Spatial Audio Raven Preamp

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.

For anyone interested who perhaps has a Raven already...  Spatial has one last pair of the original pre-production Blackbird amps that they are going to sell at a discount.  David will post them on his site shortly.  If you are interested you can find them.....

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.

@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.

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,

Thanks for your attention to my issue.  What I can find on the quicksilver site is the input sensitivity is 1.5 volts, its  impedance is 100k ohms.  Power output is 170 watts into 4 or 8 ohms.  Peak power is 180 watts at 1 Khs.  

I hope that is what you are looking for.

Richard Vince

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.

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,

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.

@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.

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.

The Bruno Putzey Class D modules are designed so they need they need about 10V drive and an input impedance of 6300 ohms

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.

My speakers are 89dB sensitivity and the volume on my Raven preamp at a "comfortable" listening level is 35.  Need those amp specs or something is amiss.

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.

I'd be curious to know your amps input impedance as at or near max attenuation would be very loud.

Wig

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

@rav6258 

Yes, it is 64 step attenuator, and the first step is 00.  It should be screamingly loud by 50, and most listening levels should fall in the 25-55 range on most systems.  Is that not the case in your system?  63 would blow the speakers out of the baffle in my system

My Raven only displays a max volume level of 63.  Is that normal?

Thanks 

Richard

I spoke with David at Spatial last week, and the time has finally come that I will be placing my order for my Raven Preamp in the next week or two while I am home for the holidays. I've been saving for a very long time being retired now. I will get to enjoy it later this spring after it's made and delivered and I return home again for the Spring/Summer. I started this thread in April. I hope ya'all are enjoying your Raven's!

Personally, I find the tonality and subjective realism of transformer-coupled vacuum tubes to be unmatched by other technologies, but that’s just me.

There are class D amps now that easily rival the best tube amps for every quality mentioned in the above post. Every bit as smooth in the mids and highs, depth properly portrayed, good low level detail and so on.

Instead of a 1/4" thick sculpted aluminum faceplate (marketing!), we put the money into custom parts that are in the audio path.

FWIW Dept.: A machined front panel can be used to reduce chassis resonance (by having a different resonant frequency as opposed to the chassis, the two rob energy from each other), making for a lower vibration environment for the tubes to do their work. If a circuit board is used, it can be isomerically isolated from the chassis, further reducing microphonic interaction. If no circuit board is used, the sockets themselves can be isomerically isolated from the chassis with similar results.  Especially if the preamp is used in the same room as the loudspeakers, this has both measurable and audible improvements- bass is better, the mids and highs smoother with greater resolution. Damping materials can be added to most chassis, further assisting to reduce microphonics (distortion).

@donsachs mentions the Bottlehead kit as an option for DIY enthusiasts. I would like to note for those of you whose budget won't allow for the purchase of a Raven, and are willing to take on a DIY project, you can purchase an Audio Note Kits (ANK) L3 transformer coupled preamplifier kit for about $2,500. This will introduce you to the benefits of a transformer coupled output as @lynn_olson references above. These kits use very nice parts and are relatively straight forward to build. I myself built the L5 Mentor, and when you look at the price of that kit, it's right up there with the Raven which is sold as a completed build. Which goes to show the cost of the Raven is not unreasonable for what you are getting. In fact, I would have expected a preamplifier of the Raven's level of quality to cost more. So cost wise if I had to do it all over again the Raven would be a serious contender for me.

Personally, I find the tonality and subjective realism of transformer-coupled vacuum tubes to be unmatched by other technologies, but that’s just me.

While I like my L5 Mentor and enjoyed building it. I now use direct coupled preamplifiers and amplifiers. No capacitors or transformers at the output. Which is where I would stray from the comment from @lynn_olson as well designed direct coupled components in my experience take the tonality and realism up another level.

We take for granted the very low prices of modern solid-state electronics. For a little perspective, look at the price of a RCA 21" color TV or Fisher FM/AM receiver in 1964. The cheapest color set was $500, and the receiver was $350. Wow, what a deal! Fire up the DeLorean!

Well ... not really. Gold was $35/ounce back then. It trades for $2681/ounce as of tonight. You could get a decent house for $12,000 back then, and a really nice car for $3000. So that color TV with a 21" screen really cost about $5000 ... for the entry-level model. The floor model with a nice wood cabinet cost $8000. Or you could buy a 19" monochrome TV on a metal cart, with very poor picture quality, for $1800. That Fisher cost $3500, with the optional wood cabinet another $300. And no discounts either ... Fair Trade prices were enforced by the FDR-era Fair Trade Commission, not the free-for-all we have now.

Quality tube electronics cost about the same now as then, which is no surprise because they are made the same way, with lots of hand labor by skilled assembly people. Cars likewise are complex and require lots of labor as well as capital investment, despite operating in a hyper-competitive world market.

If what you want can be made with integrated circuits put on a circuit board with a pick-n-place machine, and the labor is minimal, you can have it at a price less than a tenth of what it cost back in the Golden Age. And I would take my 65" Sony 4K Q-OLED display over any 21" RCA television with a resolution lower than 330,000 dot triads. That’s a super deal by any standard.

The value kings today are Class D amps with built-in streamers. Plug and play, the same as that 1964 Fisher receiver. Anything else is a luxury ... it’s up to you to find your happy medium.

Personally, I find the tonality and subjective realism of transformer-coupled vacuum tubes to be unmatched by other technologies, but that’s just me. I got on that train back in the late Nineties with the Amity amplifier, and have been on it ever since.

To follow up on what Lynn just posted.  I spent my time rebuilding vintage tube gear with modern parts, then I decided to make my own and always tried to make it reasonably affordable and be better than the vintage gear.  The Raven and Blackbirds are a departure.  What is possible if you remove the cost constraint, and instead build gear that will sound the best without regard to parts costs?  The Raven and Blackbirds are built with the best parts for sonics so they are expensive.  They are not built in insanely expensive cases, nor do they have a dealer network to add to costs, so they are not stratospherically expensive.  They are built with very nice panels and in solid cherry or other solid wooden cases.  They are expensive to build, and I understand that prices them out of many people's budget.  So something like the Bottlehead kit mentioned above is very cost effective, and I have no doubt it sounds wonderful.  My previous preamp and amps were very good to my ear and were cost effective.  But they do not occupy the same sonic universe as the Raven and Blackbirds.  Nor should they.  The parts cost for the Raven and Blackbirds exceed the sale price of the other gear.  

Obviously, the lower cost gear sounds very good and will provide the foundation for a very pleasing stereo system.  Diminishing returns is always at play.  But it is fun to make the best sounding gear you can, and then worry about the price.....

For better or worse, the Raven and Blackbird have high parts costs. Instead of a 1/4" thick sculpted aluminum faceplate (marketing!), we put the money into custom parts that are in the audio path. Pro-quality connectors, high-purity wire, custom transformers, custom Khozmo volume controls, and advanced linear power supplies all add up. Each one is handmade and hand-wired by Spatial Audio Labs.

And the circuit itself, which doesn’t lend itself to a cost-reduced build. Instead of a lot of cheap parts (think opamps), there are a few pretty costly parts. If we had the same boutique styling and marketing expenses as other companies, the price would be double or triple what it is.

@rav6258 I looked at the Bottlehead kit and indeed it is a steal for what the price was.  I expect that it sounded very good.  They cut corners for the price point, but made some very clever choices.  Just looking at the kit photo I would expect the Raven to have more inner detail, and if the rest of your system is up to the task, a lot more inner detail and tonal correctness of instruments.  But you are paying 3-4X what the Bottlehead kit costs, so it better.....

The Bottlehead could be improved by a better volume control setup, the best coupling caps, etc...  You are still listening to caps though rather than the custom wound transformer in the Raven.  But you could still do a Bottlehead for $2200 or so if you built it yourself and I am sure it is a great preamp!

Roni, my previous preamp was a Bottlehead Beepre 300.  It is a very airy sounding preamp with good soundstage and good clarity.  I just felt I could do better.  I  wanted a piece of equipment that had excellent reviews and wasn't too expensive, thus the reason for the purchase.  I also wanted this to be my last preamp and I believe tie is.

@rav6258 Thanks for the feedback. Very encouraging. My Raven is being built now so hopefully I can add to the discussion in the near future.

One question, what was your previous preamp as a point of comparison?

@rav6258   Thank you for your comments, I am saving to buy the Raven this coming spring and this verifies some of the traits I am looking for. 

Thanks for your comments Richard. It is likely you will still experience improvement in sound quality over time. From past experience the time to stabilize is different… between components… up to 1,000 hours. 

I now have about 100 hours on my Raven and fell i caan objectively give a review.  First my system; my amps are Quicksilver V4's, my phonostsge is a Modwright PH 9.0 XLT, my preamp is the Raven, my turntable is a VPI HW19 mk4. the tonearm is a Woody Stringe Theory with a Soundsmith MIMC cartridge.  

The addition of the Raven has provided an unbelievable sound stage.  
The highs are great as is the midrange.  Thee bass is much deeper  and clearer than ever before.  These were the major things I was looking for and got with the Raven>  

I also have an Oppo 205 and it also performs with all the positive things I have listed.. To elaborate a little more I was very happy that the soundstage spread out over my listening area.  The real plus is the bass improvement.  II is tight and quick. 

All in all it is very musical and very enjoyable which i can and have listened to for hours at a time.  I will say at this time this is the last preamp I will ever buy.  I hope this helps in your decision making procees.

Richard

@fthompson251 No over basseness. (If that’s a word) Uncoloured. Feel no need to tube roll but naturally will someday. 

fthomsom251, you bring up a good point. When Don and I ditched the coupling capacitors, that pretty much got rid of the most obvious way of "tuning" the Raven. You see, nearly all coupling caps have a sound, one way or another. Get rid of them, there isn't much left to twiddle with. The interconnect might be about it.

@donsachs I'll keep my eyes peeled and update if the opportunity is once more available. There are regular droughts with the supply of PC Triple C, when not paying the high premiums as a asking price that can be seen.

@jc4659   Thank you for that reply. I may just get the stock tubes as I can use a little warmth and if not then get a set of Linlai tubes later to tube roll. Appreciated.

@fthompson251 The Raven did not have this effect (more pronounced bass) in my system. I find its frequency range is well balanced top to bottom. I opted for the Linlai tube upgrade to slightly counter a warmer than neutral sound produced by my speakers and amp.  I have been totally happy with the Raven and have had no issues with it at all.

Do the sound characteristics of this preamp enhance or make bass more pronounced? I am not really looking for that. I want tonally neutral but with the tube holographic presentation they are known for and some midrange warmth or fullness. I just read a review of the Aric Audio Motherload XL and the bass description had me concerned. That one was on my list but I really don’t want to spend another $1000 and have wait longer to afford it. I certainly do not want any McIntosh type bass either. I have been saving for this since April 2024! Should have it by April 2025.

@pindac Sadly, it appears that wire is out of stock.....  Might be a fun experiment if some were available

It is not a secret on the Gon, that I am an advocate of PC Triple C wire used in a Audio System. Today I have heard it used for nearly every role a Wire is to be used, In all the demonstrations had, the use of it has been impressive and without doubt a worthwhile exchange.

Big Brand names are onto it, and the wire as Bulk Purchase is becoming harder to find.

I have also been introducing others to PC Triple C wire, with the result being they have taken to it more intensively than my own practices, hence all the additional uses I have been introduced to.

In the early days of usage, I purchased a Power Cable at approx' £150 per metre length, and terminated it with Pure Copper Connectors. This same cable when introducing the wire to others was loaned out for extended periods.

The users of the Power Cable are by nature experimental, they also produce Audio Equipment as a Cottage Type Industry, where small quantities are the objective.

Comparisons took place as my loaned cable, prompted a few Brands of Cable to be purchased. 1mtr Lengths of Cables were purchased with a Top Value Cable being mine and others being close to £100 and less.

The surprise was, that a Power Cable near the lower end of price range was the one that most impressed across a few systems the Comparisons took place on.

As Power Chords are of interest in this thread, and I am sharing interest in this thread. The Link is the Power Chord with Pure Copper Connections the group of listeners took to the most.

https://www.fromjapan.co.jp/japan/en/special/order/confirm/audio9:10000582/2_1/

@brbrock I got the Spatial Pre and Mono's. In itself I couldn't say the Ravin is the cat's PJ's as I'm thrilled with the whole system/room the Raven pre is the heart of.

I was able to compare the Spatial suite to 1.) a Lumin Amp w/ Lumin X1 and 2,) a Roger's KWM-88 MK2 Integrated Amplifier with the Lumin X1 and also a Grimm MU1/Weiss 501. Speakers are K horns and REL subs. Power is treated and ethernet is all cleaned up (After rack shows up, will update systems).

The Spatial suite using the Grimm MU1 is the best of the three. It's more musical and there's no listening fatigue. Nothing wrong with the others.  May let Lumin stuff go but not the Rodgers.

(After warm up) I can turn up the volume and with nothing playing standing a half and inch away from a speaker I can't hear anything,

The Ravin is tops. If your speakers are efficient enough the Raven Pre and Blackbird Monos are synergistic masterpieces. There's a waiting list for a reason. I got more than I paid for. Happy camper!

bump-=-

Just checking to see if anyone has any reviews on their newly purchased Raven preamp in their system.

Hello Don,

Thank you very much for your advice.

I will ask David (Spatial Audio).

Regards.

@phono2024 

I stopped shipping cords with my builds as people always tossed the cheapo one and used something better, and I was tired of the waste.  I suspect Spatial has the same policy, so you probably should enquire.  I know Lampizator doesn't ship cords with their DACs.  Honestly, any of the $50+ entry level "audiophile" cords will be far better than the cheap computer grade ones that come with most gear.  It is the standard N American 3 prong male connector.  I would just order some half decent cord.  You don't need to go crazy.  Many of us have a bit of a collection of them, so you may already have something to use in your stash.

Hello Don and Lynn,

Thank you for your additional info regarding the Raven and Blackbirds.

I have placed an order for the Raven preamp, with Linlai 6SN7 tubes, cherry finish. It will be build in the next manufacturing cycle and delivery date is expected in November/December.

I am looking forward to listening to the Raven in my set-up. The Caladans is 93dB sensitivity into 4 ohms. I can only imagine it is very very good sounding, given all that has been said about it.

BTW, given that the Raven has such good noise rejection components, is it necessary to use audiophile grade power cord in place of the stock power cord that is supplied with it? Just curious.

Thanks.

Kind of expected because:

1) the specialized damper diode rectifiers have very soft switching compared to solid-state diodes, thus much less 50/60 Hz switching noise radiated into the rest of the circuit and out the AC power cord

2) the regulated high voltage B+ power supplies have an astounding 130 dB of noise rejection from AC line noise

3) there is an another layer of VR-tube shunt regulation for the B+ power of each channel, good for about 20 to 30 dB of added isolation

4) All heaters are fed with 6.3 volts of regulated DC

5) last but not least, balanced operation of the 6SN7 circuit provides an additional 30 to 35 dB of noise and distortion rejection, without requiring feedback.

That’s why the Raven (and Blackbird) cost a bit more than other preamps and power amps. Each Blackbird power amp does all this rigamarole three times, with KT88 and 300B power tubes, which is why it’s priced where it is.

@phono2024 

sure, I am biased because I designed them, but in my system with 95 dB speakers,

the Raven and Blackbird combo is dead silent idling away.  I can put my ear to any of the drivers on the speaker and barely tell the system is on.  Hiss will not be an issue unless a tube is failing.

wsrrsw,

I have been following this thread for a while and the reviews of the Raven and Blackbirds are very good or excellent. It will pair with Clayton's Caladan.

@phono2024 Upon retiring and finally being able to put together a room/system (and after many years of research and trials) I knew I wanted 300B Mono blocks. The Blackbirds and Ravin are world class. If your speakers are efficient enough, then the Blackbird mono's have terrific synergy w/ the pre.

wsrrsw and terrapin77,

Thank you. 

That's assuring. That is one Raven for me.

@phono2024 No hiss from my Raven