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Old 6th July 2019, 02:05 AM   #31
ilcaccillo is offline ilcaccillo
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Join Date: Apr 2012
Quote:
Originally Posted by ICG View Post
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
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Old 6th July 2019, 02:09 AM   #32
ilcaccillo is offline ilcaccillo
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Originally Posted by JMFahey View Post
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...
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Old 6th July 2019, 02:19 AM   #33
ilcaccillo is offline ilcaccillo
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Originally Posted by johannrenck View Post
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.

Click the image to open in full size.

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
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Old 6th July 2019, 03:59 AM   #34
JMFahey is offline JMFahey  Argentina
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Location: Buenos Aires - Argentina
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 donīt 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 wonīt 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"
__________________
Design/make/service musical stuff in Buenos Aires, Argentina, since 1969.
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Old 6th July 2019, 09:19 AM   #35
ilcaccillo is offline ilcaccillo
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Originally Posted by JMFahey View Post
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
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