8 Channel, 3U NEVE 1073 completed

[Rocinante]

50VA  /    2 x 22vac Sec. is what I used and pretty sure that's what madriaanse spec'd  in the build guide

Avel Lindberg # Y236205

Yeah I know but then you read things like "needs 24v" and it throws me off again.  I understand the basics of how psu's work from my other audio builds; they're all relatively the same formula, I just wanted to be sure with this one .  And BTW thanks. 

Oh and thanks Martin the boards are really nice to work on and layout is awesome.  This thread has also been some interesting reading (and rereading). 
I found an Antec 50va 22v that seems to fit the bill. 
Now to figure out how I am gonna implement push buttons instead of the GoBetweens.  Back to research.

 

[audiophreak]

parallel the secondaries , it adds the current from both sec. but voltage stays at 22vac - rectified to  ~  31vdc  regulated to 24vdc by psu circuit -  JML power plant or fivefish  2448 PSU  , read the pdf build guide on page 1 , it has diagram for Phantom power , do a google search for pad schematic and implementation , although the JLM  go between is a ready made solution , I dont need phase and  chose  to do my own  phantom and pad.

  I believe 25v secondaries will work , I would stick to the build guide and 22vac secondaries.

hope this helps

 

[phelar]

So i got this rather short rack. How much heat does this 2N3055 generate, im just worried it going to mess upp the output transformer with this tight fitting. The distance between  2N3055 heatsink and transformer 3-5mm 
Any clues?

 

[critterkllr]

So i got this rather short rack. How much heat does this 2N3055 generate, im just worried it going to mess upp the output transformer with this tight fitting. The distance between  2N3055 heatsink and transformer 3-5mm 
Any clues?

Is your top vented? I would be more worried about the proximity of your input and output transformers.

 

[phelar]

Its vented...

 

[critterkllr]

Its vented...

I haven't done any testing other than placing my hand near the the heat sink. I couldn't really feel any extra heat. Of course, I've never done it after a 10 hour session or anything.

 

[phelar]

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. :-\

 

[Rocinante]

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. :-\

You know I've been wondering the same thing as I have seen some really tight squeezes that are completely noise free and don't seem to heat up at all as well as the complete opposite.
I guess it's just experiment and see what works.  I am experimenting now.

 

[JessJackson]

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.

 

[phelar]

Thanks for all hints! I´ll stick to my plan.
I have som kind of a plan B just in case s..t hits the fan, much more work though.

 

[madriaanse]

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.

Inductive coupling is real. The 1272 in its intended form (bus makeup gain) had limited gain. A high gain mic pre will go into screaming self oscillation if you space the transformers too closely, or at best, have resonation artifacts. There is a reason why all the 500 series 1073 clones with their cramped layouts all have less gain than the original - it masks the problem. The EZ1290 allows for a more roomy layout so it can handle 75dB gain with ease. It doesn't have 80dB like the  original because I simply ran out of switch positions and if you really need 80dB you're doing it wrong anyways.

 

[audiophreak]

Hi All ,
            just finished my 2 channels of EZ1290      it was a pretty strait forward build ( couple of user error hick-ups ), 2 channels in a 2U with five fish 2448 internal  PSU , made my own pad and made the stepped attenuator both using grayhill rotary's  ( I think 85 series )  my own front panel layout and graphics done in Illustrator, C&K locking toggles for input impedance and phantom.
  It sounds Absolutely Fantastic  !!!

  Thank you Martin for this incredible sounding project and excellent documentation and to this great place , I have learned so much , and so much more to learn



here is a link to more pix  -  https://goo.gl/photos/NNRYQSzH2rp4XVbo9

 

[usekgb]

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.

 

[phelar]

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.

Inductive coupling is real. The 1272 in its intended form (bus makeup gain) had limited gain. A high gain mic pre will go into screaming self oscillation if you space the transformers too closely, or at best, have resonation artifacts. There is a reason why all the 500 series 1073 clones with their cramped layouts all have less gain than the original - it masks the problem. The EZ1290 allows for a more roomy layout so it can handle 75dB gain with ease. It doesn't have 80dB like the  original because I simply ran out of switch positions and if you really need 80dB you're doing it wrong anyways.

So if i place the input transformers under the pcb´s where the circles are?

 

[madriaanse]

Much better. I'd position them even more towards the frontpanel if you can.

M.

 

[madriaanse]

Hi All ,
            just finished my 2 channels of EZ1290      it was a pretty strait forward build ( couple of user error hick-ups ), 2 channels in a 2U with five fish 2448 internal  PSU , made my own pad and made the stepped attenuator both using grayhill rotary's  ( I think 85 series )  my own front panel layout and graphics done in Illustrator, C&K locking toggles for input impedance and phantom.
  It sounds Absolutely Fantastic  !!!

  Thank you Martin for this incredible sounding project and excellent documentation and to this great place , I have learned so much , and so much more to learn



here is a link to more pix  -  https://picasaweb.google.com/114609450221624562839/EZ1290?authuser=0&authkey=Gv1sRgCISvhdL64I7xMA&feat=directlink

Nice work!! I hope you get some great sounds out of it!

M.

 

[phelar]

Much better. I'd position them even more towards the frontpanel if you can.

M.

Thanks!!

 

[Rocinante]

Yesss!  Channel 2 is alive and kicking. 

Whew. (Sigh)
Nervous there for a moment.

 

[metacarple]

Can anyone recommend a power trans to compliment the most current version of the JLM  AC/DC?

Any info would be much appreciated!

 

[sr1200]

for one or two channels, the transformer specs wouldn't change for the PS.