80 series 1073 DIY Build Guide

[MathCantin]

Hello all.
I'm sharing with you a guide on how to build your own 1073 module.
This is the first draft of a guide I've been working on for a few months.
This is meant to be used in conjunction with the 1073 User Manual .
I've learned so much from the GroupDIY community, I wanted to give back.

1073 BUILDING GUIDE V1.0

(the guide is about 89 pages, so it might take a while to load everything. Especially on cellphone.)

Hopefully this will give the courage to people who hesitated to do this beautiful build. If you want some pictures of specific details of the module please let me know and I'll do my best to make them for you.

(Special thanks to Noizetoys: he was very helpful with some last details I needed to complete this guide and to Sasarist for selling me the chassis)

Have a good read!

 

[Rob Flinn]

Thanks for that, it will be useful to me.

 

[ruffrecords]

Beautifully crafted document. You should be proud of yourself.

The only part I might take issue with is Geoff's description of calibrating the output stage. Geoff and I were both at Neve in the 70s but modules were built and calibrated in the Kelso factory so nobody at the Cambridge facility where we both worked had to do the cal. The cal is basically setting the quiescent current though the 2N3055. What causes clipping is drawing that current into a load so if you do not attach a 600 ohm load you draw little or no current. So my recommendation is to attach a 620 ohm 2 watt resistor across the output hot and cold when doing this test. The 1073 is specced to drive +26dBu into a 600 ohm load so I would expect it would have been set up and tested with this load attached.

It is entirely possible that this is why a lot of the clones don't quite have the right sound.

I have been asked several times what is the correct procedure for setting up the output stage. I asked the question on the private Neve ex- employees board and the only reply I got was from Geoff!

Cheers

Ian

 

[MathCantin]

Beautifully crafted document. You should be proud of yourself.

The only part I might take issue with is Geoff's description of calibrating the output stage. Geoff and I were both at Neve in the 70s but modules were built and calibrated in the Kelso factory so nobody at the Cambridge facility where we both worked had to do the cal. The cal is basically setting the quiescent current though the 2N3055. What causes clipping is drawing that current into a load so if you do not attach a 600 ohm load you draw little or no current. So my recommendation is to attach a 620 ohm 2 watt resistor across the output hot and cold when doing this test. The 1073 is specced to drive +26dBu into a 600 ohm load so I would expect it would have been set up and tested with this load attached.

It is entirely possible that this is why a lot of the clones don't quite have the right sound.

I have been asked several times what is the correct procedure for setting up the output stage. I asked the question on the private Neve ex- employees board and the only reply I got was from Geoff!

Cheers

Ian

Hi Ian!

This is precious information and thank you for sharing.
Would you be okay if I include your recommendation to attach a 620 ohm 2 watt resistor on the output hot and cold while calibrating in the guide?

Thank you for contributing so much to this group,
Mathieu

 

[rjstrat1]

Wow Mathieu!

An absolutely incredible guide, thank you so much for tackling this challenging build.
A question I have is, for those who have them, can you use original 183/184, instead of 283/284 boards?

Thanks again Mathieu for this great work, and thank you Ian for all of the vital information you contribute.

Rick

 

[noizetoys]

183 is interchangeable with 283 as is the 184 for the 284. Same circuit, different layout.

 

[rjstrat1]

Thanks Noizetoys,
I appreciate your help.

 

[ruffrecords]

Hi Ian!

This is precious information and thank you for sharing.
Would you be okay if I include your recommendation to attach a 620 ohm 2 watt resistor on the output hot and cold while calibrating in the guide?

No problem/

Thank you for contributing so much to this group,
Mathieu

Happy to help.

Cheers

Ian

 

[Murdock]

Wow, thanks a lot! Great guide. That will hopefully motivate me to finish my build.

 

[Rob Flinn]

Wow, thanks a lot! Great guide. That will hopefully motivate me to finish my build.

My thoughts exactly ........

 

[3nity]

Ian, the 620r load should be attached to transformer secs?

 

[ruffrecords]

Ian, the 620r load should be attached to transformer secs?

Yes, between hot and cold. I said 620 ohms because 600 ohm resistors are not readily available. But 300 ohm ones are so for the sake of perfection you could use a pair of 300 ohm 1 Watt resistors in series as a test load (or a couple of 1K2 1 Watt resistors in parallel).

Cheers

ian

 

[ruffrecords]

I did a few sims of the BA283 output stage the other day, with and without a load. I can confirm the optimum bias point does depend on the load but the dependency is much less than I expected. So probably best to do the cal with the load in place but it is not as essential as I first thought.

Cheers

Ian

 

[audiosway]

What an amazing doc. Thanks so much for this. I'm in the process of prepping to build out 16 of these for tracking in my studio. This is perfect for my little venture.

 

[Frank00]

Great guide for an ambitious project!

 

[sasarist]

Amazing work

 

[SergioGarcia]

Mega big thanks!
it must have taken a big amount of hours to make a great guide like this!

 

[thomasdf]

amazing work ! bravo !

 

[mesajoe]

Wow, what a fantastic contribution to GDIY - thank you Mathieu for this outstanding piece of work.. I am in awe..