as a mixer if you're doing this.

 

What I'd *really* suggest is that you not try to use the K10 as a mixer - at least not outside the garage.  When it's time to gig, get yourself a Radial Key Largo.  Your input levels for the two instruments will be easily physically accessible, you'll have a dedicated monitor output level control at hand to turn your K10 up or down without needing to reach behind the speaker or affect the signal level to the sound board, you'll have a high quality stereo DI for the feed to the sound board, and you'll have ground lift switches for both sets of outputs to troubleshoot hum/buzz issues.  It's a great little device if you can swing it and you can mount it on a small pedalboard next to your Mini Vent.

 

If you use your K10 as a mixer in live-performance contexts, I don't recommend using its combined output XLR to feed a signal to the FOH sound board, at least not without putting an isolation transformer of some kind between the K10 and FOH.  If they inadvertently apply phantom power to your channel you'll get a nasty buzz at the least and possibly fry some circuitry in the K10.

[HSS]

I agree with the recommendations in the post above, including flipping your QSC's channel 1 mic/line switch to mic and dialing the gain up carefully. I've done it on my QSC K12 a few times in a pinch. But IMO a Key Largo or small mixer is the way to go. 

 

If a Key Largo is too expensive, just about any decent quality small mixer can work to boost the gain out to the QSC. I usually use a small Yamaha  MGO6x.

 

Having said this, I confess that I'm gassing for a Key Largo because its routing options are geat for keyboards. 

 

FWIW... I also have small Behringer 802 or 502 mixers as backups which are cheaper and lower quality than the Yamaha MGO6 but work OK. 

[BluesB3]

Thanks this is exactly the kind of info I was looking for. I never thought about the inadvertent phantom power issue. I'm trying to work off the $2 grand I just spent on the CP73. I like the Radial products in general but the Key Largo is out of reach for a while.

 

I noticed that the CP73 has a 1/4" input for another keyboard. I haven't had time to experiment with this since the keys stay at the rehearsal garage. Would there be any advantage in running the Electro into the CP and then out through the DI to the Mic input (as suggested) on Channel A of the K10?

 

Also what is the practical length for 1/4" to 1/4" TS instrument cord without signal loss or noise?

[HSS]

15 minutes ago, BluesB3 said:

Also what is the practical length for 1/4" to 1/4" TS instrument cord without signal loss or noise?

FWIW an anecdotal number I've heard for max length for using 1/4" TS cables is 20 ft.  When I use TS cables, I try to keep mine to 15 ft or less.   I'm sure there are other more knowledgeable KC'ers than me who can clarify this more. 

[mynameisdanno]

For line-level signals like keyboards, unbalanced cable runs (such as 1/4" TS) are generally fine up to 25 feet.  You *might* notice some slight degradation at that point or beyond, and depending on the environment you might be more likely to get some noise issues, but it probably won't be anything that would distract from a rehearsal.  Guitar players have to worry more about noise and high-frequency loss from long 1/4" cable runs, but for keys it's generally less of an issue.

 

Back about 20 years ago, I used the 1/4" inputs on my Yamaha CP300 to mix in my Nord Electro 2 to avoid carrying a separate mixer.  Worked great.  I see the CP73 has added an input gain control.  Even better.

 

For rehearsal, I would suggest trying:

Nord > Mini-Vent > CP73 input

CP73 (1/4" TS) > QSC K10 line input (if input A, set for line mode)

Adjust input gain on back of CP73 as needed to balance Nord volume with CP73

 

If the overall volume isn't loud enough in that mode even with the keyboard volumes and K10 input cranked all the way, the next thing I would try is running an XLR cable from one of the CP73's XLR outputs into the K10 (with the input still in line mode).  The XLR output on the CP73 might be noticeably higher-level than the 1/4", or the K10 might get a hotter input signal when getting a balanced signal.  It's worth a try.

 

Failing that, next I'd try putting the Whirlwind IMP inline between CP73 1/4" out and K10 XLR in, and setting the K10 input to mic mode.  That may or may not result in more effective gain, depending on the K10's mic preamp, but it's worth a try.

 

If that doesn't work, Yamaha MG06 is probably the cheapest good-sounding way to get some extra gain before you hit your K10.  When you gig out, the same precaution applies as with the K10 output – don't try to use its XLR outputs to directly connect to FOH soundboard.  You always want to have a DI or other type of isolation transformer between your gear and the main soundboard, to allow you to easily lift the ground in the event of hum, and also to protect your gear from phantom power.  This also goes for the XLR outputs on the Yamaha CP73.  It's really annoying that they put those connections on there, I guess it looks "pro" but people inevitably conclude that they don't need a DI which just isn't true.

 

The "nuclear option" without spending any more on gear would be to run 1/4" TS to the K10 input A (no DI between), with the K10 input set to mic mode.  You're sending a line-level output to a mic-level input, which is way more gain than you probably want. Start with just a couple notches of gain on the K10 input, and both keyboard master volumes at zero, and bring them up very slowly.  It will definitely get more than loud enough, but it probably won't sound good; there'll be significantly more hiss and likely some distortion.  I'd probably file this under "misuse", not something I'd do long-term.  

 

[Reezekeys]

Owner of two K8s for 13 years here. Those QSCs can get loud enough to melt eardrums at close range. Your DIs are reducing the signal level from line to mic, then by your description you have your Ks set to line level - so no way can the signal drive the K's amp to a good volume. Just connect directly to the Ks from your keyboards via 1/4" cables and I bet you will hear vastly more output level. With the mic/line switch on "line" I just maxxed my K's input knob. For some band situations that's not enough - in that case, switch to mic level with volumes at minimum and raise levels carefully and you will get all the volume you should ever need. I'm aware only the "A" channel has the mic/line switch so if you need that extra juice I would put whatever keyboard has the hotter ouput in the B input.

 

If the Electro and CP have decent EQ and FX adjustments available onboard, save some money and don't get a mixer - you don't need one. BTW, keep that DI box - it's a good way to get your feed to FOH or monitors. Use the pass-through to go from your keyboards to the K. As others have noted, going from the K's mix out to FOH can be risky if phantom power is on.

[BluesB3]

 

Thanks Danno. re this statement, "the next thing I would try is running an XLR cable from one of the CP73's XLR outputs into the K10 (with the input still in line mode)."

 

I saw the XLR outs on the CP but wondered if using only one XLR output would only give me one side (L or R) of the stereo field. Of course I could run one XLR to the A channel and another to the B Channel of the K10 if staying in the Line mode.

[mynameisdanno]

4 hours ago, BluesB3 said:

 

Thanks Danno. re this statement, "the next thing I would try is running an XLR cable from one of the CP73's XLR outputs into the K10 (with the input still in line mode)."

 

I saw the XLR outs on the CP but wondered if using only one XLR output would only give me one side (L or R) of the stereo field. Of course I could run one XLR to the A channel and another to the B Channel of the K10 if staying in the Line mode.

Yes, it looks like you’ll get only one side of the CP73 if you use one XLR output. I can’t speak for the CP73, but on many keyboards, when I have to run mono, I prefer to use one side anyway, rather than a summed L+R output, due to phase cancellation - but that’s a bigger deal with some piano samples than others. I usually go with the right channel, since most keyboard manufacturers tend to bias slightly towards the treble on the right output, which suits the piano role in most of the ensembles I play with.   I also think the Mini Vent sounds better in mono when using one side only rather than both sides summed.
 

It’s worth a try both ways. Running two XLRs as you proposed will give you both sides summed to mono. 

[hrestov]

I’d put nord electro in Cp’s input and then an xlr from Cp to the Qsc. Xlr output of Cp have more volume than jack. 
I prefer use the R output, I like Cfx so. I don’t like R+L. 
 

for ventilator I think that you could use only one side also. 

[Delaware Dave]

 

 

[BluesB3]

On 2/7/2024 at 3:20 PM, mynameisdanno said:

 

Back about 20 years ago, I used the 1/4" inputs on my Yamaha CP300 to mix in my Nord Electro 2 to avoid carrying a separate mixer.  Worked great.  I see the CP73 has added an input gain control.  Even better.

 

For rehearsal, I would suggest trying:

Nord > Mini-Vent > CP73 input

CP73 (1/4" TS) > QSC K10 line input (if input A, set for line mode)

Adjust input gain on back of CP73 as needed to balance Nord volume with CP73

 

If the overall volume isn't loud enough in that mode even with the keyboard volumes and K10 input cranked all the way, the next thing I would try is running an XLR cable from one of the CP73's XLR outputs into the K10 (with the input still in line mode).  The XLR output on the CP73 might be noticeably higher-level than the 1/4", or the K10 might get a hotter input signal when getting a balanced signal.  It's worth a try.

 

Failing that, next I'd try putting the Whirlwind IMP inline between CP73 1/4" out and K10 XLR in, and setting the K10 input to mic mode.  That may or may not result in more effective gain, depending on the K10's mic preamp, but it's worth a try.

 

 

The flaw in my thinking was reading in DI brochure that said it was an 150 ohm out. If I'd have been thinking from my TV station days, 150 ohms is usually mic impedance and line impedance is 600 ohms.

 

We moved the keyboard position today in our setup from stage left to stage right. This gave me a good opportunity to repatch every thing. I ended up using a hybrid of Danno's suggestions.

 

Nord > Mini-Vent > CP73 input (Adjust input gain on back of CP73 as needed to balance Nord volume with CP73)

CP73 (1/4" TS) mono out> IMP DI box in > DI xlr out> QSC channel A xlr line in set for mic mode

 

As Reezekeys said, this gave me plenty of gain before distortion.  When I have more time, I might try the one Right XLR out from the CP straight to the QSC channel A in.