8 Channel, 3U NEVE 1073 completed

[Whoops]

Which BOM should I download  v2.5 or v2.6? I recently just purchased the  EZ1290 PCB and I have a few more on the way help is welcome as I am a novice.

The BOM is referenced to the version of the PCB you purchased.

Which version did you buy?

help is welcome as I am a novice.

Nice for Joining.
Welcome to this great and friendly Community

First help I can give you:

- Be friendly, respectful and be willing to learn

- Read this thread.
Everytime you are doing a new project read the build thread relevant to that project, have Word open and copy the relevant info to a Word doc, call it "Project Comp". It will help you out a lot when you are building the project and it will make you build a breeze

- Never ask a question and Never start a new thread without searching about that subject here in the forum.
There's a big chance there's already a thread on the same subject in the forum

- Never ask a question and Never start a new thread without searching in google first

- last advise is  Read this thread.

Have a good time

 

[joakimkarlthomas]

Hello! Ive got a 2 channel ez1290 since a few years, working and sounding nice. I biased it with DMM, setting the 2N3055 casing to 22.6V. Now I decided to learn how to use my oscilloscope and to practice I thought I would try to bias this preamp with the oscilloscope method. But when trimming the trim pot I can’t see anything happening to the waveform on the oscilloscope.

I’ve connected the signal generator to the xlr input and the oscilloscope to xlr output.

I have an output potentiometer installed. (When setting bias with DMM method I have to set the this potentiometer to 0/all the way down to no sound. If not I get another voltage reading that doesn’t change when trimming the trim pot). Is this normal?

Something Im doing wrong?

 

[Whoops]

I have an output potentiometer installed. (When setting bias with DMM method I have to set the this potentiometer to 0/all the way down to no sound. If not I get another voltage reading that doesn’t change when trimming the trim pot). Is this normal?

Something Im doing wrong?

the output potentiometer is an attenuator, so all the way up clockwise is 0 (zero dBs unity) no attenuation, all the way down is - infinity (full attenuation)

You should have it at unity gain, all the way up. If you're having problems maybe re-check the pot wiring connections.

For the Oscilloscope ask the help from a local friend that knows how to use one.
If you don't have a friend that uses an Oscilloscope, make a new friend, find someone near to you that could help you help.

I've made a lot of friends while DIYing, we still help each other up to this day and we learn with each other

 

[JW]

Can someone help me reconcile the orientation of the zobel network on the output transformer's secondary.

Here in the technical docs, https://groupdiy.com/index.php?topic=44877.0 the BA283 schemo has "M" at the top. This is the +24V connection on the primary. The second primary is "B" which connects to the the 2n3055. But if you look on the secondary, the lead that appears to be in polarity with "B" (which would ostensibly be pin 2 on the XLR in modern times) has the connection to the capacitor, while the other secondary has the connection to the resistor. 

Compare this to Martin's build guide on the first page of this thread, with the Carnhill wiring, you will see that the zobel network is reversed, with the resistor connected to the "hi" side of the secondary, and the cap connected to the "lo" side.

Which is correct?

 

[dmp]

Can someone help me reconcile the orientation of the zobel network on the output transformer's secondary.

They are equivalent. Do it either way

 

[Whoops]

Compare this to Martin's build guide on the first page of this thread, with the Carnhill wiring, you will see that the zobel network is reversed, with the resistor connected to the "hi" side of the secondary, and the cap connected to the "lo" side.

Martin have said before that he based the circuit on the 1073 but removed the EQ section. (is not even based on the 1290 schematic)
So you should reference to the 1073 docs and schematic (easily available) and the not on the BA283 docs alone.

from the 1073 docs:

and I guess this is the 1290 schematic:

 

[JW]

Thanks Whoops,

I have it currently wired like the schematic you posted, which is the same as Martin's build doc.  Interesting that the schematic I linked to a post ago has it reversed, yet it looks like a scan of a Neve document. . Maybe it doesn't matter which side the cap and resistor are on? I need to research zobel networks.

1073 is made up of BA283 amps, so I would expect them to be the same. But  . . .

 

[Whoops]

Don't know why is different in the BA283 doc. But also that doc doesn't show the transformer pinout numbers.

You can ask that to the specialist, Geof Tanner in his forums he will probably know that :

http://auroraaudio.net/forums/

Let us know what you find.

 

[Clakejr]

I was reading the V 2.6 BOM but I can't distinguish, how many of each components do I need to purchase?

 

[joakimkarlthomas]

the output potentiometer is an attenuator, so all the way up clockwise is 0 (zero dBs unity) no attenuation, all the way down is - infinity (full attenuation)

You should have it at unity gain, all the way up. If you're having problems maybe re-check the pot wiring connections.

thanks! I think I got it working now. I've attached two pictures. One showing how the signal (1kHz) looks when I've set the 2N3055 casing voltage to 22.6v with the trimpot. The clipping didn't look symmetrical so I adjusted the trimpot until it did. After this setting the voltage i 23.5v, almost as as far as I can go with this trimpot. Does it look like a good setting?

 

[JW]

So, it looks like some people have had issues with pops when the phase switch is on the input. Pops when the phantom is on? I'm just reading, not experiencing it yet. I'll have to run more wire to wire a phase switch on the output.

I can't think of any other reasons though. I guess more wire is better than popping. Is there a 'standard' way to to do this? Input/output?
(Please don't tell me relay .  . . . Front panel is already drilled for a standard switch)

Best way to ground 0V I think is home runs for each channel back to the 0V wire coming from the power supply?
And for the two power connections, +24 and +48V, they are series connections right? So, +24V to channel 1>ch 2>ch3 etc. Same with +48V?

Final question. does anyone have a part number place to find  3 conductor + shielded power cable? I'm having a hard time finding it?  Could use Canare Star quad, but the conductors are only 22awg I believe.

 

[Potato Cakes]

So, it looks like some people have had issues with pops when the phase switch is on the input. Pops when the phantom is on? I'm just reading, not experiencing it yet. I'll have to run more wire to wire a phase switch on the output.

I can't think of any other reasons though. I guess more wire is better than popping. Is there a 'standard' way to to do this? Input/output?
(Please don't tell me relay .  . . . Front panel is already drilled for a standard switch)

Best way to ground 0V I think is home runs for each channel back to the 0V wire coming from the power supply?
And for the two power connections, +24 and +48V, they are series connections right? So, +24V to channel 1>ch 2>ch3 etc. Same with +48V?

Final question. does anyone have a part number place to find  3 conductor + shielded power cable? I'm having a hard time finding it?  Could use Canare Star quad, but the conductors are only 22awg I believe.

Best way to ground 0V I think is home runs for each channel back to the 0V wire coming from the power supply?
And for the two power connections, +24 and +48V, they are series connections right? So, +24V to channel 1>ch 2>ch3 etc. Same with +48V?

Final question. does anyone have a part number place to find  3 conductor + shielded power cable? I'm having a hard time finding it?  Could use Canare Star quad, but the conductors are only 22awg I believe.
[/quote]

You can use a DPDT switch between the output transformer to the XLR to invert the polarity as shown on the original schematic. This way you don't cause a momentary break in phantom power.

Have you looked over Ian's Grounding 101? (http://www.ianbell.ukfsn.org/EzTubeMixer/docs/EzTubeMixer/SimpleMixer/grounding101v2.pdf)

For shielded power cable you can use this: https://www.redco.com/Mogami-W2549.html. I actually used a smaller gauged XLR cable for years with my 4 channel version and it worked perfectly fine. A full 1073 module draws about 150mA (I'd have to remeasure) and the ez1290 is going to be  less than that. Also most of your 500 series PSU are rated for a total of 80mA for phantom power. The Mogami 2549 is also very good copper. I know you could get away with the 2791 (braided shield) which is 24AWG as long as you weren't doing long runs. Here is a chart that may provide some insight: https://www.coonerwire.com/amp-chart/

And one more thing, the resistance for the 2549 is 0.018 ohms per foot per conductor. You can use V=IR and P=IV to figure out if the gauge of wire you are using is fine. Like I said, I was using a small gauge mic cable (28AWG for the conductors) and I never had a problem.

Thanks!

Paul

 

[gridcurrent]

Final question. does anyone have a part number place to find  3 conductor + shielded power cable? I'm having a hard time finding it? 

why the need for shielded ?
Home Depot has 4 conductor, 16 gauge, stranded,  jacketed "speaker cable",  reasonably flexible for use as  power cable.

 

[Potato Cakes]

why the need for shielded ?
Home Depot has 4 conductor, 16 gauge, stranded,  jacketed "speaker cable",  reasonably flexible for use as  power cable.

If you don't use shielded you get a bunch of noise. This I can attest to from experience.

Thanks!

Paul

 

[gridcurrent]

If you don't use shielded you get a bunch of noise. This I can attest to from experience.

well that is quite amazing.
presumable very LOW output impedance power supplies delivering DC to your Neve thingys, and you get noise.
your know, back in olden days, Neve consoles were fed fairly long distances with unshielded power cable., only the sense lines were shielded.
maybe  an issue indigenous to Nashville ?

 

[Potato Cakes]

well that is quite amazing.
presumable very LOW output impedance power supplies delivering DC to your Neve thingys, and you get noise.
your know, back in olden days, Neve consoles were fed fairly long distances with unshielded power cable., only the sense lines were shielded.
maybe  an issue indigenous to Nashville ?

Possibly. I have no idea why it would be just a problem here.

Thanks!

Paul

 

[JW]

Thanks for the answers guys. That Mogami cable is just mic cable. Not enough conductors for 48V. I already have a bunch of star quad. I should probably just use that.

I was thinking more along the lines of this: https://www.redco.com/Gotham-85225-3c.-Shielded-AC-Power-Cable.html 

It has a foil shield or it would be perfect. But I'd prefer a braided shield for my stomping feet.

 

[octavez]

I'm currently planning a 2ch EZ1290. I was wondering if anyone has made a blend/sum XLR output like the BAE 1073MP (Dual, Steve Steven's mod)?

What would be the best way to do it? Use two resistors to sum/blend the signals into one?

Thank you!

 

[mrdarwin]

Hi.
Im looking for a strong and clean psu, kit, pcb or mount to feed a rack of 8 ez1290.
24v + 48v.
Suggestions ?
Thanks

 

[TillM]

Volker has some nice PCBs for your project.
Look at the white market @silentarts