Michael Krusch

RFZ V781 racked - pix inside
« on: May 22, 2005, 02:24:50 PM »
Recently I racked some old german broadcast modules RFZ V781 for a client. Added a power supply and phantom power.
Very nice sound, warm and soft and very silky.
Every module has 2 channels, with gain switch from -30dB to 60 db. It also suitable for line levels. I have recorded some synths through it and it makes the differend sources blend together perfectly in a very special way.
So I shoot some modules at ebay for my own studio.  :grin:




Tillmann

RFZ V781 racked - pix inside
« Reply #1 on: May 22, 2005, 09:11:03 PM »
Very nice work!  Sehr gut gemacht!  That rack looks really impresssive!  Do you have any pictures of the interior of the rack?  Did you engrave the rack labels with a milling machine or or are they silk-screened on there?

I live in Berlin and am wondering if you know where I could get some RFT or RFZ preamp or EQ modules?  I'm always looking for cool old Swiss, German and East German gear and I have a pair of RFT 810/2's and I like them alot.

Gruss

CJ

RFZ V781 racked - pix inside
« Reply #2 on: May 22, 2005, 09:24:14 PM »
That's it! I'm gonna stuff myself down the garbage disposal.

Four racks in one day is a federal violation.

You guys ought to be ashamed.
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

chrissugar

RFZ V781 racked - pix inside
« Reply #3 on: May 23, 2005, 04:40:28 AM »
Looks great. good looking front panel.

chrissugar
Christian Mike Sugar
        CMS-LAB

gyraf

RFZ V781 racked - pix inside
« Reply #4 on: May 23, 2005, 04:42:31 AM »
Damn, they look good, Michael!  :shock:

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

chriss

RFZ V781 racked - pix inside
« Reply #5 on: May 23, 2005, 05:05:28 AM »
Hallo Michael,

do these units use the same strange -20V to ground and 0V to +V-powering? I had to mess with this on my MV810/2-preamps: For Phantom-Power I needed to feed + 68V to the 6k8-resistors. Very odd...

btw. looks good (except for that I can't stand blue LEDs any longer...)

Chris

Michael Krusch

RFZ V781 racked - pix inside
« Reply #6 on: May 23, 2005, 05:29:12 AM »
@Tillmann: Got mine from a guy selling it at Ebay, but this source is dried out. No idea where to get some. The panel is made by Schaeffer. http://www.schaeffer-ag.de

@Chris: It uses -24V, so a -24V & +48V power supply is needed. I still love blue leds.

I will try to hook one of the input transformer into a tube circuit to see if that spacial sound comes from the transformer or the whole box.

chriss

RFZ V781 racked - pix inside
« Reply #7 on: May 24, 2005, 03:13:21 AM »
Hmm,

maybe I did something wrong, but since the circuit-ground (-20V) needs to be connected to chassis etc. and also to pin 1 on the XLR I had to go up to 68 Volts to receive +48 for the Phantom-power. Did you do seperate ground for the P48-supply?

Ahh maybe it's because I used the same transformer for both supplies. I have just stepped up the 30 V of the transformer, so I needed to use the same ground.

And I don't have anything against blue LEDs, just it becomes common to use them to cover cheapness and bad quality. I'm not talking about your project though, don't get me wrong!

regards

Chris

tony dB

RFZ V781 racked - pix inside
« Reply #8 on: May 24, 2005, 03:37:19 AM »
Looking great man!  :thumb:

Tony

Michael Krusch

RFZ V781 racked - pix inside
« Reply #9 on: May 24, 2005, 05:53:18 AM »
@Cris: Are you shure about connecting the -20V to the chassis? I have the chassis connected to ground and the power pin to -24V.


Michael Krusch

RFZ V781 racked - pix inside
« Reply #10 on: May 24, 2005, 06:53:25 AM »
I have scans of the service manual including the schematic. I will make them available asap.

Tillmann

RFZ V781 racked - pix inside
« Reply #11 on: May 24, 2005, 08:21:17 AM »
Hi Michael,

When you have the schematics available, can you please post it here or notify me.  I would really love a copy.

Vielen Dank

Tillmann

RFZ V781 racked - pix inside
« Reply #12 on: May 24, 2005, 08:23:42 AM »
Chris,

Do you have schematics or any documentation for the MV810's?  If so, where are you, and can I get a copy.  All I have is a pinout, which makes mods and the sort a but difficult.

Cheers!

radiance

RFZ V781 racked - pix inside
« Reply #13 on: May 24, 2005, 09:42:48 AM »
Splendid work! :thumb:
"Knowing that you are dreaming, however, does not automatically guarantee full rationality.
Then again, being awake doesn't ensure good thinking, either." -  Lynne Levitan

chriss

RFZ V781 racked - pix inside
« Reply #14 on: May 24, 2005, 12:20:11 PM »
@Michael: Now since you ask... I'm no longer sure about that. I have a box that was pre-wired for Power-supply and MV810-2 and it had many electronics inside that I threw out, since it was for use that I didn't need. Just I let the In/Out-wiring, added P48 and XLRs. I will take a look at the schematics later.

@Tillmann: I'm a t home sitting at the computer :!: Send me your address or phone-number via pm and I can leave you the copies I have.

Chris

fgan81

Re: RFZ V781 racked - pix inside
« Reply #15 on: September 06, 2016, 04:11:44 PM »
Can somebody help me to bring three RFZ V781 in a rack? How i can bring Phantom Power and Power to the units?? Any advices for already existing PSU units?

DerEber

Re: RFZ V781 racked - pix inside
« Reply #16 on: September 07, 2016, 03:42:11 AM »
What do you have for now?

fgan81

Re: RFZ V781 racked - pix inside
« Reply #17 on: September 07, 2016, 04:00:35 AM »
I have 3 * V781 and eventualy a RFZ PSU N 706.
Do you know if the RFZ N 706 could powering up the tree Units?
I need also 6 1:1 Tranformers, right? Any Special type?
What is about Phantom Power? Any DIY Projects?
And last question, do you know similar racking up and good documentated diy Projects?

fgan81

Re: RFZ V781 racked - pix inside
« Reply #18 on: September 07, 2016, 06:43:20 AM »
May I use two of them: http://www.fabmodules.com/shop/index.php?route=product/product&path=59_70&product_id=81
Should run my 3 two channel V781 also with Phantom Power.
Any other hints for PSU DIY Units that gives power for 6 Cannel?

DerEber

Re: RFZ V781 racked - pix inside
« Reply #19 on: September 07, 2016, 11:58:42 AM »
I have 3 * V781 and eventualy a RFZ PSU N 706.
Do you know if the RFZ N 706 could powering up the tree Units?
I need also 6 1:1 Tranformers, right? Any Special type?
What is about Phantom Power? Any DIY Projects?
And last question, do you know similar racking up and good documentated diy Projects?

Hey fgan81,

with two N706 you could power a whole console. So it is way over for 3x V781. But still it can be done. :)
One V781 needs typically 45mA. Say not more than 80mA.

Are you aware of the fact that the V781 need -24V supply and how to handle this? Ground is on positive rail.
This is why you possible can not use the supply you linked together with the phantom. But you better ask the seller if it is possible to get positive rail grounded on the 24V side and stack the 48V on top.
Anyway I'd not build it with the N706. Recapping the thing alone will probably  cost more than building a new one with halve the weight.  But if you do not plan to travel with your preamps and as you already have it... why not. 

First of all before racking them, have you tested the units? Are they working and in good condition?
I am asking, because I know them quite well and I had lots of troubles repairing those. But mine came from an old recording truck and were in heavy use.
Would be a shame if you build a cool rack, plug them in and then..... nothing.

You do not need an output transformer if you want to run them unsymetrical. Thats totaly fine.
But most of the 1:1 will do a good job.

And I think there is no documentation for a V781 rackjob here.  But who knows.

best,
Stephan


 

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