Neve 1290 build completed!!

[snipsnip]

Ive just noticed Mathews lovely build doesnt seem to ground the audio to the case, and doesnt have shielded cable on the output (or input?).

How come this isnt effecting him and such a huge impact on my build?

Jake

 

[desol]

Do you have a photo of your layout?

 

[snipsnip]

Yes - this is a little old now. Ive actually got it in bits again, as Im building into a new case with following changes:

1) Im adding an extra pair of input XLR's, which will not be connected to phantom power. This will allow me to leave a pair of mics and a pair of (padded) line sources connnected

2) I had some issue with crackle. Some people think this was down to the heatsink on the PSU, but I had mine attached to PSU chassis. I remain convinced the crackle was movement in the input transformer wiring. So Im going to use those little fivefish PCBs that sit on the top and allow wiring to be done via a 10pin mollex header.

I have already discussed my crackle woes on the other neve thread, so I wont bring them up in to much detail again here.

As im rebuilding any tips on layout would be greatfully recieved... Although i made sure to follow most of the tips given by martin. The only thing that looks a bit off to me is that the wire from the right xlr to right input tranny is quite long.

 

[snipsnip]

Also, I had thought about using a long M4 bolt istead of the standoff at the audio ground point (by the trimmer). Im thinking this might be the prettiest way to connect the audio ground to chassis. Any thoughts?

jake

 

[MatthewF]

Ive just noticed Mathews lovely build doesnt seem to ground the audio to the case, and doesnt have shielded cable on the output (or input?).

How come this isnt effecting him and such a huge impact on my build?

Jake

Hi Jake,

My input wiring is shielded (Belden 1508A). The output wiring isn't shielded as its pretty short and is not running in parallel or close to any input wiring so capacitive coupling from output to input is pretty unlikely.

With regards to audio and chassis ground, I have mine joined in the external PSU via the 10Ω resistor and 0.1μF cap on the AC/DC PCB. Audio and chassis grounds are then carried to the preamp over separate conductors in the PSU cable.

As a side note, I found that I had to connect audio ground to output XLR pin1 when driving certain bits of unbalanced consumer gear in order to get hum-free operation. This is probably due to a shortcoming of the said consumer kit, and I had to do the same mod to my Baby Animal preamps too.

I hope that helps!

Matthew

 

[ilfungo]

I placed an order and Mouser 2N3055 is not available
Can I use 2N3772 instend of 2N3055?
Thanks

 

[desol]

Ive just noticed Mathews lovely build doesnt seem to ground the audio to the case, and doesnt have shielded cable on the output (or input?).

How come this isnt effecting him and such a huge impact on my build?

Jake

As a side note, I found that I had to connect audio ground to output XLR pin1 when driving certain bits of unbalanced consumer gear in order to get hum-free operation. This is probably due to a shortcoming of the said consumer kit, and I had to do the same mod to my Baby Animal preamps too.

I hope that helps!

Matthew

This means, use the output transformer sheild.

 

[MatthewF]

Hi Desol,

I'm not sure I understand completely, as far as I was aware there isn't a shield on the Carnhill VTB1148 (or if there is its not brought out on to a solder pin). The extra connection I made was from the ground plane on the EZ1290 PCB to the output XLR pin1. My guess is that the unbalanced kit I was driving wanted to see a proper ground connection on its input.

Best,

Matthew

 

[ilfungo]

I found this toroidal
http://www.antekinc.com/details.php?p=40
May be fine for 2 channel?
Thanks

 

[ilfungo]

http://www.antekinc.com/details.php?p=40 ?????

 

[promixe]

I found this toroidal
http://www.antekinc.com/details.php?p=40
May be fine for 2 channel?
Thanks

Yes, this should be way more than enough for 2 channels. I powered this guy -

- with 100VA 22x22 trafo for 230VAC operation in Europe and it was more than fine. It had 2 channels and a converter with user interface built in.

 

[snipsnip]

Siiiick.

Thats a nice build. So you kept the PSU board in the box and just took the torroid out? I like that idea as you can then heatsink the regs to a much bigger case, and the case for the toroid can be a bit dinkier.

By the way, whats the product code for those XLR's youve used? They look really smart.

 

[promixe]

So you kept the PSU board in the box and just took the torroid out?

Actually, there are two boards for the PSU. See this thread - http://www.groupdiy.com/index.php?topic=29758.msg361304

One is preregulation and initial filtering and power resistors for step down to +/-15V and +5V. The one inside the rack is actual regulation and more filtering.

By the way, whats the product code for those XLR's youve used? They look really smart.

If you're talking about the combo Neutrik receptables - they are these - http://www.neutrik.com/us/en/audio/204_59540618/Combo_Series_productlist.aspx

Just search for these part #s in Mouser or Digikey, they are generally always in stock.

 

[madriaanse]

It had 2 channels and a converter with user interface built in.

That's incredible! Where did you get the converter? I'd love to read more about that.

Best Regards,

m.

 

[promixe]

The converter was PCM4222EVM (TI's eval board for the PCM4222 ADC chip) and it had individual on-board low noise regulators and a lot of other stuff (much of which I didn't need). The downside is that the board is relatively big and bulky and there are no holes to mount it properly (I bet it was intentionally designed that way) =) It's a 4-layer board, so drilling it wasn't an option really. I came up with a  mounting solution using plastic brackets from Home Depot, some two-sided gorilla tape and metal strips on top. If I dig up pictures of the mounts I'll post them here. The board is VERY cheap and is available from TI's site and it sounds superb.

To control the board is a bit tricky. I was using BasicX-24p uC with a serial character display and two pushbuttons. I came up with a cool GUI where only these two buttons are needed to easily control all of the ADC's modes. You would need some glue logic to work with 3.3V ADC's logic with the uC, which works on 5V rail. I also added the level meters onto the display, but I had to sample the analog signal at the converter entrance point (after I think an 18dB pad, cuz the Neve signal is way too hot) with the uC. Processing 24bit digital data past conversion for the meters is too much for the uC and isn't really worth it (IMHO).

The PSU was my design (with help of this forum) and it's a 5-rail board: +5V (digital), +/-15V (ADC analog part), +24V (Neve), +48V (phantom).

The client is very happy and is using the unit on a daily basis. =)

I'm happy to answer more questions if you have any.

PS: Martin, your boards are great!

PPS: It turned out to be a complex project, as I had to model the entire thing in CAD first, because the space inside the chassis was EXTREMELY tight!

 

[deuc224]

Please if you have mounting instructions for the PCM4222EVM could you post em. Im about to buy the power supply for it and i was beating my brain how to mount the board in a case.

 

[ilfungo]

Great job Promixe!

Thanks for your answer ...
You know that pot should I use to trim fader (front panel)?
Thanks

 

[promixe]

You know that pot should I use to trim fader (front panel)?

I wouldn't be of help with that as I didn't use any pots with any of my builds of EZ1290s. I'm in agreement with Martin here as far as the pot is concerned - it sits in the audio path and is a sound degradation device (in a audiophile sense of course). =)

What country are you in? I'd use a high quality (like Penny+Giles) pot but I had hard time finding them here in the US last time I looked.

 

[ilfungo]

You know that pot should I use to trim fader (front panel)?

I wouldn't be of help with that as I didn't use any pots with any of my builds of EZ1290s. I'm in agreement with Martin here as far as the pot is concerned - it sits in the audio path and is a sound degradation device (in a audiophile sense of course). =)

What country are you in? I'd use a high quality (like Penny+Giles) pot but I had hard time finding them here in the US last time I looked.

Thanks  Promixe
I'm in Italy...

 

[Chrome Heart]

Hi Martin
Did FPE do the blue front panel for your 8 channel pre build? I like the little Neve logo on the bottom too.
Bob R
Richmond VA