Mixer Hi Z/Line Input vs Direct Box/Preamp

[stratmansblues]

I have a Allen & Heath Zed10fx mixer. My guitar has a Fishman Matrix Infinity pickup installed. I am trying to figure out how I should connect to this mixer. Should I use the Hi Z input or a direct box? I usually perform with one QSC K10 speaker behind me and the mixer is right next to it so I am not using a long cable.

For years I gigged a Yamaha EMX512sc powered mixer and always plugged into the guitar into the line input. The only time I ever used a direct box is when I plugged into a snake at a theater I worked in.

The reason I am asking is because there is a lot of mixed info regarding direct boxes and active preamp guitars. I have been using a Whirlwind IMP 2 into a mic input and the tone is pretty bad.

[Mandobart]

You can plug straight in to the high impedance input - I think there are two Hi Z channels on this board? That said, I've never had a good DI or preamp hurt the sound. Try it each way and decide.

[Br1ck]

It all depends on the manufacturer's definition of HiZ. My Carvin AG 300 has a Hi Z input switch, but it is only 500K ohms. That to me is the one design flaw in the amp. Piezo pickups like to see at least 1 Meg.

So a direct box/pre can address both the lengthy cord run issue, and the correct input impedance for the device input. My RedEye works great.

[Mandobart]

Originally Posted by Br1ck

It all depends on the manufacturer's definition of HiZ. My Carvin AG 300 has a Hi Z input switch, but it is only 500K ohms. That to me is the one design flaw in the amp. Piezo pickups like to see at least 1 Meg.

So a direct box/pre can address both the lengthy cord run issue, and the correct input impedance for the device input. My RedEye works great.

According to Carvin this means it is designed for impedances of 500 k or greater, not that it is a 500 kohm impedance. I don't know what the actual impedance is. I plug my piezo equipped mandolin, fiddles, mandocello and guitar right in with no box and depress the hi z button on my Carvin AG300 and it sounds fine. It also sounds fine with my Redeye, and the Carvin supplies 48 volt phantom power so I don't run down the battery on the Redeye.

[lschwart]

The Matrix Infinity is an active pickup, so you should be able to plug into any of the 1/4 mono inputs on the mixer. The high z inputs shouldn't make a noticeable difference. If you need to go in with a line longer than 10 or 15 feet, use a DI box and go into one of the mic inputs with an XLR cable.

Louis

[Cochese]

Actually with an active pickup system you should easily be able to run much longer cable runs either unbalanced or balanced. For instance I've run my Taylor T5 which is an active system with over 140' of unbalanced cable and there was no signal loss or extra noise. That's pretty extreme but long cable runs are generally problematic for high Z signals. The reason microphones use balanced cable is that mic level is generally considered -30dB which means they require a lot of preamp gain to reach unity gain on a mixer channel. Over a long cable run that type of gain can induce noise which is why they run miss balanced.

Direct boxes are used to match a high Z signal to the low Z input of a board, convert to a balanced connection if needed, flip phase etc. I work part time for T21 and we make DI's. Ours are active and I use them with both active and passive instruments. Much of it depends on what needs to be done. Our DI's are a little different in that they also offer tone shaping and are not just for interfacing.

People get hung up on the balanced thing but that's more to do with snakes that are used to run from the stage to a mixer. They are generally XLR so if you have a guitar with a 1/4" TS out you need either a DI or a 1/4" to XLR adapter assuming the guitar has a decent active system. With a high Z guitar you are usually better with an active box as it's easier for them to be designed with the proper input impedance for the instrument. It's difficult to that type of thing with a transformer. It's best to know the specs of your pickup system and the input impedance of the DI. For instance when I did a gig at Radio City Music Hall they had a Countryman DI which has a 10megOhm input and I was using my K&K passive pickup which is mean for 1MegOhm input. The Countryman will work but not optimally. I just plugged in a Boss TU2 Tiner before the DI to correct the impedance mismatch.

[Br1ck]

Originally Posted by Mandobart

According to Carvin this means it is designed for impedances of 500 k or greater, not that it is a 500 kohm impedance. I don't know what the actual impedance is. I plug my piezo equipped mandolin, fiddles, mandocello and guitar right in with no box and depress the hi z button on my Carvin AG300 and it sounds fine. It also sounds fine with my Redeye, and the Carvin supplies 48 volt phantom power so I don't run down the battery on the Redeye.

I then admit my error if that is the case, but my sound using the RedEye is audibly better. Figured it was an impedance issue.

[Cochese]

Originally Posted by Mandobart

According to Carvin this means it is designed for impedances of 500 k or greater, not that it is a 500 kohm impedance. I don't know what the actual impedance is. I plug my piezo equipped mandolin, fiddles, mandocello and guitar right in with no box and depress the hi z button on my Carvin AG300 and it sounds fine. It also sounds fine with my Redeye, and the Carvin supplies 48 volt phantom power so I don't run down the battery on the Redeye.

I just looked at the manual. It states:

Input Impedance: 1/4”: >100K or >500K ohms (switchable)
XLR: 2.2K ohms

That is a bit low for the average acoustic instrument but is still a very high impedance. Generally you want to be at least 10 times higher than your pickup but I've found that most manufacturers just tell you the recommended input impedance to plug in to. I don't really know what the actual impedance of my K&K or Barbera pickups are. K&K recommends 500k to 1MegOhm and Barbera recommends 1megOhm as well. I've used them both with our Para Driver DI which is 4.7 MegOhm and they work fine. I find with my Fishman with the 10MegOhm input is too high and I get too much bass that needs to be dialed out.

When all is said and done if you like the way your guitar sounds and you don't have any issues like feedback or overloading you can't hurt anything.