Sta Level hairiness

[Andrewfrommontreal]

Hi all,

I originally posted this at the end of an old thread but figured it made more sense out on its own.

I have the Drip stereo Sta Level. Built by Greg himself. It generally sounds wonderful. Unfortunately though, if I try to get lots of gain reduction (you know that magical ridiculous 30-40dB gain reduction - or even over 15dB’s - which other Sta Levels can do easily), it gets hairy. Even if I set the attack and release REALLY slowly I can go deepish (-15dB’s) but then it’s still kind of edgy. It’s definitely not smooth. And I definitely can’t go past that range.

I have used other Sta Levels that allowed me to compress 30-40dBs while remaining smooth. This one can’t. If I turn the input up to get that kind of compression the signal gets hairy/edgy.

I have both an input and output pad but they don’t help. The unit also has a variable threshold, variable attack time, as well as both single and double modes with multiple release times.

No matter what, if I try to get deep compression, the signs becomes unpleasant.

I really have no idea what is happening but I suspect that it is an issue with the threshold... in that it doesn’t go low enough. To try and get the amount of compression I am referring to, I am forced to push the signal too hot through the unit which I guess is too much for the output section (the 6V6 tubes). I don’t know. As I mentioned, I have a variable threshold but it feels like if I could lower the threshold further than the pot allows me to I could compress more without it getting hairy.

The unit is mostly new tubes except for the 6V6s which are NOS RCA grey tubes from TubeDepot.

I really want to solve this one as I want a mellow, rich, enveloping Sta Level... while still being able to do crazy things to room mics which this one can. ;-)

Thoughts?

Andrew

 

[emrr]

I really have no idea what is happening but I suspect that it is an issue with the threshold... in that it doesn’t go low enough. To try and get the amount of compression I am referring to, I am forced to push the signal too hot through the unit which I guess is too much for the output section (the 6V6 tubes). I don’t know. As I mentioned, I have a variable threshold but it feels like if I could lower the threshold further than the pot allows me to I could compress more without it getting hairy.

I said it in the other thread:  Threshold is also ratio in a simple vari-mu.  You turn threshold down, you lower ratio.  For some low ratio (1.6:1 is mentioned in the manual), you will still exceed the headroom of the make-up amp portion, especially on transients given the slow attack time. 

Sorry, that doesn't say what's different, and not knowing what tweaks Greg made, if any, it's very hard to address. 

 

[mjrippe]

What tube are you using for the gain reduction stage?  If it is a 6386 is it modern or vintage?

 

[FarisElek]

I spent hours upon hours working on my dual sta and changed many things with the help of Greg and with my own tinkering and help from this page. I'm interested to k on how forum.  Curious if you followed the silk,  the guides, or got other  help. My sta level is very smooth and maybe a little bright at very fast speeds but otherwise very transparent besides the heft it gives it and low or moderate speeds.

 

[Andrewfrommontreal]

I said it in the other thread:  Threshold is also ratio in a simple vari-mu.  You turn threshold down, you lower ratio.  For some low ratio (1.6:1 is mentioned in the manual), you will still exceed the headroom of the make-up amp portion, especially on transients given the slow attack time. 

Sorry, that doesn't say what's different, and not knowing what tweaks Greg made, if any, it's very hard to address.

Thanks for the response again. I apologize if you have already responded to my query. Honestly this is all confusing to me as I know very little about the inner workings of the unit. I decided to start a new thread as I was getting confused with the information from the other thread.

So if I understand correctly, lowering the threshold will actually make no difference in terms of the artefact I am hearing? I will have to test something at the studio... because I seem to recall the threshold making a difference. Seeing as I presently have a pot for the threshold and can go all the way up to the point where there is no compression, I could test to see if within the range I DO have, I can set in the input level so that the unit doesn’t saturate the signal when threshold is at its lowest and see what happens as I raise it. Might this not tell me if in fact a much lower threshold will not help?

 

[Andrewfrommontreal]

What tube are you using for the gain reduction stage?  If it is a 6386 is it modern or vintage?

The tubes are both modern, JJ 6386’s.

 

[Andrewfrommontreal]

I spent hours upon hours working on my dual sta and changed many things with the help of Greg and with my own tinkering and help from this page. I'm interested to k on how forum.  Curious if you followed the silk,  the guides, or got other  help. My sta level is very smooth and maybe a little bright at very fast speeds but otherwise very transparent besides the heft it gives it and low or moderate speeds.

Curious to k on how forum? I am not sure I understand.

As for the build, it’s Greg that built it for me. It was a commission. All I did was plug it in.

Did you have any issues? And did you find a solution? Or did your unit never do this?

 

[emrr]

I didn’t say it would make NO difference, just not as clean a relationship as you think.

  If you’re dialed down to 1:1 (off) and run audio at max acceptable level before distortion, you still have insufficient compression range when you turn threshold up to max?  If so, it’s not related to threshold in any way i can see.

When you turn the knob to the first place compression occurs, you have the lowest ratio AND threshold.  There’s no setting a lower threshold. 

 

[Andrewfrommontreal]

I didn’t say it would make NO difference, just not as clean a relationship as you think.

  If you’re dialed down to 1:1 (off) and run audio at max acceptable level before distortion, you still have insufficient compression range when you turn threshold up to max?  If so, it’s not related to threshold in any way i can see.

When you turn the knob to the first place compression occurs, you have the lowest ratio AND threshold.  There’s no setting a lower threshold.

Sorry for being so late responding, the rest of my life took over.

I also apologize for being numbskullish but I am having a hard time deciphering the use of higher and lower threshold in what you’ve written. Is it possible that we are using the terms in opposite manners?

For me, assuming all else doesn’t change, a higher threshold implies less compression. As one lowers the threshold, the threshold begins to hit the audio level. At its lowest, it is compressing as much as it can.

So to answer your first question: I don’t have a “ratio” knob as such so I don’t know when it’s at 1:1. But yes, if I pull the threshold all the way up (“up” meaning it is not going to compress because the threshold is above the audio level) and I increase the input to the highest level before distortion, then bring my threshold all the way down (“down” as in it ideally will compress as much as it can), I don’t get away with gobs of compression like regular Sta Levels. Not in most cases. It does sound amazing but I don’t get that deep compression. Or rather if I do, it feels like it’s often on the edge of distorting. It’s a little hairy.

I should clarify, I am getting tons of character, even with only 5dBs of gain reduction. More than what I got from the Retro or the Audioscape... and that I don’t want to lose. But I would like it to be able to get smoother. Perhaps it’s more about the tone... it seems to brighten quite readily, as opposed to pushing more the low mids.

Also, I get a sense that it is MUCH faster than most Sta Levels. Examining the resulting waveform, it clearly shows that the unit was squashing transients... surprising for a Sta Level.

 

[Andrewfrommontreal]

Perhaps someone knows of a tech in Montreal who would be able to figure out what is going on with the unit?

 

[emrr]

I also apologize for being numbskullish but I am having a hard time deciphering the use of higher and lower threshold in what you’ve written. Is it possible that we are using the terms in opposite manners?
I don’t have a “ratio” knob as such so I don’t know when it’s at 1:1

That's what you're failing to understand.  You have a knob labeled threshold, but it's really ratio.  Each ratio setting has a different threshold.  It's one in the same.  You affect threshold for a given ratio by changing the input level knob. 

if I pull the threshold all the way up (“up” meaning it is not going to compress because the threshold is above the audio level)

all the way DOWN is also little/no compression, if the modification truly takes the bias voltage
all the way down to 0 volts. 

(modified) threshold all the way down = 1ish:1 = little/no compression. 
threshold slightly up from there  = >1:1 ratio = slight compression at a very low threshold.  1.6:1 mentioned in manual as lowest practical ratio (and threshold). 
threshold all the way up = 3.3:1 ratio. 

Pull the 6AL5 out.  You don't have to turn it off to do this.
Turn the threshold/ratio all the way down. 
Put program material through the compressor, set it for the highest clean input level, and whatever output level you want. 
Put the 6AL5 back in, what happens? 

With slight compression from a low threshold/ratio and a high enough input level, transients will still surpass max level and distort.  With highest threshold/ratio, it may actually seem cleaner (tube comps usually do) because the higher ratio actually does something effective to keep transients away from max level. 

If it were me, I'd inspect the entire circuit and confirm every modification that's been made, or what part is stock.  Without that, it's all guesswork.  There is easily a botched modification causing the problem. 

If it compresses faster, it means the timing network has been changed.  If it's faster attack (like a limiter) and fast release (for, you know, modern!) distortion WILL be much higher.  A fast enough release keeps the timing caps from ever charging up, it's practically like raising the threshold even further, erasing space between the threshold and max level. 

 

[Heikki]

If it compresses faster, it means the timing network has been changed.  If it's faster attack (like a limiter) and fast release (for, you know, modern!) distortion WILL be much higher.

Things happen when people modify circuits they don't understand. I would expect STA-Level to sound pretty nasty with fast attack and release times. large common-mode voltages swinging up and down causing huge distortion at the 12AT7 and 6V6 stages.