Feeler: an "Eee-Zzz" christmas present...ez1073 and ez1073-500

[guitar4444]

Hi Tommy,

I tried that, in the end moved the transformer to the back of the case and rotated to the best spot, I compared that to having the transformer out side the case. Once the transformer was moved to the back of the case most of the residual hum is from an earth loop in the supply so moving the transformer further back than the back of the case wasn't worth it. The hum is at about -90db and only present when the EQ is engaged. Apparently that level of hum in the EQ circuit is about 10db better than the original Neve layout. It maybe possible to get a better result by having a completely external supply or even a 24 volt battery supply would give zero hum. Aside from that I was about to experiment with splitting the round plane on one unit but decided to leave it for the moment as in practice the noise is negligible for most applications that you would use a Neve pre for.
I will build an external supply in the not to distant future.

cheers  Greg

 

[dgoszillai]

hi,
sorry i'm not that great at english (and electronic !) .
you mean the short could be from shakproof and red arrow or bue arrow ? 

https://lh3.googleusercontent.com/-_izQyN0uJ4U/UhcyVf9siXI/AAAAAAAABOo/BPW-JqoOdXM/w1000-h666-no/IMG_2288.JPG

 

[guitar4444]

the short could be from the shake washer to the surrounding ground (earth plane), that is the large areas of copper (under green lacquer). It would not short to the tracks the arrow is pointing to. The lower one in the picture looks like it could be the problem. Although the green area is an insulator if the shake washer is a rough surface and done up very tight it could go through.
All I know is that one of my units was heating up and I loosened those bolts and centre them and the washer and when I did them back up it was fixed. So worth a try. After centring the bolts, measure with a multi meter from r12 (the side that goes to the transformer not the power supply) to earth to see if there is still a short before turning it on. It might even be worth measuring with the bolts removed and also check there is no small flake of metal from the shake proof washer or solder mask.

cheers  Greg

 

[tommypiper]

Hi Tommy,

I tried that, in the end moved the transformer to the back of the case and rotated to the best spot, I compared that to having the transformer out side the case. Once the transformer was moved to the back of the case most of the residual hum is from an earth loop in the supply so moving the transformer further back than the back of the case wasn't worth it. The hum is at about -90db and only present when the EQ is engaged. Apparently that level of hum in the EQ circuit is about 10db better than the original Neve layout. It maybe possible to get a better result by having a completely external supply or even a 24 volt battery supply would give zero hum. Aside from that I was about to experiment with splitting the round plane on one unit but decided to leave it for the moment as in practice the noise is negligible for most applications that you would use a Neve pre for.
I will build an external supply in the not to distant future.

cheers  Greg

Hi Greg.  Good info.  Did you try cutting the earth loop?

I've been able to get an original 1272 modded with extra gain to run incredibly quiet at full gain with an external PSU.  I'm skeptical about claims that original Neves are noisy.  However, I know they do often test as you mention, with noise floors in the 70s or so....

It's a question of proper grounding and using a high quality, shielded, external power supply.  (BTW  It's very good that Colin put tabs on these boards for external PS.  Adds flexibility.)  My experimental original modded 1272 was turned up with gain beyond the original gain and there was no hint of hum or noise.  I put an RCA Jr Velocity dynamic ribbon mic in a shoe in a closed closet in the next room with two closed doors between me and that closet and I could still hear my voice and all ambient sounds throughout the house amplified with no apparent noise.  I was stunned.  I never did measurements - someday!  Anyway, the classic 2 and 3-stage 1272 and 1290 based amp Neve circuits are capable of very high quality and quiet operation.  They are not just for rock and roll.    I've seen 1073s credited on classical recordings. 

 

[ruairioflaherty]

1272 doesn't have the EQ inductors like a 1073, this is the most vulnerable point for noise pick up in a 1073.

 

[guitar4444]

Hi Greg.  Good info.  Did you try cutting the earth loop?

[/quote]

No maybe when I get some spare time. I'll try the external supply route first.
cheers  Greg

P.S. if you put the ribbon mic in a high quality boot rather than a shoe you get better noise reduction.

 

[bigbeaty]

I've just ordered another two units, I'm so stoked with the two I've already built!

Thanks again Colin, the EZ1073 is an awesome bit of kit; mine see daily use on recording and mixing duties.

I think I'd better start saving for a pod of Pultecs now....  8)

 

[Aaronrash]

Hey guys I just got my kits in. Does anybody know if grey hill makes pots with longer poles? They aren't long enough for my neve knobs

 

[Aaronrash]

Also the EQ poles are too big to fit the EQ knobs on but I could just widen the hole with a drill

 

[tommypiper]

Hey guys I just got my kits in. Does anybody know if grey hill makes pots with longer poles? They aren't long enough for my neve knobs

Where did you get those knobs? 

Did you check the Grayhill website for models and options?

The gray knob you show is meant to go on a concentric pot inside a rotary switch in the original Neve design... as you may know.  So if it's an original knob it will have to be drilled, which would be a shame. ...Or find a thinner shaft pot.

You can also try drilling your blue knob for a lower positioned grub screw to reach the shaft.

 

[Aaronrash]

Hey tommy,

Yes they are all original neve knobs, I figured out a work around and got them all to fit now.

Thanks man!

 

[Sillen]

Hi
I seriously got problems with getting the power into the circuit board.. I don't really have  a clue what could be wrong, everything seems to be right according to colins color book. Although i'm a newbie at diy not so much could go wrong there, white and red wires soldered to their place, and brown to the live tag of the IEC and blue to the neutral of the IEC (220-240 v). And slow blow fuses is what I used. Iec grounded together with the transformer green/yellow and the mains safety earth. That's how it should be done I guess? Oh and yeeah the purple and grey secondary wire is soldered together also of course. What the hell could be the problem here?! :O I read 0v DC between J5 and J6, the led lamp doesn't light up, pretty sure no power is coming into the pcb actually.

All the best
Isak

 

[Slenderchap]

I have just found an incorrect mains transformer in the VTT2326 stock box.

Please can you check that the power transformer you received is indeed a VTT2326.

If you have something else, don't use it.... and let me know asap.

If you have already built your ez1073 and it is working correctly please ignore this.

Colin
www.audiomaintenance.com

 

[Aaronrash]

Hey Colin I have to correct transformer. 8)

@Sillen
Have you checked the simple things, like making sure you're getting power at the outlet and testing it with the multimeter to make sure you're getting the correct voltage? also checked the fuses etc... If all those are fine I would suggest you have a bad power transformer. It would help allot if you could upload pictures though.

Aaron

 

[Sillen]

Hey Colin I have to correct transformer. 8)

@Sillen
Have you checked the simple things, like making sure you're getting power at the outlet and testing it with the multimeter to make sure you're getting the correct voltage? also checked the fuses etc... If all those are fine I would suggest you have a bad power transformer. It would help allot if you could upload pictures though.

Aaron

No power is coming into the outlet it seems. And the reason for that I believe is that the IEC I bought had a missing fuse drawer which i didn't realized should be there untill now This must be the problem right? lol

 

[Aaronrash]

Lol yes that would be the problem. I haven't got to that stage yet but I think you're going to want to put a 100mA slow blow fuse in there.


Also did anybody build power switches into their units? I'm a bit confused on how to wire up a DPDT any DPDT switch I could find we're stated as on-off-on. Wouldn't it make more since to just use a DPST on off?  Seems like using a switch where you can terminate both the live and the neutral feeds with the flip of one switch seems best but a DPDT has six terminals. A DPST has 4.

 

[Sillen]

Hi
The power issue of my preamp is now fine. I measured 23.89 v DC between J5 and J6 though but that shouldn't be a problem huh? I've also been trying to figure out what may be causing the crackling noise and hum of my build, searched around the forum etc, didn't really find anything about it.. What is most likely the problem do you think?

Link to picture:
http://tinypic.com/view.php?pic=mvookg&s=5

/Isak

 

[Aaronrash]

I've read through the thread but I have some grounding questions...

On most builds I see everyone is grounding the XLRs through the circuit board (HOT,COLD,SCN) and they are also grounding the XLRs to a star ground on the case.

Couldn't this cause ground loop issues? It seems like one should either ground to the star ground point or the PCB but not both. Can someone confirm what is the best way for grounding the XLRs?

Also I'm thinking of using self adhesive plastic standoffs for the pcb. Will this affect the grounding in any way?

Lots of people are complaining of hum and noise when first powering on their units and it could be a simple grounding issue that hasn't really been described in detail yet.

Thanks!
Aaron

 

[sr1200]

I used the nylon adhesive standoffs on both of my units, no problem with hum, ground or anything else.  I ran ground lines to the chassis ground but didn't connect the XLR chassis to pin1 either, dunno if thats much help.

 

[Aaronrash]

I used the nylon adhesive standoffs on both of my units, no problem with hum, ground or anything else.  I ran ground lines to the chassis ground but didn't connect the XLR chassis to pin1 either, dunno if thats much help.

Cool, so your saying you didn't connect the SCN pin on the PCB? And just grounded it the the chassis instead?