Tube pre for class d recommendations


Would anyone care to share their experience running a tube preamp in front of some Class d amps?
owentdc
I had a great Cary Audio SLP98 F1 in front of Sanders and Bel Canto amps for Maggies with great results for years.  Cary phono stage on that preamp was excellent as well, and they really worked well together.
I havne’t tried this directly, but based on the ICEpower 250 modules in my amps, and how they sound, I’d suggest some modern Audio Research. They are less analytical than their past, not quite as chocolate/syrupy as CJ, but certainly a little more euphonic to my ears.

If it's any help, these particular class D modules sound a LOT like the Parasound Halo line. If you find a good tube pre for them they'd probably be about the same.

Best,
E
Just give it your best shot. Pay attention to input impedance of your amps- some tube preamps can't handle input impedances much below 30K or so! There are tube preamps that can handle low input impedances in amplifiers with no worries.
A Freya pre-amp used ahead of a Merrill Audio Taranis Class D power amp sounds great to me.  The Freya (4-6SN7s) replaced an Opera Reference 50 (dual-6H30/EZ80-rectified) pre-amp. Both pre-amps worked just fine but the sound with the Freya is more refined...detailed but relaxed at the same time.  

The Freya is very flexible offering singled ended and balanced inputs and outputs as well as pure passive, JFET buffered, and tube gain output modes.  It's very transparent and readily shows differences in tubes and interconnects.  It is also being used with a First Watt F7 amp and a Hegel H200 integrated when used as power amp.  

What sorts of things related to use with Class D are you wondering about?
@atmasphere,
Hi Ralph.  I had the UV-1 on loan after it first came out from Alternative Audio in Dundas, Ontario.  It fed the power amp of my W4S STI-1000.  We couldn’t track down the buzz and I took it back. Too bad, it did give a slight tube sound that I was looking for.

@ghosthouse,
The Freya looks interesting.  Thanks!
The past 7 years have been very satisfying with the MacBook Pro >>JRiver >>Stello>>Moon 300D>>Harbeth SHL5.  I’ve just got an itch again about mating a tube pre with the Class d.

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

Hi Ralph. I had the UV-1 on loan after it first came out from Alternative Audio in Dundas, Ontario. It fed the power amp of my W4S STI-1000. We couldn’t track down the buzz and I took it back. Too bad, it did give a slight tube sound that I was looking for.

We’ve found that the UV-1 can be sensitive to power cords. We had a customer recently that ran into this. While all the data isn’t in, he found that by simply moving the cord around, the preamp got quiet.




Interesting Ralph.
I have 2 foundation research LC2...one grounded and the other lifted ...done by Ed....that I used. Meaning, I was really giving it the old college try to make it work.
orpheus10, I’m not aware of a class D preamp. 


I’m very pleased with the Freya, Owen. Had it a couple of years now (3?) and no problems. You can spend more, you can buy better but at $700 it is a solid bargain. 5 year warranty and there’s a 15 day money back return option (less 5% restocking and shipping costs) if you don’t like it.

The first (and maybe even some of the second set) NOS Russian tubes that were supplied with the Freya were a little noisy. Schiit replaced them promptly no problem, though now running NOS American tubes. Other than occasional tube noise on rare occasions, the unit is very quiet. Volume full up with nothing playing there is NO noise at the speakers...ear 2" from the tweeter, etc. The resistor ladder type volume control does click when you change volume settings but I’ve heard the same from a Conrad Johnson pre I auditioned.

Other than ensuring impedance compatibility, as Atmasphere mentions [ensure load impedance of amp is at least 10x (some say 20x) output impedance of preamp] I don’t know any reason a Class D amp wouldn’t work with a will-chosen tube pre-amp.

As for everything audio, there are always haters. Wolf Garcia is another Freya user and advocate. Check out some of his posts on the topic. Good luck.
I am an owner of Don Sach's 6SN7-based tube preamp.  It is better than any preamp I have had in my system.  It is a bespoke preamp that has gone through several iterations of upgrades to its current state.  For around $2700 or so, you will have a SOTA tube preamp that will outperform preamps costing vastly more money.  
If class D is so good, why do you need a tube pre? Why not a class D pre?

There aren't any. There's no cost/design effectiveness in a preamp being class D. It's far simpler to go Class A, and you don't waste the same amounts of heat.

You could also make the same kind of silly argument of "if you like tubes why do you need a solid state amp?"

Best,
E
I second or third the Schiit Freya recommendation, but you'll need to swap out the stock tubes. I'm using new production Electro-Harmonix 6SN7 with very pleasing results not only with a pair of Ghent Audio mono blocks but also in front of a newly acquired Carver 275. It's versatile and the price is right.      
I have a Rogue Hydra which is a hybrid Class D and have had it paired with three preamps for extended periods of time and was very happy with all three.  Ayre K-5xeMP, PS Audio BHK and Art Audio Composer.  The latter two are tube units.  I also tried and demo'd 4 other preamps through time.  All solid state which I hated.  

The brightness that still lingers in most Class Ds can absolutely be offset by a tube pre.  I found the stock tubes on the PS Audio to leave a bit of brightness but rolling in a pair of Tunsgram's did wonders.  The stock tubes on the Composer are amazing and will temper that brightness beautifully.  Full disclosure, I am the importer for Art Audio.  

I offer a 30 day no questions asked return policy.  If you don't like it, return it and you only need to pay shipping back to CT.

I believe Rogue has been doing tube pre and Class D power for some time now.
Interesting Ralph.
I have 2 foundation research LC2...one grounded and the other lifted ...done by Ed....that I used. Meaning, I was really giving it the old college try to make it work.
Lifting grounds is not going to do it with the UV-1 since its really hard to ground loop it through the power cord.

We did run into a hum problem with a dealer of ours that was using a Topping amp which is class D. The amp was only $80.00 on Amazon so I bought one but could not duplicate the complaint with his UV-1 or any that we had here in the shop. My best guess is that there was something wrong with his amp but its all water under the bridge so I don't think we'll ever know. Otherwise we've been able to solve all the hum problems we've encountered with the UV-1 except for that one. The dealer sold that preamp and the customer seems to like it a lot.

The UV-1 has an aluminum chassis and a steel bottom cover. It can hum if placed near a power transformer or the like since aluminum does not shield at audio frequencies.


My Freya (now the "vintage" version as it has a hotter output tube section which, alas, the newer versions have tamed somewhat) sounded quiet with the supplied "mystery" tubes, but they were boring so I moved on to new Tung Sols that look great! Also boring...so...NOS Sylvania "chrome domes" and RCAs have been doing the job real well and I’m not bored with them. My power amp is a single ended Had Firebottle HO (yes, a HO...says so right there) with a 6SN7GTB (NOS alleged Amperex) driver tube and I only mention that to point out the synergy of tube types, which means nothing. What does mean something is the fact that tubes are more fun than Class D will ever be...tubes can be looked at, burn yer fingers, and swapped out willy nilly. Class D can stay in my little Ampeg "Porta Flex" bass amp, flying above your head in phased array PA speakers, and in the future perhaps a better toaster, but not in my hifi or guitar amps...no no no. Less heat, efficient power...boring.
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  
Thank-you Tim.
I'm not experiencing treble brightness. It's just that after 7 years, I'm getting the itch to try something.  The Wyred is amazing. 
Just curious after reading so many have paired tube prevwith as amp.  The beauty of my integrated is that I can make that happen.
ghosthouse3
The Freya is very flexible offering singled ended and balanced inputs and outputs as well as pure passive, JFET buffered, and tube gain output modes. It’s very transparent and readily shows differences in tubes and interconnects.
+1 Very good recommendation. Has everything remote, 4 x inputs xlr or se, best volume potentiometer you can get for less than $1k



orpheus10

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

orpheus10, I’m not aware of a class D preamp.
Forest and trees celander forest and trees.
I understand where your coming from orpheus10

"Being facetious is the word that comes to mind."

Cheers George

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
I just ordered a used ARC LS26 from an Audiogon dealer to mate up with my Wyred 4 Sound ST-1000 MKII. I should be able to share some impressions next week. 
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
@noble100 

Tim,

Thanks for the comments. 

I'm not trying to warm up anything with the LS26.  I expect the LS26 to be detailed and revealing.  I currently have a Jolida Fusion tube preamp in that system and it's pretty good, but I don't think it's letting all the music through and isn't truly balanced like the LS26. 

I have combined the Wyred 4 Sound amp I use in that system with my Modwright LS100 and it sounded wonderful.  I expect the LS26 to be similar, and if so, it will be an improvement over the Jolida.
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