Death of the pre-amp and HQPlayer digital gain?

Audio Gear Talk HQ Player
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Hey @jussi_laako

Let me start by saying your application is simply outstanding - listening test after listening test confirms that a properly setup HQPlayer in the media stream will deliver superior results in most setups. Well done.

Last night, during a listening session, my buddy and I started wondering - “Do you even need an analog pre-amp anymore?” I mean, HQPlayer has digital gain control, why not eliminate the pre completely?

After a little reading, we decided to carefully give it a go - we connected the Meitner MA-1 DAC directly to the Audio Research Reference 150 amp via XLR. It’s rated at 4.6Vrms (+15.4dBu) out balanced. A sample pre is rated at 2Vrms. So unless I’m wrong, the DAC has more than even volts out to deliver a signal to the amp - question is, can a digital gain be on-par or even better than an analog-based gain? Output impedance on the Meitner is the input impedance for the amp at 300 ohms balanced so we’re good on that front.

We gave it a go - first with just Roon feeding the DAC and using the digital gain (volume) control in Roon - works. Then we re-introduced HQPlayer and used the digital gain in HQPlayer - set min volume to -50dB and max volume to -3dB to prevent digital clipping on the high end.

I sat back and listened - and there it was, beautiful sound without a pre. I could adjust the volume in Roon which essentially adjusts the digital gain in HQPlayer. Jussi talks about using volume control in HQPlayer, and how different filter / dither algorithms behave better or worse depending on which ones you choose.

So my question - is this really possible? Is it the way to get un-coloured sound that isn’t slightly degraded by a pre, as any component you add to the chain is going to affect the sound (signal loss through interconnects, circuitry of the pre, etc.).

Much more listening time is needed in addition to some A/B testing with different pre-amps added to the signal path, but likely the digital gain control in HQPlayer is the way to go, perhaps?

@jussi_laako, can you elaborate on which filtering / dithering algorithms are better suited to digital gain? Is digital gain perhaps more destructive to the signal than using a reference quality pre?

Very curious on thoughts and experiences out there.

Cheers,

Derek

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Interesting idea. Your wording confuses me a bit. You say you set it up, and the sound was beautiful, and yet in the next paragraph you wonder if it was actually possible.

Sounds like you answered your own question!

As you experiment further please post results. I’d love to hear more about the SQ you achieve with this setup. I tried HQPlayer via the trial and thought it did add depth and clarity to my very modest system. I’ve been experimenting with a variety of pre’s over the last six months or so with varying results, from simply “no” to fairly satisfying, but nothing has truly excited me, unfortunately. In the absence of a pre that I really like I wouldn’t mind eliminating the need for one.

I plan on trying HQPlayer again via Roon 1.3 when it arrives, which is why I hope you, and others, will add to this thread. I’ll be trying your idea as well, and will add my 2 cents also.

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Last summer I traded in my Lampizator Amber with volume control in for the lampizator Atlantic. The last without a volume control. It went directly into my Belles 350a poweramp. First experiences where good, however after a while I noticed degradation of the sound when I turned the volume in hqp down with more then 20 db. The softer I played the music the worst the music got. Seems to have something to do with using bits to control the volume. The more you correct your volume the more bits are needed to do that.
So I have chosen for a passive preamp. I now use the incredible Tentlab volume control. The sound is incredible again, no matter what volume I play on. Jussi explained somewhere this degradation phenominum, but couldn’t find it anymore.

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I think we all experience a bit of “Success euphoria,” when we try something new that “works.” But further critical listening is what I meant by asking if this was actually possible.

Make sense?

Precisely why I posted this so @jussi_laako could share his thinking.

It’s an interesting idea - jury is still out. Colleague with a terrific ear is coming by today to do some more serious listening. I will report back.

Watch you don’t have an impedance mis-match between those two components. I didn’t look up the specs for you but check that before discounting digital gain control. From my chats with people way way more knowledgeable than me, a mis-match will result in crap sound.

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Perfectly! I experience this all the time. It takes time to transition your ears to a new piece of equipment.

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Awesome.

Sitting here now listening again… Jonathan is coming over in 2 hours to do some critical third party listening. Will report back shortly. Hopefully @jussi_laako will hop in on this chat shortly - very curious to hear this thoughts.

As a backup, just emailed Khozmo in Poland - anyone have experience with their passive preamps? Hoping he has a stereo balanced single-input option.

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I have been using a NAD M51 as a preamp direct into a musical fidelity power amp for years. Sounds great.

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Is that a DAC with no volume control? Sorry, not familiar with NAD model #s.

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Just a word of caution to anyone considering bypassing their preamp… software is not infallible and if you hit a glitch you could easily damage your hearing, speakers, amp or all of the aforementioned. At the very least put a stepped attenuator in the signal path that limits the maximum volume to a level that won’t do damage.

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It has a digital volume control. But though it’s in the DAC I’m sure the principles are similar to one on on a computer program before the DAC. See this from the blurb on their website.

M51 is a fully functional digital preamp with seven digital inputs and one of the world’s best volume controls. As a ‘preamp’ it is totally noise and distortion free because all switching and volume control is done in the digital domain. There are no analogue circuits except for the Class A buffer at the output of the DAC. While input selection is available from a front panel control, volume can only be selected via remote control.

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After 8 hours of listening and another 2 by Jonathan, we have concluded that this approach does sound incredible in my setup. We can’t imagine adding a pre.

Looking forward to @jussi_laako’s comments.

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you have the bdac mkx. I have connected it to active powered speakers.

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like the http://www.tisburyaudio.co.uk/mini-passive-preamplifier

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I have it all in one with the iqaudio digiamp+ hat and yes you have to be a little trepidatious when firing things up after a build for the first time but for the most part it’s pretty safe

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I recall back in the days of the Squeezebox a number of us did this and Sean Adams (the founder of Slimdevices) recommended that you put an inline attenuator in the mix for safety… You never know when software/os hits the skids.

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Thanks @evand - got it the first time! :slight_smile:

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Yes, it works well. :slight_smile: But as I warn in the manual, it requires one to be extra careful to avoid nasty surprises. Because there’s always danger that for example some application like the OS itself accidentally blasts “bling you have new email” sound or something similar to the DAC at full volume.

It is also generally best if the gain matching is such that the power amp doesn’t have so much gain that you would need to use a lot of attenuation. Because regardless of type of the volume control, doing first lot of attenuation followed by lot of gain is sort of counter-productive.

Some power amps like Benchmark AHB2 have a low-gain mode especially designed/suited for this kind of use.

Main rule is that if you output PCM, you need to use some type of dither. There are some recommendations in the manual, but for 24-bit output even industry standard TPDF dither is good choice across the board. At higher PCM rates, one use noise shaping instead to gain extra dynamic range in audio band.

Rough rule of thumb is also that is preferable to have at least 2x upsampling when using digital volume control, especially when output is DSD. So for example if input is DSD64, then preferably output DSD128 when using digital volume control. Or if output is PCM, then use at least 88.2k output rate if input is 44.1k.

The errors of digital volume control are much lower than distortion and thermal noise in analog components. Good DAC has a low noise and low impedance analog stage and output. Adding resistor-based analog volume control on the path increases intermediate impedance (typically at least by 10x) and thus level of thermal noise too. If there are active stages in the pre-amp too as there usually need to be, those also add their own distortion.

Do I have a preamp? In some cases yes, other cases no. In my listening room I have so many DACs (and new upcoming LP player) that I need source selection. Some power amps have two switchable analog inputs and such may be perfect for this kind of setup in their own way.

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In the past, I had found that using -3dB max volume in HQPlayer was efficient - no digital clipping on average. In my new setup without a pre, I find that serious listening is done at the -15dB level - would you consider that good gain matching?

Nice. RedBook I’d been up sampling to 176.4kHz. 44kHz and multiple thereof HiRes music to 196kHz. Sounds like I’m on the right page.

After auditioning many many DACs last year, I settled on Ed’s Meitner MA-1 as it sounded musical in comparison to other DACs that felt like I was listening to sound. I have been extremely pleased with the acquisition and surmise it is low noise and low impedance analog stage and output.

Good to know. Prior to January 2017, the Meitner DACs would only accept single rate (DSD64) input. In talking to Shahin yesterday (sales manager for EMM Labs), he’s asking me to send in my Meitner for an upgrade to V2 that will allow for DSD128 input - sounds like the right thing to do given your observations. Thank you for that.

Again, thank you @jussi_laako for what you do - it’s simply fantastic. In my opinion, you could easily charge 10 times what you currently charge for your software and it would still be an absolute requirement in most systems IMHO. Keep it up Sir.

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I know that many variables – DAC output voltage, loudspeaker sensitivity – factor into the equation. But in general for direct digital volume control use, what would you consider to be low gain in a power amp? Most power amps tend to be in the 27-32 dB gain range for unbalanced connections.

AJ

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Yes, sounds like a good value.