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Author Topic: BK-7m: USB or MIDI connection  (Read 2126 times)
 
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magean
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« on: June 08, 2011, 09:41:00 AM »

Hi,

I am wondering if it is possible to connect the BK-7m to a keyboard (e.g. E-60) via USB or if it is mandatory to use always MIDI cables to connect the module with a keyboard.... 

I currently do not have a USB cable with the correct connectors to test it. And before buying a new USB cable I wanted to know if the USB connector on the BK-7m can only be used to connect the module to the computer or if it also supports keyboards. The menual does not help me.   Sad
And one USB cable would be easier to install compared to two parallel MIDI cables..... perhaps anybody has already tried it?

Regards
Gerd

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Aidabab
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« Reply #1 on: June 13, 2011, 05:02:01 AM »

Hi Gerd, under no circumstances connect anything but a (midi cable)
The midi works with whatís called an opto isolator chip thatís on the inputs of every thing that is midi, from the 1980s till now; itís a very clever way of connecting gear without ever touching earth
So your outputs will always have pristine audio, with no earth loop hum noise extra
The usb part will always need a host, driver basically a computer to exchange data
It runs on a completely different system from the midi, thatís why if you use your usb , youíll notice more noise on the audio outs , as youíve made an earth connection with the usb
All midi outputs have an earth but NEVER A MIDI INPUT,
So once again NEVER connect two peaces of hardware gear with a usb cable, if the chassis are at slightly different earth potentials, you run the risk , by- bypassing the midi input isolator and frying your gear , always use midi , if you have loads of midi gear , and the last one in the chain has a usb
Always connect that to pc or mac , and all the others connected by a midi cable
Hope this helps
 Smiley
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magean
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« Reply #2 on: June 13, 2011, 10:11:24 AM »

Hi Aidabab,

thank you very much for the information.
It helped me in my decision.
I thought USB might be easier because I need only one cable (instead of two if I want bidirectional flow of data) and because it is faster than MIDI (who is only in the region of 30 kB per second).
But the earth is an important issue, I did not consider till now.
So you helped me a lot.
I assumed that the keyboard and BK-7m are connected to the same earth via the mixer (for the audio signals of keyboard and BK-7m). So I did not expect trouble with the earth. But after reading your post I think I should better use the two MIDI cables instead of the single USB cable.

Thank you very much!

Regards
Gerd
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Diki
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« Reply #3 on: June 13, 2011, 07:23:20 PM »

You got any proof of that, Aidabab? People have been hooking different gear up with USB cables for ever, and I haven't heard of people frying their gear with it much. If it was a commonplace occurence, USB would never be the standard it is. And sorry, but a USB cable doesn't transmit noise down it. My computer's actual audio outputs are very noisy (iMac 27") but use a USB cable to hook an audio interface up, that's all gone (likewise firewire).

The issue for the OP here is, using a USB cable to hook two 'dumb' things up doesn't work, because you need a computer at one end of things with a driver. It's like hooking up two hard drives with no computer in the middle. Nothing is going to happen...  Cool
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Aidabab
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« Reply #4 on: June 14, 2011, 07:45:16 AM »

Hi Diki, yep I have proof, as you know MIDI is very much a ridged standard in software, and in also (hard ware).. analogue audio got round this sort of problem back in the early days of sound, with differential audio inputs ,where there is no direct physical connection  , buy using input transformers
As we all know midi is digital , and the one thing that all things digital do better than audio is to create noise Ö I wont go into to much detail here  as I mite start to bore people to death ,
But I build and design my own custom midi pedals that I program myself using (micro controller chips)  to send out NRPN,s exclusive, controller messages   cc,s ,program change ect..
So I have to work to the MIDI spec
Ill sends you a link of me doing a hardware update on my Roland R800 if you want
I can. go into depth if you want, but as I said it will be very boring for people that are not into electronics Ö.
If you look at some Roland gear you will see a little screw with a earth symbol next to it
Itís to bleed off static e that builds up on big metal surfaces like the bottom of keyboards
Guitar pedals ect , my GR-55 has one,  so when you plug your midi lead in from another peace of midi , youíve guessed it  , you mite get your finger zapped with a few thousand volts of static discharge , but 5 volts dc is all any midi device will ever see, because they are  not physically connected to the outside world thanks to the MIDI INPUT Optocoupler  Smiley
Have a look at one here

http://www.google.co.uk/imgres?imgurl=http://www.mrstockinterfaces.com/groups/wiki/wiki/99af5/images/56dd4.GIF&imgrefurl=http://www.mrstockinterfaces.com/groups/wiki/wiki/99af5/Arduino___Microcontroller_Workshop.html&usg=__cdLhsIC2AHnWIU_m1mYWgmBtew4=&h=688&w=673&sz=17&hl=en&start=0&zoom=1&tbnid=z7z3JdJ9ev-RGM:&tbnh=158&tbnw=160&ei=ie_2Tf-qKsaw8QP31b3HCw&prev=/search%3Fq%3Dmidi%2Boptocoupler%26um%3D1%26hl%3Den%26sa%3DN%26biw%3D1024%26bih%3D649%26tbm%3Disch&um=1&itbs=1&iact=hc&vpx=565&vpy=81&dur=2432&hovh=227&hovw=222&tx=91&ty=76&page=1&ndsp=12&ved=1t:429,r:2,s:0&biw=1024&bih=649
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aviro
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« Reply #5 on: August 31, 2011, 04:23:56 PM »

groundloops 
will come with the audio and usb connection in a setup  mostly connect al togeter true a mixing panel  include the PC
close wirering  and dc-adapters are mostly the problems... never a midi kabel!!

Hard things to illuminate are the sisseling  from the PC always come from the USB connection and internal soundboard if  used (sounds mouse move,HDD activeti ect..)

I found a solution
 a USB-issolator...  very hard to find ( only for medical industry)

I found a manufactor a full function PCB with USB male/femal connector price about 60$
connect it in line with jour PC en USB device and it issolate 100% your PC  from your setup

Ronald
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Aidabab
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« Reply #6 on: September 05, 2011, 09:38:42 PM »

Opto isolators for usb, its about time, thanks for this, will check em out   Smiley
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Diki
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« Reply #7 on: September 07, 2011, 10:32:01 AM »

Weird.... I've just never had this problem. Ground loops from audio cables plenty, but my USB stuff is quiet as a mouse.

Maybe I can hear a 'hair' of digital hash if I boost the gain way past earsplitting level, but bring it back down to line levels (you ARE running your volumes at close to full, yes?) and I sure can't hear it. Perhaps you might invest in a better USB board for your computer. I must admit, laptops can have issues (I've heard other people's have problems, but they usually solved them with audio transformers, not USB ones), but I've worked in many studios, and we've never had an issue with a USB interface...
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