8 Channel, 3U NEVE 1073 completed

[benlindell]

Hey guys so I just got my first channel up and running, the only issue I'm having is with phantom power. I'm using the JLM go-betweens with DIs and when I first tested my PSU I was gettin around +46V now I connected 2 LEDs to the 48V rail (with a 2k current limiting resistor) and 1 JLM go between with it's DI. Now the phantom power is sagging way down to +30 sometimes +28V and the the relays on the DI is starting to not function properly, why is it going down so much? I'm using a SSL9K PSU board with a 50VA 25-0-25 Antek transformer

 

[Dr_J]

Hi,

i'm right now in my planing phase for builing 2x1073@1HU.
There're 2 things i'm currently not 100% shure about which direction to go,
so i like to ask you guys of your experience directly (after reading the post here ).

#1: GoBetween
How are the experience around here? A MUST, nice to have, never really used it?
(Btw. it's a great kit, which i use a lot)

#2: Trimming Pot
How are the experience around here? A MUST, nice to have, never really used it?

Thanks!
ROCK ON!

 

[erikb1971]

for go between i would say: go for it with di... I love this combi on bass!

Trim: I do not miss it all!

 

[MicDaddy]

Let me just say trim is not necessary, although with having the trim, I can dial in some pretty neat sounding gain staging.

i.e. max/75dB gain with trim pulled all the way down MD441/RE20 sound great with this (condensers not so much). 

Slowly bring the trim up to allow some signal to pass.  The timbre has a very nice texture and is another flavor in addition to the clean gain.

 

[justanalogue]

Hi Kim,

heat sinks are made from a bigger heat sink that I salvaged out of a glass ceramic stove.
Till now no problem with 1 power supply, although the aluminum box gets warm..

Kind regards,

Willem.

Finished my 4 channel EZ 1290 a couple of weeks ago, worked flawless the first time I powered it up!
Many thanks to M Adriaanse, Frank for engraving and all inspiring builds here.

Recalibrated the PSU and 1 channel today, made some pictures.

Willem.

justanalogue
    Nice job!    Did you use just one PSU to power all 4 channels and if so have you had any issue's?  And were did you get those heat sinks if you don't mind my asking? I am just building my PSU now and I thought I was going to have to build two for four channels.

Cheers
Kim

 

[benlindell]

Anyone has ideas/advice for my sagging +48V rail? Am I drawing too much on it?

 

[benlindell]

So while I wait to figure out my phantom power problem, I tested all the channels without the FET DIs (which are what's killing the +48V) and they all sound great except channel 1 which is making sound but has much lower gain and makes a nasty distorted sound when given a louder signal.

- The gain changes with the switch but is way lower than the other 3 channels.
- I jumped from the out of the input transformer to the input of channel 2 and it works and sounds fine.
- I jumped from the in of the output transformer on channel 2 to the output of channel 1 and the gain was still low.

So this means my problem lies within my channel 1 board right? any helpful advice on where to be looking?

 

[desol]

Maybe the output section? A scope would be good...

 

[benlindell]

It may be, unfortunately I don't have a scope available

I did some more testing and visual checking. For sure it's not the transformers, I used the broken channel's transformers on a working channel and visa-versa, broken channel still sounded bad and the working channel was fine.

I visually checked the whole board, reflowed a few spots but same problem.

So I checked the transistor voltages and I have some big problems:

TR1	2.87	.88	.35
TR2	22.6	2.87	2.3
TR3	22.6	2.3	1.67
TR4	3.7	2.36	1.7
TR5	16.62	17	16.6
TR6	20.3	16.6	15.97

So some serious off voltages. BUT

More visual inspection (made easy by having a working channel next to the broken one) and of course there's a 1.1K instead of a 470R. Switched that out and the world is at peace! Sometimes it helps to work and write methodically

 

[desol]

Nice. Good find!

 

[MicDaddy]

See attached a small rig I put together for location recording.

I'm finding that my 1290s are extremely sensitive to outside electromagnetic field/interference.

Both the PSU for the 1290s as well as the 1176 pictured are interfering with the preamps. 

Perhaps I need to rack the pres only with other pres and no transformers.  Then isolate the powersupply and all other units (with iron) to a separate rack away from the preamps.

With 1' of distance, from either piece of kit, relative to the pres, the hum is gone and everything sounds great.

Perhaps it is crap/poor-quality cable I'm using to patch 1290s to the interface?  Just thinking out loud.

Has anyone else had issues with hum or buzz racking next to transformers?

 

[benlindell]

So since I don't have easy access to a scope, have you guys found adjusting the trimmer to measure 22.66V on the case of TR3 is close enough or do I really need to find a place/time to bias it correctly?

 

[desol]

Mic daddy -  i've had issues with external interference on my 4 channels with backwards 31267's. The toroid from my api rack(directly above the neve rack) induces hum into just those 4 channels of the eight...so in my case it's a slight issue for those channels at the inputs. I'm thinking of wrapping the 31267's in mu foil/sheilding.

Ben - With scope, my channels seemed about right at 22.8 volts...at 22.6 volts, the wave was still slightly asymmetrical.
I'm thinking there are slight differences in builds due to component choices, etc.

 

[band_master]

hey guys,
getting ready to wrap up my build and start testing...where have you guys been sourcing out knobs? i can find a lot of 1/4" options, but i also have an 1/8" shaft for output a la the collective cases enclosure...having a hard time finding a knob for those.

cheers,
BD

 

[band_master]

quick word of warning to anyone using the V4 JLM AC/DC power supply. there is a "neve mod" printed on the underside of the PCB...if using the toroidal in the bom IGNORE these instructions and build according to martin's excellent assembly guide. trust me I learned the hard way!



BD

 

[zmgwg]

is anyone using metal standoffs for pcbs? I cant find any non conductive solution and I dont want too mailorder it [unless i'll have to...]

 

[MicDaddy]

is anyone using metal standoffs for pcbs? I cant find any non conductive solution and I dont want too mailorder it [unless i'll have to...]

I used steel machine screws and lock nuts for standoffs.

 

[zmgwg]

with bias I cant seem to make it past 22.4v, any idea? power supple works correctly. and using daw as oscilloscope. 

 

[benlindell]

When you measure with a DMM between +24V and 0 do you get 24V?

 

[zmgwg]

yes. exactly 24v.
now I see I measured case to ground instead of power supply 0v, is that it? but still waveform in daw isn't even close to equal clipping