8 Channel, 3U NEVE 1073 completed

Hi
Just finished 4 ez1290 and put them in the same case. They all sound great, and with proper cabels and grounding, they are very quiet.
I have one issue though, and I think its something with the power transformer. With high gain on more than one unit at the same time, I get dropouts, like a steady pulse, with more and more intensity with higher gain on all units. The power transformer I had laying around, was a toroidal 25-0-25 30VA. I assume the 30VA is to low, and going to order a bigger one. How big do the power transformer need to be to run 4 preamps?

Thanks!

Hey Jazzboms,

You check your regulators. Sounds like they are going into thermal shutdown. They will cycle on and off as the temperature fluctuates. Consider heatsinking them to the chassis, not just little heatsinks. Depending on other things you may have in your unit (lights, etc) you may be trying to dissipate too much heat. I had this problem with my first set.

Cheers

Hi guys,

Working on a 4x EZ1290 to go into a 2ru.  Nice and straightforward project so far, I'm looking forward to getting them finished.  Thanks Martin!

Just a quick question- I've got the v2.4 boards, and on the BOM C13 is listed as a 150uF 16v cap (Electro), however on the board they are listed as 150uf 6.3v.  I ordered the 16v off the BOM before I received the boards, I assume as these are over spec that's a totally fine substitution in that part of the circuit and I can just use the 16volters?

Thanks!

they will be fine.

jake

Thanks Jake.

So im trying to get all the parts together for a pair of pre's... (a few are out of stock until feb or march i think at all online retailers)

I was thinking of creating a little extra board to act as a switchable trim pot. 

I would connect the 3  wires that would normally go to the trim pot on the main EZ board to a little board with a switch on the front panel that would switch from the trim fader to the jumper/resistor creating an on/off.  Any thoughts on this?  If anyone has built one with/without the trim that HASNT noticed a tonal difference, perhaps this isn't needed. ???

Hi guys!

My name is Ovidiu Turcu, I'm from Bucharest, Romania. I am working on a dual 1073 by Martin's design. (no eq)

First, I'd like to say that I'm very happy that I found this forum thread! I searched for weeks for a diy Neve 1073 preamp without EQ schematic and here I found all that I needed!

I got the 2 PCBs from Martin the other day and I really wanted to say that they are absolutely great!!! Incredibly well crafted, easy to solder, etc. I think they are made using an automated machine. Thanks, Martin!!! And the price is also very good! It would have taken me 4 to 5 days at least to design and make a PCB after the schematic, and wouldn't have come out nearly as good as these boards are!! (with green laquer and everything). 40$ is a very small price to pay for this quality!!! I think these boards will live at least 100 years from now on! )

What I can contribute with to this diy thread is the power supply. I managed to find the schematic of the power supply that Martin sugested to use for the preamps, got rid of the negative rail, and made up a PCB design. The thing is not tested, so I'll wait until then to post here the PCB layout (and the schematic) and BOM for the power supply. It seems really simple. I got it from the pictures at JLM audio's site and deduced it from their PCB. Here it costs me less than 10$ to make it. I don't know how much those LM317s are.. but they can't be that much!

If you want the design until then so you can study it, you can e-mail me at ovi_turcu at yahoo dot com

Wish me luck!

Ovi (dutu)

Would anyone be able to give a suggestion on how i can take the 24v coming in and step it down to 12v.  I ordered the regular ACDC and probably should have gotten the powerstation (would have been able to just send a 3rd rail in) but this was an afterthought for an aesthetic addition to the case.  Thanks  ;D

Im not sure I understand.

What do you need 12v for? The ACDC is a good PSU for this project, which runs on 24v.

Cheers

My apologies, im a real novice when it comes to this stuff.
I have the 24v for the project (and the 48 for phantom)...
I have a VU meter i wanted to throw in the case which according to spec operates at 6-12v.  (not even sure I'm going to keep it in there until they're all done)  just wanted to see if i could fit it in there as a visual reference (and they look really cool)

Im no expert when it comes to powering VU's on projects that dont have dedicated supplies, but you should be able to drop the 24v down with a resistor (probably need 2watt for a drop that big).

Also research VU buffers, so it doesnt effect your output.

was thinking of kind of side chaining it so the output goes straight out and the meter is just leeched off of it and not in the signal path directly.

Without fully understanding your plans, I think you will still need a buffer.

Cheers

I see your point.  JLM has a nice buffer kit that will work fine with the 24V coming in from the PS.  (as you stated, just gotta add an extra resistor for proper functionality) ;D

I finished my build and it sort of works...It seems to be fine up until about 50db...55+cause either lots of oscillation or noise or even sometimes a clicking sound.  In reading the schematic, being semi-new to this, am i right in assuming the problem must be in the BA183NV section?  It looks to me like only 55db plus is sent to that section.  Also, when checking my transistor voltages, they all seem a few volts high compared to what they should be... I think it's 6 (no longer in front of it) was like 29 v compared to the 20.6 it should be.  Thanks for any help!

May be a dumb question, but what are people that are using an external PS using for the cable between the PS and the Pres?  Should i be using shielded cable/ unshielded?  And the wire listed in the BOM seems REALLY thin for power.  Any thoughts?

i've had good luck with non shielded cable as its just DC travelling from PSU to case.
Its up to you...as a matter of taste.
Thanks.

I used standard 3 conductor mains cable you can get from any hardware store.

Cheers
Jake

So, I posted a few posts back about some problems with mine above 50db.  I checked the transistor voltages, and they are all fine except #3, the 2N3055.  For that I'm getting a C/B/E voltages of 23.5/1.64/1.01.  So my Collector is higher than it should be and the other two are lower...could this be the culprit?  I think my next step is to resolder the Grayhill switch because I feel like that's the most likely place to have made a mistake.  Any thoughts?  Thanks guys!

MikeFFG said:

So, I posted a few posts back about some problems with mine above 50db.  I checked the transistor voltages, and they are all fine except #3, the 2N3055.  For that I'm getting a C/B/E voltages of 23.5/1.64/1.01.  So my Collector is higher than it should be and the other two are lower...could this be the culprit?  I think my next step is to resolder the Grayhill switch because I feel like that's the most likely place to have made a mistake.  Any thoughts?  Thanks guys!

Click to expand...

Mike
I had the same problem on 1 of my 4 pres. It turned out that I had connected the wires from the PCB to output transformer wrong. Another problem I had was that the input/output transformer was to close, causing oscillation from 55db and up. Moved them a little apart and then everything was fine.
Hope this helps.