But the reasons they give for the differences between an active preamp and a passive preamp don’t apply to the DS’s passive output. The DS has a flat output impedance across the frequency band that stays flat regardless of load (the attenuator is just a shunt after all.) No normal amp will be a significant load for the 120 (or so) ohm output of the DS.
The other item is that high capacitance interconnects can interact with the transformer output (whether active or passively driven) to cause a resonant section. On the high level setting of the DS this causes peaking a little ways out of the analog frequency band, and a dip on the low level setting. Hence if very long or high capacitance interconnects are used (or if a passive attenuator and higher capacitance cables… are used) the sound quality can also vary (plus or minus) depending on whether the 20dB attenuator is used.
If your system is level matched you may get better results directly from the DS to the power amp. But using a preamp allows proper level matching with any source (including the DS) and can allow longer interconnects (or higher capacitance interconnects) right before the amp without transformer interaction.
BHK very specifically says he does not know why an active tube preamp sounds better than a passive device. All he knows is that it does sound better. Paul is off camera saying that he prefers a tube preamp between his DSD and his amp. I do too.
I’m not trying to argue, just add some info that may not be obvious to everyone. A slight expansion:
There’s nothing wrong with preferring a preamp (I use one and recommend that everyone try one with the DS), I just said that the results are system specific and some systems can sound better without one. I also mentioned a variable that Bascom (and Paul) don’t normally talk about: the transformer/cable interaction that is independent of whether the DAC is active or passive.
I also stand by the simple statement that passive devices don’t (necessarily) play by the same rules as a passive preamp, I’m definitely agree that the compromises of a passive preamp keep them from being ideal in most systems, but passive output devices have fewer constraints on them than passive preamps so lumping them together is not always appropriate.
DSJ has a stated output impedance of 200 ohms (balanced). My active speakers (JBL 708Ps) have an input impedance of 300 ohms (balanced). Would they be a good match? (From my single ended days I’ve read repeatedly that the input impedance should be 10 times the output impedance.)
Please limit replies to knowledgable sources yet simple enough for me (a dumb as a bag of rocks guy in electricity) to understand.
Are you certain about those numbers? A 300Ω input impedance is extremely low and no, if that were actually true, I would not suggest feeding it with a 200Ω output impedance.
Thanks for the reply Paul. Got quoted the 300 ohm number directly from a JBL tech. Based on Ted’s discussion above (which is over my head) was hoping it wouldn’t be a problem with DSJ.
It’s highly unlikely that the JBL 708P’s have an audio input impedance of 300 Ohms - they are designed to work with professional and consumer level inputs. You’d want to use the -10dBV input sensitivity selection.
FWIW the output impedance of the DSJ doesn’t change with frequency over the audio band and I suspect the 708P’s input impedance is uniform too.
The 75pF / meter is the most relevant spec: you might hear something with 10 meters of interconnect, but almost certainly not with only a meter or two.
Hi Ted, you said “if you system is level matched you may get better results directly from the DS to the power amp.” Which levels of the source and the amp are you referring to? Further, if they aren’t matched, what would you believe is an acceptable range between these numbers? Or must it be matched precisely?
It’s a combination of your amp gain, your speaker sensitivity and the DS (in general it’s a combination of the output levels of each box, the input sensitivity’s of each box and their gain) Preamps let you fix any mismatches… You could maybe take the output voltage levels of the DS, your amps’s gain, your speaker sensitivity and your knowledge of how loud you like to listen and figure things out, but it’s much more reliable to just try it with the actual components you want to use.
Being off by say 6 or 10 dB (a factor of two or three) isn’t a big deal, but 20 dB (a factor of 10) could be a problem (hence the 20dB attenuator option.)
IMO you probably want a good preamp in your system (or at least available to your system) to make it easier to try any new components, amps, speakers, etc. If your system sounds better without the preamp between the DS and the amp, good, but you still probably want a preamp to help with any future changes…
Well you’ve all got me thinking. Because while I do have strong opinions which I try to base on good reasoning and sensible experimentation, often enough I’m still wrong. Maybe a pre-amp circuit would, for some reason, make my music more enjoyable. So I would like some of your opinions please on whether the option I’m looking at might be a good one or not.
My Musical Fidelity M8 stereo power amp has two pairs of bridged mono circuits operating in fully balanced mode, and I want to take advantage of that. Running balanced direct from the DS Sr’s transformer output stage I avoid ground loops and benefit from some common mode noise rejection. (My interconnects aren’t braided so the noise rejection is compromised, but it’s still heaps quieter than my previous single-ended system.)
I don’t need any gain. In fact I would probably set the pre-amp to about -20dB to push the DS noise floor away and then just use the digital volume most of the time. (The pre-amp I’m considering doesn’t have a remote control.)
I have only one source component – the DS. I have zero interest in adding more of them, so I don’t need a lot of inputs.
Physical space is limited, as is budget for this experiment, and frankly I’ve never heard a vacuum tube I’d want to live with, so the BHK and similar class of product are not an option.
Given all of that, the most suitable product I’ve been able to find so far is the Auralic Taurus MkII, which just happens to also be a headphone amp. The main concern is that it converts from balanced to single-ended to perform attenuation with a stereo Alps pot, then puts that signal through a phase inverter to produce a newly balanced output.
Any opinions on the Taurus? Any solid state balanced alternatives I should look at? Is the Stellar GCD likely to deliver the goods being used solely as a pre-amp?
I heard the Auralic Taurus MkII a couple of years ago as a headphone amp. It is very, very good. My recollection is it has preamp outputs as a freeby, but they are not optimized for the unit to serve as a preamp. They make a dedicated pre which is a better choice for your application (I think it also has headphone out as well if this is important.).
My experience is that one needs a really good preamp for it to be additive and to improve the sound when inserted between the DS and an amp. The BHK falls into that category but I understand you do not want to try this pre.
I would not hesitate trying either Auralic. My experience was positive and their headphone amp or pre may work superbly in this role.
Thanks Elk. No more dedicated pre from Auralic – the Taurus MkII is all they offer today. The pre-out modules are still class A balanced affairs with very low output impedance. I’m not sure in what way that could be sub-optimal as a pre-amp, though one review spoke about different voicing for the different roles.
Searching for a good explanation why using the DS as a digital pre amp with the -20 dB attenuation is so good at least when connected to a class A solid state power as the Accuphase A-60 using the balanced mode and pure ofc copper cables (no silver at all). Set the A-60 to -3db got me the best S/N with an holographic precise image of the soundstage making MQA files from Tidal difference from red book even more impressive.
My experience runs against the norm so I thought I should speak up to balance things a bit. I tried the BHK preamp and I did not get an improvement in my very revealing system. I also tried a bunch of excellent NOS tubes. They were better but still not as good as no preamp.
If your system is well matched for impedance and you don’t need extra gain, I believe no circuits are preferable. Unless you want to colour the sound in some way. If impedance levels are a problem (rare these days) then a cheaper option would be to try a buffer stage.
I suggest you try the preamp in your system and see for yourself. PS Audio is very kind to let us do this.