Custom Mixer

[00940]

A Behringer X Air XR18 got an input impedance of 1M/2M (unbalanced/balanced) and costs 400 bucks, it's set up by a laptop, tablet or phone. The Soundcraft mixer is 500. I haven't found mixers with a higher input impedance than 2M yet.

The soundcraft notepad 12fx is 180$, the a&h zedi10 about 200$. But neither actually specify the impedance of their HI-Z inputs

 

[johannrenck]

Thank you everyone for the feedback, will keep my current solution until I find a better one, there are some 2 channel preamps that are very good but pricey, missing one channel FELiX – Grace Design

 

[ICG]

The soundcraft notepad 12fx is 180$, the a&h zedi10 about 200$. But neither actually specify the impedance of their HI-Z inputs

That are actually good suggestions. The most cheaper Soundcraft mixers which got a high-Z input just have 300k, though the A&H ZEDi10 got an input impedance of 10M (page 7, 5.2). For that price a very good feature. It got only 2 instrument inputs, the other all expect line level, that maybe drops it out of the list.

The ZED SIXTY-10FX and ZED SIXTY-14FX got both 10M too and are more versatile. The SIXTY-10FX is with around 350 bucks not cheap anymore though.

 

[JMFahey]

You don't want connecting ultra high impedance Piezos to anything with a long cable AT ALL ; long here being more than 1 meter; so either put a preamp inside the instrument or belt-strap-shirtpocket preamp or at least buffer; with the added benefit that mixer/amp used becomes irrelevant.
Don't fear batteries; a 9V alkaline feeding a single TL061 will last 1600 hours active time; in practice shelf life (>3 years)

 

[ICG]

You don't want connecting ultra high impedance Piezos to anything with a long cable AT ALL ; long here being more than 1 meter;

1m? That seems extremely exaggerated, that wouldn't even cover the distance from the pickup to the preamp or DI box he's using right now - and he seems to have no problems at all.

 

[johannrenck]

Ian from The Leon Audio Company wrote me the following:

The simplest and by far the cheapest option is to use a commercial 4-6
channel mixer with the features you require to mix your 3 channels.
The stage amp is fed from an AUX output and the main mixer is fed via a
DI box from either left or right main outputs. The DI is needed to
break the earth loop that would exist between your stage rig and the
house PA.

I assume you are aware of the comb filtering that will occur when mixing
the 3 pickups/mics.

 

[johannrenck]

The ZED SIXTY-10FX and ZED SIXTY-14FX got both 10M too and are more versatile. The SIXTY-10FX is with around 350 bucks not cheap anymore though.

This is a great feature:

 

[ICG]

A&H got a lot of very good details and features. I like them very much. I've more than once thought about the GLD-80.

Anyway, I am not sure the impedance problem is as big as some think, especally the cable length. Yes, high impedance source signals suffer from long cables, mostly from outside interference (like induced electromagnetic fields) and losses (resistance, inductance, capacitance). The former is eliminated by the symmetrical signal and can be reduced by dual shielded cables, leaving the biggest sensitivity to it mainly to the pickup itself. The latter influences mostly the high frequencies. Since the impedance of the piezo pickup drops with increasing frequency, it's less sensitive to it there.

 

[Whoops]

Every mixer got a preamp for every separate channel. You can pre-adjust the level with the gain-knob. And ofcourse then adjust the level with the faders too.

Not what johannrenck asked for.
He needs different input impedances.

He needs 2x unbalanced Hi- Impedance inputs, and more even than that one of his Hi-Z inputs should be 10Mega for optimal performance (something quite normal with Piezos)

And no the loss cannot be EQued back to the same state, it's better to have the proper input impedances right from the start

 

[Whoops]

This is my current solution: DI Box for the Pickup, Piezo PreAmp pedal and a mixer

Thats a pretty good setup, you got the impedances right

 

[Whoops]

though the A&H ZEDi10 got an input impedance of 10M (page 7, 5.2).

If thats really true and not only a marketing thing in the user manual (I couldn't find an electronic specs sheet for those mixers), then it's a really really nice feature for Piezo pickups.

Most DI boxes are 1M input impedance (fine for Magnetic pickups),
and most inputs labeled Hi-Z are 1M or less.

DI's with 10 Mega input impedance are the Countryman type 85, the Radial PZ-DI.
Radial Stage Bub SB-4 is 5 Megas

Type 85 Direct Box | Countryman.com

PZ-DI - Radial Engineering

 

[Whoops]

You don't want connecting ultra high impedance Piezos to anything with a long cable AT ALL ; long here being more than 1 meter;

Well, that's correct, it's true that High impedance signals will be affect by cable capacitance (loss of high end) and that capacitance will increase each meter, but I as most people find 2 to 3 meters completely acceptable.
With 3 meters I don't notice High End loss, but I start to notice after that, with 5 and 10 meters long cables.

Of course you are right the shorter the better,
but you are fine until 3 meters, then after that is a matter of taste...

 

[Whoops]

Hi!, I am a musician that is looking for someone to build a custom mixer for my double bass.

I currently use 3 sources to get an amplified sound out of my instrument:
1) Condenser MIC (Shure PGA81)
2) Piezzo Pickups (Fishman BP-100)
3) Magnetic Pickup (Krivo Pickup for Upright Bass)

My project is to build a mixer, with volume and eq for each channel, that can output a balanced line level and a instrument level one. For the conndenser mic must also provide phantom power and the idea is that it should be portable.

Any tips who could build something like this would be much appreciated.

Thanks!

Johann

Although I think your setup is fine I really think your first idea is quite good,
to have a custom mixer.

If you know soldering you can even build it yourself.

Go to this forum, Groupdiy.com, there's a lot of projects there you can use for your mixer.

From the projects in Groupdiy I recommend the following:

Condenser Mic preamp: you can use a Neve 1290 preamp, API 312 or SSL 9K type of preamps, any of those will sound really good

Piezzo Pickup: Bo Hansen DI with the mod for 10Megas (described in the forum)

Magnetic Pickup: Bo Hansen DI with 1Mega impedance (normal/stock circuit)

For EQ:
Neumann W492 project
Calrec EQ
SSL 4K EQ

_______

check that forum out
It will be more expensive than you current (and working) solution,
but you will have really high quality circuits and maybe you have loads of fun building it, if you're into DIY yourself

 

[JMFahey]

Cool.
Just let me remind that capacitance loaded Piezos (be it cable capacitance, input capacitance or any added on purpose) does not actually "kill highs" by any means, simply attenuates output, since now you have a capacitive attenuator; both branches being capacitors and attenuation depending on ratio.

I make Musical Instrument amplifiers and everything related, and my "cheap trick" when Customers have many "added Piezo" instruments but for cost or complexity reasons they don´t want a lot of preamps, with the added size, installation and power complications multiplied, is to add a ceramic capacitor in parallel

Practical example: if you add a .01 or .0047 ceramic in parallel with Piezo (usually across output jack) now you have turned a "10M Piezo" into a "1M" one, and you can safely plug it into a conventional 1M input Guitar Amp.

Yes, signal will be attenuated.

No, it won´t become unusable, depending on instrument signal out is already VERY loud and in any case adding gainh (or plain setting folume pot higher) is way easier than building a dedicated "10M" input preamp.

Beauty is that you now can use a regular Guitar cable into a regular Guitar (or Bass) amplifier.

Being in Argentina often pushes me to find simple and practical solutions "now" instead of driving to the nearest Guitar Center (think 6000 miles away ) or ordering from Mouser (U$35 "economy postage" + 1-2 weeks + dealing with Customs even if I order a 5 cent resistor)

Oh well, "what does not kill you makes you stronger"

 

[Whoops]

Cool.
Just let me remind that capacitance loaded Piezos (be it cable capacitance, input capacitance or any added on purpose) does not actually "kill highs" by any means, simply attenuates output, since now you have a capacitive attenuator; both branches being capacitors and attenuation depending on ratio.

Thank you so much for the o info