Unbalanced Synth –> Guitar Pedals –> Active or Passive DI?

[Echos]

If I'm running synths with unbalanced outputs (Rev2, Opsix, TD-3) into an unbalanced patchbay and then routing them through guitar pedals, do I need an active or passive DI to get them into a console's Mic inputs?

[ef37a]

If I'm running synths with unbalanced outputs (Rev2, Opsix, TD-3) into an unbalanced patchbay and then routing them through guitar pedals, do I need an active or passive DI to get them into a console's Mic inputs?

You definitely need to balance the synth signals to put them into an XLR mic input. You don't really need an active DI since the synth and the pedals will not require the 1 meg Ohm input that passive guitars like to 'see'. So, a passive, i.e. transformer DI will suffice. The only possible drawback is that synth signals go much lower than guitars which cut off at about 80Hz and a poor transformer will distort the signal. How much it is hard to say and it all depends upon the levels the synths deliver, in any case you might LIKE the 'mojo'!

The other drawback of actives is that they need batteries or phantom power.

Since you can buy a bogo standard passive DI for about a score I would get one and see if you like it.

https://www.gear4music.com/PA-DJ-and-Li ... LUQAvD_BwE

Well stone me! Will you look at that? Not worth dicking about about!

Dave.

[Sam Spoons]

Well it looks better made than the Berry D120 but they are truly appalling. And it's barely more expensive even if you need two...

[Echos]

If I'm running synths with unbalanced outputs (Rev2, Opsix, TD-3) into an unbalanced patchbay and then routing them through guitar pedals, do I need an active or passive DI to get them into a console's Mic inputs?

You definitely need to balance the synth signals to put them into an XLR mic input. You don't really need an active DI since the synth and the pedals will not require the 1 meg Ohm input that passive guitars like to 'see'. So, a passive, i.e. transformer DI will suffice. The only possible drawback is that synth signals go much lower than guitars which cut off at about 80Hz and a poor transformer will distort the signal. How much it is hard to say and it all depends upon the levels the synths deliver, in any case you might LIKE the 'mojo'!

The other drawback of actives is that they need batteries or phantom power.

Since you can buy a bogo standard passive DI for about a score I would get one and see if you like it.

https://www.gear4music.com/PA-DJ-and-Li ... LUQAvD_BwE

Well stone me! Will you look at that? Not worth dicking about about!

Dave.

Thanks for replying. My logic was that because I'd need to attenuate the synth signals to get them to play nicely with the pedals, I'd need an active DI, but I guess attenuating won't change the impedance will it? So the impedance will still be low, and therefore a passive DI will work. Is that logic correct?

[Hugh Robjohns]

If I'm running synths with unbalanced outputs (Rev2, Opsix, TD-3) into an unbalanced patchbay and then routing them through guitar pedals, do I need an active or passive DI to get them into a console's Mic inputs?

Either would work perfectly well with synths and/or FX pedals, these devices being unfussy about the DI box impedance (passive boxes have a lower input impedance than most active boxes).

However, if this is for home studio use (and you're in the UK) I'd recommend the Orchid (active) micro DI.

http://orchid-electronics.co.uk/micro.htm

Excellent performance, superb price, no unnecessary frills. I use them myself for the same application. Here's my review:

https://www.soundonsound.com/reviews/or ... s-di-boxes

[ef37a]

Well it looks better made than the Berry D120 but they are truly appalling. And it's barely more expensive even if you need two...

Have you tried that passive DI then Sam? I have had the Behringer and yes, cheap noisy ****! Mind you, I took mine apart and IMHO the design was daft and resulted in the noise. Long time ago now so I don't recall the details but I 'think' they did the attenuation THEN put in amplification.

Dave.

[Sam Spoons]

Yes, when I first started with the PA company (when the boss first set it up on a very tight budget) we had a few. They sounded crap and robust is not a word I'd associate with them. I reckon the Orchid Micro's* we replaced them with would comfortably withstand been run over by a small tank while the Berry's would disintegrate if a toddler on a trike passed in the next street

* As Hugh says Orchid DI's are excellent, I have half a dozen myself. They are a little more expensive since John has stopped selling direct but still good VFM.

[Wonks]

You shouldn’t need to attenuate the synth signals before putting them into guitar pedals. Synth outputs are generally not that much hotter than a hot guitar’s output, and if necessary, just turn the synth output down a bit.

The original performance synths e.g. Minimoog, ARP Odyssey etc. were often played through guitar amps, so the output was commensurate with that. And the synths that followed have generally kept to a similar output level on unbalanced outputs. I won’t say all, as there will be some with higher outputs.

[ef37a]

Yes, missed that Wonks. Most pedals can handle -10dBV signals (316mV) and as you say, most synths seem to be about that level but I only know this because a few years ago I was trying to help a guy with a problem and I tried to find out the level specc' of a few keyboards and synths. They seemed rather tight lipped on the subject! However, I found enough to see neg ten is where most of them are at.

Dave.

[shufflebeat]

I have a couple of the Orchid dual units.

Excellent.

[Arpangel]

https://www.gear4music.com/PA-DJ-and-Li ... LUQAvD_BwE

Well stone me! Will you look at that? Not worth dicking about about!

Dave.

“ Full frequency response ensures high fidelity reproduction”

Well, that’s that then.

[Echos]

Thanks everyone.

So my understanding now is I can probably get away with just reducing the volume of the synth, then it's just low to high impedance mismatch which isn't a problem. But what happens here if I run the signal through the pedals and into a line input. I'm assuming that even though the original signal is line-level, it's impedance won't be line-level when it comes out the other end of the pedal chain, so it's going to need a DI to get it up to mic impedance to go into the Mic inputs.

I actually have a Radial EXTC stereo which I guess would solve this problem, but I have three synths, a drum machine and two sets of stereo send/returns, so the cost of picking up another five is more than prohibitive.

[Echos]

Thanks everyone.

So my understanding now is I can probably get away with just reducing the volume of the synth, then it's just low to high impedance mismatch which isn't a problem. But what happens here if I run the signal through the pedals and into a line input. I'm assuming that even though the original signal is line-level, it's impedance won't be line-level when it comes out the other end of the pedal chain, so it's going to need a DI to get it up to mic impedance to go into the Mic inputs.

I actually have a Radial EXTC stereo which I guess would solve this problem, but I have three synths, a drum machine and two sets of stereo send/returns, so the cost of picking up another five is more than prohibitive.

[Wonks]

You probably won’t need to reduce the synth output by much, if at all.

If you want to use mic inputs, then yes, you’ll need a DI box, both to reduce the signal level and provide a balanced signal. But you could try running into a line input if you’ve got enough of those. However the unbalanced connection could lead to ground loop issues, but it’s still worth trying.

[ef37a]

You are getting bogged down by your ideas about "impedance" Echo. Except in a few, special circumstances* it rarely matters.

Certainly running your pedals into a mixer's line inputs should be no problem, even if they are balanced inputs there should be more than enough level and "level' is the most important factor when exchanging signal between pieces of kit. Too little and you have to crank the gain and you can increase noise. Too much and signals get distorted (but rarely is any harm done)

Yes, a DI box, active or passive, will 'transform' the source impedance from the lowish level of about 1k Ohm from a pedal to about 10 Ohms at the XLR mic output (that will however depend somewhat on the internals of the pedal) but the most important fact is that the level will be dropped by about 10 times (20dB) making it suitable for a mic pre amp. The signal will also be balanced and 'earth free' if you use the ground lift switch. That very low impedance, balanced source also means you could use very long mic cables with little interference or loss of HF signal.

*Important in the case of a passive guitar which should be plugged into one meg Ohm but lower impedances will not cause the sky to fall! You will just get less signal and screw the frequency response.
Valve output stages must 'see' the correct load impedance for the right power level at minimal distortion but even here, a 2 to 1 'mismatch' is hardly likely to do a decent amplifier any harm.

Dave.

Where "matching" is most important is with video and digital signals, usually specified at 75 Ohms in 'our' world.

[Wonks]

Yes, don't get too worried about impedance when running from a synth (low output impedance) into a guitar pedal (very high input impedance). Because when running from a guitar pedal to a guitar pedal you have exactly the same scenario of running from a low impedance output into a very high impedance input, and nobody worries about that at all. You can have a whole string of pedals and it's fine.

These days the only pedals that worry about seeing a particular output impedance on the input are very old germanium fuzz and wah designs where they need to be the first thing in the pedal chain connected to a guitar, otherwise you get a very different sound from them.

But assuming that you are talking about reverbs, delay, choruses and the like, or any 'modern' (late 70s and onwards) distortion/overdrive pedal, then impedance really isn't an issue.

[Echos]

Thanks guys.

My mixer is a Zoom L20 which has a line input per channel so plenty to use.

So is it fair to say that the place where impedance is very relevant is when going straight from a pickup into a console, i.e. instrument level straight into a line, but if that signal passes through a (modern) pedal, this is less important, so you can get away with more going pickup - pedal - line. If I run a guitar direct into the line input I see a big loss of signal in highs and upper-mids as expected, but it has two hi-Z inputs for guitar.

[Wonks]

Pretty much so.

[Hugh Robjohns]

So my understanding now is I can probably get away with just reducing the volume of the synth, then it's just low to high impedance mismatch which isn't a problem.

I fear your understanding is knocked off kilter by the tangential confusions above.

Recap the basics:

Mic level is notionally around -50dBu (depending on the mic and source it could be up to 30dB lower of 50dB higher).

Instrument level (from guitars and synths) is about -20dBu (although hot pickups and synths could reach 30dB higher).

Line level is nominally +4dBu (and peaks out about 20dB higher)

The majority of audio connections are designed to have a light output impedance (~100 Ohms) feeding a high input impedance (1.5k Ohms for mic inputs, more than 10k Ohms for everything else).

A major exception is the electric guitar which has an output impedance of 5k Ohms or more and needs to feed an input impedance of 1000k Ohms (1 Meg Ohms) or higher.

Synths generally have a low output impedance and provide a signal level somewhere between instrument level and line level, but they almost have volume controls so you can optimise the level feeding whatever is next in the chain.

So there's no issue feeding your synths into the very high impedance inputs of effects pedals. Both are unbalanced connections. If the synth output is a bit too hot for the fx pedal, just turn its output level down. Simples.

However, the output from a pedal is likely to be too hot for a mic input. Plus a mic input is relatively low impedance and balanced and could have phantom power on it.

For all those reasons, if you want to connect an fx pedal to a mic input you must do so via a DI box. Active or passive doesn't matter in this application. The DI box attenuates the signal to mic level, converts it to a balanced form, protects the fx pedal/synth from phantom power, and is designed to feed the relatively low impedance mic input (where an fx pedal might not be too happy).

But what happens here if I run the signal through the pedals and into a line input.

It will be fine — although possibly a bit quiet. Remember instrument level is lower than line level. Most console line inputs have a gain control, so you can compensate for the lower input level.

The fx pedal / synth outputs are low impedance, and the line in is high impedance, so there's no problem there, and if the desk line inputs are balanced they'll still be fine with unbalanced sources (although beware ground-loop issues).

I'm assuming that even though the original signal is line-level, it's impedance won't be line-level when it comes out the other end of the pedal chain...

Impedance has nothing to do with signal level. It's a physical property of the electrical interface. In general, outputs are low impedance (but not electric guitars), and inputs are high(er) impedance.

Mic inputs are lowest at around 1,500 Ohms, line inputs are around 10,000 Ohms (or more), and things expecting to have guitars plugged in to them are around 1,000,000 Ohms.

I actually have a Radial EXTC stereo which I guess would solve this problem...

That unit converts between balanced line level and unbalanced instrument levels, in both directions, in stereo.

I have three synths, a drum machine and two sets of stereo send/returns, so the cost of picking up another five is more than prohibitive.

Its not the right tool for the job anyway!

If you have spare line inputs on your console just patch the synths/fx pedal outputs straight in.*

If you need to use mic inputs on the console use DI boxes, as previously discussed.

*As mentioned earlier, there is a possibility of ground-looo hums and buzzes with direct patching to line inputs. If this is a problem use line-isolation transformer boxes. Orchid do them for a similar price to a DI box, for example.

[Echos]

@Hugh Robjohns thanks so much. I have it now!

[Hugh Robjohns]

[skipper01]

Just kinda related, I recently tried a tonal experiment with my Novation Summit (which i like a lot) to hear what it would sound like using the UAD Unison on the mic pre's (via a Passive stereo DI box) instead of using the line inputs on my Apollo 8 (as ive always done to date).
It was very easy to A/B compare/match levels one pair via Line and one pair via the Mic Pres on different channels on the same sound/s given the Summits dual engines.
I guess i was just interested given the Summit is (in my opinion) quite a modern clinical sound.
I first tried the 1073 pre as the unison model (no EQ).
I really couldn't hear any tangible difference with the line channel one with the unison 1073 on and off (although that wasn't my main test comparison).
However, with the 1073 set to Low impedance model on the Mic pre one via the DI box it (to my ears) offered a new dimension to the sound best described as a bit more 'weight' and '3D' against the line channel one.
The downside was the increased level of noise/hiss which i guess is due in part to the extra circuitry and reduction in level from the DI box (-20db) to then be amplified again via the Apollo 8 mic pres/modelling.
Still, I actually preferred it even with the noise increase and seemed to make it sound a bit more 'retro' dare i say.
I appreciate the technical benefits of the isolation aspect of using a DI rather than line inputs.
I assume the more noticeable tonal changes are largely due to the modelling of the transformer stages of the mic pres that the line inputs may not have ?

Therein, I'm guessing studios that have ie real analogue synths are likely to be interfacing with large consoles via DI/mic pre's?
Maybe in addition to the benefits of the real synths there is the potential for the benefits of the likely high end mic pre's they have too?
It just interests me how the keyboards of many older records sound so nice/big/3D. I appreciate there are numerous factors of course but maybe this aspect is one of many too!

[Hugh Robjohns]

Switching to the low input impedance probably had the greatest effect. The di box slmost certainly has an output transformer, and the frequency response in particular will be significantly affected by the load it sees (ie. the input impedance). The distortion might become more significant too — the combination leading to a warmer, more 3D vintage sound character.

[skipper01]

Thank you for your thoughts.
Its definitely imparting something different and positive on one hand but the noise has increased quite a lot too which is a trade off i guess.

[skipper01]

Sorry this is a branch from a branch from this original but kinda related discussion-
I have an old EMO E525 stereo passive di box that I used for this test/process.
Basically I used the instrument ins from the summit on the Emo box although the manual states it has a suggested level max of 1 volt.
I keep the Summit overall volume at noon and have a strong sense from using the line ins and gain before im within that signal level. Also it doesn’t sound clipped or overloaded to me in use with the instrument in.
The Emo low z balanced xlr out is already -20db. The jack line ins apparently reduce by another -20db on top and the signal becomes very very low so im gonna have to stick with the instrument in.
Basically because the summit is dual engine/dual stereo pairs (which is handy) I’d like to bring the summits second aux outs into the Apollo the same way given I’m digging the sound via the unison mic pres.
I’m thinking about a second EMO e525 for parity and having actually heard it.
However, mine is really old so I wonder if ie the transformers are still the same etc in new ones?
I’m also wondering whether there’s a 4/6/8 input rack or desktop di unit product that may be more cost effective given the e525 is not cheap?
I suppose the quality of the transformers and build is the main cost factor?
I’ve seen an ART and Palmer product that are passive (which I assume is broadly more suited to my application)?
I’m swaying toward another E525