Hello all… Thank you to @souldriver for inviting me to this thread. I am a long time head-fi member and someone who loves music above all else. I am definitely not a gear head, but do have a lot of fun gear. I am not a collector per se. If I don’t use it, I get rid of it as I don’t like the feeling of stuff sitting my shelf collecting dust. I feel guilty and want to find it a good home, no matter how good it may be. It is obviously not being used and so it must go. My system consists of 2 Roon End Points. Fed by a Roon Rock and a streamer. One with an EC Aficionado and a CFA3 running off the Musician Taurus, and the other is my Radu 4P1L HPA and a Mjolnir Pure BiPolar MK2. Both my CFA3 and Pure BiPolar MK2 are the only particular versions made the way they are and I love having both a tube amp and a bipolar SS amp running off of each end point. My DAC on my other end point is the Cen.Grand DSD Deluxe. The PB MK2 is the only one Birgir built and is truly wonderful. My CFA3 is also built specifically to my preferences and specifications and while I have heard several other CFA3’s, it sounds different. Better, no, just different. I am not someone who likes to piss on other’s people’s stuff. We all have our preferences, budgets and things that we love and as long as people are listening, that is all that matters to me.
I just picked up the 4P1L about a month ago and have listened to it principally since it arrived. That isn’t to say my other amps have gone dormant, but I am really enjoying this amp and love listening to it. There are a lot of similarities to the way people describe the sound of the 300B to this amp. I also believe I have the only one he has ever made in headphone amp form of this particular configuration. He has built this amp in power amp form to great results and that led him to try it and build it as a headphone amp. He is using 4 of the Pentodes in triad mode where he is only using 3 of the 5 electrodes to create a triode sound. Having a DHT amp, I can say that he very much succeeded in his quest. The amp weighs 45-48lbs, which I was not strong enough to put on my desk and needed help from a friend as I have a very rare terminal illness on the ALS gene and it is taking away my strength faster than I’d like. The amp has the exact quality that was stated above many posts before in that the pocket is set with a very nice, full and textured bass and drums, while the midrange has a halo effect where the midrange instruments circle above the pocket and allow the melodies to jet at you from all angles. I have gotten to know Radu and how he designed this amp, and why he designed it the way he did. When I got it, the guy who sold it to me felt it sounded too much like the Stratus V3, which he owned and let it sit on a shelf for more than a year unused. Having heard the Straus V3, it doesn’t sound like that amp at all. But we all hear differently so who am I to judge. He sold it, and I bought it. So, I have had to go through the break in process and have watched the amp transform gracefully in the past few weeks. It still has a bit to go, and that is the opening up of the top end resolution which I hear in snippets, so I know it is there, but just not completely opened up all the time yet. However, the amp is still so wonderfully built and the sound is simply beguiling.
Radu is a very nice, very talented builder who takes great pleasure in providing products for people who enjoy what he does and the sound he creates. It might not be to everyone’s liking, but it suits my needs and preferences perfectly. I listen to a lot of bluegrass, jam bands, jazz, funk and motown (A Detroit kid), with a healthy dose of Bob Seger (grew up next to his manager and know Bob well), and I absolutely love Springsteen’s Live Series Songs on Keys on the Radu as well. Among many other artists from Beck to Xavier Rudd and so many others. The gutteral quality of Bruce’s vocals and the clear sound of his piano are laid fully bare on this amp and while not a traditional DHT amp, it sounds as much DHT as many 300B amps I have heard from the Cayin to the Feliks Envy and others. In addition, my ECAF is a 2A3 amp outfitted with single plate 2A3s and a metal base GZ-34 and sounds fantastic. However, EC amps are a different thing all together. It is an extremely fast, neutral and unique amp with wonderful qualities that are very different from the 4P1L, as well as any other DHT amp I’ve heard. A very close friend has a special version of the Studio B, and he also finds that EC amps tend towards extremely fast with a hint of dryness that is easily mitigated with the right chain. I mitigate the speed of that amp with an R2R DAC that helps to give my ECAF more decay and slows it down just enough to allow its extremely large soundstage and unique properties from the tertiary windings a chance to really shine.
The Radu is just different. It sounds as much like a DHT amp as many that I have heard and the way it handles mid range instruments and image specificity is a really beautiful thing. I am having a hard time pulling myself away from this amp. I have rolled NOS tubes in it and have also used the New Stock tubes it was meant to go with on purpose and have had varying effects, but also the NOS tubes get the amp a little hotter than it should be, and so I use them very sparingly.
I find the amp is ready to listen after 5 minutes, but sounds best and is fully biased after 20+ minutes. It is a very 2nd order dominant sound, and was designed to keep them as far away from 3rd order and other harmonics to give the amp as clean, natural and transparent a sound as possible. In addition it has the same TKD Volume solution as the 300B end game and he uses Lundahl Transformers throughout. So, the amp is not as expensive as the 300B, but from what I am hearing, I don’t feel that anything is missing. It is simply a fantastic amp and one that I am super happy and proud to own. It has incredible synergy at 2.65 vrms SE out of my Deluxe DAC. As for headphones:
I have used all manor of headphones and the amp puts out a nice 3 watts into 32 ohms. My Code X, HEKv2 Non-Stealth, Abyss JOAL, Caldera Closed, Atrium Open and Final D8K Pro all sound great on the amp. I prefer my JOAL, HEKv2 and Code X on my bipolar amps as they love the speed and power of those amps, but I wouldn’t feel anything was missing if I didn’t own those amps as well.
Anyways, just thought I would add something to a thread that has been dormant for 15 plus months. Another Radu is in the thread now, and at some point I will add some pictures, and I am still deciding if my hands are strong enough for me to write another review and give the amp its due and post on here and head-fi. I absolutely love the Atrium Open on this amp and have never heard that headphone sound better. Mystifying to me that I am pulling out even more from a headphone that isn’t the most technical, but has an incredibly alluring quality that makes it a headphone that is just meant for listening, not analyzing and I mostly listen to music that is meant for enjoyment, not analytical ensemble music. I met someone who told me that unless you listen to classical, you aren’t a true music lover or audiophile. That my reviews which I have been writing for a while being devoid of classical music makes them obsolete in his eyes. It is the only way to listen to music. Well, I have been to close to or more than a 1000 concerts and have a pretty discerning ear. And while I don’t like classical music, being an audiophile, or a music lover has nothing to do with anything other than loving what you like and finding the best way to hear it. Since I can’t go see 50 shows a year anymore, I have turned that passion and all the money I spent traveling as a weekend warrior to shows into this hobby and have built a system that I love. This amp is a welcome addition and has made my listening that much more enjoyable. In any logical plane I exist, that is enough for me…
Currently listening to a FLAC Billy Strings show. An incredible cover of the Alice in Chains song Nutshell into the traditional Dreadful, Wind and Rain done famously by Garcia and Grisman. Billy’s guitar is a revelation and he has some great pickers next to him, and he says “My name is Bill and its been a thrill”. The Radu is a thrill with each passing day. It is not a 300B/Hashimoto, but Radu and I have discussed building me one and he feels with my preferences that it might be a bit laid back for my tastes as I tend towards fast amps, and the 4P1L is certainly very dynamic with a wonderful 2nd order sound.
Thanks!