ZMF Aegis Official Thread

[AnyDave]

So I believe you use the Chord Dave with Mscaler. I was going to say going from the RCA to the Mullard was like adding the mscaler to the Dave. Brings the clarity, separation and layers to another level. So I can imagine if already starting with this as your source, the gz34 is going to be hyper real and probably no longer musical.

I’m using a Naim HE, which some might claim is mid-fi compared to the Chord setup but I prefer its sound signature of having more PRaT with more bass presence. Previously owned the Chord combo before the Naim. So could be that my preference on tubes is balancing out the Naim HE and increasing the resolution. Vs starting out with ultimate resolution and softening it a hint. Same with how cables increase/decrease clarity and warmth.

But even if we were all listening to the exact same setup, we’d come away with different impressions. I’ve seen this at CamJam. We all have our own preferences and also hear differently. So when making decisions based off others, have to take all that into consideration. I bought RCA rectifier based off rave reviews but was disappointed but other hand gz34 fat base also highly recommended and worked out for me.

I currently have a Dave/Mscaler at the office. At home, I have a TT2/Mscaler, as well as a Benchmark DAC3, Holo Spring2/L2, Denafrips Aries, Chord Qutest ,and iFi iDSD Sig (and maybe something else I'm forgetting about at the moment).

 

[iamoneagain]

I currently have a Dave/Mscaler at the office. At home, I have a TT2/Mscaler, as well as a Benchmark DAC3, Holo Spring2/L2, Denafrips Aries, Chord Qutest ,and iFi iDSD Sig (and maybe something else I'm forgetting about at the moment).

So what’s your favorite pairing with the Caldera open? And I guess what’s your current favorite ZMF headphones other than something not yet disclosed.

 

[DACattack]

Now that I've finally finished reading through the thread from the beginning, some quick comments.

I'm still very new to the Aegis universe, though not to tube amps in general. However, all my previous experience has been primarily with the 61NP and 6SN7 tube families and their equivalents, so this has been an entry into a brave new world. I've managed to collect a decent assortment of tubes to roll now, but I've been very deliberate to listen extensively to both the stock tubes, and the TAD bundle, to really internalize their sound signatures, so it's easier to discern differences as I roll.

Three things are very evident in this new playground: (1) Aegis sounds really great "out of the box" with both the stock tubes and the TAD bundle; (2) The sheer variety of tubes you can roll in Aegis is frankly astonishing (it's a far larger pool than any other tube amp I've heard or owned) and this flexibility is both intoxicating and overwhelming (thank heaven for the tube capability spreadsheet and all the commentary in this thread); (3) Sonic preferences between users are indeed personal (what someone hears as endgame doesn't necessarily mean it's endgame for all), so what's "best" varies user by user*--and I'm certain headphones and genre preferences play a big part here--but no matter which compatible tube you put in Aegis it's nearly guaranteed to sound good. Beyond that it's simply varying levels of good and great and finding synergy with your prefs and other equipment in your chain. (DAC pairing plays a big role too it seems.)

Once more, I have to say, well done @L0rdGwyn and ZMF. Aegis is a fabulous amp and I can't wait to hear where this tube rolling (and headphone) journey will take me.

* - for other amps, especially those with more limited rolling options, I've found stronger consensus over what's considered the ultimate roll.

 

[AnyDave]

So what’s your favorite pairing with the Caldera open? And I guess what’s your current favorite ZMF headphones other than something not yet disclosed.

I'm not sure I have a definitive answer on that, as lately I've been too busy to do a lot of tube swapping. Right now, my production Aegis has 5691 preamp tubes, Mullard EL37 power tubes and a GEC U52 rectifier. In my DIY Aegis at home, I think I have 5691 preamp tubes, Tung-Sol 6550 tubes, and I don't remember what rectifier. I recently snagged a pair of Mullard ECC35 tubes, so I am looking forward to trying those out. But lately when I make changes, it hasn't been a lot of back and forth dedicated listening. I have just been throwing the new thing in and using it for a bit. If I don't like it as much, I change back or to something different.

As far as headphones go, whatever I'm currently working on tends to get the most time on my head for practical reasons (which is often multiple models). Even for the released models, it's not unusual for me to have 2 or 3 different variants (generally prototype versions) kicking around. My favorite tends to be a bit of a moving target. Sometimes, it'll be the newest, unreleased thing I'm working on, but sometimes I'll revisit an older product model and I'll get pulled into that one for a while. I like certain things that each model does, so my mood will often drive what I choose to listen to if I am listening for pleasure (which admittedly has been in short supply lately).

That's a bit of a non-answer, but it's the life an acoustic engineer. Things are a bit different when your hobby is also your career.

 

[iamoneagain]

I'm not sure I have a definitive answer on that, as lately I've been too busy to do a lot of tube swapping. Right now, my production Aegis has 5691 preamp tubes, Mullard EL37 power tubes and a GEC U52 rectifier. In my DIY Aegis at home, I think I have 5691 preamp tubes, Tung-Sol 6550 tubes, and I don't remember what rectifier. I recently snagged a pair of Mullard ECC35 tubes, so I am looking forward to trying those out. But lately when I make changes, it hasn't been a lot of back and forth dedicated listening. I have just been throwing the new thing in and using it for a bit. If I don't like it as much, I change back or to something different.

As far as headphones go, whatever I'm currently working on tends to get the most time on my head for practical reasons (which is often multiple models). Even for the released models, it's not unusual for me to have 2 or 3 different variants (generally prototype versions) kicking around. My favorite tends to be a bit of a moving target. Sometimes, it'll be the newest, unreleased thing I'm working on, but sometimes I'll revisit an older product model and I'll get pulled into that one for a while. I like certain things that each model does, so my mood will often drive what I choose to listen to if I am listening for pleasure (which admittedly has been in short supply lately).

That's a bit of a non-answer, but it's the life an acoustic engineer. Things are a bit different when your hobby is also your career.

Thanks that’s a pretty good answer for someone who has unlimited access to ZMF headphones including prototypes. I suppose one of the many benefits of working for ZMF. It also makes sense that you wouldn’t consider there to be one perfect headphone but many different ones to suit different needs. Would make it hard to work on newer models if only in pursuit of the one perfect headphone and already found it.

 

[SunRa Fan]

So strange, just put the The RCA 5R4GY DD back in and no longer hear the strange soundstage. It sounds right. But I understand why you’re using the better headphone cable. The RCA rectifier is lacking clarity compared to the Mullard. And it’s lacking precision. It’s a nice sound but I would be looking for a better cable as well. But with the Mullard gz34 fat base f31, the 2k Copper works since don’t think I’d need anymore clarity. Also the RCA is missing the high end sparkle of the Mullard. Be aware this is only with the f31 fat base version. The f32 resolution is probably about the same as the RCA, the fat base brings things to another level but it cost a lot more but to me worth it. Haven’t heard the metal base version but read the fat base has stronger bass, so that would be my preference.

Edit: sorry I was editing it and got few likes before the edit. It’s early on West Coast so thought had time to delete what’s no longer true.

Just did quick comparison with The Halo Benders - Virginia Reel Around the Fountain and with Mullard the separation and layering are definitely on another level. It’s possible someone still might prefer the RCA since it’s smoother and guitar is less harsh but find it accurate with the Mullard. The Mullard also has much tighter bass control.

The Mullard f31 is on the list for me. It makes me happy that you had another go and at least no longer experience the reverb issue. The GSP is more than a cable as far as I'm concerned. The resolution increase might as well constitute a next generation Caldera. ZMF really should talk this up more on their website or even highlight a bundle. They're just so good together. Not so much with the Atrium.

 

[iamoneagain]

The Mullard f31 is on the list for me. It makes me happy that you had another go and at least no longer experience the reverb issue. The GSP is more than a cable as far as I'm concerned. The resolution increase might as well constitute a next generation Caldera. ZMF really should talk this up more on their website or even highlight a bundle. They're just so good together. Not so much with the Atrium.

When getting new cable I did think about that GSP cable but knew I didn’t need any more resolution with my tubes. The GSP with Mullard fat base might be too much, just like how I imagine the Chord dacs would be.

I’ll keep the RCA rectifier just in case but don’t see me swapping it out with the Mullard anytime soon. And so far happy leaving in the kt90’s. Still so musical with maybe more pinpoint accuracy over the kt88. It’s that accuracy with the Mullard is something I haven’t heard since listening to Focal Utopia straight out of Dave/mscaler combo. Tried Caldera straight out of Dave at CamJam and wasn’t a good pairing.

 

[SunRa Fan]

When getting new cable I did think about that GSP cable but knew I didn’t need any more resolution with my tubes. The GSP with Mullard fat base might be too much, just like how I imagine the Chord dacs would be.

I’ll keep the RCA rectifier just in case but don’t see me swapping it out with the Mullard anytime soon. And so far happy leaving in the kt90’s. Still so musical with maybe more pinpoint accuracy over the kt88. It’s that accuracy with the Mullard is something I haven’t heard since listening to Focal Utopia straight out of Dave/mscaler combo. Tried Caldera straight out of Dave at CamJam and wasn’t a good pairing.

As far as Chord DACs go, farther down the ladder is fine. I’m using the Qutest with the Aegis.

 

[martelanc24]

As far as Chord DACs go, farther down the ladder is fine. I’m using the Qutest with the Aegis.

I was using a Chord Mojo (first version) and it also sounded just fine. I then, last month, made myself a DIY R-2R DAC using a Soekris dam1021 DAC module. The sound opened up, I have a better sense of space and where sounds are coming from, I can pick up even more details than before, just this sense of clarity all around, compared to the Mojo. The only thing is the bass that hits ever so slightly less in some EDM tracks. I would say it pairs nicely with the Aegis.

Anyone else using any Soekris DAC with their Aegis?

 

[iamoneagain]

Oh I’m not saying Chords dacs would be bad pairing at all. Just saying the higher ones has so much detail retrieval that might not pair as well with the gz34 fat base is all.

The mojo is sort of par with the original Hugo. That was more musical than detailed and can see why moving away from it opened things up. Original Hugo has small soundstage. Hugo 2 and Qutest are around the same level of detail. I’m wasn’t a fan of the Hugo 2, so was sort of afraid to try the Qutest. Never really heard the Hugo TT or TT2. Skipped right over and got the Dave/mscaler. Hyper detailed but still musical.

I was contemplating about keeping the Naim HE but with new power cable and recent firmware update, it sounds great with the Aegis. So no reason to spend money for the sake of spending. Think I’m all set for now. See if can just live with my setup and not change anything for as long as possible.

 

[theveterans]

I was using a Chord Mojo (first version) and it also sounded just fine. I then, last month, made myself a DIY R-2R DAC using a Soekris dam1021 DAC module. The sound opened up, I have a better sense of space and where sounds are coming from, I can pick up even more details than before, just this sense of clarity all around, compared to the Mojo. The only thing is the bass that hits ever so slightly less in some EDM tracks. I would say it pairs nicely with the Aegis.

Anyone else using any Soekris DAC with their Aegis?

Beef up the PSU filtering on your Soekris and experience earth shattering bass impact and extension

Don’t forget about power cords and fuses too since they do help with the bass as well

 

[SunRa Fan]

Oh I’m not saying Chords dacs would be bad parings at all. Just saying the higher ones has so much detail retrieval that might not pair as well with the gz34 fat base is all.

The mojo is sort of par with the original Hugo. That was more musical than detailed and can see why moving away from it opened things up. Original Hugo has small soundstage. Hugo 2 and Qutest are around the same level of detail. I’m wasn’t a fan of the Hugo 2, so was sort of afraid to try the Qutest. Never really heard the Hugo TT or TT2. Skipped right over and got the Dave/mscaler. Hyper detailed but still musical.

I was contemplating about keeping the Naim HE but with new power cable and recent firmware update, it sounds great with the Aegis. So no reason to spend money for the sake of spending. Think I’m all set for now. See if can just live with my setup and not change anything for as long as possible.

Even though the Qutest and the Hugo2 have the some core FPGA, they aren't voiced the same. The Qutest was given a warmer sound vs the Hugo2 which is known to have a leaner sound. With regards to the Naim, you should consider keeping it always because Naim is no longer the Naim of old. Ever since they got swallowed by Focal their products have been declining in quality. I've seen longtime dealers start to abandon the brand and a lot of the engineers behind the famous power supplies have started to show up at other companies. I own two Supernaits so this pains me to say.

 

[iamoneagain]

Even though the Qutest and the Hugo2 have the some core FPGA, they aren't voiced the same. The Qutest was given a warmer sound vs the Hugo2 which is known to have a leaner sound. With regards to the Naim, you should consider keeping it always because Naim is no longer the Naim of old. Ever since they got swallowed by Focal their products have been declining in quality. I've seen longtime dealers start to abandon the brand and a lot of the engineers behind the famous power supplies have started to show up at other companies. I own two Supernaits so this pains me to say.

Not to get sidetracked from the Aegis but good to know about the Qutest. It was that lean sound of the Hugo 2 with the Utopia that bothered me. The Naim HE was a much better match and have continued to hold onto it once got the Caldera and added the Aegis. And there’s been talk on Naim forums about Naim’s new direction and issues with sound of their firmware but the latest version, which also goes into their $30k ND 555, seems to have restored some people’s faith in the brand.

 

[ckhirnigs113]

KT90’s still rank up there as one of my favorite output tubes in the Aegis. I realized I had too many of them, so I recently sold some of my extra pairs. I still have one pair of version 2's and one pair of version 3's. To me, they sound practically identical, though from what I've read, version 2 is more sought-after.

As far as rectifiers go, it really comes down to personal preference. The two metal-base GZ34’s I had ended up not being my cup of tea. They had great resolution and speed, but they made the Aegis a little too much like a solid-state amp to me. On the other hand, I have yet to find a tube roll that I don’t like with the RCA 5R4GY w/ DD-getters. I really liked the GEC U52, but in the end, I didn’t like it more than the RCA, so it was an easy decision to sell it.

For reference, I use a Yggy A2 and mostly swap between a Meze Elite and Atrium Closed. I occasionally use my OG Auteur as well. All three headphones sound great with the Aegis.

 

[betula]

Betula's rectifier comparison post

Intro

I had a chance to compare three premium rectifiers: Mullard 5U4G (thin base, welded plates, pan getter), GZ34 metal base (TV1, 1956) and GEC U52 (cup getter). I own the Mullard (found a great deal on it) and U52, the GZ34 was loaned to me by the generous @JTbbb, thanks again!
To my ears these three premium tubes easily beat all the other rectifiers I previously tried. I tried the Chatham (potato masher), RCA 5R4GY single D getter, RCA 5R4GY double D getter, Brimar CV717, Svetlna winged-C 5U4G, stock Aegis rectifier and TAD bundle rectifier, also Mullard GZ32.
Please note, this write up is subjective and only reflects my experience. Comparing tubes is not the easiest task as in different amplifiers with different headphones, preferred rectifiers can change. Personal taste can also overwrite all observations from others, especially when it comes to premium equipment.

Previous experience with Aegis rectifiers

- Stock rectifier and TAD bundle rectifier: they do the job, but they are nothing really special. (Of course, they are already special versus most solid state amplifiers, as I said it is all relative). Pretty much all other rectifiers sounded like a step up in naturalness, fullness, staging qualities and fun compared to these 'stock' options.
- Chatham: Did not like it: sounds hazy, warm and unclear. Perhaps the only rectifier that is not really a step up from the stock versions. It just sounds thicker and hazier.
- RCA DD getter: this is nice; a proper step up from stock. Natural, full, entertaining: real tube sound. Best budget rectifier (I bought mine for £25); excellent value for money. (The single getter version sounds less clear.)
- Brimar CV717: pretty much like the RCA DD, but with slightly improved treble clarity and dynamics. I prefer this to the RCA, although the difference is not huge.
- Svetlana: Huge bass, thick and fun sound. Clarity is lacking even compared to the Brimar or RCA, but still with the right combination of input and output tubes this can be fun with a lot of bass. (Someone earlier in the thread said that this is a cheap replacement for the GZ34 mb. I see where he was coming from: tonality, thickness and bassy character are similar, but the GZ34 is just classes above the Svetlana in clarity and resolution.)
- Mullard GZ32: Pretty much on Brimar level, but perhaps smoother. Another very nice budget rectifier. Sweet mids, good balance, overall no faults with the sound: a safe purchase. Nothing really stands out though and bass is weaker than on the Brimar or on the RCA DD.

At this point I have to mention that I had been and could be happy with some of these more affordable rectifiers. I highly recommend picking one of these up over the stock or TAD bundle tubes, but if you want to enhance your Aegis even further, at some point you will arrive at these three super-premium rectifiers I am about to compare. To me all these three tubes offer a clear and obvious step up from any of the previously mentioned rectifiers. This trio sounds more refined, more spacious, more detailed, more complete and more coherent than anything else.

When I compare these three, please remember that everything I say is relative to each other between these three tubes. It is also worth noting that 5U4G/U52 rectifiers are not compatible with the DIY Aegis by default, only after modifications. The commercial Aegis can use them without issues. It is the opposite with 274B tubes, which is another group of excellent rectifiers, but I haven't had a chance to test them yet as I own the commercial Aegis. (Commercial Aegis can take SE 274B, but some users had issues with that too and SE wouldn't be my first pick of 274Bs.)

This is my pyramid. Your pyramid can differ. To me these are the clear steps up in quality/refinement/balance.


The premium trio:

GZ34 TV1, metal base

Going price is between £350-£450, although some opportunist eBayers list them for £600.

I love the sound of this one, but it is definitely a flavour tube, with a very rich and dense tone: a tasty and lush, addictive flavour. It still reaches maximum clarity and resolution within the realm of a lush and rich presentation. It is more detailed than any of the 'budget' rectifiers, but not quite as resolving as the U52 or Mullard 5U4G. The stage has good size, but not quite as spacious as the U52 or Mullard 5U4G. Depth is great, width is fine, but height is lacking in direct comparison. This tube is dynamic and energetic, but never sharp. Macrodynamics are outstanding, microdynamics are not as clear and refined as on the other two tubes. Leading edges/transients are a bit more on the rounded side, but it is not slow or soft. There is energy and clarity, but everything is rounded, there are no sharp edges. This good energy and impact is contained and controlled. The GZ34 seems to run out of treble extension and air in the highest registers versus the other two. Treble is smooth and natural but a bit rolled off.. Both on the U52 and Mullard rectifiers the upper treble feels more open and clearer.

The GZ34 metal base sounds musical, fun, and entertains with a great flavour and flair. It is not as clear and accurate/balanced as the other two premium tubes, but arguably more fun than the U52 and more engaging if you like a bit more colour. I think it is best to mix this rectifier with clear and more analytical input/power tubes; it does not need any extra warmth. I imagine this rectifier with Ei KT90s might sound pretty awesome, although the stage will be on a relatively smaller side. This tube has a lovely rich tone and it is an excellent choice, just needs to be paired well with clear sounding inputs and outputs. Mids are nice, sweeter than on the U52 but not quite as detailed. Bass has big muscles on the GZ34, but again not quite as refined as the U52. The Mullard 5U4G has the bass clarity, refinement and control of the U52, but with almost the body and slamming qualities of the GZ34. Neither the Mullard, nor the U52 has the strong, uniquely sweet flavour of the GZ34 mb. This tube is for those who like their coffee with two sugars.

GEC U52 (rounded base, inverted cup getter)

Going price is around £250-£300, although some opportunist eBayers list them over £400.

This is another exceptional rectifier, no wonder it is loved by many and reached a legendary status. The U52 sounds more spacious, more neutral, more accurate and more precise than the GZ34. This is a rectifier that you can (and should) pair with thicker and lusher sounding input/output tubes. The resolution and refinement of the U52 is nothing short of exceptional. This tube sounds thinner than the GZ34, but tonally more natural due to a more neutral overall approach and better balance. Treble clarity and openness is a step up versus the GZ34; treble clarity is really exceptional. This tube is clean, clear, highly resolving but still with a pleasing and sweet tonality. This rectifier is the most neutral out of the three and almost/pretty much as technical as the Mullard 5U4G. The U52 sounds natural, refined, delicate and accurate. Sound through the U52 is more accurate and more realistic than it is through the GZ34, but for some, the GZ34 can be more fun depending on tube combination and taste. GZ34 sounds thicker, fuller, but not quite as clear, spacious and accurate as the U52. Pairing can bring out the best of these rectifiers and then the choice depends only on mood. Both of these rectifiers are fantastic. If I had to criticise the U52 (feels like criticising a Ferrari), I would say the thinner overall sound and the occasionally brighter treble with certain tube combinations won't be to everyone's liking. Compared to the other two, the U52 is leaner, more neutral, brighter, and bass has less body. I would never call it dry, but it is a bit drier than the other two. There is still good bass slam, but from the accurate/precise type and not from the 'window-shattering' version. This is still an absolutely fantastic rectifier and I would probably use it more often than the GZ34, if I only had these two. With the Mullard in my collection, I am afraid neither of these will see much use.

Mullard 5U4G (thin base, welded black plates, pan getter)

This tube is usually listed around £700+, but with patience and luck you can find listings below £500. These are even more rare than the other two. There are cheaper Mullard 5U4G versions with different plates and getters, so the internals need to be checked before purchase. Here I am discussing the version with thin base and the following mica, pan getter:

Tubes often remind me of fine wines or special single malt whiskys. There are truly fabulous and enjoyable single malt whiskys around £70-£90. And then there are some unique rarities going for £200-£300 or much more for a bottle. This Mullard 5U4G is one of these rare specialties.

This is the best rectifier tube I have ever heard and bests both the GZ34 MB and GEC U52 pretty easily (at least for me and for @Wes S). Detail levels are equal if not higher than on the U52, but with better body, a thicker and even more lifelike tone and timbre. We could say, this rectifier combines the best qualities of the U52 and GZ34 MB: supremely clear, refined and highly resolving, yet with a thick and realistic timbre and more note weight/meat than the U52. This rectifier tube has a special and addictive musical quality that reminds me of the Mass Kobo 465 amplifier: it offers a subtle, hard-to-describe sonic/musical sweetness that feels addictive and makes you want to listen more and more. I guess this is what we call 'high engagement level'. Bass is perfection: pretty much the quantity of the GZ34 and quality of the U52 combined. Mids are super clear and supremely lifelike: even clearer than the U52 (they equal in treble clarity, but the Mullard is smoother). Bass clarity is similar to the U52, but the Mullard has more meat and kicks harder. Tonally this tube is even more pleasing and definitely more balanced than the GZ34, with less and more tasteful colouration. Treble, while equally clear compared to the U52, doesn't have the slightest bright edge, just sweet naturalness. The U52 can very rarely display some treble edginess with certain tube combinations. This Mullard always sounds natural, clear, lifelike, without any compromise in bass or anywhere else. To put it simply, for me this is the king of 5U4G/5R4G tubes.

These are my subjective points. Your points can differ. Also, please note that this is not a scientific evaluation. A couple points here and there can change even for me, depending on circumstances.

Conclusion:

All of these three top rectifiers sound beautiful to me and at the end of the day I could be happy with any of them. GZ34 is not quite as resolving as the other two, and also has a smaller stage comparatively. What it offers though is an enjoyable, warm, slightly coloured tone with exceptional bass. U52 and the Mullard resolve very similarly, there is airiness and clarity to a high degree. Mid clarity, separation and depth are even better on the Mullard. The main difference between these two is tonality and body: U52 sounds more neutral and slightly thinner. The Mullard offers U52 resolution with further improved mids clarity, better body, texture and an additional sweetness in its tonality which makes listening immensely engaging. The Mullard is not as thick and coloured as the GZ34, it is perhaps somewhere halfway between U52 and GZ34. I love a highly resolving sound, but only when it is tonally accurate and natural with good timbre characteristics and note weight. On the GZ34 I feel I need to compromise when it comes to resolution, on the U52 I have to compromise a bit on timbre and body (versus the Mullard). This Mullard wonder-tube is absolutely compromise-free to me. Is it worth the extra money? Well, it depends on the deal you find and on your preferences. In theory, rectifiers should live longer than power tubes. If this tube lives two years in my amp (or at least one), I will say it was absolutely worth it. This tube is a rare combination of faultless technicalities and exceptional musicality.

When I started my Aegis journey nine months ago, I was very happy with the RCA DD. It was a huge and real upgrade versus the stock or TAD bundle rectifiers on the Aegis. In fact, one could be happy with this little NOS upgrade forever, but I am one of those curious ones who has to try them all. When it comes to rectifiers in the Aegis, to me there seems to be a clear upgrade path, regardless of the input and output tube combinations. It seems, I have found my king/queen in the shape of this specific Mullard 5U4G. If I didn't have the Mullard, I would probably use the U52 more often than the GZ34. The GZ34 is still fantastic, but I think, compared to the other two tubes, its characteristics somewhat limit the number of music genres it is good with, at least in the Aegis. That said, my wife, who is not into audio, preferred the GZ34 to the Mullard. Another friend here in the Aegis thread prefers his RCA DD versus the U52. Everything is relative, and the choice of rectifier will depend on many different factors like headphones, taste, gear, music, mood and so on. This was only betula's pick. Enjoy the music, folks!