Running a Quickie into a Crack - volume question

[wullymc]

Hi there,

I am running a Quickie into a Crack and my question regarding the volume is:

Should I control the volume with the Quickie and put the Crack at 100%

or Should I control the volume with the Crack and put the Quickie at 100%?

...or does it really matter?

Thanks!...Dave

[denti alligator]

I'm running a Quickie into a SEX and I keep the Quickie at full volume and control volume with the SEX. I think the other way around is preferred, but I got a little crackling from the Quickie volume knob, so I went this way and it sounds great.

[Paul Birkeland]

I would put the volume up on the Crack as much as possible, though you may turn it down slightly to control the noise floor if necessary.

-PB

[wullymc]

Thanks!  Much appreciated.

[adamct]

Paul,

I'm curious, can you explain why that is? I'm not questioning your response, just trying to understand how to think about this kind of issue.

1. Is that because the Quickie is noisier than the Crack, so you are better off amplifying the signal in the Crack as much as possible?

2. Or is it because by leaving the Quickie at a lower volume setting, where the system isn't operating at its extremes, it produces a cleaner signal and you avoid double-amplifying noise (actually, that might be the same as my first question...)?

3. Or does it have something to do with how these two units match up?

4. Would your answer change at all if someone were using the Quickie to feed a S.E.X. 2.1?

Best regards,
Adam

[Doc B.]

Since this is a rather unconventional setup my first question is what is the rationale behind using the Quickie ahead of the Crack? Knowing that might help offer the best way to set the controls.

[adamct]

The short answer is: I'm not running a Quickie into a Crack. 

[In fact, I have a pair of inline attenuators installed in my Crack to REDUCE gain...]

I originally bought my Quickie (which I haven't assembled yet) to feed a Decware Taboo Mk II (which does benefit from a pre-amp). Since then I've ordered a S.E.X., so the Taboo might not stick around too long.

But if I do wind up using the Quickie as a pre-amp for the Taboo, the S.E.X. or possibly a power amp for speakers, it would be useful to know how to think about this issue.

Best regards,
Adam

[Doc B.]

If you are going to use the integrated S.E.X. amp as a power amp, then just set the volume control of that amp at full volume, which essentially makes it function as a regular old input resistor.

Then when you go "crap, too much gain!" just turn that control down until you find an appropriate range of control on the Quickie volume control.

Or just skip the Quickie. Unless the source has a very low output, or you need two inputs, the Quickie in front of the S.E.X. is redundant.

[adamct]

Thanks, yeah, I don't expect to need the Quickie in front of the S.E.X. But the Taboo is another story altogether. It may have changed with the most recent iteration, but the version I have needs a very, very high input signal, more than my DAC can muster on its own. Otherwise it quickly runs out of steam with my planar headphones (HiFiMAN HE-6).

Best regards,
Adam

[Paul Birkeland]

I'm curious, can you explain why that is? I'm not questioning your response, just trying to understand how to think about this kind of issue.

2. Or is it because by leaving the Quickie at a lower volume setting, where the system isn't operating at its extremes, it produces a cleaner signal and you avoid double-amplifying noise (actually, that might be the same as my first question...)?

This is closest to my larger concern.  There's nothing wrong with throwing away some signal at the input of an amplifier (we'll just consider the SEX to be a power amp in this context) if it improves the noise floor.  Otherwise, you could potentially run out of gas from the Quickie and actually get the preamp to clip, all because the input of the power amp is padded down a little too much.

Usually this goes the other way, the power amp and speakers are ultra sensitive, so everything else appears to be noisy.

-PB

[adamct]

Thanks, Paul. Makes sense. So just to confirm, the power amp won't clip, even if turned up to maximum volume, unless the input signal is high enough to cause it to clip? In other words, clipping isn't just a function of how high you set the volume, it is a function of the volume setting coupled with the strength of the input signal. Is that right?

[Paul Birkeland]

Yes, the amp will only clip if you send enough signal into it to clip.

If the preamp clips, that distortion will just be fed into the power amp (which isn't so great).

-PB

[Paul Joppa]

I have a long-ish article on the subject of signals, noise, and signal to noise ratio, which addresses this is some detail. It's on the Community page.

[adamct]

Thanks!