Midas Venice Input Transformers
« on: September 05, 2019, 01:57:15 PM »
Hello All, I have a Midas Venice 320 and would like to attempt installing microphone input transformers on some of the channels.  Midas left space on the pcb for such an add-on, and even sold the transformers as an optional upgrade back in the mid-2000's.  I need a bit of help as it appears there is a small PCB that is required to install it.  I spent several weeks tracking down as much information as I could  and here is what I know:

The original transformer that Midas sold was called VINTX-M.  They are no longer sold anywhere and Music Tribe customer support doesn't have any spec sheets on them.  Sowter Transformers in the UK sells a 9610 200/20k Microphone input transformer that they say would work in a Venice.  Based on that, it appears that a Jensen JT-115K-E would work also. 

The instructions document for the install shows the transformer is suppose to attach to a small PCB, which then attaches to the main PCB.  There is no information on this small pcb and so I'm a little lost as to how to attach the transformer.  Could I attach directly to the main pcb and bypass the small pcb entirely?  Or would it be possible to create the small PCB based on the schematics?  I don't have the electrical engineering skills to figure this out myself, unfortunately.  I'm a 'follow a kit and solder' type of level.

Attached are the install instructions from Midas.  And here is a folder of everything I've been able to find, including schematics:
https://www.dropbox.com/sh/9hw84z2zlqek5bd/AAD9Nqrmv7QK-2l7jAKvrSRJa?dl=0


Thanks!
-Kevin


ruffrecords

Re: Midas Venice Input Transformers
« Reply #1 on: September 05, 2019, 04:22:22 PM »
Looking at the schematic, the mic pre seems to have 60dB gain without the transformer. Inserting a 200:20K transformer would add another 20dB gain. So I think it is more likely a 1:1 transformer would be a better bet.

Cheers

ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

MountCyanide

Re: Midas Venice Input Transformers
« Reply #2 on: September 06, 2019, 12:27:18 AM »
Jensen makes the JT-MB explicitly for adding iron to transformerless mic pres like those.
https://www.jensen-transformers.com/wp-content/uploads/2014/08/jt-mb-cpca.pdf

Re: Midas Venice Input Transformers
« Reply #3 on: September 07, 2019, 09:31:02 PM »
Thanks, guys!  Any thoughts about the small pcb?

ruffrecords

Re: Midas Venice Input Transformers
« Reply #4 on: September 08, 2019, 02:56:01 AM »
Small PCBs are dirt cheap from China. Design your own and have a bunch made. Then you can offer them to other Venice users.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Re: Midas Venice Input Transformers
« Reply #5 on: September 08, 2019, 12:41:34 PM »
Hi Ian,  the original reason I posted here is because I don't know enough about electrical engineering to design the pcb myself.  I've supplied the schematics and instructions that show the small pcb, and was hoping someone could step in to help me out.

RuudNL

Re: Midas Venice Input Transformers
« Reply #6 on: September 08, 2019, 01:01:45 PM »
In order to create a PCB for the transformer, you need to know exactly where the connections are. (Physical dimensions.)
Ideally you would need an original transformer PCB as an example.
Of course you could hand wire the transformer PCB to the input PCB, but that would be a lot of extra work...

By the way: what do you expect to gain with the added transformers?
There is a solution for every problem!

http://www.vansteenisaudio.nl

Re: Midas Venice Input Transformers
« Reply #7 on: September 09, 2019, 02:14:00 PM »
I was hoping to gain some more meat on the mic inputs.  I love the Midas Venice, and just thought having a version with transformers would be unique and make tracking drums all the more sweet sounding.  But if the general consensus is that it isn't worth the trouble then I'll walk back the idea. 

I've seen a few gearslutz posts with people inquiring about how to do this, but I've yet to come across anyone who has done it or anyone who has access to the transformer pcb. 

Eliani

Re: Midas Venice Input Transformers
« Reply #8 on: September 16, 2019, 10:33:20 AM »
Kevin,

I was looking at this and I share Ian's thoughts on adding a 200:20k input transformer on a low impedance input like a microphone pre-amp. Adding a matching transfomer like the VTB2407 from carnhill will have the desired coloring effect you might be looking for. I've built a 16 channel coloring box for a buddy of mine that uses it for that exact purpose, although you should consider the fact that in this way you will nog be able to use the phantom power coming from the venice, because it will not pass through the transformer. If you wire them in in the venice where the original transformer mod would be seated then I guess that will work...





"Iron Projects" at Eli-Audio.com

ruffrecords

Re: Midas Venice Input Transformers
« Reply #9 on: September 16, 2019, 03:33:36 PM »
The VTB2407 is a 600:600 output transformer so is is a bit of an odd choice for an input transformer. it is unshielded so it is very likely to pick up hum.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'


alexc

Re: Midas Venice Input Transformers
« Reply #10 on: September 17, 2019, 12:30:03 AM »
Nice work, Eliani  :)
I ping therefore I am

gyraf

Re: Midas Venice Input Transformers
« Reply #11 on: September 17, 2019, 02:52:36 AM »
..and big line-isolation cores like that add - perhaps too much - grainy-ness because of barkhausen effects. Actually pretty noticeable on reverb tails when using dynamic mics.. This probably why inputs were nearly always mu-metal core.

Jakob E.
..note to self: don't let Harman run your company..


 

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