Control volume with DAC or Preamp?

And that we'll never know, as it is the graph shows roll off starting at 100hz already and that's with a 100k!!! loading, Stereophile usually also give a 600ohm loading, strangely omitted this time.

Uh, George, you missed my point entirely.

@wolverine1 The scenario you describe sounds unusual. I have the same preamp as you, the HPA4 (LA4 + with headphone amp). My Benchmark DAC3B has no volume control but if I were to have a DAC with volume I would set the DAC's volume to fixed. The manner to set it to fixed differs by DAC.

This flutter sound you hear should be investigated with Benchmark technical support. Give them a call and they will help you get sorted out. 

You should also hookup your DAC by XLR (if supported) to the  LA4's input #1. That input has some optimizations for DAC's.

My only complaint about this preamp is the RCA inputs, I wish they were all XLR's.


BTW - the LA4 is an incredible preamp. If you want a great volume control, a few source inputs, and total silence. I do not think you can find a better preamp. Almost all DAC's are noisier than this preamp.

That audionet gear looks great. I was reading about the amps and may try replicating the independent power supply transformers for each rail in my amps too. I've already got an extra one just sitting unconnected in the power supply as is so it'll just be a little 10 minute mod. Thanks for the information!

Hey UNSOUND:
I have the Audionet Pre G2 and the Max Amps.  Also the MM Tambaqui DAC.
Happy Holidays!  Ken

 its likely the loading is internal in the unit itself. 

And that we'll never know, as it is the graph shows roll off starting at 100hz already and that's with a 100k!!! loading, Stereophile usually also give a 600ohm loading,  strangely omitted this time.

Would be nice if someone that has one and can do the measurement, to see what happens with a 10k loading as many Class-D's have.
So to those going direct with this make sure your amps input impedance is >100k other wise as the bass "could" be anemic as  ozzy found out a few posts back.

Cheers George

   

If you look at the graph George posted, be sure to observe the vertical scale as it is in fractions of a dB. -0.8dB down is not bad for a transformer coupled unit. However it should be noted that output transformers need to be loaded properly for optimal response. Given that PS Audio would not know what the unit was driving, its likely the loading is internal in the unit itself. This would mean the external load of an amplifier is likely irrelevant.

From the same Stereophile review:

In each case, the audioband response has a very slight rolloff in the low bass, reaching –0.8dB at 10Hz, but is otherwise flat up to 20kHz.

Just for accuracy... The DS Dac is transformer coupled. You can see it here:

https://images.app.goo.gl/oDW85e3k2MKCXJP98

Same difference cap or trany coupled, they both will roll off the bass when used together by the input impedance of the next stage if not large enough as in this graph showing it’s bass roll off already starting at 100hz!!! and becomes more severe the lower the input impedance of the poweramp becomes, a 10k Class-D which many are would have zero bass output.
https://www.stereophile.com/images/914PSDSfig04.jpg

Cheers George

@madavid0, So rather than for a reason, it’s for a preference? And I don’t post this to discount your preference.

@unsound DAC chips can control volume in the digital domain and many DACs use this feature of the chip to do so. In my own experience this leads to clearly inferior results compared to a pre. I would never consider using a DAC for volume control unless the DAC has a real analog pre stage of some kind, or at the very least an analog volume control chip. Not to say that it's any good, but adjusting volume in the analog domain is the first prerequisite.

Indeed, you, like me and many others, have found that quality preamps do indeed serve their designed purpose.

Of course George will tell you that your ears (or components) are wrong.

What's important is that future readers understand his bias, and that the only way to know for themselves is to try the alternative approaches in their system.

Clearly results differ in different systems and for different ears. 

@fastfreight, May I ask which Audionet pieces you are using?

I purchased PSAudio DS DAC and BHK 250 stereo amp.  I was not thrilled, and added the PSAudio BHK preamp, for no other reason except sound quality.  I was rewarded (to my ears) with better overall sound through the preamp.  I did not need it for other sources.  I have since moved on from PSAudio, but reconfirmed several times that my DAC sounded better through a quality preamp.  I also firmly believe that synergy is involved between the preamp and the amp(s).  I now have amazing Audionet gear, and again have confirmed (through my ears) that the preamp between my DAC and amps afforded (a funny word right?) better sound.  These are my personal observations.  Believe me, I wanted to get away without the preamp cost.  Easy to believe that anything additional in the signal path will not help, but that was not my findings.  Poor interconnects between Preamp and amp will of course affect this outcome.  And I believe only a truly good preamp will give these same results.  Stay safe!  Ken

@atmasphere, My previous post was in regard to your more recent post and newly mentioned “passive controls” and whether or not that was indeed the OP’s subject at hand.
 In response to that original post, I think it prudent to mention that depending upon the partnering amplification, some DAC’s have many more bits available to handle volume control with little to no risk of bit stripping for even 24 bit hi rez formats.

I’m not sure that one could accurately describe the OP’s direct from DAC to amp application as “passive”?

@unsound Check my original post in this thread.

@madavid, why should ...”Volume control via DAC chip is to be avoided period.”...?

The OP's is not passive you are right but in the thread above you will see GeorgeHifi comments about " Ralph is product (his active preamp) " etc. and for some reason (and I have nothing against GeorgeHifi) he has some feud with Ralph, he even quotes Ralph's phrases " This statement is false," so the thread deviated into this arena ...

Only if the DAC has an a proper analog line pre stage. Volume control via DAC chip is to be avoided period. In generally a high quality separate pre will always be better.

@atmasphere, I’m not sure that one could accurately describe the OP’s direct from DAC to amp application as “passive”?

Ralph is product (his active preamp) protection mode, omitting the reason behind a "why" the "rare" times a passive "may not" be the least coloured, least distorted, and best dynamically

The reason passive controls tend to sound more colored is they are unable to buffer the control, they are unable to control the otherwise audible artifacts of the interconnect cables. They sound best (more bass, more 'realness' across the audio band) when the control is set to maximum but of course this isn't practical. 

Just for accuracy... The DS Dac is transformer coupled. You can see it here:

https://images.app.goo.gl/oDW85e3k2MKCXJP98

ozzy
I used to own the PS Audio Direct Stream Dac. Running direct to my amps it was a bit anemic.

That’s totally understandable when you see this frequency response graph, the roll off in the bass with a 100k load starts at 100hz and gets worse as it goes down to 20hz, which indicates to me it’s capacitor coupled.

And that capacitor "could" be too small (impedance mismatch) when it sees the input of what ever amp/s you have or even 10kohm Passive preamp load as well, it could be much worse and roll off the bass even more than with 100k, and resulting in your "anemic " sound

https://www.stereophile.com/images/914PSDSfig04.jpg

Cheers George

I think it depends on the Dac.

I used to own the PS Audio Direct Stream Dac. Running direct to my amps it was a bit anemic.

Now that I own the Lumin X1 it sounds waayyy better running direct to the amps. I ended up selling my Ayre preamp. 
Which helped pay for the Lumin.

ozzy

Ok, There are circumstances where a passive may be best and ones where an active will work best. This based on objective as well as subjective reasons.   

Ralph is product (his active preamp) protection mode, omitting the reason behind a "why" the "rare" times a passive "may not" be the least coloured, least distorted, and best dynamically

Only when there is a impedance mismatch which is maybe 5% of the time, when the ratio is lower than 1:10
 
As most sources can easily drive a 10k passive, and a 10k passive can easily drive power amps that are 33k or higher input impedance, most are, the industry standard 47k and most tubes are 100k.
Only some silly Class-D are 10k input, passives don't suit these, as to many tube pre's don't either

Cheers George  

George is omitting the rest of Nelson's comments when he makes that quote. He seems to do this as part of his 'product protection' program, since he sells (actually a very good, but also obviously not of his own design) passive volume control. Here is the rest of that passage, starting at exactly the point that George stopped:

I suppose if I had to floor the accelerator to drive 55 mph, maybe I’d think the life was being sucked out of my driving. Then again, maybe I like 55. Nice and safe, good gas mileage…

Is impedance matching an issue? Passive volume controls do have to make a trade-off between input impedance and output impedance. If the input impedance is high, making the input to the volume control easy for the source to drive, then the output impedance is also high, possibly creating difficulty with the input impedance of the power amplifier. And vice versa: If your amplifier prefers low source impedance, then your signal source might have to look at low impedance in the volume control.

This suggests the possibility of using a high quality buffer in conjunction with a volume control. A buffer is still an active circuit using tubes or transistors, but it has no voltage gain – it only interposes itself to make a low impedance into a high impedance, or vice versa.

If you put a buffer in front of a volume control, the control’s low impedance looks like high impedance. If you put a buffer after a volume control, it makes the output impedance much lower. You can put buffers before and after a volume control if you want.

The nice thing about having volume control in both pre and dac is that it allows you to find out for yourself.

What you have is basically two preamps running in series into each other, who does wants to do this craziness. 🥴

When I did that I found that the pre-amp improved system performance in every way.

What you found is you preferred the coloration/distortion that way, that the extra preamp gave you. (you need to fix the sound of your source because you don’t like it)
Next you’ll say 3 or 4 preamps in series it sounds better 🤦‍♂️🤦‍♂️🤦‍♂️or🤦‍♂️

Bascom King and many others have found the same.

Of course they do, they sell preamps 

@georgehifi I respect your perspective, but you can't tell people their ears are wrong when they find that an active preamp improves system performance. 

The nice thing about having volume control in both pre and dac is that it allows you to find out for yourself. When I did that I found that the pre-amp improved system performance in every way. Bascom King and many others have found the same. Some others like you have not. As always, you have to try it in your system to know which will hold for you.

Unless there’s some problem, the lowest noise is always achieved if you use all or most of what the source has to offer.
If not your throwing away source signal to ground (earth) with the active preamps volume pot just so the "gain stage" (that not needed) of that active preamp can make it back up again!!!!!

Nelson Pass tells everyone that here, why is it so hard for many to understand, (mental blocks perhaps).

Nelson Pass,

“We’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more.

Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.

Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control.

What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.

And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp.”

Cheers George

I had a DSD as well and a variety of preamps.  I considered scrapping the preamp because I know folks who were just using volume control on DSD.

I tried several A/B tests using the DSD vs an Ayre K5xeMp, PS Audio BHK Pre and Art Audio Conductor.  In all three cases, the preamps significantly outperformed the DSD.  I found the preamp stage on the DSD to be less than ideal though I hear it does better matched with PS Audio amps.  

The best connection is set the volume on the DSD to 100 and use the volume control on the Benchmark.  What you are doing by maxing out volume on the Benchmark and using the volume control on the DSD is probably giving you the worst possible outcome.  

I had a PS Audio DSD for almost 3 years, before going to the Emm Labs DV2 and Ref Pre. With the PS Audio running directly to my Classe' CA M600 I found the presentation far to edgy. (Dedicated circuits, great cabling) Not to mention noise! Run the PS Audio directly, without playing any music listen to your speakers while turning the volume up on the DAC. You will be amazed at the noise level! It should be dead quiet!  This indicates to me the pre in the dac is sub par. Depending on what gear you are using, I understand colorization. However, the right gear (what ever that means) Dac Pre combo is hard to beat. Its all about transparency. As George mentioned about bit stripping, I also was aware of the claim by PS Audio that there is no bit stripping. I find that hard to believe.
Within the next month I will compare the DV2 to the DA2 with the pre and see if I can detect any sonic differences? 

Quite often the volume control in a preamp is better than one in a DAC

This statement is false, it’s 50/50, and in case of a tube pre it’s more in favour of the solid state dac output stage

Both the dac and preamp volumes can be adjusted by remote control.

You achieve nothing doing this just preamp colouration and extra distortions, and extra interconnects,.
Your basically running a preamp into another preamp two volume controls and extra interconnects, it’s always best to use all the source has to offer when it has a digital volume, which your case has two high/low preset gain settings in the output stage.
Use it direct into the poweramp, on either the high or low preset that allows you to turn turn up the digital volume to the top of it’s range for loud listening.

By going direct with your setup you basically achieve what Nelson Pass says here, forget the reference to the passive pre, you have one stage better again than this if you go direct!!.

Nelson Pass,

“We’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more.

Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.

Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control.

What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.

And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp.”

Cheers George

Thanks for all the advice.  I had been using the Benchmark LA4preamp at the highest volume and adjusting the listening  level with my PS Directstream DAC. As I mentioned, I heard a fluttering noise from the speakers while doing this.  I tried the reverse...DAC at full volume and adjusting the listening level on my Benchmark preamp.  The fluttering went away and the sound seems much clearer.   Both the dac and preamp volumes can be adjusted by remote control. 

Quite often the volume control in a preamp is better than one in a DAC. This is usually true if the DAC employs a digital control, since digital controls usually shut off bits to lower the volume, resulting in lower resolution as the volume is reduced. There are a few different techniques that DACs use in this regard, but generally speaking, you set the DAC all the way up and control volume with the preamp. This usually allows you more resolution than you can get by driving the amps directly with the DAC, since the DAC (in order to comply with Redbook specification) makes way too much output for most power amps to be driven past overload.

Connect the DAC directly to the amp and ditch the preamp if your system is purely digital. You should be able to achieve greater transparency because you removed the coloration from the additional interconnects, component, and power cord. 

It appears the answers here are all over the place.  If it was me I would contact PS Audio to get an answer directly from the company.  

 Are you referring to the Benchmark DAC3 HGC? One volume control and lots of imputs/outputs. Eliminate your preamp. I think solves all your problems. Have one and love it. 

wolverine1 OP
My DAC (PS Audio Directstream) has a volume control and so does my preamp(Benchmark), of course. What’s the best way to control the volume of my system to get optimum sound

Best quality least distortion and coloration, and best dynamic swing, dac direct to poweramp using the dac as the volume control will be the best. Without any debate. As the PS audio’s dac output stage will as good if not better than the Benchmark preamp and has up to 3volts output at full, which is more than enough. You have 2 output max levels you can preset set, choose the one which gives you the highest volume level enough for the loudest you need to play.

BUT!!! if the dac "bit strips" on the lowest volume setting your using then there is debate. See where your volume is on the dac for normal listening then ask PS if it "bit strips" at that level, then your home and hosed, very simple thing to do.


I was just sent this PS Directstream volume control info, your PS DS does not bit strip with lower volume, so your good to go direct to poweramp/s for the very best SQ

The internal volume control keeps complete precision: every bit in the input affects the output of the DAC for any volume level. Except for the sigma-delta modulation process itself there is no rounding, dither or other trimming, not to 24 bits, not to 32 bits, not to 48 bits, but rather a full 50. The incoming PCM signal is 30 bits from the upsampling fi lter and the volume control is 20 bits wide so all 50 bits of the output are used throughout the sigma-delta conversion, requiring more than 50 bits of precision.

Cheers George

I say try it out and see how it sounds to you.  If the volume control in the component (doesn't matter what it is) is at fault you should hear it as some difference/degradation in sound quality.  I don't think it needs to be more complicated than that (at least initially).

Preamp

If the preamp is an analog volume control, potentiometer or relay-driven voltage dividers, that would be preferable to the DACs volume control, which may be playing with bit depth to achieve that function, leaving you with less than bit-perfect audio.  Set the DAC to full out or just below and use the preamp.
 

I have a PS Audio BHK preamp and DirectStream DAC.  I set the DAC at 100% and control volume with the preamp.  Works for me.  

I have a pure analog McIntosh system were I often control the volume using the MC2600 power amps gain controls and the 31V preamps volume control.  I can fine tune the listening level better that way. 

Adurerca- I did that and it sounded very good.  But I wanted to use a turntable and a tuner so I needed the additional inputs.  I started looking for a preamp that would be like connecting my DAC to the amp, give me the necessary inputs and accept balanced cables.  The Benchmark checks all those boxes.  Sounds about the same with the Benchmark as a direct connection to the amp. 

Another option, try driving the amp directly from the dac.  How does that sound compare with the pre in the chain?

OP here. Thanks for the input. I experimented and found that, with the Benchmark preamp at maximum volume, I could hear a fluttering, vibrating noise from my speakers when standing close to them with nothing playing...sounded like the speaker cones were making it.  If I turn the Benchmark preamp volume down a little and the DAC volume up, the fluttering stops and the sound is clearer. 

I have a Berkley Alpha in my small system (with preamp) and Berkley says set their dac to 51 (volume) when using a preamp.  There should be an optimal setting on the dac and you should control the volume with the preamp.  Volume control on the dac is tough to get right.  Listen to what happens to the midrange as you increase & decrease volume digitally.  

The most important thing here is that typically and I personally don't know about the Directstream Dac but most dacs do it, you set the Dac at full volume, you will most likely bypass any DSP stage, DSD to Pcm internal conversions, and possibly even filters leaving the source mostly untouched, if your preamp is good I think that would be the best way to go

You have a really nice preamp that adds no noise or distortion to the music path.  I would go with using the Benchmark pre for volume control.  You should then turn the dac volume to 100% so you get the full signal going to the pre.  The way it was explained to me is you want to push a full signal to the last car in the train before attenuation.

When I inserted the Benchmark pre into  my system, I  noticed immediately better sound at lower volumes and much much better and granular volume control than the dac.  You may have to adjust the pads at the XLR outlets to properly match your components but that is better explained in the user manual of the Benchmark.

I'm not sure on that exact DAC but generally think you want to run the DAC in "DAC only" mode which skips the DAC volume control and puts the full DAC output (balanced or unbalanced) into the pre-amp. Then use the pre-amp for the volume control. 

However, there are some pretty sweet combined DAC and pre-amps but assuming this is more of a headphone amp type setup?

With that said it is fairly easy to try it both way and listen for yourself. I have a simple topping DX3pro as my DAC and used it a as pre amp temporarily with mediocre. But it was not built to be a real hifi pre-amp but a headphone amp so knew this was far from ideal. 

Listen, is best advise. But full throttle on anything, may not be the best Idea.. My server and SACD, both have volume control. I set the volume at 60-80%. I get pretty good SQ there and a little pre and source  headroom.

Just for the heck of it, does the manual address the issue?

Regards