AMS Neve 1073 Sweeps

[Aaronrash]

A great deal of the PCB is bypassed via wiring most things straight off the components instead of going back on to the board. Also shielded wire is wired and grounded like my AMS modules.

Simply put, a great deal of tracks were bypassed with wire instead of tracks. Adm the shield scheme is per original schematic.

Sort of like how guitar enthusiasts swear by PTP wiring vs a board. There is a difference.

Anyways, at this point it isn't a EZ1073. It's a complicated highly modified 1073

Ready earlier post.

 

[haystack]

Hi Aaron

Just one request if possible.

Would it be possible for you to show me how you wire up the output trans to the various places avoiding the pcb please.

That would be really great.

Cheers

Hay

 

[ding]

what's puzzling me now is that I'm still trying to see what's really new about these mods. Back in January, you already had the AMS input and output transformers mounted on the chassis. What changed along the way?

I have to wonder about this also. On page 4 of this thread, reply #74 you can clearly see that you have the input and output transformers wired by hand. I imagine that the input transformer grounding issue was not discovered. Also it looks like the secondaries were wired to the pcb pads instead of directly to the switches. I imagine that the input transformer grounding had the most significance to the sound. I am still unsure how much influence just a few inches of wire had. I'm referring here to the input and output secondaries being wired directly to the switches instead of to the pcb pads. I have been putting of finishing mine so I can ponder over this thread. I think I will just finish it the way I had planned and do some testing and continue to mod from there. The only pain in the ass is getting the solder from those pads. This board is particularly difficult with a standard pump. Hopefully some people would try some of these things and report back.

 

[haystack]

Ding, Aaron


Is it still possible to ground the input transformer properly even though it is soldered to the pcb ? I am a bit confused here,
does pin 11 need connecting to pin 6 for proper grounding?

I would also love some help on the wiring of the output transformer - anyone(?), as i can take that off the pcb. I feel a bit apprehensive
to just steam in before I know where he coloured leads should be connected.
I will try and terminate the output xlr with a 680 resistor.

Hope other folk have a go at Aaron's mod ideas. Also has anyone had a eq sweep of their unit?

 

[ding]

Take a look at the build guide. Don't terminate the output without first jumping the 620 ohm termination resistor already on the board. The schematic and pcb layout portion of the ez1073 build guide should help. Maybe flip the output transformer 180 degrees. Check the input transformer to ground and see if you even need to do that. I haven't installed mine yet so I can't check. The difficulty here would be soldering the zobel network on to the flying leads of the output tx. I would be interested in audio samples before and after. Good luck.

 

[dmp]

The VTB9045 isn't internally connected. For instance, take your multimeter and test for continuity between the screw by 6 and then the other side, 11. There will be no continuity... The AMS versions do have continuity so they are in fact different. I've confirmed this by testing all my AMS transformers.

Pin 6 should be connected to ground, pin 11 is not used. If 6 and 11 are internally connected in the AMS and you did not ground pin6 in the Carnhill, that alone could have made a difference in performance.

 

[haystack]

Thanks Ding and Dmp.

I soldered the input as per the instructions so I assume it's connected to ground (pin 6).

I wonder what the 500 series ez1073 sounds in comparison to the rack - if there are pcb differences etc (more or less tracks)

Thanks again

Hay

 

[ding]

haystack,

Before you start the mods why don't you get a base recording and sweep for reference. That way you got something to compare to. 

 

[Aaronrash]

Sorry I have been very busy,

I will try to answer some questions.

Ok so if you leave the input transformer mounted the PCB pin 6 is getting ground but it's getting B-0 instead of Cgnd witch is not correct. It is correct that pin 6 and 11 are not internally connected on the Carnhill VTB9045. The AMS version of the input TF10003 they are connected internally. If you look at the Neve schematic it will make sense how it should be wired.

From pin 10 on the input transformer and pin 7 pin 10 must be the shield and it needs to ground on the switch. It has allot to do with capacitance here. So live to switch on 7 and shield that live with pin 10 and ground it on the switch, just look at the original Neve schematic.

Don't jump anything it won't make a difference. Since you are coming straight off the output stage and not the pads (that are internally zobeld) it won't matter. Solder the zobel directly to the transformer mounted directly to chassis., also pay attention to wire shielding.

You can rock with or without the 681 ohm. The high's sound a little better without it, but make sure you get the little transformer bump around 40Khz or something is off.

Last but not least. Make sweeps before you start doing anything!

 

[Aaronrash]

Here's how your output zobel needs to look.

DC and Negative Phase on pin 3
Positive phase on pin 1
Positive phase out on pin 5
Negative Phase out on pin 8

Twist the wires from the output stage to the transformer really tight

 

[haystack]

Aaron - Thank you very much indeed. I appreciate that you are busy as well. I do have some further questions, but any answers if you have the time would be fantastic.

Just some queries: 

1. Input transformer- mine is soldered onto the pcb now, is there a way to get pin 6 to cgnd instead of B-0 ( I have the 1073 schematic downloaded), also what is A, B and V at the mic input. I assume that is the xlr live, shield and grnd? Which is which?

2. Output trans- I understand the zobel arrangement, but don't understand your last post -in particular:

what are:  phase , positive phase, positive phase out, phase out.

Sorry for these very basic questions.

I will download REW and do the sweeps.

Thanks again and I hope this will help other folk intending to do any mods.

Hay

 

[Aaronrash]

Sorry about that, I edited my earlier post so you can understand it a little better.


For the input transformer just use your DMM and track witch pins on the PCB mount go to AGnd  and snip them with some little scissors.

To get it to chassis ground just drill a hole in the chassis somewhere and run it to pin 6 and you should be good to go, but then you can't wire of the input or secondary properly

Better off just leaving the PCB mount on top of the transformer but taking if off the PCB and mount it to chassis so it can be wired

 

[ding]

I'm still a little fuzzy on why one would use analog ground vs chassis ground to ground a transformer if someone can give me some insight I would apreciate it. I know that analog ground will end up attached to chassis ground at one point (star ground.) On the mic input transformer pcb it looks like you can just snip 2 pins off the pin headers and free pin 6 from analog ground. I am curious how this small change would affect the sound.

 

[Aaronrash]

I was on the phone with Avedis yesterday for quite some time yesterday. We talked for a while about grounding and how important it is while he was helping me track down some other issues.. Case ground is different from analog ground. He says he plans to do a webinar in the future about it to help techs better understand it.


There is a reason the orgingal schematic has it that way.  I would just follow it instead of wondering why. Measure the differences you get and use your ears. That's all I did, and I got some pretty big differences. Just experiment you gain experience that way

 

[TheJames]

Well..This development prompted me to pull a NV73 from the rack and play with it.  My unterminated frequency response matches that of the unmodded EZ1073.  Tomorrow I'll try wiring in the output transformer bypassing the PCB.  I'm not too hopeful about much change with the output transformer.  I'm just starting there.

One question...

Atached is a snippet from the 1073 schematcis I have.  Is it telling me that pin 8 of the output is tied to the shield of the cable which is in turn tied to chassis ground?  Am I reading that right?

 

[Aaronrash]

Nooo not pin 8 that's connection #8 they are labeled by numbers

 

[TheJames]

Look at the bottom of the secondary winding.  It's labeled "8" and attaches to the zobel capacitor, and then looks like it attaches to the shield of the cable to the polarity switch.

The schematic definitely doesn't show continuity to the switch on that connection like it does with pin 5.

 

[Aaronrash]

That's just Neve's way of saying to ground the shield on the transformer end only.

But yeah, sorry I was looking at the connection number, not the pins. You will come off of pin 5 and 8 of the secondary

 

[TheJames]

No worries...I really appreciate your efforts in sorting out the "sound."

I'm attempting to get this response on a 500 series module.  Unfortunately, wiring up the output transformer didn't seem to make things any different.  I've got twisted wire to the output primary, shielded wire off the secondary to the phase switch, shielded wire from the phase switch to the output points on the edge connector.  My response is unchanged, terminated or unterminated.  I get a smooth response that's down about 4db at 40khz.

Output iron in use is the VTB1148 which is supposed to be identical to the VTB9049 which is the "right" iron from Carnhill right?

Perhaps the secret is in the iron afterall?

Anyway....Next up is the input transformer. 

 

[ding]

Aaron's sounds wasn't to his preference even with the original transformer. Let see how you do with the input side of things.