@betula Exceptional write-up. Thanks for doing that. Not sure I'll ever be able to find and afford that specific Mullard 5U4G, but happy you've found your grail rectifier.
ZMF Aegis Official Thread
- Thread starter AnyDave
- Start date
Wow! Well said, and such a fantastic writeup! @betula you are a huge asset to this community.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!
You are too kind, but thanks!Wow! Well said, and such a fantastic writeup! @betula you are a huge asset to this community.
If anyone is interested in my GZ34 that betula used, drop me a PM. It won’t be silly prices.
On a different note, I decided to let some rare EL50s go, if anyone is interested.
Wow again! Someone better jump on those, if you want one of the best tubes out there. I am all stocked up and money is tight at the moment, or I would buy those in a heartbeat.
Schuie Driver
100+ Head-Fier
Awesome write up!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!
I do not like to promote any tube combinations for two reasons. First, the choice of a working combo is highly dependent on personal taste, headphones in use and DAC. Secondly, the more we promote a certain tube type, the higher some sellers will bump up their prices. Some prices are already completely unreasonable and feel like sellers are trying to pray on a rich and/or unknowledgeable buyer.
Still, in a way I feel I owe the community with sharing my current favourite roll (which keep changing, it is not set in stone).
In my rectifier comparison post you have seen that my ultimate rectifier (at least for now) is the Mullard 5U4G (slim base, welded black plate with pan getter). My input tubes have long been the Mullard (slim base!) ECC35s. These to me easily best the popular TungSol VT229 or RCA 4654 red base inputs with clarity, depth and definition still with a natural tone that the others cannot quite match. (Some listings for a pair go around £400, but not impossible to grab a deal for £220.).
When it comes to power tubes, there are endless possibilities and several (!) exceptional choices on the Aegis based on sonic preference and main preferred music genres. EL34 tubes are fine, but I found all KT66, KT88, KT90, EL38, EL39, EL50, 4654 an improvement on the stock EL34s. KT66 has great mids, but not as clear as the others. KT88 has great balance and clarity. In fact, I am interested in trying some higher quality KT88s like GEC. I only heard the TAD bundle KT88 and acknowledged the potential in that type, but the TAD version didn't quite impress me.
I found the EL38 fantastically spacious with large images but lacked refinement and detail/resolution. EL39 was better than EL38 with a denser and more interesting, more coloured tone: lovely tubes. KT90 is very precise and detailed but doesn't quite have the spaciousness and stage of EL38 or EL39. Still the Ei KT90 (MK2) is a lot of fun in its detailed precision and pretty good tone. Perhaps the only tubes I kind of regret selling.
The regret however disappears when I reach for the EL50 family. These to me best all previous power tubes. There is spaciousness, refinement, detail but with a lot of 3D positioning and natural tone/timbre. The mesh plate version has the best mids: lush, clear, lifelike. The solid plate versions have better clarity, detail, refinement, but a hint less rich in the mids. I am curious to hear other 4654 variants and the EL51. Maybe one day.
Anyway, Mullard 5U4G (slim base, welded black plate with pan getter) + Mullard slim base ECC35 (1952) + RT (Philips) red base, solid plate 4654 are killing it for me. Clarity, resolution in spades, exceptional 3D spaciousness, depth and layering galore, bass definition with great punch and precise slam, sweet, clear and lifelike mids, open, natural and detailed treble. Versus stock, this combo elevates the Aegis to next level for sure. IMO with expensive NOS tubes like these, my Aegis in its current form outperforms some amps twice the asking price. A happy camper here, thanks @L0rdGwyn.
Still, in a way I feel I owe the community with sharing my current favourite roll (which keep changing, it is not set in stone).
In my rectifier comparison post you have seen that my ultimate rectifier (at least for now) is the Mullard 5U4G (slim base, welded black plate with pan getter). My input tubes have long been the Mullard (slim base!) ECC35s. These to me easily best the popular TungSol VT229 or RCA 4654 red base inputs with clarity, depth and definition still with a natural tone that the others cannot quite match. (Some listings for a pair go around £400, but not impossible to grab a deal for £220.).
When it comes to power tubes, there are endless possibilities and several (!) exceptional choices on the Aegis based on sonic preference and main preferred music genres. EL34 tubes are fine, but I found all KT66, KT88, KT90, EL38, EL39, EL50, 4654 an improvement on the stock EL34s. KT66 has great mids, but not as clear as the others. KT88 has great balance and clarity. In fact, I am interested in trying some higher quality KT88s like GEC. I only heard the TAD bundle KT88 and acknowledged the potential in that type, but the TAD version didn't quite impress me.
I found the EL38 fantastically spacious with large images but lacked refinement and detail/resolution. EL39 was better than EL38 with a denser and more interesting, more coloured tone: lovely tubes. KT90 is very precise and detailed but doesn't quite have the spaciousness and stage of EL38 or EL39. Still the Ei KT90 (MK2) is a lot of fun in its detailed precision and pretty good tone. Perhaps the only tubes I kind of regret selling.
The regret however disappears when I reach for the EL50 family. These to me best all previous power tubes. There is spaciousness, refinement, detail but with a lot of 3D positioning and natural tone/timbre. The mesh plate version has the best mids: lush, clear, lifelike. The solid plate versions have better clarity, detail, refinement, but a hint less rich in the mids. I am curious to hear other 4654 variants and the EL51. Maybe one day.
Anyway, Mullard 5U4G (slim base, welded black plate with pan getter) + Mullard slim base ECC35 (1952) + RT (Philips) red base, solid plate 4654 are killing it for me. Clarity, resolution in spades, exceptional 3D spaciousness, depth and layering galore, bass definition with great punch and precise slam, sweet, clear and lifelike mids, open, natural and detailed treble. Versus stock, this combo elevates the Aegis to next level for sure. IMO with expensive NOS tubes like these, my Aegis in its current form outperforms some amps twice the asking price. A happy camper here, thanks @L0rdGwyn.
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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!
You always dazzle me with your writing! Just exceptional
It really gets very preferential and system dependent once we get to the crème a la crème tubes
ckhirnigs113
Headphoneus Supremus
Excellent write-up @betula! I've tried most of the rectifiers you described except for the super-rare slim-base Mullard 5U4G. Interestingly, I would describe the metal-base GZ34 and U52 in almost the exact opposite way from you. You could swap the words "GZ34" and "U52" in your paragraphs, and it would match my findings with these two rectifier types. I found the U52 to be the warmer and more natural-sounding, while I found the MB GZ34 to be the thinner and more analytical-sounding. You seem to have had the exact opposite findings, haha. It's amazing how differently we can hear these tubes.
I'm glad you found the best rectifier for your preferences. I won't be able to resist trying this elusive Mullard 5U4G if one ever pops up for a sane amount of money. Thanks for taking the time to provide all your impressions in such detail. It's much appreciated!
I'm glad you found the best rectifier for your preferences. I won't be able to resist trying this elusive Mullard 5U4G if one ever pops up for a sane amount of money. Thanks for taking the time to provide all your impressions in such detail. It's much appreciated!
As an owner of the DIY Aegis, my wallet is happy that 5U4G/U52 rectifiers are not compatible 
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Think I need to take a break from this thread. I’m enjoying the best sound I’ve heard from my current tube combination but then you read other posts, and gets you thinking. But as mentioned, someone else’s great combo might not be yours. Glad there unlimited possibilities.
As an owner of the DIY Aegis, my wallet is happy that 5U4G/U52 rectifiers are not compatible
I haven’t even modded mine with the 4uF caps so my wallet is also safe from the Taks 274B
I'm prolly gonna do that when I decide to upgrade to comet silver foil caps.I haven’t even modded mine with the 4uF caps so my wallet is also safe from the Taks 274B
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