Neve style 500 series mic pre 1290 1073

Ok, I'll whack it out of there just to be safe, no biggie, in case I go to 51x one day. Thanks!

onlymeeee said:

Well either really!  I use it as a handy place to put the fuse instead.

Click to expand...

Onlymee, have you got a pic of what you mean?

So you can apply the fuse to the board for people using the API lunch bunch - 16 volts?

doesn't look like you need that fuse  in for 16v
i'm 51x, this is nice to know... i'll swap out my jumper wire with the two spare fuses from the BOM then.

re: relays... seems there is some kinda world shortage! anyone have two spares they wanna part with?

I think i do. Let me get back to you tomorrow.

canidoit said:

onlymeeee said:

Well either really!  I use it as a handy place to put the fuse instead.

Click to expand...

Onlymee, have you got a pic of what you mean?

So you can apply the fuse to the board for people using the API lunch bunch - 16 volts?

Click to expand...

+100

So for +-16V operation I use the 2 fuses.  It's the first component inline with the incoming +16V rail and first component inline with the incoming -16V rail.

Like so...


For 24V operation I put a fuse, instead of the long jumper.  Also, you can leave out a few parts that I'm not I mentioned, no worries if they're put in. They won't do anything.

Like so...


(also no biggy, but for 24V operation you can leave out the 4 components at bottom right of main PCB as they just affect the -16V (F2, fltL2, fltC1 and fltC3)  If they're left in they won't cause any issues at all. They won't do anything, that's all.

onlymeeee said:

So for +-16V operation I use the 2 fuses.  It's the first component inline with the incoming +16V rail and first component inline with the incoming -16V rail.

Like so...

For 24V operation I put a fuse, instead of the long jumper.  Also, you can leave out a few parts that I'm not I mentioned, no worries if they're put in. They won't do anything.



(also no biggy, but for 24V operation you can leave out the 4 components at bottom right of main PCB as they just affect the -16V (F2, fltL2, fltC1 and fltC3)  If they're left in they won't cause any issues at all. They won't do anything, that's all.

Click to expand...

So, I can put here a small jumper ?

For +-16V operation in an API lunchbox?  Instead of fuse?  Sure.

It's just a break between the incoming 16V rail and the NV73 circuit

onlymeeee said:

For +-16V operation in an API lunchbox?  Instead of fuse?  Sure.

It's just a break between the incoming 16V rail and the NV73 circuit

Click to expand...

Thanks

That looks a little confusing to me. So what you have installed there in the pic is actually a fuse, I thought that was a yellow capacitor  ???

Also you wrote
"So for +-16V operation I use the 2 fuses"
You mentioned 2 fuses, so where is the second fuse in your pic? Is it the second yellow looking cap on the right hand side under "f2" print?

What are the specs for those capacitor looking fuses, can I please have a link to where you sourced those fuses? What are my options in model fuses, cause I do not really want to fork out $30 for shipping just for that little fuse. I much prefer those little fuses that come in a little glass bulb where it is interchangeable where you do not have to desolder or solder to change it. Hopefully Oz has something similar and local.

They're on the mouser carts, general BOM etc. 
They're PTC resettable fuses  652-MF-RX030/72-0

Might look like caps, but don't use them for decoupling duties!

ok so thats cleared that up, nice.
also, why is there a hole in the metal under the gain switch?

any word on them relays anywhere?

kepeb said:

also, why is there a hole in the metal under the gain switch?

Click to expand...

So you can fit the switch in the metal work.. sit it nicely... then solder a few pins through the bottom.  So it sits nice and straight and also in the middle of the metal work

Regarding the unit. If you put the gain knob at 0, that means it will accept line level? Is that correct?

I read somewhere that the neve 1073 has 80db of gain. So these units have 15db of gain from level 0 cause your gain numbering only go to 65 and the trim pot goes to 0?

Just curious how hard would it be to put a DI in there and if there is any space?

canidoit said:

Just curious how hard would it be to put a DI in there and if there is any space?

Click to expand...

pretty sure you'd have trouble fitting a DI in there - maybe if you sacrificed the trim pot...?

canidoit said:

Regarding the unit. If you put the gain knob at 0, that means it will accept line level? Is that correct?

I read somewhere that the neve 1073 has 80db of gain. So these units have 15db of gain from level 0 cause your gain numbering only go to 65 and the trim pot goes to 0?

Just curious how hard would it be to put a DI in there and if there is any space?

Click to expand...

Yes, will accept line level (same as a Neve 1063, which used just the one transformer for line and mic duties)

Gain.... Not sure I follow.. but 0dB setting, means no gain, unity.  65dB setting means 65dB gain.  As it's a 12 position switch I couldn't have the same 22 positions as a 1073, so chose the most logical steps in my experience.  With the Lo Z pressed, you get another 5dB or so too if you need it for old ribbons.  Wouldn't take much to change the top gain setting to a larger gain, if you needed, but I find 65dB to perfectly fine.  (plus the extra gain from Lo-Z to be perfect)

DI... Not impossible, but a little tricky.  There's space between the gain switch and phantom (with space behind), but you'd have to fly quite a few wires about the place.

Onlymee, this build is meant to follow a 1290/1073 pre-amp but I am curious as to why it does not have the 80db gain that comes naturally with the 1290 and 1073 preamps if this build follows it? This is only 10db higher than a 1272 and 15db lower than a 1073.

Won't you be loosing some of the magic of pushing the unit hard, if you tame down the gain?

How do you make this unit the same gain as a real 1073/1290? Can you please tell me how it's done. I use ribbons and would like the 80db gain and would like to build this as close to how a 1073/1290 is.

Thanks

If you compare the schematic from mine to AMS site's schematic...
It's not circuit changes.
It's a mechanical restriction due to not having more positions on the switch.
For example, if you have an original 1073 on 65dB setting.. it has the same circuitry as mine at 65dB.

If you want 80dB instead of 65dB, (which having used many original Neve's and many ribbon mics, have never personally needed) then it's pretty easy to mod...

This will give you an extra 10dB at highest setting...
Add a wire like so (black wire top right)
http://www.thedonclassics.com/bottompcbMODfor75dBgain.jpg
(that'll get you to 75dB)  Check for oscillation...

If all's well and you need the extra 5dB on the highest setting, then I'd jumper over 3.9k (R20) (and then make up the difference in the pad 'string' so the other switches don't change) so I'd change R21 to 7.2k.   

That.. (as I'm looking at it late at night) seems the way. 

But have a look at both schematics... either way is exactly the same as Neve did it.  It's just which positions on the switch do you want.

onlymeeee said:

If you compare the schematic from mine to AMS site's schematic...
It's not circuit changes.
It's a mechanical restriction due to not having more positions on the switch.
For example, if you have an original 1073 on 65dB setting.. it has the same circuitry as mine at 65dB.

If you want 80dB instead of 65dB, (which having used many original Neve's and many ribbon mics, have never personally needed) then it's pretty easy to mod...

This will give you an extra 10dB at highest setting...
Add a wire like so (black wire top right)
http://www.thedonclassics.com/bottompcbMODfor75dBgain.jpg
(that'll get you to 75dB)   Check for oscillation...

If all's well and you need the extra 5dB on the highest setting, then I'd jumper over 3.9k (R20) (and then make up the difference in the pad 'string' so the other switches don't change) so I'd change R21 to 7.2k.     

That.. (as I'm looking at it late at night) seems the way. 

But have a look at both schematics... either way is exactly the same as Neve did it.  It's just which positions on the switch do you want.

Click to expand...

Wasn't there any switches available that will give you the 80db that Neve has?

What do I do if it oscillates when I add the wire?

Is it possible to use the switch we have already to start at say 15db and end at 80db instead of starting at 0db and end at 65db or doing these other additional mods to get it to 80db? When you add that wire, what exactly happens to how the switch works, does the increments change, like the 12 positions could become, eg. 0, 5, 10, 15, 20, 25, 30, 35, 40, 60, 70, 80

I think what will help is if I try and explain the gain structure of a Neve 1073 better...  (have you been looking at the schematic?  Use it for reference)

Mic signal comes in...
Hits input transformer...
Then it goes to a pad (loss of level) this is what we switch - giving variable gain.

Then it goes to the BA283NV
The BA283NV then either has no resistor (normal) between T and ground, or a 330R resistor (extra +5dB) or 120R (extra +10dB)  this also switches when we have no pad left to reduce!


From there it goes to the output attenuator pot (unity or loss of level)
Then to the output amp BA283AM
and out to the output transformer.


When on 55dB and higher...

Mic signal comes in...
Hits input transformer...
Then it goes to the BA284NV
Then it goes to a pad (loss of level) this is what we switch - giving variable gain.
Then it goes to the BA283NV
The BA283NV then either has no resistor (normal) between T and ground, or a 330R resistor (extra +5dB) or 120R (extra +10dB)  this also switches when we have no pad left to reduce!


From there it goes to the output attenuator pot (unity or loss of level)
Then to the output amp BA283AM
and out to the output transformer.


So my question to you Canidoit is this.....
Look at this picture...  http://www.thedonclassics.com/images/nvgainstructure.jpg

On 35dB gain setting.... what is the value of R1 and R2.... and also, what option for pin T would you choose for 35dB setting ?




In regard to whether or not a different switch is available... you mean a 24position switch instead?  They're not common,  and also it's quite a tight layout to get one in, with extra resistors for the different positions.

If you get oscillation.. then we'll cross that bridge then.  Possibly using a bit of metal L bracket to shield the input transformer may fix it.  Or just remove the wire?!

Originally I built this with 20dB to 75dB in 5dB steps.. and me and several engineers found it's very annoying not having a 0dB setting for line and also for loud drums, NS10 cone etc...
So I built one with 0dB and then a jump to 20dB to 70dB... on this we found it extremely irratating that when I'd mic up guitar amps,  0dB is too quiet and 20dB distorted.. so that brought us to the current gain setup I have.