Don,
It is loud but not screamingly loud. I just wanted too make sure I did not have a problem. My speakers have a measured sensitivity of 91.5. It is more than loud enough for me. Thanks for the response.
Richard
Spatial Audio Raven Preamp
Spatial is supposed to be shipping the first "wave" from pre orders of this preamplifier in May, does anyone have one on order? Was hoping to hear about it from AXPONA but I guess they were not there. It's on my list for future possibilities. It seems to check all my boxes if I need a preamp.
250 responses Add your response
Any info on your power amps? Input sensitivity (volts RMS to clip the amp) and input impedance should tell the tale. Transistor amps (with feedback) are typically 1~2 volts to clip amp, and input impedance is typically 10K to 22K. The Bruno Putzey Class D modules are designed so they need they need about 10V drive and an input impedance of 6300 ohms. This non-standard input is intentional; it gives the third-party amp designer the freedom to design an input stage that has the tone color they want: op-amp, solid-state discrete, or vacuum tube. |
Actually if you want to be safe you should expect to drive 2000 Ohms rather than 6K or higher. Typically an input buffer will provide roughly 12dB of gain and allow an input impedance of more like 47KOhms. That would put the total gain in the region of 22-25dB which is plenty for most speakers. |
True. I surmise leaving the input section of the Bruno Putzey modules as they are was a deliberate design decision on Bruno’s part. The modules are an almost-complete power amp, but are incompatible with existing RCA and XLR interfaces, due to the low input impedance and medium-level voltage drive requirements. The OEM is then free to add as much or as little sonic flavor as they like. If they are catering to the ASR crowd, there are superb op-amps these days with truly exceptional measurements (they also sound good). If the OEM is up to a challenge, they can design a discrete transistor circuit, but it is very unlikely it will match the specs of the best modern op-amps. The days of the evil 741 and the mediocre 301 are long gone. The 5532/5532 is very old, dating back to 1979, but is still seen in pro gear. And if the OEM wants to earn the contempt of the ASR folks, they can use one or two vacuum tube stages, which will increase the distortion of the Putzey module a hundred or a thousand-fold. |
@lynn_olson If you simply design an instrumentation amplifier that is balanced and using good opamps, it will work just fine. It seems to be a bit of a testament that so many class D products using Bruno's modules fail at this task thru no fault of the modules!! You don't need much gain either (2 is fine) so you stay well within the requirements of modern opamps, allowing them to be completely neutral. Even then, despite the low distortion of the opamps, they will dominate the distortion character of the finished amp. The power supply requires special attention as well. Class D amps can go from almost no load for a power supply to quite a heavy load, so the power supply has to be overbuilt if you want the design to be musical! It is the variables of the input buffer and power supply as to why you read so many disparate experiences that audiophiles have with class D amps.
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Yes, the requirements for the input/buffer stage are actually quite modest, not even a headphone amp, really. But the current fad for floating 12 or 15V supplies from a switching wall wart limits the output swing and current available. Barely enough for an op-amp (+/- 6 volts), plus losses from local sub-regulation. It makes sense for the op-amp (or discrete circuit) to be fully isolated from the Class D switching module. The Class D module generates program-modulated switch noise ... it's effectively a low-frequency AM transmitter contained within the chassis. That's where the efficiency comes from, after all ... when there's no program material, switching is still going on at 200~500 kHz, but no power is going through the output devices, and very little is drawn from the support circuits. There's no residual Class A idling as there is with Class AB amplifiers. The output devices are either on or off, with only extremely brief switch transitions. As program material level increases, more power and switch noise is created by the output switcher, and filtration demands on the speaker output and AC power supply increase. It is not trivial to silence a 200-watt AM transmitter in a can ... that energy is going to escape any way it can. Through the speaker wires (which make a great antenna), through the AC power cord, and even through the input jacks if it can find a way. Or leaks in the metal can itself. The adjacent linear audio equipment will have varying levels of tolerance for nearby RF emitters, which not usually tested in most test scenarios. Oddly enough, this is an argument for input filtration using transformers to prevent RF emission on nearby equipment. I doubt many will do this, though, since designers that use Class D modules also like the very low distortion of those modules. In the Class D world, distortion specs (and the respect of the ASR crowd) make a difference, |
So I doubt few, if any, designers of Class D amplifiers will use input transformers. The vast majority will use their favorite op-amp, or maybe try discrete op-amps designed for studio consoles. Boutique vendors that have a trademark "house sound" will design discrete transistor circuits that create the house sound. |
@lynn_olson Just to set the record straight, I don't think any class D designer or those planning to use and existing class D module would ever consider using a wall wart as a power supply for the input buffer! The switching noise is far lower than you suggest! In fact so low that many tube amps radiate more noise (due to their rectifiers). As a result, its quite practical to put the input buffer opamps on the same board with the class D section as a complete module and still have it so quiet that you'd struggle to hear its noise floor on a horn system. You really do want the switching noise quite low because if it radiates it can mess with digital devices. Noise is really a matter of good layout. Typically its nice to have the radiated noise about 60dB below the level required to meet EU standards to obtain the CE mark. We used an input transformer on our prototypes. It worked quite well. But they are impractical due to reflected impedances- how well they drive the load has a lot to do with the output impedance of the source driving the transformer. Since the preamp is what we're talking about, the result would be variable; in some cases the transformer would drive the input of the comparator circuit quite well and in other cases, not so much, just because of the preamp driving the transformer.
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Hi Richard, that amplifier input load sounds very easy to drive. 1.5 volts to full clipping at 170 watts is very sensitive, and would require a quiet preamp. Any preamp, including ours, should drive it to ear-shattering levels. As for Ralph’s point about wall-warts, lots of DACs are powered by wall-warts these days. And lots of people use the DAC as the system volume control, since that’s a common feature of many DAC chips, such as the ubiquitous ESS Sabre chipset found in entry-level and uber-expensive flagship DACs. In an all-digital system, it’s up to the user if they want to use a separate preamp or not. In principle, a direct connection to the power amp from the DAC would have the cleanest sound. But in practice, it doesn’t always work out that way, and a dedicated linestage between the two sounds better. In that setup, the user disables the DACs volume control, so it runs at 100% output, and the preamp handles volume and signal selection. |
@lynn_olson DACs are quite different from actual class D amps- the latter draw considerably more power. DACs OTOH do not- and have internal regulation. onboard with the DAC. So different kettle of fish. There are inexpensive (less than $200 or even less than $75.00 using Texas Instruments chips) class D amps that do use wall warts but I've yet to hear one that you can take seriously. |
I was thinking of the oddball use case of a wall-wart powered DAC driving a Purifi Class D amp module directly. Stupid, I know, but I bet some folks have tried it. I imagine it would (just barely) work. It certainly wouldn’t sound good, though. Measurements would probably be fine, though, if the DAC module had a decent op-amp output buffer. |
I’ll amplify Don’s post. The last pair of pre-production Blackbirds are most likely the cheapest ones you will ever see. Spatial Audio Labs will try to hold the line on prices, but there are a number of imported parts in the Blackbird amplifier ... the European-made Monolith transformers, various cathode-bypass capacitors, and other key parts. If the proposed tariffs materialize, that will affect the build cost not just of our amplifier, but many other audiophile components. I’ve got my fingers crossed the proposed tariffs never appear, but if they do, nearly all audiophile components will go up in price. If you are thinking of a major capital investment, now is the time to buy. |
Well.... here we are. It happened. We now have a tariff war and I happen to know a number of parts in the Raven come from Canada. Others are European so let's hope the USA doesn't get into a tariff war with Poland or Belgium. There are some American parts too..... Like everything else, the Raven contains parts from all over the world, but it is built in the USA. I suppose I should stop typing. Since I am in Canada there may soon be a tariff on my words:) |
I was hoping Trump was using tariffs as a negotiating tactic, but it appears that very unfortunately he’s gonna implement them. Much like the recent government spending freeze that may have been well intended but not at all thought through and ultimately having to be rescinded, this tariff thing will have significant ripple effects not only in the audio industry but across our economy and not to our benefit, especially if you were hoping for prices to decline from here. Financial capital, like water, flows to the area of least resistance and forcing it to flow here through tariffs will have significant ramifications. As just one example, there are very sound economic reasons why many cars are manufactured in Mexico rather than here or in Europe. Trump appears to be looking back to the era of President McKinley’s use of tariffs but seems to fail to realize that this is a far more globally-oriented economic world than it was back then, so while their goals may have been similar and well-meaning in fostering US business interests the unanticipated and far-reaching negative consequences of employing broad-based tariffs today will be considerable and very painful especially to us as consumers. Please know I’m not saying these things from a political perspective at all but as a finance person and purely from an economic perspective. What Don has said above will ripple through countless other industries and products we buy here, and I sincerely hope this tariff thing gets reconsidered and/or renegotiated before it does some real and considerable damage to both our economy and our personal bank accounts. |
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Interesting you mention Musk. I read an article talking about him buying five really expensive speakers... ~100K... I think for a gaming system. Then some assistant thought folks were trying to rip him off by suggesting $20K or more amps... and paired them with cheap consumer amps... and blew out all the tweeters... something like that. |
Well, tariff land is avoided for 30 days. A certain someone loves to inject uncertainty. He fails to realize that business in all countries likes certainty. I have never seen my fellow Canadians more united across the political spectrum than they have been in the past 30 days. I am not sure that certain someone has any clue about the resolve of Canada, and how he has damaged the relationship with his most trusted neighbour. Sad..... I have many American friends and colleagues and that will not change, but the relationship between the two countries has been seriously damaged. Just so sad and unnecessary. Let's hope the whole situation settles down and is over. I doubt it will happen for 4 years though.... |
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I think this bears emphasis. Trump said whoever made the trade deal made a very bad deal when in fact it was HIM who did it! 🤪🙄😖 I was born in the US, and I find it insulting to the point of being disgusting that he’s even floating the idea Canada becoming a state. That’s just utterly pointless and does nothing but harm and absolutely no good. I’m pretty middle of the road politically and don’t like to even bring it into the conversation on this site, but this is really just ridiculous and frankly absurd. Peace out. |
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@fthompson251 What preamp are you currently using with your CODA S5.5? I am looking forward to hearing your take on the Raven preamp with the CODA. I have the CODA #16 amp. My long-range plan is to have a tube preamp in this system. A thank you to the 2 preamp designers for your comments on this thread and on AudioCircle. BTW - How close to the Raven preamp do you need to be for the remote to work?
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@yyzsantabarbara I ended up not needing a preamp, I use a Legacy Audio Wavelet II as my Preamp. I drive the top of my Legacy Focus XD's with the Coda and the internal amps in the speakers drive the bass. The Wavelet II has room correction software in it. |
@yyzsantabarbara The remote on the Raven works very well even at 20-25 ft as long as it has a clear line of sight to the preamp |
@yyzsantabarbara The Raven employs an output transformer so should support AES48. There is a correct loading for the output transformer that will prevent it ringing- you might inquire how that is handled. Traditionally if the output transformer is designed to drive a low impedance balanced line, it will be designed to drive 600 Ohms. On older gear if the load wasn't present on the line there would often be a switch allowing a 600 Ohm resistor to be placed across the output of the transformer to prevent ringing. A that point a much higher impedance load (10K-100K) could be placed across the output with no worries about being able to drive it. Perhaps @donsachs will respond with more information. |
The Raven will drive any power amp with an input impedance between 10K to 220K, in either RCA single-ended mode (which uses half the transformer secondary) or XLR balanced mode (which uses the full secondary). The output transformer is optimized to deliver clean square waves over this impedance range. |
Transformer coupled line amplifiers were the recording, broadcast, and television-audio standard from the Thirties through the Seventies. After that, discrete-transistor op-amps (discrete output transistors have enough power to remain in Class A with 600-ohm loads) became the industry standard. [A bit of history: when 16 and 24 channels became the industry norm, tube line amps became impractical due to heat and size concerns. The first integrated op-amp specifically designed for professional use was the Signetics 5532/5534 released in 1979, while the discrete-transistor Jensen JE-990 became an industry favorite after 1980.] The Raven is simply a modernized and fully balanced version of a studio line amplifier from preceding decades, with modern power supplies, computer optimized transformers, Khozmo fully balanced switched-resistor volume controls, and point-to-point wiring. |
Don and I are not part of Spatial’s pricing decisions. We just design the things and provide technical support, and show up on the forums when people have questions. He’s in British Columbia, Canada, while I’m in Colorado, USA, while the preamps and power amps are built and sold in Salt Lake City, Utah, USA. Like most other electronic products, the sources are global. It is impossible for any country in the world to make a 100% domestic product if it is electronic ... that’s a pipe dream. What was true in the 1950’s and 1960’s is definitely not true now. Which means the on-again, off-again tariffs/taxes, or whatever they’re called this week, are disrupting supply chains. In the old days, manufacturers had big warehouses full of product, both for finished goods and raw parts, and that worked well with the high shipping costs back then (before containers and cheap airfreight). Nowadays, there are few warehouses, most electronic products are built on demand, and shipping is quick and simple. But ... if supply is uncertain, and future pricing is up in the air, everyone in the industry starts to hold back, and adopts a wait-and-see attitude. Parts availability can get spotty. That’s why I strongly urged readers to buy back in December. Products that use international components are (very) unlikely to get any cheaper. I have zero idea what pricing and availability ... of anything ... will look like six months from now. Nobody knows, from Warren Buffet on down. Supply chains could completely break down if tariff wars erupt. Or maybe people could easily adapt to a 25% premium with the resulting rise in retail prices. Or not. If anyone has a crystal ball, let me know. |
@lynn_olson +1 The tariffs will be doing no-one any good at all; just shortages, inflation and ill-will. |
@donsachs +1 |
Big +1 @lynn_olson @atmasphere @donsachs I speak as a finance/economics person this tariff thing is patently insane. It’s not gonna help US manufacturing in the least and is just gonna hurt hard-working folks by making them have to pay more for audio products and for stuff at Walmart, Target, etc. It’s just nuts. 😖😖😖 Wasn’t this guy largely elected to lower prices? I can’t even. |
Actually, he is violating the CUSMA free trade agreement (which HE negotiated during his first term). There is a clause that says you can get out and establish tariffs under "national security" reasons. So they invented the fentanyl problem at the Canadian border to do so. Less than 1% of fentanyl (far less than 1%) that enters the USA does so through Canada. A significant proportion of the illegal guns that enter Canada do so through the USA, but we prefer to have diplomacy about that issue rather than start trade wars. It is a made up excuse so he can tear up the trade agreement and start a tariff war. Why? Who knows. Every sane economist says it is a horrible idea, but he listens to Navarro, who has been ridiculed by the economics community as an idiot. So here we are in a tariff war for no reason whatsoever except the whims of a couple of people in power. This will hurt everyone... sad, but true. |
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Electronics in particular are globally sourced. Here’s a simple example: say there’s a circuit board that AtmaSphere, or Spatial, buy in small quantities, say in the low hundreds. That’s a lot of circuit boards for a high-end manufacturer. The circuit board might be assembled in the USA, Canada, the UK, the EU, Japan, South Korea, Taiwan, China, Vietnam, Thailand, the Phillipines, or many other countries. But that’s the finished board. It contains semiconductors, which come from any of the countries mentioned above. And resistors. And capacitors. And the glass fiber for the board. And the copper in the circuit traces. From the perspective of AtmaSphere or Spatial, we just see a circuit board that does what we want, and we hope (and pray) we get a timely delivery without getting snagged in customs. Delays are a huge deal to any manufacturer. Every part is a critical part, and parts shortages shut down production, which is very expensive, because it costs money to keep the lights on, pay off capital expenses, and pay for trained staff. Every day without production is a day closer to bankruptcy. On-again, off-again political posturing about tariffs, quotas, additional customs screening, etc. etc. is calamitous for small manufacturers. The big boys like General Motors and Ford have the capital reserves to ride things out for several months, but the little guys (that’s us, folks) are working on very thin margins with a fickle customer base. By "fickle" I mean a customer for a Ford F150 is going to buy a full-size pickup truck no matter what. They might switch to a Chevy Silverado, but they’re not going to buy a VW or BMW that cost the same, because those are totally different products. By contrast, a high-end customer can always wait another year or two, and can choose from scores of different products at a wide variety of price points. I’m not crying in my beer, because what I just described is how the entire high-end business works, and you just have to accept uncertainty as part of the deal. But you wonder why artisan-assembled high-end costs more? That's why. |
I will be buying the Raven preamp (which has CanCon) and also spending 6 weeks up in Toronto this summer. Spending my money in the Canadian economy to fight the good fight. My young son is a picky eater, and it seems he likes a lot of stuff that is grown in Canada (buying in Costco). We will pay that extra 25% and support Canada. Will be buying Canadian as much as I can from here in the USA. |
I started as an audio designer at Audionics in 1973, so I’ve seen a few ups and downs in the audio industry. Don’s been doing his thing in Canada since the early Eighties, so between the two of us, we’ve seen what’s been happening in the North American market for quite a while. Players come and go, fads come and go, as well as turnover in big-name reviewers and gradual shifts in consumer tastes. Will the high-end itself survive, given the aging demographics? Good question. Headphones, and the specialized amps that serve them, are a growth area, since they have a compact footprint and can live on a computer desk as a peripheral. Late-night headphone listening is also well suited to young families living in urban apartments. Big-rig systems that take up a whole room? That seems to be a declining market, unless the system is domestically acceptable within normal living room decor ... the traditional "stereo system" we saw in the Sixties and Seventies. Swap in a digital streamer for the classic FM Stereo Receiver of the Sixties and Seventies, and it looks pretty much the same. One thing Don and I find gratifying are a new breed of medium-to-high-efficiency speakers that work well with 25-watt amplifiers. This is a sweet spot in the market that’s been ignored a long time ... moderate power amplifiers that are optimized for listening pleasure, not bombast, and speakers that have low distortion and effortless dynamic range. More, please. |