Crack volume control bypass?

[Mudhiker]

I don't have it yet (just ordered the other day), but how should I make sense of all my volume controls?  Computer has one.  Then the DAC has one.  Then the crack has one.  So I have three different ways to make it go to eleven.  Can I just bypass the volume pot (or the stepped attenuator I was planning to install) in the crack and run the output full blast, controlling loudness via the buttons on my source?  Though of course if I later decide to run using a phono stage I'll need it...

 

[JC]

I don't know the schematic, but usually the easiest way is just to turn the VC all the way up.  Presuming that it is wired like the SEX, that will essentially take the VC out of the circuit.

If you want to make it a bit more permanent, you can always jumper around it; then, of course, remove the jumper when you add something without its own VC!.

 

[Paul Birkeland]

I would crank the volume up on everything before the Crack, then use the Crack's volume control.  The noise floor in a computer can be pretty high, and running the crack wide open may reveal that unintentionally.

 

[Mudhiker]

I would crank the volume up on everything before the Crack, then use the Crack's volume control.  The noise floor in a computer can be pretty high, and running the crack wide open may reveal that unintentionally.

I'm using the optical audio out of my imac... is noise floor a concern with digital audio?

 

[dmatt]

Someone with more knowledge on this could help me out here, but I believe that if you control volume while the signal is still digital (through the computer and possibly the DAC) that at a certain point of volume reduction, you start losing bits of information.  So it may be better to leave the upstream volumes at max (and some actually try to bypass the volume control on computers) and control the volume with the Crack. 

I know this is a common discussion item on the Squeezebox forums (since those all have digital volume controls as well).  The only time I have attenuated volume in the digital domain was in a situation where the balanced output of my DAC was clipping the input of my integrated amplifier (weird, I know).

David

 

[Grainger49]

As Paul B. mentions, you don't want to run the Crack volume WAO (Wide A$$ed Open).  But you are also correct about running a digital way down.  So try this:

Digital at 1/2, then go with the Crack's VC.  If you can run the Crack WAO, then lower it and raise the digital VC to 3/4 and try again.

 

[jrebman]

By all means, set your playback software on the Mac to be full volume, bypass volume control, whatever it may be called.  That's the first step in getting the best digital out of a computer.  Also, if  you're running iTunes, think about switching over to "Play"..  I'm not a Mac guy myself but I know a lot of them and this is what they tell me.

If you can bypass the volume control in the dac too, that can only help.

I have no pots or digital volume controls in my main system and the jump in transparency, detail, and dynamics without any mechanical wipers in the system is incredible.

Good luck,

Jim

 

[JC]

Yes, I think that it goes without saying that if you have noisy sources, you may want to modify your gain structure accordingly in any audio system.

 

[howzz1854]

sorry to revive an old thread, but seeing that is a topic i am looking for clarity. i thought i'd share some of the findings.

here's what the guys at Head-fi have to say about digital volume control. i take NO credit at all.

response was by user Head Injury
https://www.head-fi.org/f/threads/volume-control-woes-its-too-loud-desktop-usb-schiit-bifrost-rca-bottlehead-crack-w-speedball-hd650.742594/

tl;dr Turn your computer volume down, you're fine.

Here's how digital volume control (like the one your computer uses) works:

Digital resolution is limited by the bit depth. As the volume increases or decreases, the digital signal has to round it to fit one of the values the bit depth can resolve, and this rounding creates noise (called "quantization noise"). The more bits, the smaller the volume steps and the less rounding, so less noise. It turns out that each bit lowers the noise floor by -6 dB. 16-bit signals have a quantization noise floor of -96 dB, and 24-bit signals have -144 dB.

The problem is, since this noise floor is determined by the bit depth, it will not go down when you turn the digital volume down, like the noise introduced by an amp will. So if you have a 16-bit file and turn the volume down by -10 dB (1/2 the volume), the peak signal that was 96 dB above the digital noise floor is now only 86 dB above it. The signal-to-noise ratio was reduced by -10 dB as well. This is why people recommend using the analog volume control.

This is made moot by the fact you're probably not listening much louder than 80 dB, and your room's ambient volume is likely around 30 to 50 dB, and you're probably not even getting 96 dB of signal-to-noise ratio from your gear anyway.

Plus, if you're using your DAC in 24-bit mode, you have 8 extra bits to use for volume control. Meaning you could lower the volume by 48 dB (that's about 1/28 the volume) in the digital realm without reaching the noise floor of the 16-bit file you're playing, or the noise floor of your equipment. Digital volume control will only matter if you're raising the noise floor above the rest of your noise, and you're not realistically going to do that.

So turn down your computer volume, you're fine.

sounds like if you're outputting digital in 24 bit mode, you have enough dynamic range room that allows you to turn down the digital volume all the way down to 1/28 of the total range before the noise floor / signal to noise start becoming an issue.

can anyone chime in on this? any sound engineer experts here?

 

[howzz1854]

Doc/PB,

is this inline RCA Attenuator exactly the same thing as soldering a 75K resistor on each side of the channel + 33K resistor at each pot level?

https://www.amazon.com/Harrison-Labs-Line-Level-Attenuator/dp/B0006N41B0/ref=cm_cr_arp_d_product_top?ie=UTF8&coliid=IEAW6JWA19DCL&colid=2L03UQY178ZVF

meaning reducing the input signal at exact same principle? i'd like to avoid soldering if possible hence was thinking about getting the inline attenuator.

i am playing around with a couple different scenarios for testing purpose. ie. testing digital attenuation vs analogue. with the scenario of analogue attenuation testing, i'd like to keep the digital volume at 100% to maximize the dynamic range, hence the resistor option question.

 

[Paul Joppa]

It is not exactly the same, since it presents a 10K input impedance instead of 100K. Other than that, it's fine. I use them myself in a Eros-ForeplayIII-Paramount system.

 

[howzz1854]

It is not exactly the same, since it presents a 10K input impedance instead of 100K. Other than that, it's fine. I use them myself in a Eros-ForeplayIII-Paramount system.

thanks, i'll give it a shot and see what i like better, ie. Digital Attenuation or Analogue. for all we know, it might even sound exactly the same lol.

 

[howzz1854]

hi all. the 12db inline attenuator arrived today.

so far i haven't noticed any coloration or immediate out of wack sound signature. it does allow me to dial up the digital volume up from original -22db level (25%) to -12db (45%), and also allow some more wiggle room on the crack's knob as well (now sit at 50%).

one thing i left out in my previous post, that i forgot to ask is. does this kind of RCA inline attentuator affect the output impedance of the crack at all? my understanding is that the crack has a 120 ohms output impedance, which is perfect for the likes of HD650/HD800s. will this affect the output impedance?

i am now looking at other attentuators that can possibly do 20db so i can possibly raise the digital volume knob all the way up to near 100%. for my sound card (Asus Xonar Essence STX), 100% volume is 0.52 db (outputting through optical SPDIF to my schiit bifrost, then RCA connector from Bifrost to Crack), so if i can get up to 99%, i should be theoretically at 0db digitally full dynamic range. any downside in using a 20db inline attenuator? like am i going to introduce some added noise on the crack's amp side?

 

[Kris]

I went similar rout to yours and didn't like attenuators nor resistors mod. My final solution to that was (and still is) Submissive ahead of Crack. If funds allow, I'd strongly suggest that passive "preamp". No coloration at all, just pure, neutral sound and in addition to great attenuation you'll get more inputs and fun building it.

 

[Adrian]

I went similar rout to yours and didn't like attenuators nor resistors mod. My final solution to that was (and still is) Submissive ahead of Crack. If funds allow, I'd strongly suggest that passive "preamp". No coloration at all, just pure, neutral sound and in addition to great attenuation you'll get more inputs and fun building it.

I only use CD, Tuner, and EROS as inputs for on system (no computer input) but ... I run the Submissive ahead of all the amps (Crack, S.E.X., Paramount) and then turn the amp volumes up to max (out of the circuit or bypass) and use the Submissive for volume control.
On my desktop I run my laptop through a Modi 2 DAC into an S.E.X. 3.0.  I set the computer volume controls to Max and control the volume on the S.E.X. and do not perceive any noise or loss of signal - sounds great through my Decware Trapezium speakers.
The gain in my system with the laptop controls at max feeding through the external DAC is not excessive.  I can run my S.E.X. volume at about 50% with good voliume in a near field setup.

 

[howzz1854]

so no concerns about affecting the output impedance of the crack? sorry i am not very electrical inclined. i fell asleep during class in high school many many years ago that one time they were going over electrical. still kick myself to this day. LOL

 

[Paul Joppa]

No concerns - the output impedance is not affected by the input attenuation scheme.

 

[howzz1854]

No concerns - the output impedance is not affected by the input attenuation scheme.

thanks Paul Joppa.