Whoops

Re: 8 Channel, 3U NEVE 1073 completed
« Reply #2280 on: January 24, 2020, 08:08:30 AM »
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

Re: 8 Channel, 3U NEVE 1073 completed
« Reply #2281 on: February 17, 2020, 05:52:05 PM »
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

Re: 8 Channel, 3U NEVE 1073 completed
« Reply #2282 on: February 17, 2020, 08:22:07 PM »
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

Re: 8 Channel, 3U NEVE 1073 completed
« Reply #2283 on: February 28, 2020, 11:14:40 AM »
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

Re: 8 Channel, 3U NEVE 1073 completed
« Reply #2284 on: February 28, 2020, 11:50:15 AM »

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

Re: 8 Channel, 3U NEVE 1073 completed
« Reply #2285 on: February 28, 2020, 08:27:20 PM »
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

Re: 8 Channel, 3U NEVE 1073 completed
« Reply #2286 on: February 28, 2020, 08:40:37 PM »
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

Re: 8 Channel, 3U NEVE 1073 completed
« Reply #2287 on: February 28, 2020, 09:02:22 PM »
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.
« Last Edit: February 28, 2020, 09:05:33 PM by Whoops »

Clakejr

Re: 8 Channel, 3U NEVE 1073 completed
« Reply #2288 on: February 29, 2020, 09:54:58 AM »
I was reading the V 2.6 BOM but I can't distinguish, how many of each components do I need to purchase?

joakimkarlthomas

Re: 8 Channel, 3U NEVE 1073 completed
« Reply #2289 on: March 02, 2020, 08:44:40 AM »
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?


 

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