8 Channel, 3U NEVE 1073 completed

[North]

The pads, phase reverse, phantom power and DI's I found the least hassle to get as kits from JLM audio. They build quick and sound great leaving me to spend more time on other things about this build.

 

[analogstud]

The pads, phase reverse, phantom power and DI's I found the least hassle to get as kits from JLM audio. They build quick and sound great leaving me to spend more time on other things about this build.

+1 

 

[bruce0]

here's the vero layout i made for the dc/dc converter 48V to 2x 24V.
i tried running both pres from one TIP121 but two regulators (one for each channel) are better. one alone can handle the current draw but it

What DC/DC convert did you use?

 

[StaticRick]

So it looks like its my turn to ask for some EZ1290 troubleshooting help...

I built two channels of EZ1290.  One of them is working great, the other one isn't.  The output is much lower and shows asymmetry on the scope.

I've spent a good amount of time visually comparing the two channels.  They look to be identical.  So, before I start pulling components off the board, I'm looking for suggestions of what to investigate first based on the scope pic below.

The pic is using the same 1kHz input signal that was used to bias the working channel, but I had to turn up the Y-axis resolution due to the lower output.

Left to my own, I'll probably start swapping transistors.  I'm hoping that some input here will save me some bench time.

Thanks GroupDIY!

 

[critterkllr]

So it looks like its my turn to ask for some EZ1290 troubleshooting help...

I built two channels of EZ1290.  One of them is working great, the other one isn't.  The output is much lower and shows asymmetry on the scope.

I've spent a good amount of time visually comparing the two channels.  They look to be identical.  So, before I start pulling components off the board, I'm looking for suggestions of what to investigate first based on the scope pic below.

The pic is using the same 1kHz input signal that was used to bias the working channel, but I had to turn up the Y-axis resolution due to the lower output.

Left to my own, I'll probably start swapping transistors.  I'm hoping that some input here will save me some bench time.

Thanks GroupDIY!

Can you check voltages using a DMM? Before you start swapping around parts, it's best to run down the circuit with a DMM and a schematic handy. Alligator clip the negative probe to ground and start probing with the positive. Keep notes on all transistor voltages. If one seems odd, you'll know what to start looking. I had a similar problem with one of my first EZ1290s and it turned out I had a bad cap. I would have never found it if I didn't go through the entire circuit to check voltages.

 

[Chrome Heart]

So it looks like its my turn to ask for some EZ1290 troubleshooting help...

I built two channels of EZ1290.  One of them is working great, the other one isn't.  The output is much lower and shows asymmetry on the scope.

I've spent a good amount of time visually comparing the two channels.  They look to be identical.  So, before I start pulling components off the board, I'm looking for suggestions of what to investigate first based on the scope pic below.

The pic is using the same 1kHz input signal that was used to bias the working channel, but I had to turn up the Y-axis resolution due to the lower output.

Left to my own, I'll probably start swapping transistors.  I'm hoping that some input here will save me some bench time.

Thanks GroupDIY!

Can you check voltages using a DMM? Before you start swapping around parts, it's best to run down the circuit with a DMM and a schematic handy. Alligator clip the negative probe to ground and start probing with the positive. Keep notes on all transistor voltages. If one seems odd, you'll know what to start looking. I had a similar problem with one of my first EZ1290s and it turned out I had a bad cap. I would have never found it if I didn't go through the entire circuit to check voltages.

I agree. If you have a working unit I would just A/B between the two and find the trouble spot.

 

[Chrome Heart]

Hi Michael,

Yes, the DPA appears to be using lots of SMD components and uses a vastly different layout compared to a vintage 1073/1084 as found in 80 series consoles. I've heard people say the DPA is a very nice sounding mic pre however. I think you'll hear more resemblance between a well maintained (this is key!!) vintage 1073 and the EZ1290. In order to make the EZ1290 I had to dissect and desolder a perfectly good module to get all the details sorted out. It hurt but was worth it in the end. I'll see if I can dig up some recent clips a friend of mine recorded with an EZ1290 and Wunder CM7 and an R84 (no processing) to give people an idea of the sound.

Best,

Martin

I have recorded more than a couple records on an 8068 and I can tell you, the 1290 pre holds it own. It has everything your looking for in this type of design.

 

[sr1200]

I finally finished my 8ch unit (after 4 years).  Started with 2ch, then got 4 more... finally got the last 2 this year.  Its been quite a ride!
heres the album of putting the 8 together.
https://imgur.com/a/HefJp

 

[useme2305]

awesome.

that'S 3U, right? what kind of power supply did you use?

 

[sr1200]

JLM powerstation with an 200VA antek transformer. 

edit: and yes 3u.  The link has pics of almost the entire build.

 

[madriaanse]

I finally finished my 8ch unit (after 4 years).  Started with 2ch, then got 4 more... finally got the last 2 this year.  Its been quite a ride!

Great work! Congratulations on a job well done! I hope you get many years of enjoyment out of it.

Martin

 

[analogstud]

Guys, I don't want to forget, just wanted to thank you for all the info here, Martin for the boards and everyone involved with fabrication and hardware! Built my 4x1290 and everything worked the first time! Sounds amazing and couldn't be happier with it! You guys rock! Now on to the REDD47 pre.......

 

[Analogue Nubian]

Hi guys! First of all I also would like to express thanks for everyone here since I've learned so much building this project and Martin, thanks for the boards of coarse!

I'm very close to completing my dual 1290. I went the Carnhill route and am sooo curious now that the finish line is in sight.

Let me apologize for this nuub question  :

I've seen a few things written on the trimmers and would prefer mine to be stepped. Would it be an option to use Elma or Grayhill switches instead of the more standard 10k log pots?

Martin, any future chances on you do a trimmer pcb the way you've done the switches on the 1290 board (gobetween style).

Thanks guys

Lucien

 

[useme2305]

i think you can use the grayhill conversion boards from capi for this.

 

[djn111]

Hi,

The trimmer is meant to adjust the amplification between the switched steps, to make them accurate for your need.

If you make them stepped, they are not fully adjustable any more, only by a fixed increment.

So choose what you want and why.

But you can use a 24 step switch, with resistors of course.

DJN

 

[Analogue Nubian]

Thanks useme, do you have a link for that? I've search and scavenged but no luck

Hmmm... Okay good point DJN.

So in that case go for the highest quality then

 

[useme2305]

http://classicapi.com/catalog/product_info.php?cPath=51_133&products_id=238

 

[analogstud]

Analogue, the key in choosing the trimmer is to avoid carbon pots. Go with a conductive-plastic pot, 10k, such as those from Alps. True, a stepped switch sorta defeats the purpose of being a continuously variable "fine" adjustment.

 

[Analogue Nubian]

True Analogstud. I've decided to go the 10k route! Thanks useme for the link

After months of really scouting and getting the part I'm almost there.

 

[useme2305]

The trimmer is meant to adjust the amplification between the switched steps, to make them accurate for your need.

i think it's not quite what the trimmer does but someone correct me if i'm wrong.
i think the trimmer actually controls what goes from amplifier stage 1 to stage 2.

on a differnt note....has anyone tried using a 600ohms T-Pad pot behind the output tranny for attenuation?