The Zu Formula?
I'm the second owner of an Osprey 3.1. I heard it in your room at the Lonestar Audiofest and was knocked out with the pairing of it with your reference monitors. I found one on USAM shortly thereafter and pulled the trigger, hoping it would be a good marriage with my Zu Soul Supreme speakers. I'm coming from single ended tube amps (Almarro 318b and 205 Mk2) which after judicious tube rolling, cable choice etc., sounds terrific. Needless to say, the Osprey is a completely different animal (pun intended). The dynamics are a revelation, the power on my 97 db speakers adds a fantastic dimension. My DAC is a NOS tube buffered MHDT Orchid. Needless to say, my goal in sound is not the most "hifi". It's for a real, natural sound. Alas, I'm struggling with glare on a lot of my digital library (no vinyl here). I'm not complaining about crappy recordings sounding crappy. The problem is recordings that sounded great on my also very revealing Almarros. I saw a video on Youtube where James mentioned having experience picking good tube sets for Zus. I'm interested in hearing about that. The previous owner had completely different speakers (Harbeths) and invested in upgraded tubes both at time of purchase, and then more upgraded sets afterwards. I have rolled all this stuff as well as some of my own and not found something that tames the top end. I've got different speaker cables/interconnects/digital cables and played with all of that. The tamest stuff is all in place. The one thing I haven't played with is power tubes. It's got the stock Tungsols 7581As. Aside from the 6C33Cs in the A318b, which there's exactly one source for, I've acquired all kinds of vintage tubes and firmly believe in their benefits. It's one thing to shell out for 2 EL84s and a 12AX7 to completely retube the A205, or a 6SN7/6LN7 to retube the preamp section of the A318b and buying a quad of highly sought after 6L6GCs for the power section of the Osprey. So, this leads to my question of what is the formula you've found with Zus? Following up, how much change can I expect from a power tube transfusion? Of course, the ones to get are the RCA blackplates. Not an inexpensive upgrade, but the sonic characteristics sound like the best attempt to solve the tipped up treble with my Soul Supremes. I'll list what I got with the amp so you can see what I've played with.
Came with the amp:
Phillips JAN 12AT7WC
Siemens ECC81 (medical grade)
GE JAN 12AU7
Raytheon blackplate (organ tubes) 12AU7
RCA clear top 12AU7
I've tried pairing the tamest (British) ones in the 12AT7 positions and it's still not enough. I don't really have a laid back 12AU7, something I still need to try.
Thanks for any insight. If I had the cash, I'd just buy your monitors, but that just isn't happening.
I think you are going to have to call me. 936-662-5100. I have never heard of a Raven amp having "glare". Something is just not right. And the Tung Sol's are a good power tube. Not my absolute favorite, but I can listen to them any time without wanting to change. Yes, the RCA black plates are the best ever made, but they will not have that much effect on your situation - taken into consideration all you have explained. It has to be something else.
There has been a change I can't really explain. I have a REL T9 subwoofer that has been connected "high level" and wanted to check out the 80Hz bypass on the Osprey. I bought a sub cable, connected it, changed the crossover setting, enabled the bypass and boom!. Huge improvement. I don't have an explanation for why this would change high frequency presentation, but it does. The bass has better definition and less bloat, and you can tell the added available power just adds authority. You can really crank this to high volume levels and it stays very composed. Maybe you have some way to explain how this made the treble grain disappear.
I'm going to let James Connell answer this one, as he is the expert in answering speaker and subwoofer related subjects, and explaining situations like this with full subject matter. He is a gifted speaker designer and knows exactly how this all works.
I am just glad that you figured it out. I knew it wasn't going to be tube related, nor amplifier related. There are just too many Raven/ZU customers out there. I am glad you have it figured out. The subwoofer outputs are absolutely designed to work like this - and in this configuration you have finally gotten to. My expectation is that your situation will keep getting better and better in tiny increments as you feel out, listen to and adjust the system to your room and speakers. What you are going through now is realizing just how good that amplifier is, and how well it will eventually team up with those very capable speakers.
After you get to where you think you have reached the peak performance level, then - and only then - is it time to slowly go through and listen to that tube complement pair by pair, which has some excellent ones in it.
My suggestion is going to be - start with:
Row 1: Siemens ECC81
Row 2: Brimar 13D9 or Philips Mullard ECC81/12AT7
Row 3: JAN GE 12AU7 black plates
The next move would be to change or swap - one pair at a time - Row 1 with Row 2 and find out which is best for your room and speakers. Leave the GE's in Row 3... they are your best Row 3 pair for now. The Raytheon 12AU7 black plates are going to be excellent tubes also, but will be slightly less controlled I suspect, especially with the ZU speakers. They may be a little warmer, but you will miss the tight clean bass slam and deepest frequencies - unless your room is going to have some reflections that defeat those frequencies. I also suggest that - if you can, your listening chair NOT be all the way up against the back wall unless you have drapes to dampen the bass reflections. Also, always have your system on the long wall in a room. This will make a HUGE difference in overall resolution and lower wall reflections.
The biggest rule of setting up a listening room is - have as much reflection dampening uneven surfaces as you can stand. Paintings and artwork on the walls, uneven surfaces as much as possible to break up standing waves. If you are a vinyl buff, put those racks along the side and back walls if there is a large enough room to do so in. Large vases with plants, oriental or tall floor-standing rectangular or round lamps, thick couches with lots of padding, possibly with secondary seating on each side of the main listening chair or couch will all help.
A room that soaks up reflections will ALWAYS sound better than an empty room with wide open walls with nothing or little on them. If you have hard floors, a big area rug, the thicker the better, will help immensely. From some of what I heard you describe, this may have been occurring in that room, although without crucial information, or pictures - I am just guessing and explaining what has always worked for us in the past - being that we have been in a hundred hotel rooms across the nation over the last decade. Cluttered rooms with a lot of stuff hanging on the walls, and carpeted or rug covered floors (in the center of the room anyway) will help you get the most out of your system.
It will also save you thousands over having someone come in and design a room full of expensive diffusers, bass traps and all that stuff. Clutter is your best friend. It can absolutely be done with taste and music business flare. This is also why intimate clubs with a full crowd always have the best sound for live music - or with a good sound system. Flat walls and lots of big windows, and also large screen TV's sitting right in the middle of your back wall between your speakers - are NOT your friend.
Sorry for the long response, but this is a forum designed to help Raven and other audio nerds get the best out of their systems.
After spending a good bit of time (and money), I have come upon a cocktail of tubes that works with my Zu Soul Supremes and I thought I'd share in the event it might help someone else trying to find their "happy place". Of course, this depends on everything else in your system. For me, with a digital library running through an MHDT Orchid DAC, this produces a very enjoyable, balanced sound that produces no fatigue across a very wide range of music.
Factory provided Tungsol 7581's or RCA Black Plate 6L6GC's
Raytheon Triple Mica JAN 12AT7WA
Mullard 12AT7WA Square Getter 3 hole Plates
Raytheon 12AU7 Black Plate
Another one that works well is the RCA 6201 Black Plate (12AT7) but it's just edged out with the Mullards. I acquired the RCA 6L6GCs and was very underwhelmed with the preamp tubes that came with the amp (including some upgraded tubes), so I went back to the Tungs. I've always had good luck with Raytheon tubes in other amps so I decided to go that direction. How it's possible that a manufacturer of tubes has a "sound" across models is kind of beyond me, but they do. The Mullards were one I had read worked really well with Ravens. Once I had that trio together and was really happy with it, I put the RCA 6L6s back in. Now they sounded like everyone described. At the moment I prefer them over the TungSols, but it won't be too long before I switch them back. The 7581 is more dynamic and has better snap. I have a bunch of tubes I tried that didn't get me where I wanted that I can also share if anyone is interested.