Digital versus analog volume control - one more datapoint

edorr

WBF Founding Member
May 10, 2010
3,139
14
36
Smyrna, GA
I was planning on buying a DAC with build in analog volume control, but ended up getting the EMM labs DAC2X which has no volume control. I am using a Trinnov processor as input, using its digital volume control, attenuating up to -50db. As a result - I was assured by many - I was loosing resolution.

I use the DAC2X in an integrated MCH and 2 channel system, so when the respectable EMM Labs Switchman 3 (6 channel analog pre) showed up used at a fair price, I scooped it up without hesitation.

I compared analog (Switchman) and digital (Trinnov) domain volume control in my system. Even at relatively high attenuation levels the digital volume control wins hands down. What my ears tell me is that any type of preamp in a very transparent system is subtractive, i.e. the best you can do is minimize loss. Apparently any loss of resolution due to dithering in the digital domain is far less than inserting a set of cables and an active preamp. The gap may narrow and may be disappear completely as you move up the preamp food chain. But the Switchman is no slouch, and the gap was very substantial.

I had previously taken out a 10K tube preamp because it did not offer me any improvements over digital volume control. This second round comparison confirms my initial findings. Dedicated analog preamps are necessary only for analog sources. In an all digital system they are obsolete. The future are various types of boxes offering any combination of the following: music server, DRC / EQ, volume control (digital or analog domain), digital input switching, D/A conversion.
 

amirm

Banned
Apr 2, 2010
15,813
37
0
Seattle, WA
If the digital volume control is done properly which means conversion to floating point, level adjusted, dithered and then truncated to target rate, say 24-bits, then the math says you have not lost any resolution. Noise floor is raised slightly but 24-bit samples are already 4 bits of noise. An analog pre-amp as you say, adds distortion and noise so it is not perfect either.

That said, my subjective testing sometimes shows better quality when a pre-amp is used. Not sure if this is placebo or real :).
 

DonH50

Member Sponsor & WBF Technical Expert
Jun 22, 2010
3,947
306
1,670
Monument, CO
1. Everyone yells about "losing" resolution and while technically true it really does not matter. If you are turning the volume down by 50 dB and the system responds by lopping off 8 bits, you are using the same 8 bottom bits (in a 16-bit system) you were using before, and you are that much closer to the noise floor. You are using fewer bits, but you don't need as many, either.

2. Many systems process with much higher bit counts, and use additional DAC bits to help compensate. If you started with a 24-bit DAC and dropped 50 dB, you again lose 8 bits but now 16 bits are left. that is quite a bit of resultion and dynamic range...

3. Systems may use a digitally-controlled volume control that does not vary the "resolution" as the volume changes, it just provides "digital" control increments (steps). I have no idea what is in your system, just noting that not all "digital" volume controls are equal.

If you have found no issue with the digital control, why worry? A myriad of parameters go into the trade space for an audio system, don't get hung up on one unless it is a real problem...

All IMO, FWIWFM, etc. - Don
 

edorr

WBF Founding Member
May 10, 2010
3,139
14
36
Smyrna, GA
If you have found no issue with the digital control, why worry? A myriad of parameters go into the trade space for an audio system, don't get hung up on one unless it is a real problem...

I am finally coming to terms with the reality that no preamp is going to sound better in my system than no preamp. Next, I hope EMM Labs will implement the digital volume control in the DAC2X, which technically they can do through firmware.
 

DonH50

Member Sponsor & WBF Technical Expert
Jun 22, 2010
3,947
306
1,670
Monument, CO
Anything you add is going to add something, good or bad. It will always add a little noise and a little distortion. What matters is how you define "little". At times through the years a Big Deal has been made of the argument for going without a preamp, or using a simple passive volume control and nothing else. IME, most components benefit from an active buffer that isolates the source from the load and thus often provides better sound despite the "little" noise and distortion it adds.

YMWV (Your Mileage Will Vary) - Don
 

microstrip

VIP/Donor
May 30, 2010
20,806
4,698
2,790
Portugal
We had a thread on this subject in WBF - even a poll.

http://www.whatsbestforum.com/showthread.php?6898-Opinions-on-the-role-of-the-preamp-in-a-modern-single-source-system

I will quote myself: I have tried several times to avoid the active preamplifier - high quality passives, integrated amplifiers that had just a potentiometer at the input, digital sources having analog or digital volume and good driving capability, but never got a fully satisfactory result. IMHO, it is a key component in a system, as it conditionates the choice of the source and the amplifier.
 

edorr

WBF Founding Member
May 10, 2010
3,139
14
36
Smyrna, GA
We had a thread on this subject in WBF - even a poll.

http://www.whatsbestforum.com/showthread.php?6898-Opinions-on-the-role-of-the-preamp-in-a-modern-single-source-system

I will quote myself: I have tried several times to avoid the active preamplifier - high quality passives, integrated amplifiers that had just a potentiometer at the input, digital sources having analog or digital volume and good driving capability, but never got a fully satisfactory result. IMHO, it is a key component in a system, as it conditionates the choice of the source and the amplifier.

I have the exact opposite experience. I tried various preamps hoping to get better sound. It worked with the original PS Audio Perfectwave (I used it with the Modwright 36.5 LS/PS). Then with the MKII upgrade to the DAC the benefits disappeared. With the DAC2X, SQ takes a step back with a preamp. One could make the inference that if the the analog output stage of the DAC can drive the poweramp, the preamp is subtractive. If it is not, the preamp may be an essential component in the chain.
 

flez007

Member Sponsor
Aug 31, 2010
2,915
36
435
Mexico City
I have tried all possible routes, even to the extent of using some highly regarded passives, my conclusion - since I have more than one source -is that a was preamp needed in my case, and it is more than impendance matching, since a preamp in the chain fixes all together comparing with the little roughness that no preamp brings into the equation.

I tried this with SS and tubed amps alike, digital and analog volume controls and different implementations of passive preamps.

Again, this is just my case and in my system.
 

garylkoh

WBF Technical Expert (Speakers & Audio Equipment)
Sep 6, 2010
5,599
225
1,190
Seattle, WA
www.genesisloudspeakers.com
If the digital volume control is done properly which means conversion to floating point, level adjusted, dithered and then truncated to target rate, say 24-bits, then the math says you have not lost any resolution. Noise floor is raised slightly but 24-bit samples are already 4 bits of noise. An analog pre-amp as you say, adds distortion and noise so it is not perfect either.

That said, my subjective testing sometimes shows better quality when a pre-amp is used. Not sure if this is placebo or real :).

My results concur, but I would say that my subjective testing sometimes shows preferred quality when a pre-amp is used.
 

FrantzM

Member Sponsor & WBF Founding Member
Apr 20, 2010
6,455
29
405
My results concur, but I would say that my subjective testing sometimes shows preferred quality when a pre-amp is used.

Same here .. I had a DAC with a very good Volume control. It seemed to me that going through a Preamp resulted in better overall sound .. Must say that the Preamp had a wonderful Phono stage and at the time I was fully invested in analog ...
 

edorr

WBF Founding Member
May 10, 2010
3,139
14
36
Smyrna, GA
Thanks all for weighing in. Given all the nuance expresses here, I am just surprised about my experience. It was not even close. The preamp made things worse by a considerable margin.
 

AudioExplorations

New Member
Apr 5, 2012
653
5
0
Preamp vs. no preamp round 2....

FWIW, I started that other 22 page thread mentioned earlier. The conclusion from that was, for people who actually did testing with and without preamps, 19 out of 29 members here on WBF prefer the sonics with the preamp.

There are a number of reasons why this may be the case, I won't go into that (see last page of said thread).

I have run my system power amp direct for the last 12 months (source is Weiss Medea Plus converter). Against my better judgement I am now (again) trying out a preamp in the chain just to confirm my previous findings that they do not being anything sonically. I have been able to borrow a Lyra Connoisseur 4.2L SE for a week. If any pre out there will better the sound it will be this one... I will report back as to whether it will be staying.
 

edorr

WBF Founding Member
May 10, 2010
3,139
14
36
Smyrna, GA
Preamp vs. no preamp round 2....

FWIW, I started that other 22 page thread mentioned earlier. The conclusion from that was, for people who actually did testing with and without preamps, 19 out of 29 members here on WBF prefer the sonics with the preamp.

There are a number of reasons why this may be the case, I won't go into that (see last page of said thread).

I have run my system power amp direct for the last 12 months (source is Weiss Medea Plus converter). Against my better judgement I am now (again) trying out a preamp in the chain just to confirm my previous findings that they do not being anything sonically. I have been able to borrow a Lyra Connoisseur 4.2L SE for a week. If any pre out there will better the sound it will be this one... I will report back as to whether it will be staying.

19 out of 29 is very consistent with the reasonable hypothesis that what sounds best is system (and may be personal preference) dependent. Let us know what you learn from the shootout....
 

AudioExplorations

New Member
Apr 5, 2012
653
5
0
Adding the Lyra into the chain resulted in a loss of resolution and addition of distortion/grain across the audioband. The pre also added a slight hum but this was not bothersome. At first I was under the impression that the pre brought some extra drive/body to the sound but no longer think this is the case at all.

That's it for me now on the preamp debate, I have tried 4-5 high end preamps, and now the $25K Lyra connoisseur 4.2L se and the sound has always been better going power amp direct (from my Weiss Medea Plus into both a burmester 911mk3 and a dartzeel nhb-108b).
 

About us

  • What’s Best Forum is THE forum for high end audio, product reviews, advice and sharing experiences on the best of everything else. This is THE place where audiophiles and audio companies discuss vintage, contemporary and new audio products, music servers, music streamers, computer audio, digital-to-analog converters, turntables, phono stages, cartridges, reel-to-reel tape machines, speakers, headphones and tube and solid-state amplification. Founded in 2010 What’s Best Forum invites intelligent and courteous people of all interests and backgrounds to describe and discuss the best of everything. From beginners to life-long hobbyists to industry professionals, we enjoy learning about new things and meeting new people, and participating in spirited debates.

Quick Navigation

User Menu

Steve Williams
Site Founder | Site Owner | Administrator
Ron Resnick
Site Co-Owner | Administrator
Julian (The Fixer)
Website Build | Marketing Managersing