Tube pre for class d recommendations

owentdc,

     From my experience owning 3 class D amps and those I've heard in others' systems, I believe they all have some common sonic characteristics: very good bass response, low noise floors, good dynamics, are highly detailed from top to bottom and and have an overall sound best described as neutral like 'a straight wire with gain'. 
     The neutrality of class D amps are beneficial since the sound imparted by the preamp, and the sound discrepancies between stock and swapped tubes, are usually easily discernible.due to the amps just faithfully amplifying the inputted signals without any audible sonic additions or subtractions. 
     The variances I've noticed between all of the class D amps I've heard is mainly with treble responses that typically are very detailed but also have ranged from smooth and almost tube-like to a bit overly bright. 
     Fortunately, I've perceived the treble of the 3 class D amps I've owned as detailed but still smooth and, on good recordings, there's even some tube-like euphonic sweetness I hear. 
     I've read some good reviews on your Wyred4 Sound STI-1000 but, apparently, you perceive some treble brightness.
     I've actually perceived more treble brightness from my previous class AB amps (Adcom, McCormack and Aragon) than my subsequent class D amps. 
     I auditioned many good tube preamps  searching for one to sweeten the treble on my high powered ss amps driving my Magnepan speakers.
      This was about 1990 and I recall many tube preamps I tried in my system not sounding as warm and euphonic as I was hoping such as Audio Research, Cary and a few others.
     The right solution for me turned out to be a VTL 2.5 tube preamp but I had to swap out the stock Russian or Chinese tubes for a set of 4 expensive ( $200 at the time) NOS Mullard tubes to get the warmth I wanted.
     Currently, however, I've discovered my system sounds best for music and ht just connecting my main source, an Oppo-105,  directly to 3 class D amps without using any preamp at all.  The Oppo serves as a Blu-ray player, cd player, Dolby Digital 5.1 surround sound processor as well as a dac for streaming internet radio and NAS cd/hi-res files. 
     Sure, this configuration is typically dismissed by fellow A-gon members and others as sub-standard, but I don't mind a little ridicule since it's so streamlined and sounds so good to me.  I also know some are just not aware of the high quality and versatility of the Oppo BDP-105
     You may want to try this first if your sources allow before adding a tube preamp.  If not, I'd suggest finding a good local dealer who'll let you try out some loaner tube preamps to audition at home in your system.     
Tim  

orpheus10:

"If class D is so good, why do you need a tube pre? Why not a class D pre?"

Hello orpheus10,

     I’m not aware of any class D preamps, either. But it’s my understanding that there’s no sound quality or other benefits to be gained from creating a class D preamp unless the goal is to incorporate some DSP (digital signal processing) functionality into the preamp in addition to the typical preamp functions of a switching control for source selection and a volume control.
     Traditional preamps, whether solid-state or vacuum tube driven, are low voltage and wattage devices that typically operate in class A. The normal class D benefits of low electrical consumption, low wasted energy converted to heat and low operating temperature are much less significant with a preamp than an amp.  There's also a wide variety of traditional preamps available that each imparts its own unique sound qualities to the total system sound.   My opinion is that this is a form of signal processing since it enables consumers to either pick their flavor or attain a more neutral overall system sound
     Good quality traditional preamps whether ss or tube, however, have proven to be excellent preamplification devices for very low voltage source signals. They work equally well paired with class D amps as they have for decades with traditional linear amps. provided care is taken to properly impedance match; the general guideline being that the input impedance of the amp should be at least 10x the output impedance of the preamp.
Why not a class D pre? The answer is there’s really no need unless digital inputs or DSP is required on the preamp.

Tim

owentdc,

     I googled your integrated and found a review on 6 Moons.com.  Here's a link:
https://6moons.com/audioreviews/wyred3/sti.html

     It's a very positive review and it contains separate evaluations of the linestage preamp and power amp sections of your integrated.  
     The line stage preamp section was isolated for evaluation by the reviewer connecting his own amp to your integrated's input/output loop.  His stated results were that the line stage had a very neutral quality similar to  passive preamps he's heard.  
     Unfortunately, he didn't evaluate any separate preamps for the review, ss or tubed.  
     With the existing line stage preamp section of your integrated being so neutral, this tells me that using various external tube preamps will provide a significant change to your system's overall sound qualities.  Good news.
     But I also believe your integrated likely incorporates an input buffer circuit in the line stage input section which may explain the lack of brightness on your integrated. 
     I'm not certain how this buffer circuit would affect the sound quality when a separate tube preamp is connected to the loop.  Perhaps others know and can chime in.

Tim

Hello big_greg,

I’ve read that tubes, when pushed hard, tend to add even order harmonics to source signals while solid-state tends to add odd order harmonics.
Both are inaccuracies, but we perceive even order harmonics as pleasing to the ear as a sense of warmth while we perceive odd order harmonics as unpleasing without a sense of warmth and more a sense of neutrality or even brightness when excessive.
I’ve tried a few newer ARC preamps in my system but not the LS26. I wouldn’t describe any of the ARC preamps I demoed as warm.
Swapping out the stock tubes for aftermarket ones, however, could add varying degrees of warmth depending on the brand and type of tubes used, if that’s you’re goal.
Just thought you’d like to know,
Tim

big_greg,

     Great to hear you're wanting the ARC LS26 to be detailed and revealing because that's what I experienced with some newer ARC preamps in my system.  They sounded more like very good ss preamps to me.    Hopefully, the all tube ARC and Jolida combination will be to your liking

Best wishes,
   Tim