Gain / Amplification

If you are talking an Oppo 205… there was a long thread on AVS where they concluded you could set the Oppo volume as low as 70 without screwing up either bit density for sound quality or noise… if you needed to do so in order to set the preamp volume higher. 

snapsc 

Thanks that’s helpful I’ll search it.   I’m doing half-ass A/B comparisons (lower Oppo 205 gain, more amplification versus the opposite).

Jim

Here is the link. 
 

All transistor amps/preamps measure best at full throttle. So, no matter what you do you will not be operating in the best power range. 

 

Ok, dumb question maybe….maybe the more troll-like members could chill on this one.

Nice polemic opening. 😉
(But many of the “trolls” seem to be more rooted in engineering and theory.)

I was just wondering, is there likely a quality-of-sound difference between utilizing maximum gain (say, out of a CD player, to keep it a simple scenario) and needing much less amplification from your amp, or is it in any way different to set your CD gain/output volume at a lower level and let your amp do its job? Let’s say balanced connections, so that’s added gain as well.

Yeah a lower gain amp usually has lower noise.

With balanced amped are not uncommon to find ~20dB of gain, and single ended are normally about 26dB of gain.

Question just kind of occurred to me when I fired up my Oppo for first time in awhile and it was **LOUD**. Which is not an issue, I was just wondering, circuit design-wise and engineering-wise, should one or the other provide a better sound ?

Whether one can hear the lower noise is pretty questionable as the room is usually noisier than the amp, but tweeter his should be lower, and might be noticeable??

But if one is running a passive pre, then lower CD output and less attenuation in the passive is better.

Lower gain in amp and higher gain in pre could be better for two reasons:

- It moves more gain to electrically quieter environment (pre)
- It reduces relative electrical noise pickup by interconnect.

Of course it depends how power amp reduces the gain (my AHB2 has three gain positions).  If it is just divider at the input then first point doesn't apply, but reduction of IC noise pickup is still important.
 

If it is just divider at the input then first point doesn’t apply, but reduction of IC noise pickup is still important

It totally applies there @kijanki - imagine 10 nV on the IC and then amplifying that small, medium or large.

Small is always smaller than large, and noise will be smaller.
The only reason to go to medium or large is if it not loud enough.

That is a good amp you have, but maybe you can see (hear) if it makes a difference with the music not playing?
(Turn the pre amp +way+ up.)

It totally applies there @kijanki - imagine 10 nV on the IC and then amplifying that small, medium or large.
 

Then you're talking about noise pickup by interconnect.  That was mentioned as second reason.   First reason was that amp with fixed gain and signal divider at the input will react the same way to electrical noise pickup inside of the amplifier at all positions of the input divider, while amplifier with lower overall gain will be less susceptible to electrical noise pickup inside of the box.

It’s about matching the volume of various inputs so you do not need to adjust the master volume much, certainly avoid any loud jump from an input change

Often you are talking about more or less attenuation rather than gain.

Much equipment, like my McIntosh Preamps SS C28 and Tube mx110z have ’trim’ controls for the phono and aux inputs to match them to each other. They were located near the front on the top, you pull the unit forward a few inches, adjust them and push the unit all the way back.

My Tandberg Receiver had trim controls in the back.

Any unit I have had, like Onkyo DX-7500 CD Player

https://www.hifi-classic.net/review/onkyo-dx-7500-430.html

had 3 outputs, rca; direct; and variable. I couldn’t hear any difference, neither could my friends.

Likewise, I had 3 oppos, and the output variations sounded the same to me. Turning off the display may be measureable on the bench i.e. .00002, but its marketing IMO.

Gain usually comes with additional noise. The less gain you have overall the less noise.

Phono stages have the most gain, and most prone to noise, followed by line level preamplifier circuits.

That is all in theory though. Over the last 20-40 years solid state has gotten very very quiet so it’s not usually worth sweating these details vs. say room treatments, listener location, etc.

The one pet peeve I have though is that most preamps still have WAY too much gain, maybe due to the days when radio might pick up a weak station and you had to compensate for it with the volume control.  If I used a tube pre especially I'd be tempted to reduce the gain quite a bit.

is there likely a quality-of-sound difference between utilizing maximum gain (say, out of a CD player, to keep it a simple scenario) and needing much less amplification from your amp, or is it in any way different to set your CD gain/output volume at a lower level and let your amp do its job?   Let’s say balanced connections, so that’s added gain as well.    

If the balanced connection supports AES48, the balanced line standard, there may be no difference of signal level between balanced and single-ended.

The newer more sophisticated digital volume control systems are a bit better at resolution. Older ones cause a loss of resolution as you turn them down since bits are subtracted.

This is why there is a market of line stage preamps since they often have better volume controls as well as often are able to minimize cable interactions better than most sources.

Years ago I did exactly what you are asking. I plugged my Oppo straight into my amps and it worked just fine, but because CD’s were not the only thing I listened to, I went back to my ARC tube preamp, that not only had input switching , but had a different sound that I preferred.

All the best.

This is interesting.  I have a server with software interface volume setting for fixed or variable feeding my DAC ( no vc). Although variable control would be more convenient as my tube preamp has a manual stepped attenuator I set software to fixed output. I've listened both ways and even eliminated the preamp from the chain without noticing much difference. I've thought digital software driven volume control was supposed to be inferior? I like having the tube pre in the mix although unnecessary in my system so it's acting more like a buffer with gain. By the way my preamp has 12db gain. I tend not to go back and forth between configurations so I'm used to getting up to manually adjust volume. 

I can't speak to the Oppo but I have a similar situation with an NAD C-658 DAC/preamp. I used to use it as both a DAC and premap with a set of Rogue M-180 monoblocks. I finally came up with some cash and bought a new Rogue RP-7 so now I use the NAD as a DAC only. What I found is if the NAD is set to higher than 70% output I can only go to 125 or so in volume on the RP-7 before I begin to hear some "noise" in the form of distortion. The NAD has a feature where I can set the output signal to a value and not worry about additional noise from my system. The "70" number mentioned for the Oppo seems to hold true for me too since after I set the NAD to 70% output fixed I no longer have the noise issue. It took a little trial and error but the 70% output set value seems to be te ticket for me.

Let’s put clear cut opinions on the side. To answer this correctly, we need details on each stage, the nature if its gain, and how it is controlled. Its worth everyone understanding that in general the idea that "more or less gain is employed here or there" is a misunderstanding of how circuits re designed. In 90-99% o cases, gain is fixed in both places. What is varied is **attenuation** (some form of variable volume control). These are lossy and passive in most cases, but again there are myriad ways to implement.

In terms of ranking the quality of volume control methods, the digital domain (certainly how its done in PCs, macs, phones, and tablets) is often the worst, except in certain cases using very select DAC chips (among them the ESS 32 bit chips). I believe the Oppo used these. Beyond that -- and again God is in the details -- as you change volume you may change output impedance and matching.

The rule of thumb - big picture -- is set any DAC or PC to 100% volume and control it with the better quality analog volume control in your preamp. In the case of the ESS -- if its implemented correctly, it might actually be better there.

Justme

note: sometime back on another topic i did a long rant/explanation of various methods of contorting volume and the significant benefits/problems of each.  Sorry i cant be more helpful pointing to it.

itsjustme 

thanks that’s exactly what I think I was looking for.    Yes, it’s an Oppo 205 with great ESS chips, and I run it thru a Parasound Halo Pre to a Parasound A21+.

Despite the ESS chipset, if analog volume control (at the preamp) is [circuit design/engineering wise] “better” than how it’s done in the digital domain, that’s what I was trying to confirm.    Obviously everyone’s situation will be a little different depending on their specific gear and other variables.

 Thanks all.  

atmasphere 

thanks for the education & confirmation on volume control in digital vs analog domains.    I never really realized the difference til now.    

Given what you just said, i took a look at the parasound. Apparently it uses a relatively new B-B (TI) chip based resistor pair volume control. I have a bunch of experience with such chips, but NOT the BB. They are very good, but my experience drove me to design my own discrete equivalent. Maybe the BB unit is better than the several i designed with.

So.... if the ESS let’s you do volume control via digital math without the "truncation problem" - i would tend to use the ESS volume. On the other hand the BB chip in your Prasound is basically a bunch of chip resistor pairs with chip switches selecting one pair vs another which is also pretty darn good.

So i don't think you have a clear cut winner either way.

If you want to learn more about digital volume control and its norml issues and why ESS is different they have a good PDF slide presentation on it available publiucly.

Warning: math.

Further thought (edit/add): the downsides of these "digitally controlled analog volume array chips" (what a mouthful) are the basic material used, and the fact that 90% of them depend on the inclusion of a chip opamp gain/buffer stage. Its one reason i ruled out many of them. here’s the point that’s relevant to you: those distortions exist whether you employ the volume in the Parasound or not. Its not like by setting it to full volume, the opamp is eliminated. Its still there as a buffer. I am not criticizing the design BTW - there are convenience / cost / sound / tade-offs everywhere.

Interesting.... @jhajeski , I’ve played about with pre v. gain for awhile, settled down to 50~80% pre for volume control, and leave the amps running @ 75~80.

Unless running a ’stress test’ on a diy...then I unleash it. *L*

Room is louder than the system, so I keep that in ear....

Yak se mas?