Neve 1290 build completed!!

[desol]

Yes, you want your preamp case sharing power supply case AC ground. I found the frontpanel needed a good ground, otherwise the greyhills were a little static'y when touched. Also, my input transformer cases, mounting plates and shielding plates on the back of the cards (my cards are vertical) are all case grounded.

 

[redmojosteve]

Thanks Desol. That's really helpful advice. It sounds like it should me a few problems later.

 

[funkymonksf]

Briomusic,

I had a very similiar sound coming from my transformers. Turned out to be a grounding issue. I forget where, but it may be a start in finding the issue.

Sorry I couldn't help more,
brice

 

[briomusic]

thanks funkymonk,

indeed, connecting the pcb ground to the case helps - even though the case itself is not connected to anything at the moment. those wacky electrons!

I still have a weird problem on one channel, everything sounds great up to the base of the 2n3055 then it gets really loud-distorted and hissy. kinda reminds me of an open loop op-amp freaking out. is there a negative feedback loop in the BA183AM? maybe the path that goes back from the bias trimmer to the base of TR1?

I swapped all three transistors in the output amp, slowly running out of ideas here....

ETA: problem solved, I had two capacitors soldered from the underside to make room for heatsink and swapped some directions  :-[ everything working fine now.

 

[ilfungo]

HELP!!! ???

hello
I just finished 1290 with 2 x PSU Mnats
work well but when I get the last 3 steps of the volume the sound becomes distorted ...
What can be?
can be a power problem?
thanks

 

[briomusic]

did you build two channels? is it happening on both of them?
are you sure it is not just distorting because of too much gain on an already strong signal?
another explanation would be that grounding/wiring/transformer-placement issues become most obvious at the highest gain settings, so you might want to look into that as well.

good luck
briomusic

 

[ilfungo]

for those who want to use Mnats PSU!
I just finished 1290 with two channels Mnats PSU (perfect)
I used this PSU for 24v and 48v (phantom)

I simply did the following:
- 24 = 0 connected tothe PSU case via 0.1 uf + 10 hom
  0 = +24 goes to pre
+ 24 +48 = goes to pre phantom switch

the only problem I had was for the last three steps of the volume (distorted sound)
I just connected one point of PCB to the case and the problem disappeared
now everything works great and sounds wonderful  ;D

Thanks to all and especially to Madriaanse for this wonderful project!!!!!!!!!!!!!!!!

 

[Chrome Heart]

Has anyone used 22G foil shield install cable on a build instead of mic cable? Or do I really need the heavy jacket?

 

[briomusic]

I don't know 22G foil shield install cable, but I am using install/patch type lead for my internal balanced/shielded wiring. there is no need for mic cable as there won't be people walking over the leads inside your case. (hopefully  )

 

[desol]

Has anyone used 22G foil shield install cable on a build instead of mic cable? Or do I really need the heavy jacket?

I'm using Mogami console cable. Around 22AWG, very fine copper strands...easy to work with and run.

 

[Chrome Heart]

Goodness. I guess I should have said 22AWG. I figured it might be OK, but Ive seen so many builds with mic cable I just wanted to be certain. I have extra around and would just as soon use it.
Cheers

thanks desol

 

[JoeMorris]

Hi,
currently building a pair of EZ1290s - thanks martin, great boards...

just wondering if there's any problem using one of these Block toroids  from Farnell instead of the digikey Amveco one in the BOM?

http://uk.farnell.com/block/rk100-22/transformer-100va-2-x-22v/dp/1419557

Joe

 

[wolfgang]

I dont see a problem!
But i think you dont need a 100VA Transformer!! 50VA should be plenty enough?

regards,
Wolfgang

 

[JoeMorris]

Thanks for your reply Wolfgang - would this be OK then?:

http://uk.farnell.com/block/rk63-22/transformer-63va-2-x-22v/dp/1419550

It's rated to 1.43A whereas the Amveco one in the BOM was 2.27A, which is why I was looking at the 100VA one - don't know if this is a problem, but this one would certainly be much more cost-effective (about half the price) if it does the job.

 

[mitsos]

this one is better. and cheaper.

http://uk.farnell.com/block/rk63-25/transformer-63va-2-x-25v/dp/1419551

 

[wolfgang]

Hello!

I would take the one with 22V secondarys!
So you have with a bridge recitfier 22V*1,41-1,4V=29,62V before the regulator!
With 25V you will get 25V*1,41-,4V=33,85V before the regulator. So the Vreg have to dissipate 4Volts more!
It will get much hotter! And this isnt necesary!

Or am i wrong here?

regards,
Wolfgang

 

[JoeMorris]

Oh OK thanks - so 25V secondaries and 1.26A current rating is all good for this is it? If so that is a real result (I was wincing a bit at spending £48 on a toroid)
(edit - just saw Wolfgang's post - posted at same time)

So which is it people?

 

[desol]

What power supply are you using? Are you building one?

If your using the JLM ACDC...it's 24 vac in.

 

[JoeMorris]

Yeah, its the JLM one. So the 25V transformer is probably ok then?
Joe

 

[JoeMorris]

ill stop being annoying soon, but before I go can I just get someone to clarify that a 1.26A transformer is fine for running 2 EZ1290s?