Active EMG pickups - use Hi-Z instrument inputs or line-level inputs?

Gear
1

Somehow I ordered an SSL 12 audio interface today - one moment I didn’t know I needed it, the next moment I had an order confirmation in my inbox.

It has 4x combined line/mic inputs and 2x Hi-Z instrument inputs.

Which one would be ideal for active EMG pickups?

Also: I would like to leave the instrument cables connected to the audio interface, one for each bass and just connect the bass I’m playing to the right cable…
It’s just cause I’m too lazy to change the level, every time I switch to another bass. This way I just have to plug the right cable into the bass and off we go.

Unfortunately, unconnected cables cause humming sometimes. Is there a way to avoid the humming with discnnected cables?

2

I’ve got 2 DI’s set up and running to my mixing board (which acts as my DAI). I can mute each channel, I don’t know if your interface has that option, either physical button or software?

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Not in hardware … in software it should have it, you’re right! Appearantly the SSL also has already (supposedly) DI’s built-in for the Hi-z input.
I’m still in Motu M4 “mode” and need to get used to the wonderful world of software routing for DAIs!

Don’t know if this will resolve that. I just tested with my “old” Motu M4, and if I touch the jack (of the cable ^^) it clicks once and hums after.
The humming I can bring down to almost silent with level. But it still has side effects even with volume to 0, for example when it repeatedly touch the jack (of the cable ^^).

Also: still don’t know, if the Hi-z’s (which suppuse to have the buil-on DI) ideal for active EMGs…

4

Hi-Z inputs are basically for going from your bass directly into your DAI.

If your bass is going through a pedal chain, preamp, etc, or had an active pre-amp on board then you don’t need the hi-Z input.

You can swap all this around, but you are likely to hear some distortion or other degrading of the signal etc depending on the I out (instrument).

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5

Thanks!

This is exactly my use case!

Do I understand it right that an active pre-amp on board is NOT the same as an active PU?

If it’s the same: I can use the line level inputs, right?

I’m looking for the best way to use my SSL 12.
And Hi-z is “only” two inputs … the backside combo is 4 inputs

I guess, my misunderstanding is, that the backside inputs of the SLL 12 look the same as the inputs of my Motu M4 (combo), but in fact are different, as the SSL 12 has line/mic combo and the M4 has instr/mic combo!?

6

Active pickups are not the norm and require matched preamps.
Most active bases have passive pickups with preamps that make them “active bases”.

Any thing boosting the signal in your chain does not use the high-Z input.

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This is not necessarily true.

Hi-Z is for instrument level outputs that need a high-impedance input. Many/most pedals also output at instrument level, as do basses with active preamps; all DI’s should be at microphone level.

But regardless of level, basically it’s all about impedance matching here, kind of the same as with high-impedance headphones. You want the input impedance on the interface to be much higher than the output impedance of the instrument.

I would try it both ways and see which sounds better.

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8

Again, this is not correct. Another thing to note with these inputs - you’re not switching between “instrument level/impedance” and “already amplified”. You are switching between “instrument level/impedance” and “microphone level”.

Mics have much, much lower output impedance than guitars and basses, and so do not need the high-impedance input.

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9

I just checked the output impedance of a random active EMG pickup (35TWX) and it as listed as 2Kohm. This is lower than any passive bass pickup (usually in the 20-100Kohm range or even higher), but it is also higher than most mics (usually 100ohm-1Kohm). This doesn’t factor in the rest of the bass of course (i.e. the other pickup).

So, I would try it with both a high and low impedance input. It will probably be fine with a normal mic input.

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10

Having a DAI with a “passive” Z that’s adjustable between 2.2K and 1M and an “active” Z that’s 10k, it has no noticeable effect on my 2 active basses :slight_smile:

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11

Ha!

Well, luckily most (but not all) preamps should have a relatively low output impedance anyway, so will probably work fine with a microphone level input instead of a high-Z input.

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Which DAI do you have?

@Everybody - cool, how a question about my misunderstandig (combo line/mic is not the same as combo instr/mic) leads to an interesting discussion, where I learn a lot (again).

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13

I have not looked at a schematic but I strongly suspect that the difference is literally a single resistor being added to the circuit when you press the button

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14

Would that be the same with pad buttons on amps?
Capture
(schematic of a DG amp)

15

Hmm. That’s adding a feedback to an opamp, which is not at all what I was expecting :rofl:

Guess I was wrong. I was thinking it would be something like a switch in parallel with R1 in this circuit (or rather, in series with a smaller resistor in parallel to R1):

image

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I had to look up schematics symbols there. Indeed, that would not be a resistor. But I suspect DG to simplify their schematics on purpose :sweat_smile:

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Yeah that’s a symbol for a generic amplifier.

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18

I asked the same question in zzzeee Zzzerman forum (I always double check everything), and one guy uses the SSL2 (which is the reduced version of the SSL 12) with active EMGs and the BTS - on the backside line/mic combos.

He says the BTS is like an amp. I don’t know nothing about anything, but to me it’s just an active EQ.
I use the VLPF , whic in my opnionion is just a simplified version of the BTS.

So that would mean: it works.

Hopefully, I can test this tomorrow. Thomann is a little slow currently…

19

I owned a SSL2 and used both active and passive basses with it without issue.

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On the backside? Which DAI do you use now?