Neve style 500 series mic pre 1290 1073

[Unit7]

I removed the nut on the GH switch and also got a longer shaft version of the Bourns pot and I'm now able to fasten the ELMA knobs! Since I've added a HPF I'm using a 10k pot instead, so I won't promise or be responsible for the choice of replacement 5k pot. But according to the Bourns papers the model number middle digit of the three middle digits specifies shaft length, so what you should be looking for is a 3310C-011-502L instead of 3310C-001-502L. If that's not available you could look at alternate configuration of the terminal pins which is specified by the letter after 3310. Mouser had the 3310Y in stock for my 10k pot so that's what I used. But again, please take my noob suggestion with a grain of salt before someone more experienced can confirm this...
edit: I just added screws to compensate for the missing nut on the GH switch, so took a new pic

edit 2: I got a lot of help from David on the HPF on my unit, so for other noobs like me, here's a little info: http://groupdiy.com/index.php?topic=54228.msg692372#msg692372

 

[bobbybrave]

I found a good way to make the ELMA knobs with holes too high fit.

Just sand them underneath till the whole knob is "skinny enough" for the shaft to reach the screw. (thanks to my dad for suggesting this)

Being aluminium it won't take too long and you only have to do few mm.

Only problem is losing the clear circle part on the red knob. (If you were game you could sand further and glue the clear disc part back on though.)

So happy with the preamp, sounds amazing on bass guitar  8)

 

[AntonSwe]

Hi!

I just finished building two NV73. They really sound great but one is consistently about 11dB quieter than the other on all gain settings... Any ideas where I could start looking?

Here are the frequency response graphs I made on the line settings. I have offset the quiet one (green line, NV73 2) with +11.32 dB to make it easier to compare the response. They are a bit different but maybe this is normal?

Thanks
//Anton

 

[kato]

Does R51 (270R) need to be a full 1w?
I've got 1/2 watts in that value. Though I don't want to risk a burned out resistor. I also don't want to place another Mouser order.  :-\

 

[jandoste]

Thanks David,

I missed this sorry I didn't see your response... Voltage is ok 21V on the case of 2N3055. I just hear a noise from VTB1148 or maybe DC conv... something strange with this noise it doesn't stop and I don't hear anything from mic! so do you think the DC Conv is it dead? all voltages are ok...

Thanks

Voltage OK on the case of the 2N3055?

Do you have a signal probe or oscilloscope?  Just trace along the circuit until you find where the signal disappears...

 

[jandoste]

Ok, I changed the lambda dc but my problem is not solved

please tell me for the legs of the Lambda Dc that I soldered all legs to PCB but now I'm seeing David's picture and two legs are not soldered on the PCB... so maybe my problem is here?

Thanks

 

[jandoste]

It's me again,

The second one doesn't have My problem starts when I build a new 51X Rack so I put my gears accidentally wrong! so 2 NV73 and 2xEQN got now the same issue! I get the new lambdas but the issue is there!  first unit(NV73) has power noise but I think that the Relay also damaged... with this unit I got all voltage Values correct but no sound! the second one doesn't have +48V on the BA283 ... maybe VTB1148 IS dead or relay can't let him to work?

Any advice?

Thanks

 

[kato]

Easiest now to wire it for 51x, skipping over the DC converter and the relay. It sounds like the problem lies somewhere in the 500-to-51x conversion.  Good luck!

 

[jandoste]

it's late ??? because I have cut  the latest pins...

Thanks

Easiest now to wire it for 51x, skipping over the DC converter and the relay. It sounds like the problem lies somewhere in the 500-to-51x conversion.  Good luck!

 

[jandoste]

bump :-[

 

[jandoste]

Hey guys,

I hope someone will understand this noise; is it tranx or DC?  https://copy.com/VidbTpzZIiuMbP6e

Thanks

 

[jandoste]

Hey David,

I hope you'll see all my posts asap
I measured 2N3055 and there is nothing (.230V) I changed it three times but can't understand why i don't get any voltage on it?

Thanks

 

[jswagler55]

I Just finished 2(both 16v) of these builds and both have some issues but they are different.

the first one works fine but once you flip phantom power on it the actual pre makes a high pitched noise. The same kind of noise like the slow start circuit but it stays on until I power down my lunchbox.

the other has a loud white noise when phantom power is engaged and even still has a bit of noise when phantom power is off.

I know these pre's will have some noise but this is pretty noticeable and doesn't sound like noise from a 100% functioning mic pre.

 

[tamtamstudio]

Hi all.
I've just finished a couple of this pre, in 24v version for my 51x rack.
Both have got the same behavior, on 2N3055 i've got 24.6v and i can't change from trim.
that's normal?
i found some others guys with the same problem, but no answer at the end.
anybody solved this?

best
Corrado

 

[Tomess]

Hi!

I finally did some (technical) testing on the finished mic preamp: as far as i can tell, everything works like it should...with some minor issues, i guess:

I did some mesurements with a rhode & schwarz analyzer and an oscilluscope. The frequency response looks good as far as i can tell (see pictures: https://www.dropbox.com/s/vyw9z4uyhidfwxo/Mesurements.rar?dl=0 ), but the leves above +55 dB seem to be wrong. They droped about 8 - 12 dBu. Reverence is allways 0dBu. Maybe i wired something wrong? What could be wrong?

Secondly, i tried to get the right level for the big Transistor (the 22V to Ground), but i wasn't able to get the equal klipping. Is that a problem? i turned the variable resistor as far as i could in both directions, but it never looked like the pictures in the GroupDIY Forum: http://groupdiy.com/index.php?topic=36831.msg564844#msg564844 . There was allways clipping at the negative voltage, but never on the positive. Any idea?

Thanks, Tomess!

 

[tamtamstudio]

Hi all, i've got some trouble with 1 of 2 mine pre.
This is the problem, from 2 weeks when i switch on, it doesn't sound at all, but turning up the gain at 3/4 it started to play.
Now the things are changed, the pre doesn't sounds at all.
Have u got some ideas?
some suggestions are welcome.
best
Corrado

 

[Glutamatjunkie]

Hi,
I'm looking for a good quality Output-poti with 1/8" metal shaft.
I've found a Vishay 10k 10% but 500mW!
Is that one ok or should it be exactly 250mW?

Maybe you can recommend some

Thanks

 

[fatheaddrummer]

Can Anybody tell me if Variations about 1 V are ok, for the BC Transistor Voltage Values?
Or is that too much?

Thank you very much!!

Best,
Christian

 

[Glutamatjunkie]

Don Audio is selling now the Elma Marconi Style.

http://www.don-audio.com/Elma-Vintage-Audio-Classic-British-Wing-Knob-Blue-CAE038039

Maroon and Grey are also available.

 

[KDE]

I forgot to mention this but in another thread on the site I have some details on using vintage parts in the build. Had a set of 4 built for me using some original transformers and transistors. Big thanks to David for letting me do my own faceplates

Link: http://groupdiy.com/index.php?topic=53393.0