1176 noise floor

Hi all,
I have three 1176 versions a g1176, 2 x mnats 1176 and a blue face 1176.
They all seem to suffer from exsessive noise just after compression, I'm wondering whether this is normal first of all and if I can reduce this noise floor.
I want to try and use the vocal chain of U67 into either Neve/api into 1176 then into la-2a.
At the moment I can't understand why anyone would use this configuration due to the noise after the transient?

What are the positions of the input and output controls. The normal starting point is with them at 12 o'clock.

Cheers

Ian

to be honest i don't know what your getting at Ian, all these units which are all a bit different make the same sort of hiss after the transient, the DBX160 and SSL 4K compressors don't make this sound, so for me i'm using them now, but all of what i've read, everyone uses the 1176 before the LA-2A to get their vocal sound, but i find it unusable due to the noise after the  transient of the vocal.
I appreciate there may be something in my system no quite right but when using for instance my U67 into Neve 1290 pre amp then into DBX160 then into LA-2A it sounds great, same chain replace DBX with SSL 4K sounds great.
As soon as i use one of my 1176 doesn't sound good, and i really want to fault find whats going on, as when using the plugin i dont hear the noise floor rising after the sound.

If my terms are being vague please let me know!!

Do you have an audio example of the noise you're getting?

when slowing down the release the noise floor is reduced dramatically, i'll do a audio example.
Also what it maybe is that i have never been able to correctly set any of these compressors up fully to what the setup instructions say, they all compress quite heavily, so maybe this noise floor problem is that the compression is just compressing to much?

if i put the release slow the noise floor is much lower, if i put the release fast the noise floor is awful.

to be honest, on the G1176 the input pot seemed a little crackly, so i've cleaned it and generally given it a wiggle and it sounds much better now.
Also i was summing out of the box into a preamp and then into the 1176, so ive now taken out the preamp as im pretty sure the hiss was due to impedance mismatch.
now playing around with the blue face, i seem to be able to give the input much more and have smaller amounts of compression, so overloading or high input levels may have been the cause.
the stereo Mnats version i havent yet been able to get any better yet, so this may need to go back on the bench.

Spencerleehorton said:

to be honest i don't know what your getting at Ian, all these units which are all a bit different make the same sort of hiss after the transient

Click to expand...

All your 1176 have a control labelled input on the left hand side. Correct.

Right next to it is a control labeled output. Correct?

You should start with these controls set to 12 o'clock otherwise you may get too much compression.

All compressors will raise the noise floor because they turn the gain up in the quiet bits.

Cheers

Ian

Yes I appreciate they all raise the noise floor but i'm comparing the 1176 to DBX160 and SSL 4k, also it maybe a little bit of pilot error is using these units but i'm interested in, if these have been used in conjunction with the LA-2A on so many hit records, what is an acceptable noise floor?

Hit records don't care about noise  8)

would any of you guys be interested in putting up some audio files so i can compare?

later on i'll post some bad examples and then i'll try and reduce the noise as much as possible.

Spencerleehorton said:

Yes I appreciate they all raise the noise floor but i'm comparing the 1176 to DBX160 and SSL 4k, also it maybe a little bit of pilot error is using these units but i'm interested in, if these have been used in conjunction with the LA-2A on so many hit records, what is an acceptable noise floor?

Click to expand...

Using an 1176 followed by an LA2A on vocals  is a new one to me. Where did you get that from?

Cheers

Ian

1176 is notoriously hissy - even with the "LN" (low-noise) circuit.

Reason being that you attenuate your input signal down to not more than 30mV across the attenuation FET, otherwise it will start distorting because it gets outside of it's resistive behavior zone.

The makeup gain you now need to reconstruct full level, in conjunction with the 27K source-impedance-series-resistor (R6) will build the noise on you.

Note that while compressing, source impedance reduces to less than the 27K, which reduces sourceimpedancenoise as well.

Jakob E.

The noise in a 27K resistor is about -107dBu. In the 1176 there is a 26dB gain amplifier after the the FET which raises this noise to -81dBu and then there is the output stage. Assuming this has its pot . set to 12 o'clock, it will be about unity gain which means the output noise should be around -80dBu. If you turn the output pot past 12 o'clock the noise will increase.

Cheers

Ian

All interesting info from you guys, I'm about to make a stereo pie compressor so hoping these will be better noise wise.
One thing I didn't mention is that my mnats versions have line balancer output rather than transformers, so I may look at this and change them both for transformers.
My g1176 seems to sound pretty good now along with my blue stripe, might even try and mod the mnats version into a blackface, as I have worked on a little daughter board which changes the circuit.

When you are compressing you are sort of pushing up the noise floor, more so in the low end. At least that's what I've seen on the AP.. It's so that you can squeeze a smaller signal with less dynamics into the same amount of headroom so it appears louder and brings out EVERYTHING that has less amplitude including the noise from previous stages and it's self noise. The whole unit may increase in noise based on it's following load to drive as well..

1176's in my experience tend to have a bit more noise than most other compressors, but they are still extremely usable. If your noise is "too high to use" I might think something is wrong.

Can you bypass the sidechain and maybe see how the  amp alone is working in terms of noise? 

Hate to spoil the party, but the pye comp is not better noise wise than 1176.

well, then i most probably have a problem, with at least 2 of my units, if not all, as they all dont setup as per the instructions.
I need to find time to comprehensively go through each one and get to a stage where they setup as per instructions.

That's a good idea. Pay extremely close attention to the wiring directions and component orientations from the schematic for the exact revision of board you have. If your controls are working backwards ( not sure if backwards is the exact case?) you may only need to flip some wiring. Use shielded wiring if you can to reduce noise since there is a decent amount of wiring involved there. Keep wires well twisted together and keep them away from the higher current/power sources.

best of luck, 

And don't forget that the setting of the trimmer in the 1176 makes a big difference to the operating points.

When I calibrate mine, it's a balance between allowing a decent amount of GR vs  sufficiently low noise floor at 'silence'.

In the first couple of years of use, I would go for 'more available GR' and accepted the increased noise at idle.

Nowadays,  I cal them for less available GR and lower noise.

Again, it's easier to see on the CRO and harder to describe!

Also, I would note my input and output traffo choices are different than stock g1176, so my gain staging is different.

My 'input' and 'output'  knobs 12 o'clock would be quite different from the g1176, let alone the originals, which I've used  but don't own  (blue stripe with LN mod).

But yeah! noise floor is a 'matter' in all of my g1176 builds - the mnats pcbs are pretty good though.

With good tidy wiring, and good gain staging, should be able to get a decent signal-to-noise of 70dB at idle.

And yes - putting an 1176 before an LA2A is awesome!

Try putting a Finalizer after all that, with the multi-band gate on; to really damp down the noise at idle (silence). Heaven for a guitar 

I find the finalizer mbg  to be a good measure of 'noise in use' - when it's not triggering on 'idle', it is very good; when it triggering on idle, I am at the onset of 'unacceptable'.

Ironically it is here where everything sounds best   On the edge of acceptable system gain to the ear!


In dBu speak, I would say that would be around -74dBu  or so 

Great info Alex!