Neve 2254 build with ba185, ba191, ba192, ba283

[Spencerleehorton]

Got a funny feeling my HF noise problems are my hackintosh audio problems!
Im going to bypass the onboard audio kexts and hopefully the cpu noises etc will go away!!
I've got a weird MB where the audio side isn't exactly easy to sort and I think I need to get it properly sorted!!
I seem to remember it didn't make these noises before I tried  to install the audio kext.

 

[Spencerleehorton]

Have taken out the offending hackintosh kext and using loopback for my system audio, seems to have greatly improved the noise floor.
My squire bass I have taken out all the non screened cable and replaced with screened cable and is much better now.
2254 does still seem a little hissy but it's so much better.
Replacing all necessary caps for polystyrene caps once they are delivered.
And going to finish the mumetal cases for the input txf.

 

[Spencerleehorton]

I've changed all caps that should be polystyrene apart from the 4700pf which isn't hear yet and no real difference in noise floor?
What noise floor should I be see anyone?

Is there any known improvements to the noise floor?

 

[Rob Flinn]

I've changed all caps that should be polystyrene apart from the 4700pf which isn't hear yet and no real difference in noise floor?
What noise floor should I be see anyone?

Is there any known improvements to the noise floor?

What noise floor are you getting ?

 

[Spencerleehorton]

Neve quotes-73dBm (20Hz – 20kHz), without any gain reduction as noise floor.

I'll figure out REW and see where I'm at compared to the -73dbm

 

[Spencerleehorton]

Little update, I've changed the input 1k post for stepped lorlin and changed the other 4700pf.
Have had a listen and compared channels, ch1 has all the caps changed and the lorlin and is now audibly quieter than ch2.
I'm going to try and setup RWAA software on another laptop with windows 10 on it and do some noise floor measurements.
My gnd scheme is slightly different on each channel so will also test if one is better than the other

 

[opacheco]

I have wound all new transformers as most of the problems i was having, was due to miss match of transformers.
now getting good signal through both channels but I have had to take out of case again and layout on bench.
One channel is not compressing at all, and the other is but the threshold control has problems and its a bit hit and miss?
will look at signal going into BA191 and see if i can trace the signal which leaves the SC back into the Limit SC.
I think the signals output form the limit SC is (A) and goes back into the control Amp on BA185 by (M)?

is this where the compressed signal comes back in?

If anyone could explain the signal flow of the compressed signal please?

Spencerleehorton, this is an incredible project!!, fantastic at all and a complete learning process undoubtedly!. I am thinking o do the transformers by myself too and I would like to know if Could you let me to know the winding information that you used for winding the transformers please ??

Thanks anticipated
opacheco.

 

[Spencerleehorton]

I've upload the winding sheets in the technical documents section under neve.
It will depend on what core and size you are using so you will have to change if not using exactly the same as the sheet.
I'm not going to say how I did mine as mine are completely different but just the same specs.

 

[opacheco]

I've upload the winding sheets in the technical documents section under neve.
It will depend on what core and size you are using so you will have to change if not using exactly the same as the sheet.
I'm not going to say how I did mine as mine are completely different but just the same specs.

Spencerleehorton, let me to check them there!

Thanks
opacheco

 

[Spencerleehorton]

Finally seem to have this thing working right, the noise I was getting I think! Was a faulty api preamp that I was using as when I di bass through a 1290 neve preamp there is no hiss and the sound is amazing!!!
More testing needed but I feel I'm actually getting somewhere now.
Next test is to put some drums, guitar and vocals through, then a full mix.

 

[Spencerleehorton]

just changed and checked the recover lorins for 8 stages and everything works so much better now!!
Have done a little video on youtube.

https://youtu.be/dJ6KCBNpsD4

 

[Spencerleehorton]

Going to revisit this build as I’ve never been happy with the nest of wires and bodged way I built this, I did have it sounding good at one point but was luck more than anything.
Time to neaten it all up and get it sounding how it should!!

 

[Spencerleehorton]

When putting in 5v sinewave into Channel 1 without gain on output and no compression I only get 450mv out!!
With max gain I get 2.9v output
Going through each pcb today and found quite a few wrong components!! I must have been in a rush when I first out this together!!
Channel 1 seems to output more and get really work better than channel 2, so I’ll start to take apart channel 2 and start building it again nice and neatly.

 

[Spencerleehorton]

Channel 1 seemed to have a few errors with values of capacitors and the transformers were not wired correctly!! I must have rushed through this build before!
channel 1 is working fairly well, good level from bypass to on.
Lots of compression, and tone wise sounds great.
Bit of HF noise I can hear which may just be not having the top part of the case on?
Ordered some more screened cable and will rewire channel 1 with a more neater approach.
Channel 2 works but lacks bottom end?
Will try and trace to find what’s going on.
I’ve also ordered some new txf for this which I’ll replace.

 

[Spencerleehorton]

Channel 2 ba283 seems to be fine problems start going into ba185.
Will test voltages on working ba185 and then compare.
Suspect it maybe wrong SC txf.

 

[Spencerleehorton]

Channel 2 waveform Is a bit off and and this is obviously the low cut, I have traced signal and can’t see any value errors, only thing that is different from channel 1 is that ch2 used BC184 transistors rather than the bc550c in channel1.
I’ll replace them and see if the waveform shape gets fixed.

 

[Spencerleehorton]

The problem isn’t the transistors, it seems it’s the input txf. Ordered new input transformers but they delivered wrong ones!!
Waiting on correct ones.

 

[Spencerleehorton]

Sorted a few more issues that I missed, channel 1 now sounding good and compressing well, channel 2 sounding good fixed low cut problem but can’t seem to get it compressing as much as channel 1.
Have recorded all ch1 voltages and traces and going through ch2 to find the problem.

 

[Spencerleehorton]

yet more wrong values!! im gonna have to go through it all as ive used some wrong values for the capacitors.
i will check my patch bay as well as im getting some hiss which may or may not be a dodgy connection?
ch2 is behaving though and sounds grear, just need to get this hiss gone and im there!!

 

[Spencerleehorton]

i think the problem is again the transformer and it is an impedance miss match which im hearing!!
will repair and test