8 Channel, 3U NEVE 1073 completed

[Whoops]

What you can do to be sure if you have a “normal/expected” amount of hiss or if it’s more than usual is going to a friends studio that has or an original Neve or a comercial clone from a manufacturer (Vintech, Golden Age, Heritage audio, etc) and test what’s the amount of hiss you have compared to commercial units.

The circuit is the same between DIY units, Original and commercial clones so if everything is fine with your unit the amount of hiss has to be the same

 

[Pike]

So happy to found this topic. Thanks a lot for the instruction and detailed bom!

 

[dmp]

I recently completed a pair of these after many false starts and was wondering if anyone else found their EZ1290 hissy in the highest gain ranges? I don't expect dead silence from a vintage design at 70db gain but it's kind of a surprising amount of hiss. Just wondering if it's something I could improve or if it's the nature of the beast.

Mine do not seem to have high hiss. If you have high hiss and all your components are correct, you might have a noisy transistor.
But it would be good to know what level of hiss you have.
You can terminate the input with a 150 ohm resistor (between pin 2&3, just build up a xlr). Adjust the preamp gain to high, 70 dB. Then measure the RMS voltage of the noise with a scope.
Take the V_noise and convert it to dB with 20*log(V_noise/.707)
Then subtract that 70 dB gain to know your appx EIN, noise level.

If you don't have a scope or don't want to go to this trouble, do a comparative measurement with your DAW. take a preamp you have that is quiet, set to high gain, attach the 150 ohm xlr, and see the dB in your DAW. Then measure the NEVE the same way and see the dB in the DAW. Subtract them, and adjust if the gain settings were different (i.e. if the Neve was 70 dB and the other preamp was 60dB, subtract 10dB from the Neve dB). That tells you how much noisier the NEVE is than a typical quite preamp (which would be something like ~120dB EIN)

If the Neve is really high noise, reduce the NEVE gain to the point that the BA183NV is not in circuit (50 dB gain I think) and do the measurement again and see if the noise performance is better.

 

[Pike]

Does anyone have a few components from the BOM that are no longer needed for sale?

 

[vitopower]

This was my first groupdiy project, from the prodigy-pro days. Thank you again, Madriaanse! Early version with lots of tants and ceramics and no film or styrene. Recently started getting noisy and loss of level. Tried another working PSU, same issue. Was going to recap electrolytics, but was hoping someone could help me understand where I should start checking components based on these voltages?

 

[Whoops]

Recently started getting noisy and loss of level.

Sounds like a bad contact, cold or broken solder joint or busted transistor

You should describe what type of “noise” you have, better even to record it and post here

Was going to recap electrolytics

That’s a waste of time, Lytics are not your problem

 

[MicDaddy]

Worth checking to make sure that 2N3055 heatsink is seated solidly.

 

[vitopower]

Thanks all. Reseated the screws on the bottom of the 2n3055 to the board and all is well. Seems like a thin layer of oxidation may have been the culprit.

 

[Dave_Eropkin]

Here's the 8 channel EZ1290 I finished last year. It was a fun build, I learned a lot.

 

[MicDaddy]

Here's the 8 channel EZ1290 I finished last year. It was a fun build, I learned a lot.

What are those other pcbs in there? Looks great

 

[Dave_Eropkin]

What are those other pcbs in there? Looks great

Thanks!
I authored some PCB's to make hooking up the transformers easier, along with a monitor switching PCB to make the output from the DAW switchable when the "REC" button is pressed - allows for direct monitoring of the signal so that no matter the DAW there is no latency for the talent. This did require changing how the output transformers were wired so that I could have 2 identical outputs, which sacrificed about 6dB's of gain (if I'm remembering correctly...) I also included a TB circuit with LR monitor dimming for the control room. It was a fun build.

 

[Whoops]

Here's the 8 channel EZ1290 I finished last year. It was a fun build, I learned a lot.

Congratulations, looks great and it's clear the amount of work involved

 

[sr1200]

I have a weird thing happening with 3 of my channels. If anyone has any tips on what i should look at before i spend mucho $$ on replacing the components. Theres a firey or static type noise coming from them at random. They'll be fine for hours on end, and just randomly start spitting out noise. there will be a little pop and then they'll be fine for a while longer. Thoughts?

 

[Whoops]

Theres a firey or static type noise coming from them at random. They'll be fine for hours on end, and just randomly start spitting out noise. there will be a little pop and then they'll be fine for a while longer.

You might have some problems with your transistors, maybe the output transistor.

Start by measuring all the voltages at the transistors when there’s no noise, and then measure the same voltages when the noise happens.
Compare the readings with the voltages in Martin’s 1290 doc and also post them here.

How is your heatsink for the output transistors? Post photos here

 

[dmp]

I had a NEVE EQ build with popcorn like noise. Problem turned out to be defective BC184C transistors. Bought new from Mouser too, so not fakes.
Replaced and problem disappeared. But this was immediate when built.
I have not ever encounter this as appearing later and I've built 4 neve preamps and 4 EQs and have used them for years without problems.
Still, if you rule out the power supply, I expect it is a transistor. Rule out the power supply first.

 

[sr1200]

Voltages are all good during noise and when its not giving me trouble.
So my guess is that its gotta be in the drive stage, as i did hook up the pot between the gain and drive stage and even if i have the trim pot all the way down, the noise remains. I opened the unit (its tight in there, 8ch unit 3u) and i noticed when i knocked into the big transistor in the back with the back of a non conductive probe, the noise got louder for a sec then ducked out. I think I'll start there. Was really hoping it was a transistor and not a cap, because trying to track that down would be rough... I have bunch of the BC184's i used originally to put the beast together so i could swap those out, but that big guy in the back... the 2n3055.... im hoping that's it. I think i have a few left over, gonna see if i can swap it out.

 

[Whoops]

even if i have the trim pot all the way down, the noise remains.

So it's probably the 2N3055 or any of the 2 transistors before it.
Do the 3 channels that you have problems have the same Brand and type of 2N3055?
if so it could be a bad batch of 2N3055.
If not, then it's really strange, maybe there's something wrong in the build that toasts transistors, let's hope this is not the case.

Start by replacing the 2N3055 transistors for another brand and batch

Was really hoping it was a transistor and not a cap

I never up to this day seen a cap be the culprit of the type of problems you describe.
The type of noise you describe I've only seen been produced by transistors or a bad/cold solder joint

 

[sr1200]

So it's probably the 2N3055 or any of the 2 transistors before it.
Do the 3 channels that you have problems have the same Brand and type of 2N3055?
if so it could be a bad batch of 2N3055.
If not, then it's really strange, maybe there's something wrong in the build that toasts transistors, let's hope this is not the case.

Start by replacing the 2N3055 transistors for another brand and batch



I never up to this day seen a cap be the culprit of the type of problems you describe.
The type of noise you describe I've only seen been produced by transistors or a bad/cold solder joint

So out of the 8 channels 2 were built together, then another two like 6 mo later then another 4 a about a year later, so def not the same batch of anything except the BC184 transistors which i bought in bulk before they went obsolete. there was one from each group of builds thats exhibiting this. I found a bunch of 2n3055's in the stock pile im gonna try and ill order some new ones to be sure. (so we're talkin channel 1, 3 and 7). 1 just started doing this. 7 has been doing it for a while but REALLY intermittantly, just started acting up lately again. 3 only did it once and seems to be fine now... gonna swap it out anyway just incase. I think while i have the 3 out, ill just swap out the bc184s in the drive section to be safe as well... the way i wired this thing, its not easy to get them in and out. Might as well. The unit is over 10 years old at this point. It's seen some use.

 

[sr1200]

Got down to the bottom of it. Channel 1 and 7 were the only ones that needed parts. Replaced the 3055's and good to go. Channel 3, just had a couple of cold solders which i touched up and I've had them running for a few hours now and not a peep out of them! Thanks for the advice, saved me a few hundred on trying to recap all of these things!

 

[mgb54]

Hi all

I built one channel of ez1290 which is working great except for a constant ringing tone at 520Hz (and harmonics going up, 1040Hz, 2080Hz etc etc). The tone is present regardless of if there is an input source connected or not, and as the gain is increased the tone follows suit.

Transistors are these 2N3055 & BC550C and the power supply is a Meanwell RID-125-2448 SMPS (housed in a separate enclosure). Bias set by adjusting 5K trimpot until 2N3055 casing measured 22.66V.

I'm using Ian Thompson Bell's 4-toggles board for phase, mic/line, pad and 48v control.

Any tips on where to start investigations would be much appreciated!