8 Channel, 3U NEVE 1073 completed

[desol]

Are those two acdc's? Looks like it.

I ended up using a single powerstation at 1.5 amps per rail.
Martin recommended 500ma per...needing 4amps.

At 3amps this gives 375 ma per...which i figured was good nuff.
Can always upgrade if need be. I decided on 1u for power stuff.

 

[MicDaddy]

sgenevay      WOW!!  it's builds like these that are both so inspiring and also will humble a fellow real quick.  Very nice build!!

desol  You're getting away with just 1 powerstation for 8x channels?  Have you had a chance to push all your pres hard, simultaneously, say in a drum session or other demanding scenario? 

All you guys rock!!  My boards have been sitting for a few months now but I think I just felt a spark under my butt.  ;D

 

[desol]

The powerstation with the 6amp rectifier is good for a full 3 amps...1.5amps per +24v rail.
Also disabled the negative rails as they were uneeded and strapped for full rectification, which allowed for a cheaper/smaller toroid.
Single 24vac winding. (don't need 2x24 winding for neg rail-why waste money)

http://www.groupdiy.com/index.php?topic=22828.580

This is my build:
http://img835.imageshack.us/i/dsc02837.jpg/
http://img839.imageshack.us/i/dsc02842z.jpg/
http://img31.imageshack.us/i/dsc03059mf.jpg/

It was explained to me, that once the pre's are done ramping at the beginning(which is alot), they don't use more power(single or together) and run at about 130ma ea. I figured 375ma per outta be enough. Sgenevay seems to be running pretty much the same config.

 

[sgenevay]

thx MicDaddy !!  really loved to build it...

for ACDC...Look .. i made measurements on a single board... then on a 4 boards pack....

-The single 1290 board needed about 280 mA during first 2 sec....   then stabilized to about 80 mA

and the 4 boards pack used about 1,2 Amp at startup (as i said) and stabilized to about 280 mA
the ver4 of ACDC is now at 1,5 A ... but the only problem is that Joe (from JLM) told me  that his ACDC board provides 1 amp for V+/V- rail
Which means 500 mA for V+ and 500 for V-... and told me that u normally can't have 1 full Amp on V+ even if u have no use of V-...

but anyway.. i'm feeding 4 boards with a single 1,5 Amp ACDC board...   in worse case i have 750 mA for V+ and it's enough to face the 280/300 mA needed for the 4 Boards (the startup didn't provide any problem up to now...)
and in better case... i have 1,5 Amp which, i think is enough even for startup...

I was close to take the powerstation but i was unable to know what transformer to use to feed it (i'm a kinda lost in power and transformer stuffs....)


Sylvain.

 

[desol]

but anyway.. i'm feeding 4 boards with a single 1,5 Amp ACDC board...   in worse case i have 750 mA for V+ and it's enough to face the 280/300 mA needed for the 4 Boards (the startup didn't provide any problem up to now...)
and in better case... i have 1,5 Amp which, i think is enough even for startup...

I was close to take the powerstation but i was unable to know what transformer to use to feed it (i'm a kinda lost in power and transformer stuffs....)

I was too. Still am a little...

Transformer i got from Avel lindberg --- 12x12 @ 6.66 amps or single 24vac at 3.33 amps. 80va. $30.
Primary in parallel. Sec in series.

What transformer do you have? Do you have link to specs?

Connection for neve is here(both single or dual winding-with explanation): http://www.groupdiy.com/index.php?topic=16184.0

 

[sgenevay]

I'm in 220v and u se the reference That Martin gave in his 220v pdf...   TE62085-ND in digikey.
a 50 VA transformer. Joe from JLM told me it was enough...
As i told you i'm really lost with transformers... i don't even know if i have enough power at startup .. but all i know is that i'm far over the boards need when they are stabilized...
And for now it's working well...  At least i used the preamp 3 full working days (like 10/ 11 hours/day) and it's still here...
But  yes if someone can tell me more about it... that would be good to learn...  

Sylvain.

 

[desol]

Hmm.

The way Martin has the ACDC configured is for 750ma at half-wav rectification on the + rail...centre tapped connection(0v connected on transformer secondary(red/brown) - this splits the amps 750ma + 750ma -). Probably an ok configuration for one or two channels.

4 boards with this, would then be getting 187ma ea, connected to the postive rail.

You have the capability to get more with what you have, so i would probably do it...but you would have to remove a few things from the acdc's (neg parts) and hook up the transformer secondary to the acdc differently and add strap to bottom right capacitor.

The way i would hook it, is to removed the negative parts off the acdc's(as per joe's diagram), then hook only the 24vac connections to the two 24vac in's...hook nothing to the zero volt (centre tap) connection on the ACDC. Just shrink tube that connection. Leave primary as is.

This would give you full wav @ 1.5a to only the + rail....yielding 375 ma to ea channel....per acdc.
Not much work for a better supply to the Neve's.

I think this is correct. If Martin or anyone would chime in to confirm, that would be great.

 

[sgenevay]

So if i understand well what u mean....  as i already removed the negative voltage regulator... i only have to remove the link to 0v from the transformer to the board ?
sounds weird... where does the 0 come from then ? :-s
Sylvain

 

[desol]

Check joe's diagram for parts removed. (above link)

There is no zero volt reference as acdc is no longer bipolar, +/-/0v. (trying to be sure i have this right
0v to boards is simply other side of 24vac input...neutral.

So negative parts off board and 24 vac secondary to 24 vac in's(nothing to zero volt), and also....jumper across bottom right capacitor.

Half way down:
http://www.groupdiy.com/index.php?topic=22828.580

If you change, make sure to disconnect boards and have 500ma fuse connected in case short or something.
...and double check all this with Joe, just to be sure.

 

[zmgwg]

is "jumper" a good place for inserting passive eq?

 

[letterbeacon]

I know it's possible in theory to fit two 1073 pre amps in a 1U case, but has anyone actually done it in practice?

 

[snipsnip]

yes, loads of people have done it. there are examples in this thread and others in the other 1290 build thread.

 

[sgenevay]

Hi everybody...

I dunno if someone already gave those datas but i think it could be very useful, as this is the first thing i thought about when my preamps were finished...

what should be the "hiss" level at higher gain ?

Here are 2 audio files recorded from an original Neve 1073DPA channel directly in protools HD interface: aif  - 96kHz/24Bits - Mono.

-On the first one, the 1073DPA gain switch was set on higher gain, and the trim pot set to 0:
http://sgenevay.o2switch.net/Invite/Higher%20Gain%20-%20trim%200.aif

-On the second one, the 1073DPA gain switch was set on higher gain, and the trim pot set to 10 (its max level):
http://sgenevay.o2switch.net/Invite/Higher%20Gain%20-%20Trim%2010.aif

U can then easily import those files in your DAW application and compare Hiss level with your ez1290 Preamps....
At least it can give an idea about a correct level.

Hope that will help

Best.

Sylvain.

 

[sr1200]

I have almost NO hiss even at max gain on mine.

 

[desol]

Sylvain, did you do anything with your powersupply or leave it as is?

 

[sgenevay]

I'm finally building a new one in a serie-20 box of par-metal.com... More space... And vent holes...
I will put 2 power supply in the same box to feed my 2 8-channel racks.
With separate switches, a led per channel and voltage rail... and same design as the preamp.
Didn't try what u said yet but I'm working on it and will ask Joe about it.
Just didn't have a lot of time yet cause so much work in studios lately. But the preamp is still working well this way...
So it could take several weeks to recieve and mount everything... Will tell u more

best,

Sylvain.

 

[MicDaddy]

Hit a snag, as I'm populating cards I don't see anyone else using axials for C4, C6, and C7  Electrolytic 100uF 25V.

I purchased MAL213836101E3  which is an axial package and I see all the builds on here using radials....  where did I go wrong?  I've double/triple checked BOM against digikey/mouser/allied and they tell me axial package....    are the VishayBC axials I have ok to use for these 3 designators?  See attached photo...

 

[0dbfs]

Those are 105C caps. Should be fine as long as they are oriented correctly. Won't cause it to not work. Original had 80uF in those positions according to the schematic but I believe that Martin explained why he went with 100uF previously in this thread.

Cheers,
jonathan

 

[desol]

80uf isn't available any longer. Those will be fine..
Radial or axial doesn't matter. I used axial bc caps on mine.

 

[sr1200]

@MicDaddy
Mine was like that too, they work fine, however, you might need a little bit of wiggle room for when you get the heat sink on there.  I had to bend those caps slightly away from the heatsink so they didnt touch.