8 Channel, 3U NEVE 1073 completed

Here are some build progress pics of my 8ch mic pre:

https://s3.amazonaws.com/Neeb/1frontpanel.jpg
https://s3.amazonaws.com/Neeb/1frontpanelzoom.jpg
https://s3.amazonaws.com/Neeb/2inside.jpg
https://s3.amazonaws.com/Neeb/3ez1290.jpg
https://s3.amazonaws.com/Neeb/4backpanel.jpg

It is finished! All channels have been tested, biased and are working as they should individually. I used Carnhill VTB9045 and VTB9049 for I/O. The PCB's you're seeing are the EZ1290 pcb's that feature two pre stages, a driver stage, rotary switch, and all the other decoupling caps, resistors to make a proper 1290/1073 mic preamp.

This project has been a lot of work and in hindsight I probably would have built two 4ch, 2U units. Either way it has given me a lot of respect for the people who build consoles and modules.

Sorry for the grainy pics!

M.

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EDIT:

I wanted to consolidate all the build info for these preamps here, see below:

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IMPORTANT!
For the latest revision - V2.6 - download the latest BOM and assembly instructions here:
https://s3.amazonaws.com/EZ1290/1290BOM26.xls
https://s3.amazonaws.com/EZ1290/assembly6.pdf

For version 2.5 and older use the following BOM:
https://s3.amazonaws.com/EZ1290/1290BOM25.xls

I still have some PCBs left over. Please email me at: 1290preamp (at) gmail.com if you're interested.

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Front Panel Design for 2U, 2ch (uses Circuit Specialists ET2/35B):
http://s3.amazonaws.com/EZ1290/circuit_specialists_2u_panel.fpd

Front Panel Design for 2U, 4ch (uses Circuit Specialists ET2/35B):
http://s3.amazonaws.com/EZ1290/circuit_specialists_2u_panel4.fpd

Front Panel Design for 3U, 8ch (uses Par Metal 3U case 14-19163x):
http://s3.amazonaws.com/EZ1290/par_metal_3u_panel8.fpd

To open .fpd files, you need Front Panel Designer. Free download from: http://www.frontpanelexpress.com/

Gerber file:
https://s3.amazonaws.com/EZ1290/EZ1290V26.zip

Design spec for PCB house:
Board size: 6.5 x 3.75" (165.1 x 95.3mm)
Material: FR4
Min hole size: .3mm
Gold fingers: No
Finished copper: 1oz
Board thickness: 1.6mm (.062")
Solder Mask: Green
Surface finish: HASL with lead
Layers: 2 layers
Min track/spacing: 6/6mil
Silkscreen: White
Via process: Tenting vias

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FAQ:
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How did you get the rear panel drilled?

I laid it out with a ruler and center punch, pre-drilled with 3/8" drill and then punched with a 15/16" Greenlee punch. 15/16 is perfect for Neutrik XLR's. Then put the connector in the hole (use a carpenter's square to align the connectors straight on the case) and mark the small 4-40 flat screw holes. Drill those with a 1/8" drill.
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Can I use some other transformers besides the Carnhills?

Yes, original St. Ives or Marinair 10468 and LO1166 would be a good start. Other than that it's Carnhill or bust in my humble opinion.
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BC184C is now obsolete. What should I do?

You should be able to find them on eBay if you're really wanting to use BC184. Another option is to use MPSA18. One important detail about using MPSA18 in place of BC184C is that MPSA18 will need to be mounted backwards (rotated 180 degrees on its vertical axis) on the PCB. Other than that it is a great substitute: http://www.digikey.com/product-detail/en/MPSA18RLRMG/MPSA18RLRMGOSCT-ND
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Can I use BC184L instead of BC184C?

Don't use the L's. The pinouts are different.
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How much does it cost to build one channel, complete with case and power supply?

Count on about $200-$300 per channel, not exactly free but a good deal nonetheless.
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At higher gain settings, all I get is a very high pitched noise, or screeching, audio drop out??

That's the sound of oscillation. This is usually caused by:
not using shielded wire throughout
running mic input wires too close to line output wires (especially unshielded)
having the 10468 (VTB9045) too close to LO1166 (VTB9049)
malfunctioning 2N3055

Also check the resistor values around the gain switch.
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Is it ok if I use unshielded hook up wire for audio connections such as transformer to XLR, transformer to PCB etc?

Not recommended! Just use some mic cable (in the BOM) - it has a shield.
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What cable should I use for the 4pin XLR cable (PSU case to Rack case)?

I recommend some 3 (or 4) conductor 18AWG, stranded, with shield (use the shield to connect both cases together). Most electronics stores will carry this type of cable as it's commonly used for alarm installation. Home improvement stores might also carry it. I have not been able to find it in small quantities online (less than 1000' spools).
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What type of standoffs (mounting pillars) should be used to mount the EZ1290 boards?

Any nonconductive (nylon) standoffs will work. Don't use metal (conductive)
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I'm getting 50/ 60Hz hum?

Try moving the power transformer away from audio, preferably outside the rack case.
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Can I fit it all in a 1U?

Yes, but you have to use the narrow board output transformer: VTB1148 available from: http://www.audiomaintenance.com/ you may also have to mount some of the larger capacitors flat, and bend the fins on the 2N3055 heatsink down a bit.
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Do I have to bias this preamp? I don't have a scope and/or signal generator.

I would highly recommend getting a scope and generator, but in a pinch you can adjust the 5k trimpot on the EZ1290 board until TR3 collector (the casing of 2N3055) measures 22.66 volts to ground.
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How do I add Polarity/PAD/DI to this preamp?

I think this is probably the easiest way: http://www.jlmaudio.com/JLMDI.htm
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I'm having some problems.

Here's a random list of things to check:
check transistor voltages
check resistor values and capacitor orientations.
Reheat all solder joints (including on the transformers, XLR's). 
Did you solder in the jumper (labeled jumper on PCB).
Is 2N3055 bolted to the PCB using conductive (metal) standoffs?
How's the PSU voltage?
Meticulously check the wiring on the input/output transformers.
Are you using shielded cable for audio connections?
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Any other hints?

Be careful with mains voltages! (120V-220V) It can really hurt (or kill) you! Don't touch anything on the PSU while it is plugged into the wall

Be sure to adjust the PSU for correct voltage **BEFORE** you connect to the EZ1290

Also, be sure to follow the assembly guide, BOM and this FAQ very precisely; read them a few times before you start. Those that have usually end up with a properly functioning, amazing sounding mic pre.

Words cannot describe my jealousy/ admiration !

sweet!

:shock: :shock: :shock: :shock:

Not Worthy...

H-H-How do they sound?

wonderful build, outstanding documentation...respect :grin:

pronografic



very

very nice build

:shock: :shock: :shock: :green: :green: very good looking!

where did you get the PCBs?

Id love to see the documentation but when I download it its only giving me the transformer diagrams... page two I believe over and over again. Could you email me at capnspoony (at) gmail (dot) com? Thanks!

looks terrific! I'm about to embark on a set of four myself.

best

Richie

WOw! Verrry sexy! Professional implementation all the way! Congrats!

Charlie

that is an AWESOME writeup/pdf. nice job!

fantastic job, amazing craftsmanship! :thumb:

I am finishing off an eight channel preamp myself, not a Neve though... will post pictures soon.

Wow, very nice build. Looks pretty neat and i guess it was a difficult task to squeeze so much preamp into one case.
Don't want to be an smartass but if you think about it, it's not a 8 channel 1073. It's more like a 1290 since the 1073 is a preamp and eq.

Flo

Killer Job !!!!

Like those Knobs. That box must have cost a small fortune in transformers.

great 8 channel preamp, very pro look.


Also, Where is the link to the EZ1290 PCB Layout , can some one post it here ?

Hey thanks for the kind words everyone!! This project's been a long time comin' but all the work, sweat, tears and $$$ are finally paying dividends. The pres sound FANTASTIC!! I absolutely love them on pretty much everything. I blind pick them over my other mic pres 9/10 times and would have no problem tracking an entire album with just these.

I designed the EZ1290 PCB myself;  please email me if you're interested: 1290preamp [at] gmail.com.

Infernal; you're absolutely right about it not being a 1O73, and more like a 129O without a trim fader. But..... I stopped worrying about proper naming the moment Neve issued the 1O73DPA/DPD. 

As for the trim fader; I deliberately left it out because I don't have a need for one.

All the best,

Martin

fantastic drum recording box - stunning work! congrats :guinness: :guinness: :guinness:

Martin,

How about just emailing those files to the GroupDIY gmail account?

Thanks!
Charlie

Hi Charlie,

See first post

All the best,

M.

[quote author="madriaanse"]
Infernal; you're absolutely right about it not being a 1O73, and more like a 129O without a trim fader. But..... :green: ..... I stopped worrying about proper naming the moment Neve issued the 1O73DPA/DPD.

Martin[/quote]

Haha yeah you are right. Well you gotta admit 1073 just sounds cooler than 1290 :razz:
Anyway, as i already said, it's very nice build ! :thumb:

Flo

Also, I'm currently revising this PCB so that you don't have to cut any pins on the rotary switch just to make life a little easier. I've ordered 8 test PCB's, but the manufacturing company is jacking around with their pricing and wants to charge me $10 extra per PCB to drill 9 little holes - pfff. We'll see how it goes; I may take my business elsewhere.

M.

:shock:

I would be interested in a couple of boards.

Adam