Sta Level Distortion, Grrrrr....

[Andrewfrommontreal]

Don’t hold to that thought.  Threshold is ratio and it affects GR.

What is the implication of that?

I should mention that I took out the 6AQ5... distortion was still there.

 

[emrr]

....that the distortion is necessarily after the GR.  That is unproven by the changing threshold.  Now, if the threshold changing with no 6AL5 affects distortion, there must be a power supply problem as threshold is a bias voltage tap from the PSU, but you may not mean that.  No 6AL5 does not mean the GR tube(s) aren't the problem either. 

 

[radardoug]

Surely threshold and ratio are two different things, but are often one affects the other.
Also, with the 6AL5 removed, it should just be a straight amplifier. So put tone on it and scope each stage.

 

[Sorr]

May I suggest that you check the feedback between the two 6V6 anodes and the 12AT7 cathodes?
This is C5 & C6  and R19 & R20.  Check that they are the correct values.  Check that signal actually gets there between each 6V6 anode and 12AT7 cathode.  And check that the feedback signal from the 6V6's goes to the correct 12AT7 cathodes.  Not the other way around.

 

[emrr]

Surely threshold and ratio are two different things, but are often one affects the other.

There’s one control that changes both, like most simple vari-mu. 

 

[Andrewfrommontreal]

Evidentially, I am FAR from knowledgeable in this field. But what I hear in terms of distortion seems to come from a certain level of signal, controlled by either the level going into the unit at the front or by increasing the level with the input level knob. Bringing that up increases the distortion, or instigates distortion if there was none in the first place.  Playing harder creates distortion as well.

But also, when  the signal is brought down by compression, the distortion can actually go away, regardless i am controlling the ratio or the threshold or both as they are intertwined.

Therefore it seems clear to me (again, just basing my interpretation of a very base knowledge of what is going on inside) that the amount of distortion is related to the level of the signal following the compression. Does that not make sense? Is there another explanation based on the situations I am describing? Again, please don’t take this as a challenge... I am beyond curious. At this point I plan to send the unit back to the builder... especially because there are also major hum issues.

 

[emrr]

Can you measure the input level at which it occurs?

 

[PRR]

You can always over-drive the input to a limiter.

If the limiter is working with sane settings, it should at this point be in very deep compression, deeper than real musicians need.

Therefore I would ask if the compression is working properly. Test bench! Measure the input, the output, and the grid voltage.

 

[Andrewfrommontreal]

Can you measure the input level at which it occurs?

I can do some basic measuring today but I am leaving town for a few weeks. I will do so upon my return. I don’t have the proper tools or knowledge so I will have to ask a friend to do so. That being said, there are other factors that make me wish to simply send the unit back.

 

[Andrewfrommontreal]

You can always over-drive the input to a limiter.

If the limiter is working with sane settings, it should at this point be in very deep compression, deeper than real musicians need.

Therefore I would ask if the compression is working properly. Test bench! Measure the input, the output, and the grid voltage.

I should mention here that this is a stereo unit. So I have one channel that is working as intended (without the violent distortion) and even it is odd in terms of its limits (pun maybe intended).

The distorting first channel is clearly not functioning properly. But neither is the other as compared to other Sta Levels. This is one of the main reasons I wish to send the unit back to its builder.

I have used various Sta Levels in the past. They allow for gain reductions of up to 30 or 40dB’s without major issues. With this second channel I can’t get more than 8db’s without it the unit beginning to overdrive (getting hairy as opposed to totally crapping out) unless it is at its slowest setting. It has a narrow sweet spot, unlike usual Sta Levels. Example, when using the Retro Sta Level, I could be in double mode and get the unit to compress deeply and come back pretty quickly without overt overdriving.

Also, I should mention that both sides are sadly afflicted with serious hum issues... even after balancing the 6V6s.

I don’t have the proper tools so I am not able to test the unit seriously other than general compression amounts, which I will do today with my DAW. But my primary inclination is to simply send it back. At the same time I believe it has great potential.

 

[Andrewfrommontreal]

Hi everyone,

So I have had the Drip stereo Sta Level back for some time. It sounds wonderful. Unfortunately it still has that hairy quality if I try and compress more than 10dBs in most cases. If I set the attack and release REALLY slowly I can go deeper, but then it’s not really doing gobs or compression considering that it stays in the 18dBs of compression range the whole time. And I definitely can’t go past that range.

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

I have both an input and output pad but they don’t help.

I suspect that it is an issue with the threshold. 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.

Thoughts?

 

[iangomes]

Hi everyone,

So I have had the Drip stereo Sta Level back for some time. It sounds wonderful. Unfortunately it still has that hairy quality if I try and compress more than 10dBs in most cases. If I set the attack and release REALLY slowly I can go deeper, but then it’s not really doing gobs or compression considering that it stays in the 18dBs of compression range the whole time. And I definitely can’t go past that range.

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

I have both an input and output pad but they don’t help.

I suspect that it is an issue with the threshold. 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.

Thoughts?

Any Luck? I've got an original sta-level and it seems I can't turn up the input loud enough to get a decent amount of compression without some distortion. I'm yet to dive in fully, but am hoping it'll be an easy fix.

 

[Andrewfrommontreal]

Any Luck? I've got an original sta-level and it seems I can't turn up the input loud enough to get a decent amount of compression without some distortion. I'm yet to dive in fully, but am hoping it'll be an easy fix.

Not yet. I have just returned to the unit and the issue. I would like someone knowledgeable to look at it to get a sense of what it happening.