8 Channel, 3U NEVE 1073 completed

[metacarple]

Where might I find the transformer specs? I don't recall seeing any in the build guide? Or maybe it's there and I overlooked it?

 

[Potato Cakes]

I'm currently working on a 4 channel EZ1290 with a case from Dan at Collective Cases. I plan on adding a trim after the input transformer for the obvious reasons. I was going to add a variable pad kit to the JLM Go Betweens I'm using, but I believe that just adds more attenuation before the input section. Is there particular place that anyone who has built one of these would recommend adding a trim pot, or can I just add one directly after the transformer?

Thanks!

 

[muffy1975]

you will need to read through the thread a bit to see where this is attached but needless to say, this has been answered a few times.
Hope this is what you are looking for?
Good luck with your build

 

[Potato Cakes]

Yes, that is great. I was debating on doing just variable Bourns pot, but I decided that the stepped option would be a tad sexier.

Thank you very much for the diagram!

 

[audiophreak]

Hello 

  After using my two channels of this wonderful mic pre , I have noticed that channel 1 ( closest to the PSU I put IN the case) has a little noise  :'(    thought I might get a way with it ... it was not to be ... so off to put the PSU in an external enclosure.

 

[Suicide Sushi]

hello I've searched the thread for an answer but I couldn't find anything. How important is it to use tantalum caps? A lot of people around me at my work has a lot againt them. Still, I guess they have an influence on sound? Since they are still around?

 

[Suicide Sushi]

Hello. Another little question. Im designing my own psu. How much current does a single preamp draw?

 

[madriaanse]

Tants have a bad reputation because their failure mode  is to form a short circuit. This can be a bummer in, say, power filtering applications. As used in the Neve circuit (audio coupling), failure won't have catastrophic consequences. They make up part of the Neve sound. Stick with Tants.

hello I've searched the thread for an answer but I couldn't find anything. How important is it to use tantalum caps? A lot of people around me at my work has a lot againt them. Still, I guess they have an influence on sound? Since they are still around?

 

[madriaanse]

Hello. Another little question. Im designing my own psu. How much current does a single preamp draw?

Actual usage is about 125mA per channel. Design for about 500mA per channel for inrush and low noise.

 

[Suicide Sushi]

Okay. Thank's for your reply. 

 

[Suicide Sushi]

Hello. Im getting a strange hissing sound from my input transformer (I think). Its only when I connect my signal generator. Its sings in the same frequency (1000 hz) as my signal generator. I find it very wierd. I connect it to  2 and 5 on my trafo. Ive never ever heard if anything like this before. Every cable is shielded. Any suggestions?

 

[Suicide Sushi]

Hello. Im getting a strange hissing sound from my input transformer (I think). Its only when I connect my signal generator. Its sings in the same frequency (1000 hz) as my signal generator. I find it very wierd. I connect it to  2 and 5 on my trafo. Ive never ever heard if anything like this before. Every cable is shielded. Any suggestions?

Okay so the hissing / oscillation sound stopped when i removed my oscilloscope probe from the output trafo. I must have done something stupid. The input impedence in my scope is 1 meg ad the capitance is 140 pF I think. I hope it sounds right when I test it with a mic.
Thanks
Jeppe

 

[Suicide Sushi]

Hey afte putting the pre through its test everything seems to work fine.
Thanks a lot to Martin for this very nice build.

Merry xmas.
Jeppe

 

[NannerPuddin]

Hi, I am new to posting here, but I am about to get started on  a Neve project I have been planning on for quite a while!  I bought 8 of the EZ1290s from Martin in about 2010 or so and I am just about now ready to put a 3U unit together.  Is there anyone possible that can give me some advice?  I am looking at buying the parts and the Case 14-19163x is very expensive, $200+, but is seems I can use a different version of the recommended enclosure from the 2U for the 3U..  Martin reccommends the ET2/35B for the 2U but it seems the ET3/35Bwill also fit and is less than $100.  Does anyone have some experience with this?

Thanks,

Doug

 

[madriaanse]

Hi Doug,

Any 3U case will work. Just make sure it's the same depth or more. You'll probably have to mod the mounting holes of the front panel a bit if you decide to use the fpd file from my first post.

M.

 

[audiophreak]

Hi All ,
            Just wanted to report back that I removed the PSU from inside the case and put it in an external enclosure ( as everyone else has done  ;D  )  and all is good     
          note :  the channel that was furthest away was completely quiet with the PSU in the case, however the other was not ... not too bad, but it was slightly noisy. 
    ... one thing I did notice is that with the gain all the way up , one channel had a verrrry slight 60cyl buzz when I touched the gain knob , the other channel did the same thing but intermittently as I slightly jiggled the gain knob.

    not sure what this is , but its verrrrry slight only at max gain , I had a bad  Grayhill switch in the gain position on the 1084 EQ ,, signal was cutting out with the slightest jiggle of the switch shaft, I even think thats the same part# Grayhill.     

Love the way these things sound  !!!!

 

[Winetree]

I finishing a 4 channel 1290 pre. I want to be able to  attenuate  the output  level going to tape.
The suggested Trimmer is just trimming the 1st stage into the 2nd stage amp. So I'm not putting one there.
I'm adding a 600 ohm T-Pad  output attenuator,    (  http://classicapi.com/catalog/product_info.php?cPath=48&products_id=256 )
using shielded cable,  between the output transformer and the output XLR.  Should there be any problems in this placement.

 

[Whoops]

I'm currently working on a 4 channel EZ1290 with a case from Dan at Collective Cases. I plan on adding a trim after the input transformer for the obvious reasons. I was going to add a variable pad kit to the JLM Go Betweens I'm using, but I believe that just adds more attenuation before the input section. Is there particular place that anyone who has built one of these would recommend adding a trim pot, or can I just add one directly after the transformer?

Thanks!

Sorry but I didnt understand why do you want to add a trim after the input transformer? I dont see any reason for that.

A Pad at the input before the transformer  and an output trim make sense.

 

[Whoops]

Hello 

  After using my two channels of this wonderful mic pre , I have noticed that channel 1 ( closest to the PSU I put IN the case) has a little noise  :'(    thought I might get a way with it ... it was not to be ... so off to put the PSU in an external enclosure.

For people that want to have the toroid transformer inside the case I advise to use a "Trafo shielding sheet" around the transformer. did that in mine and it's really quite now.

you can get them in this link:
http://www.don-audio.com/radiation-shielding-magnetic-shielding-tafo-hum-trafo-shielding-electro-magnetic-sheets-grain-oriented-electric-sheets-electro-magnetic-foil-shielding-foil-shielding-sheets

 

[Whoops]

So how do i know when i got trouble with proximity effect in this preamp. It looks like a couple of 500 formats have their transformers sqeezed togheter. :-\

mate... don't worry about it, look how close together they were in the 1272. Just use good shielded hookup wire.

I would like to point out one important thing in this picture.  The transformers are at a 90 degree angle from each other.  This angle reduces the magnetically induced crosstalk between the two transformers.  If you have to put them close to each other, do it like this.

This is totally right, when you have close transformers the Angle orientation is really really important. If they have to be close they should be oriented in the positions theres the least amount of induction.
Thats why you see  some arrangements with the transformers close to each other and there seems to be no problems, while an other builds it's just a nightmare. The nightmare it's because no attention was put into the angle orientation between the 2 transformers.
But if you have space in your case there no reason to have them so close, so just do your layout so that they are further apart., and as much as possible.