Midas venice overhaul

[capashizzor]

Hello all, thanks for letting me in !

I've had a midas venice sitting idle for some years and decided to make it more fit for my studio needs. I bought it new back in the day, and wasn't comfortable with that much money collecting dust, so I gathered all the schematics (which I'm willing to share of course) and devised a three-step plan :

1) Replace all the caps values in the EQ section to have a lower low-cut, a lower low-shelf, wider Q for the swept mid bands, and a higher high shelf. Since I like to keep formulas outside of my head I re-created all the separate circuits on EveryCircuit to test new values, here they are :

low cut : EveryCircuit - Low cut
low shelf : EveryCircuit - low eq
low mid : EveryCircuit - low mid eq
high mid : EveryCircuit - high mid eq
high shelf : EveryCircuit - high EQ

You can scope the result while changing values in real-time with the tools under the schematic.

The cap values are meant to match the WIMA fkp2 and fkp3 available values.

2) Since I like the sound of mic input transformers fed with line level like I have on another very old mixer, I will try to fit a carnhill VTB9045M 1200:1200 mic input transformer with a mu-metal can behind the xlr connector PCB. There are 2 phantom blocking caps to remove, 2 rows of 3 pcb connections for the primary and secondary, and a fixing hole for each transformer as explained in the mod manual from midas.

3) With the help of a colleague of mine who's been raised by a cabinet maker, we are going to replace the plastic sides with an acceptable wooden frame, that will support a VU-meter bridge fitted with sifam AL19 meters that will be fed by the unused unbalanced inserts on all mono channels, groups, and master.

That's it, I hope this thread will maybe bring back some love for these now inexpensive desks, I'm also hoping some of you would share their ideas, insights, warnings etc.

cap

 

[Tubetec]

Its probably the greatest analog live console of the last 20 years , but dont try polishing a turd as the saying goes ,extract a few caps and measure out of circuit ,if there not out of spec dont bother exchangeing new lamps for old .

 

[capashizzor]

I'm changing the values of the EQ caps to have different EQ curves, maybe I explained it in a weird way

 

[k.steeze]

Hey capashizzor,

So your Venice has mic input transformers?  Did you buy them as an upgrade option from Midas way back when?  I've been wanting to add transformers to mine forever, but no one could ever give me any info about them.  What model board is yours?  Thanks!

 

[capashizzor]

I tried to buy the intended "vint-x M" transformers from EVI audio here a few years back to no avail but the salesman provided me with mounting information, so I bought 24 carnhill vtb-9045M and have already modded 2 channels. Wiring is simple, you just need to remove 2 48v blocking caps and wire the transformer primaries in series to the positive side of where the caps were, and the secondaries in parallel to the negative side, then the mu-can pin to the chassis ground, and the internal shield pin to signal reference. The hard part is to fit them in, they are too large to fix to the connector PCB so I have them with 8 cm wires and glued to the bottom of the chassis

 

[Bajuta]

I tried to buy the intended "vint-x M" transformers from EVI audio here a few years back to no avail but the salesman provided me with mounting information, so I bought 24 carnhill vtb-9045M and have already modded 2 channels. Wiring is simple, you just need to remove 2 48v blocking caps and wire the transformer primaries in series to the positive side of where the caps were, and the secondaries in parallel to the negative side, then the mu-can pin to the chassis ground, and the internal shield pin to signal reference. The hard part is to fit them in, they are too large to fix to the connector PCB so I have them with 8 cm wires and glued to the bottom of the chassis

Hi everyone here, am glad you let me in!
I have been searching for this kind of Mode to my Midas Venus 320, and finally I found verry interesting news here. How far with the EQ and Transformer mounting on PCB? How is sound after compared to Original? I am really curious to mode mine and make my Studio Sound how I want it to sound.
Any quick response would be much appreciated!
Much Love.
Bajuta.

 

[capashizzor]

All 24 mono channels are done ! Eq caps changed to WIMA FKP with the new values, 5532's changed to JRC brand, high band opamps changed from JRC2060 to MC33079, and aux/FX/monitor send pots 1&2 fed respectively from post-pan L&R busses ! Now working on the master card, replacing JRC 2068 summing amps with LME49720, auxiliary sends sip8 TL072 with dip8 TLE2072, and NE5532 with JRC 5532.

 

[Newmarket]

What was the motivation to change to JRC 5532s ? What brand originally ?

 

[capashizzor]

Original brand was TI NE5532, there's one after the transistor preamp positive and negative line buffers (JRC 2068) to sum them, and one buffer/fixed amp after the line fader. Tried several makes of 5532, along with 4556 and lme49720, switching the same material back and forth a modded channel and a stock channel, liked the JRC 5532 most, though it was subtle. NE5532 sounds nice but a bit synthetic, 49720 sounds sterile, and JRC 5532 sounds the most natural and musical to my ears. 4556 sounded more gritty but I was worried of additional current draw.

 

[LincolnBL]

I am attempting to sort out my old mint condition Midas Venice by installing Lundahl 1538 transformers. I believe I need an adapter for each channel.Is there any lads/lasses who can tell me where I may find these adapters?I’ve purchased the 16 LL Lundahl 1538 xformers from Sweden already.Any help would be greatly appreciated.A mate of mine can do the work but his lady is in poor health so I shan’t bother him until she hopefully gets better.Thanks.Cheers,Lincoln B

 

[thomasdf]

Curious to see how the build turned up, with the wooden side, transformers and all
Love this little console too !

 

[capashizzor]

I am attempting to sort out my old mint condition Midas Venice by installing Lundahl 1538 transformers. I believe I need an adapter for each channel.Is there any lads/lasses who can tell me where I may find these adapters?I’ve purchased the 16 LL Lundahl 1538 xformers from Sweden already.Any help would be greatly appreciated.A mate of mine can do the work but his lady is in poor health so I shan’t bother him until she hopefully gets better.Thanks.Cheers,Lincoln B

LL1538 is probably not the best choice because it has a ratio of 1:2.5 or 1:5, which means an additional 9dBu or 18 dBu of gain, provided your source and the midas input can work with the reflected impedance that will be twice the ratio. The venice transformer input is made for a 1:1 isolator, not a step-up transformer with that much gain ! You can try them though, sometimes happy accidents happen, but it might affect the frequency response. Also I don't know of any adapters for that.

You need to unsolder the 47 uF 63v capacitors C4 and C5 from under the XLR connectors (biggest ones right under the XLR) ; you have to gently turn them in different directions until the legs break and then you can unsolder them without too much iron heat dissipating in the PCB and frying the copper tracks. These capacitors protect the preamp circuit from positive 48v phantom power, so the positive side that's closer to the XLR is where you solder the primary ("input") side of your transformer, and the negative side is where you solder the secondary. That means :

- Pin 1 (input +) on the Lundahl goes to positive side of where C4 was
- Pins 2,3 and 4 (input - in series so ratio = 1:2,5) are soldered together on the transformer with some bare copper cable or bar and then go to C5 positive side
- Pin 6 (ouptut +) goes to C4 negative side
- Pin 7 (ouptut -) goes to C5 negative side
- Pin 8 (faraday shield inside the transformer) goes to the tiny ground between either legs of C4 or C5, just solder it on top it won't go through

Curious to see how the build turned up, with the wooden side, transformers and all
Love this little console too !

Not finished at all ! In the process of soldering the transformers but then I discovered the Venice has the dreaded pin 1 problem (no noise though), and a serious question arised :

Since all the pin 1 on the XLR's and TRS jacks are tied to the signal ground AND the chassis, where do I solder the carnhill's farady shield and Mu metal can pins ? Do I have to cut the PCB where the chassis and pin 1 go to signal ground around the connectors ?

 

[Nen'O]

All 24 mono channels are done ! Eq caps changed to WIMA FKP with the new values, 5532's changed to JRC brand, high band opamps changed from JRC2060 to MC33079, and aux/FX/monitor send pots 1&2 fed respectively from post-pan L&R busses ! Now working on the master card, replacing JRC 2068 summing amps with LME49720, auxiliary sends sip8 TL072 with dip8 TLE2072, and NE5532 with JRC 5532.

Impressive work!
What is power supply inside your Midas?
I'm on the similar mod path with my A&H ZED R16. The first thing I did was to swap stock SMPS to external linear power supply. Recapping is the next step.
Interesting point about difference in between Op-Amp manufacture... My board came with UTC 4580 as preamp and summing Op-Amps the rest are JRC 072, did you ever heard of UTC?

Back in the days I was in between buying Zed R16 or Midas Venice F16, never regretted for going with Zed R16.

 

[thomasdf]

Since all the pin 1 on the XLR's and TRS jacks are tied to the signal ground AND the chassis, where do I solder the carnhill's farady shield and Mu metal can pins ? Do I have to cut the PCB where the chassis and pin 1 go to signal ground around the connectors ?

The Xfrmr shield / mu metal goes to ground too

 

[LincolnBL]

LL1538 is probably not the best choice because it has a ratio of 1:2.5 or 1:5, which means an additional 9dBu or 18 dBu of gain, provided your source and the midas input can work with the reflected impedance that will be twice the ratio. The venice transformer input is made for a 1:1 isolator, not a step-up transformer with that much gain ! You can try them though, sometimes happy accidents happen, but it might affect the frequency response. Also I don't know of any adapters for that.

You need to unsolder the 47 uF 63v capacitors C4 and C5 from under the XLR connectors (biggest ones right under the XLR) ; you have to gently turn them in different directions until the legs break and then you can unsolder them without too much iron heat dissipating in the PCB and frying the copper tracks. These capacitors protect the preamp circuit from positive 48v phantom power, so the positive side that's closer to the XLR is where you solder the primary ("input") side of your transformer, and the negative side is where you solder the secondary. That means :

- Pin 1 (input +) on the Lundahl goes to positive side of where C4 was
- Pins 2,3 and 4 (input - in series so ratio = 1:2,5) are soldered together on the transformer with some bare copper cable or bar and then go to C5 positive side
- Pin 6 (ouptut +) goes to C4 negative side
- Pin 7 (ouptut -) goes to C5 negative side
- Pin 8 (faraday shield inside the transformer) goes to the tiny ground between either legs of C4 or C5, just solder it on top it won't go through



Not finished at all ! In the process of soldering the transformers but then I discovered the Venice has the dreaded pin 1 problem (no noise though), and a serious question arised :

Since all the pin 1 on the XLR's and TRS jacks are tied to the signal ground AND the chassis, where do I solder the carnhill's farady shield and Mu metal can pins ? Do I have to cut the PCB where the chassis and pin 1 go to signal ground around the connectors ?

I put them in my old SSL xformerless desk n have 4 channels finished and they sound sexy as hell.Have many pre’s:Redd.47’s,TG2s,BAE’s,Heritage,Portico’s n I finally have a wonderful analogue studio.I’ll have 10 more channels finished this weekend.Thx to Holger Schaarschmidt of Lundahl

 

[capashizzor]

The Xfrmr shield / mu metal goes to ground too

https://groupdiy.com/threads/mic-input-transformer-grounding-questions.72733/
This thread says it shouldn't :/

 

[thomasdf]

This thread says it shouldn't :/

Well you have your answer, then
It’s true that both situations exists. Most of the time in my builds my signal ground is going to earth, and so is the chassis ground... never had a problem

 

[capashizzor]

Yes but at a single point I suppose ? In the venice there is such a point where 0v from the PSU and earth go to the chassis, but then 0v goes to the chassis in many other places, like every TRS connector and psu screws to the chassis

 

[LincolnBL]

https://groupdiy.com/threads/mic-input-transformer-grounding-questions.72733/
This thread says it shouldn't :/

After using my Lundahl 1538’s on my old SSL I think the Midas will be a live desk for any shows I want to put on w/or w/out a supporting band.Love the Midas pure analogue warmth.

 

[istlf]

Was there more schematics? Would love to see more. Love my Venice 160 and would love to improve it one day