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[Mike Caldwell]

Thanks Art.  So the keyboard "sees" higher impedance at the DI which effectively attenuates the signal around 20db?  Then from there its effectively low impedance on to the mixer, at a much reduced signal strength?

In the case of a passive DI the higher input impedance does not load down/attenuate the output from the keyboard.
It's the transformer winding ratio between the input/primary side and the output secondary side that creates the attenuation of the signal.

[Andrew Hollis]

The DI box setup results in a 21db lower signal strength than I get going directly into the 1/4" inputs on the mixer. What on earth is going on?

This is normal. 99% of DI's used in live sound are attenuators regardless of active of passive status. Mike is correct. Impedance has little to do with what is going on.

What is happening is more straightforward: you are taking a weak line signal and dropping it to mic level, so now that signal is subterranean.

What would better serve you is a 1:1 unity transformer, similar to this. No venue will have one, so it might be useful to stick it on your keyboard for gigs. Or just get a little mixer for your keyboards, that's common.
https://hermanproav.com/product/4272/RDL-TXAFC1M-Unbalanced-to-Balanced-Audio-Transformer

All that said, any mic preamp has enough gain to 'fix' the normal DI attenuation of a line level source. Afterall keyboards are all pretty much the same.

There also aren't many technical (I'm not saying operational) reasons to not run a keyboard analog master pot at 100%; the analog pots on keyboards are attenuators from unity, so when you run at 50%, you're giving up headroom and noise performance.

[Don Martz]

This is normal. 99% of DI's used in live sound are attenuators regardless of active of passive status. Mike is correct. Impedance has little to do with what is going on.

What is happening is more straightforward: you are taking a weak line signal and dropping it to mic level, so now that signal is subterranean.

What would better serve you is a 1:1 unity transformer, similar to this. No venue will have one, so it might be useful to stick it on your keyboard for gigs. Or just get a little mixer for your keyboards, that's common.
https://hermanproav.com/product/4272/RDL-TXAFC1M-Unbalanced-to-Balanced-Audio-Transformer

All that said, any mic preamp has enough gain to 'fix' the normal DI attenuation of a line level source. Afterall keyboards are all pretty much the same.

There also aren't many technical (I'm not saying operational) reasons to not run a keyboard analog master pot at 100%; the analog pots on keyboards are attenuators from unity, so when you run at 50%, you're giving up headroom and noise performance.

Thanks Mike and Andrew.  Very interesting.  So the transformer in a passive DI (and circuitry in an active one too) tends to attenuate all signals?  I guess it makes sense since the DI is feeding an XLR input that is designed for really weak signals.   

I've been using 50% volume on the keyboard so that on quiet piano-only songs, I can boost the volume to be heard but yet retain the mellower tone of a quietly played piano.  This afternoon, I boosted the keyboards global gain 6db and I think that, coupled with me raising my keyboard volume knob to 75% should give the FOH a strong enough signal while still allowing me some upper volume adjustment on the keyboard.   I'm going to have to dig into the design of DI boxes to learn more.  This is interesting stuff.

Thanks for your responses.

-Don

[Steve M Smith]

A passive DI has a transformer.  The turns ratio of which will reduce the signal somewhat.  Having said that, they are regularly used for just such as purpose and the extra gain of the mic channel they are plugged into will compensate.

However, if you need extra gain, an active DI would be a better choice as it will buffer the signal without attenuating it.


Steve.

[Mike Caldwell]

Thanks Mike and Andrew.  Very interesting.  So the transformer in a passive DI (and circuitry in an active one too) tends to attenuate all signals?  I guess it makes sense since the DI is feeding an XLR input that is designed for really weak signals.   

I've been using 50% volume on the keyboard so that on quiet piano-only songs, I can boost the volume to be heard but yet retain the mellower tone of a quietly played piano.  This afternoon, I boosted the keyboards global gain 6db and I think that, coupled with me raising my keyboard volume knob to 75% should give the FOH a strong enough signal while still allowing me some upper volume adjustment on the keyboard.   I'm going to have to dig into the design of DI boxes to learn more.  This is interesting stuff.

Thanks for your responses.

-Don

Also lets not for get that a DI's transformer and or active circuit provides the low impedance balanced output our mixers all want to see coming out of the snake cable.

As for your mention of adjusting your own level during songs that's OK for solo or small shows with no one running sound but at a larger show with someone running sound that will drive them crazy!

[Taylor Hall]

As for you mention of adjusting your own level during songs that's OK for solo or small shows with no one running sound but at a larger show with someone running sound that will drive them crazy!

I don't know how many times I've wished for a scimitar to lop off a DJ's digits who can't keep them off the flipping master knob! We've seriously thought about investing in our own CDJ rig just so we can put our own "physical limiters" on the gear...

[Kevin Maxwell]

As for your mention of adjusting your own level during songs that's OK for solo or small shows with no one running sound but at a larger show with someone running sound that will drive them crazy!

I may be misunderstanding what you are saying. I work with a lot of different bands and I really like it when musicians increase their own volume when it is time for their solo and decrease it back to where they started when they are done with their solo. That is what volume pedals are for. They will know their music better than I do.

But I find that this hardly ever happens. If they do change their levels they either over shoot and turn up too loud or they forget to drop their level back down when done with the solo. So sometimes I have to decrease their level when they do a solo. I am actually surprised at how often nothing is done by the musicians when they take a solo. I can usually tell from the music that a guitar or keyboard or a horn is soloing but unless I am really familiar with the song and their arrangement of it I may miss a few notes. I think it would be great if the musicians knew how to play as if there was no sound system. And the system is there to make then loud enough for the situation. It seems like I have become the conductor. 

I have said in the past and continue to say when a band is really good I have a relaxing time of it. When they aren’t I am working so hard to make it work (not just solos and I usually  get a lot of compliments either way) but, I am exhausted at the end of the show with the band that I have had to work hard to get that way.

[Tim McCulloch]

I'm thinking there is something else going on.  Even the -10dB setting on the Roland should be capable of driving most tiny-transformer DIs into saturation at low freqs.

Even if it doesn't saturate the transformer core, there should be sufficient signal to require no more input strip gain than an SM58... or some one, somewhere, had unrealistic expectations of level.

[Roland Clarke]

Passive DI’s are more problem than they are worth.  On acoustic instrument I find they can be a pain.  As general DI’s for events when I’m taking all comers I use just active boxes and do away with the faff.  Keys are usually fine with a decent passive box, but a pair of the BSS 116’s are always fine, even things like the lowly Behringer DI 100 boxes will always work.

[Don Martz]

I'm thinking there is something else going on.  Even the -10dB setting on the Roland should be capable of driving most tiny-transformer DIs into saturation at low freqs.

Even if it doesn't saturate the transformer core, there should be sufficient signal to require no more input strip gain than an SM58... or some one, somewhere, had unrealistic expectations of level.

Mike, Taylor and Kevin, I agree, I have run sound for other bands and have been frustrated by volume changes too. 

To give you an example of a volume change I may make, we occasionally "bring things down" during a performance and play a song with just piano and vocals, say Journeys "Faithfully".  As you know, a piano's tone will change the harder it is being played and I prefer to start this song with a soft tone which requires that I don't attack the keys which means that my output is correspondingly low.  To compensate, I temporarily increase the keyboard volume from, say, 12:00 to 2:00 and play the song.  After the song is over, I return the volume to 12:00.  I continually try to listen and adjust my playing so that our sound is always balanced with respect to volume of instruments and vocals.  Point well taken.

Tim, I haven't yet wrapped my head around this line-in vs. DI conundrum.  It still amazes me that there is 20db (21db in my experiment) difference between using 1/4" line inputs vs. DI box-fed XLR inputs on the console.  As Debbie and others have stated, line outs on keyboards, drum machines and similar devices generally are pretty hot relative to microphones or even passive electric basses for that matter.  So how is it that a DI box can attenuate that strong of a signal 21db and yet a much weaker electric bass signal through the same DI can still have a usable signal strength at the console?   As I said earlier, the keyboards output is huge (just under clipping at 50% volume on the keyboard and unity gain at the mixer) when connected to the 1/4" line inputs of any channel on the mixer so I don't believe Roland has employed a -10db output setting.  I don't know for sure but I would bet that all their "pro" stuff is +4.  I'm just going to have to do more research and read more of this forum's excellent posts to understand this better.

Thanks,

-Don                       

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