The issue here isn’t the cables (their impedance is insignificant when compared to the output and input impedances of the DAC and amp and sub), however, by placing two parallel loads on the DAC’s output, the DAC “sees” a lower load impedance on its output, which, depending on its output impedance, can attenuate its output and potentially affect the frequency response.
Also the articles you cited are about transmission lines, waveguides and coaxial cables operating in the RF band, not interconnects in the audio band.
You can feed the sub a high level input from the main speaker outs. Most decent subs for hifi use have high level inputs which are preferred as you get same signal path for all speakers, not line level which is used for sending LFE from a surround amp. Hi
But then, you’d face a similar impedance problem: the subwoofer would lower the impedance of the power amp’s load, which is already low. You’d also have to worry about the subwoofer’s power handling limits. I think it would be easier to screw things up.
A powered subwoofer with speaker level inputs presents a high impedance to the external stereo amplifier. The goal is not to draw any current from the external stereo amplifier, only to tap the signal, which then gets fed to the internal amplifier of the powered subwoofer.
AJ
3 Likes
James_I
(The truth is out there but not necessarily here)
117
Yeah it’s right that it’s no issue to plug your subs into the speaker taps on your power amp. REL recommends this. There’s no impact on speaker sound. IMHO if a sub doesn’t have high level inputs, it’s a HT sub!
I have found that it does impact sound to split a preamplifier output. However…many preamps have both balanced and single-ended outputs and I have found that using both of those usually doesn’t impact the sound. YMMV.
Thanks for the info. I didn’t know that. My subwoofer has speaker inputs, but I never considered them, because I wouldn’t have a dedicated LFE channel anymore. Even for music, it may be better to take advantage of the receiver’s LFE settings.
You can use both at same time on any decent sub they are not exclusive. In a Hifi setup LFE is redundant unless you’re listening to 5.1 as you would need a 5.1 processor and power amp to tap the LFE so your back to a preamp for that. But you can have the LFE connects to your AVR and high level connecting to the amp outputs and you get best of both. This is how BK Elec recommend to use their subs. The av manages bass for LFE where the sub does for highlevel input.
I think I mentioned earlier in the thread that I do use a pre-amp in my main rig. Besides Roon for music playback, I also feed the TV output to the hii-fi via a miniDSP. The miniDSP is programmed with the same REW room correction profile as I have in Roon’s DSP. After significant room treatment, a little frequency response smoothing was still needed. I was going to mention @Johnny_Too_Bad here regarding his signal purity/cognitive dissonance comment (DSP allows final tweaking of a treated room, but as it acts in the digital domain, it’s free of noise and distortion. Analogue preamps add noise and distortion, although some less than others), but it seems he earned himself a ban, presumably for over-zealous use of the flag functionality. Maybe he’ll read this when he’s back agian in July…
Roon goes into the DAC via USB and then balanced from the DAC into the preamp (Benchmark Media HPA4), miniDSP goes into the preamp via RCA.
Anyhoo, my power amps are Benchmark AHB2s and they perform best at minimum gain (9.2dB) at a sensitivity of 22 dBu (9.8 V RMS). This is way beyond the output level of most normal preamps. Most normal balanced preamps output at 14.3 dBU (4 V RMS). Benchmark has its roots in pro audio where signal levels are much, much higher. The HPA4 output goes up to 28 dBu (20 V RMS). Combined with the AHB2, it gives ridiculous amounts of incredibly clean, ultra-low noise and ultra-low distortion gain.
I can pull a -120 dBFS test tone up to audibility with this setup. System “synergy” really is a thing, but not in the way the hi-fi press describes it. There’s a sweet spot where impedance and gain matching between pre and power gives the best measured performance. It’s not arbitrary and needs an understanding of the properties of each component.
Maybe I’m still missing something, but I’m not sure you get the best of both this way. If the two entries are not exclusive, will the subwoofer sum them up? If so, the output would be guaranteed “correct” only if the receiver’s LFE output was idle (e.g. in a “pure stereo” mode) OR if the receiver removed the bass it sends to LFE from the channels it collected it from. I’m not sure that happens if you configure your front speakers as “full range”. If the receiver sent bass to both LFE and front speakers, that would basically double the bass in the L and R channels at subwoofer. Not only could that cause clipping, it would also mess up any room correction (which I use). The safest bet is to keep the channels independent, as intended.
THis is correct. ALmost did this with chromecast and airplay on an anthem mrx540 trying to volume control from the phone on roon. Its terrible suddenly skips 20 steps and BOOM.
You’re not misunderstanding but in certain use cases it not really the option to choose but for many it is. It’s designed so you can have an avr and Hifi amp be able to use the same sub and use highlevel for Hifi where its desirable as it’s using the amp circuits so its sound signature is also passed on to the sub.
So one is connected to the Hifi amp the high level input and one is connected to the receiver the low level input. You could also connect both to an AVR if you want to have a different input for movies or music listening.
The sub has its own crossover and volume settings for the highlevel input you configure this for hifi listening. The sub has setting to bypass its own bass management for line level so the avr can manage this. You would set fronts to small speakers and set the crossover accordingly. The amp will route all to lfe and highlevel isn’t active at all.
If you need to have the front speakers set as full in a surround setup then using highlevel inputs really are not suitable as yes you will likely cause overload and clipping. Both can be connected but you don’t use both at same time although it’s possible to do so. Common sense prevails here.
If you need to set fronts at full then highlevel isn’t something you would use.
I you speak with most any dealer he will tell you that YES, of COURSE a preamplifier will do wonders for your SQ. Even if you have a 20K DAC, a GOOD preamplifier will add value to your signal path. I have a SONORE RENDU SE and A Mola Mola Tambaqui DAC and wouldn’t consider using Roon without my Krell preamp. That said, if you are considering using a basic or entry level preamplifier, than by all means do direct from DAC to amplifier
What specific value to the signal path does the Krell preamp add? Something other than switching and volume control? What is altered from the DAC output?
The best advice I can offer is to watch Bill Parrish explain in this video. Bill is the master USA distributor for premium brands like Mola Mola (whose Tambaqui DAC I own), as well as the formidable Audionet line from Germany, and Vivid speakers to name a few. I regard Bill as one of the preeminent authorities in high end, as do many others. He would know.
Hello,
I put the preamp output of my Auralic (Altair G2.1) and Meitner (MA3) directly into my power amp. Before I always had my McIntosh preamp (C2700) in between.
Long story short, with both devices it was clear relatively quickly that the preamp had to remain. I liked the SQ much better in terms of spatiality, resolution and display.
And yes, the preamp has tubes, which in my case affect the SQ.
Another point concerning the volume control…I have several ZIPP Copenhagen for the garden via Airplay. It happens to 70% that the ZIPP play on full LS the first time you turn it on and play (only via Roon). I don’t have to have that over my stereo system in the living room.
Just try it, there will be no consensual opinion and arguments here. It also depends on the respective devices who does a good job and how.
From my point of view, it is by no means only the dealer who benefits from a preliminary stage.
It’s been said (and refuted) that a preamp can only add noIse and distortion. Another thing a preamp can do is create an optimum gain structure for some HiFi setups. Modern DAC’s have fairly high output levels.
For example my Schiit Yggdrasil has an output of 4 Vrms with a noise level of -110 dB ref 4 Vrms.
Let’s feed that into my McIntosh MC 2301 power amplifier. Its output is 300W into 4 ohms (34.6 Vrms) with an input voltage of 3.4 Vrms with a noise level of -117 dB. This power amp then has a gain of approx 10 V/V or 20 dB.
The Yggdrasil’s noise output of -110 dB will get amplified by 20 dB and appear at the MC 2301’s output at -90 dB. That’s referenced to the amp’s full output voltage @ 300W. But I listen at about 3 watts output mostly, which is 20 dB below full output.
So referenced to my nominal listening levels I now have a system with an snr of 70 dB.
So even if the digital attenuator is perfect the analog output stage of the DAC is far from it.
So I’m my case I need the 20 dB (or more) attenuation provided by my preamp to maintain the noise floor set by my power amp. My preamp is very quiet at 20 dB of attenuation so it does not add to the noise of the power amp.
Your mileage may vary. Do the math on your gear and see what happens. My gear is not state of the art spec wise so you find gear where the DAC can directly drive the power amp with no degradation.
When Lumin upgraded their entire product line via free firmware process to Leedh Processing—basically a novel digital volume control—I became an adopter of their streamer direct to amp approach. A high-end Swiss manufacturer—Soulution—similarly adopted Leedh. Joël Chevassus, a well regarded French reviewer who contributes to 6 Moons, basically stated that the process virtually outclasses all the high-end preamps of which he is aware. At any rate, it’s not for everyone but it’s a nice way to both preserve SQ and eliminate another box and cables.
My experience is exactly the opposite. 0-50% on the slider is huge. I think it may depend on where you have the volume on your preamp set (assuming you have one). If you are using the dsp to control volume it makes the most sense (imho) to set the preamp at max (or disable it if that is an option on your unit). Likewise, if you are using the preamp to control volume, it makes the most sense just to leave the roon volume at max.
