@spazzghettie Looks like a nice amp. LC coupled and they use all DHT tubes. On the downside it is single ended so it won't have the bass punch nor the power of a push pull 300b. Also, I have moved on from LC coupling as I prefer custom interstage transformers, but that is my taste and it doesn't mean that Allnic amp is not a wonderful sounding amp. I also prefer solid state rectification and regulated supplies in power amps, but again, my taste. I am sure that is a very nice amp if your speakers can live with a 10 watt amp and you like the sound of tube rectification in power amps. It also has 6 dB of negative feedback. That isn't necessarily bad, but our amp project has zero feedback and you can tell. So again, they have made a nice compromise with good tubes, obviously good parts and a bit of feedback. I am sure it sounds really nice.
300b lovers
I have been an owner of Don Sachs gear since he began, and he modified all my HK Citation gear before he came out with his own creations. I bought a Willsenton 300b integrated amp and was smitten with the sound of it, inexpensive as it is. Don told me that he was designing a 300b amp with the legendary Lynn Olson and lo and behold, I got one of his early pair of pre-production mono-blocks recently, driving Spatial Audio M5 Triode Masters.
Now with a week on the amp, I am eager to say that these 300b amps are simply sensational, creating a sound that brings the musicians right into my listening room with a palpable presence. They create the most open vidid presentation to the music -- they are neither warm nor cool, just uncannily true to the source of the music. They replace his excellent Kootai KT88 which I was dubious about being bettered by anything, but these amps are just outstanding. Don is nearing production of a successor to his highly regard DS2 preamp, which also will have a unique circuitry to mate with his 300b monos via XLR connections. Don explained the sonic benefits of this design and it went over my head, but clearly these designs are well though out.. my ears confirm it.
I have been an audiophile for nearly 50 years having had a boatload of electronics during that time, but I personally have never heard such a realistic presentation to my music as I am hearing with these 300b monos in my system. 300b tubes lend themselves to realistic music reproduction as my Willsenton 300b integrated amps informed me, but Don's 300b amps are in a entirely different realm. Of course, 300b amps favor efficient speakers so carefully component matching is paramount.
Don is working out a business arrangement to have his electronics built by an American audio firm so they will soon be more widely available to the public. Don will be attending the Seattle Audio Show in June in the Spatial Audio room where the speakers will be driven by his 300b monos and his preamp, with digital conversion with the outstanding Lampizator Pacific tube DAC. I will be there to hear what I expect to be an outstanding sonic presentation.
To allay any questions about the cost of Don's 300b mono, I do not have an answer.
Showing 50 responses by donsachs
NFB covers a lot of sins. You have to do everything right to have a stable circuit without it. It is actually considerably more complicated than that, but that is a good way to think about it. That allnic amp ad boasts a perfect square wave response. The feedback helps with that. It doesn't mean you cannot build a nice amp that uses NFB, but that "air" and sense of "realism" that you treasure is hindered by NFB. I can see what is inside their amp and have a pretty good idea what it sounds like. It is a dance. We have been working on this amp for quite some time and it will go into production late fall. We have tried many coupling methods and topologies and the fact that there is zero feedback lets you hear major differences between them. Again, there are many great amps in the world, most of which have some amount of NFB to make them really stable and limit distortion. That approach works, but has costs in terms of realism and spaciousness. That said, it doesn't mean those amps sound bad. Just different. I know the sound I value and I cannot get it with NFB, but others have different tastes or the need to drive speakers which are not at all tube friendly. So there are many paths.....and different sounds associated with them. There is no right way, just what we like. |
What @pindac described is exactly what I heard when I first built the rather primitive initial "silicon assisted" stereo version of this circuit with a CCS on the plate of the driver tubes and a single regulated supply for each channel. I could hear things like subtle inflections in vocals, or the resonance in the low notes of a piano in a way that I had not encountered in all my years of building and restoring amplifiers. I had heard the stirrings of such things in single ended triode amps, but not with the drive and authority that this circuit presents. So then we spent 18 months or so experimenting with every permutation and combination and ended up with mono block amps with dual independent regulated supplies and all custom interstage coupling, and some old school VR tubes as well. I have not heard anything like it.... and the final version walks all over the one presented in Seattle. It sounds like it does for the reasons described above.... |
Lastly, I have said this before in this thread. It is about your design goals. We could make a low powered amp that uses 45 tubes in push pull and it would produce maybe 5-10 watts and stay in class A. I am sure it would sound incredible. If you had 94+ dB speakers it would probably be plenty of power. But 45 tubes cost a LOT, and many folks have 88-90 dB speakers and maybe a larger room. So our amp is 25 watts, well really about 27 watts, and has easily driven 88 dB speakers to screaming levels. Would the 45 amp sound better on more efficient speakers? I don't know. It would certainly sound a bit different, and possibly better. We tried to make an amp that had a much wider appeal and used modern production tubes that didn't cost a fortune. So it depends on your design criteria. The Citation II amp will drive darn near any rational speaker. It has three nested feedback loops and is very stable. It is one of the few tube amps you could let idle away for an hour on a bench with no speaker load attached and it would not oscillate. That said, it doesn't have the clarity and just spaciousness of the zero feedback DHT circuit. It makes wonderful music and is non-fatiguing to listen to, but it doesn't have "the piano is in the room" sound of the 300b project. I know this because I rebuilt about 80 of them, and lived with one for a few years. I could rebuild one in my sleep:) Ultimately, it depends on what you want the amp to do. I want an amp that will drive a pretty large number of speakers and have the clarity of a flea watt DHT, with the drive and authority of a push pull amp. So that is what this project is about. Trying to get a sweet spot that will make a lot of people happy and not cost a fortune to re-tube, and to run the tubes at really sane operating points so they last a long time, while pushing the state of the art sonically. There is no single design that can make everyone happy and drive all speakers and retain all the sonic characteristics we desire. There are always compromises. Tubes vs SS, SE vs PP, etc... Within SS and tube worlds there are many topologies, devices, and tube types. So there are many choices. For me to say our way is the best is ridiculous. So our comments in this thread just point out why we have made the design choices we have. |
Charles, I am not sure what Meyer would think of the Blackbird! There are some elements of it that are aligned with his thinking and others that are radically different. I would be interested to hear some amp of similar power that he has built in the same system as the Blackbirds. It would be fun:) As I said above, Thomas Meyer builds SERIOUSLY good amps. The man has his own tube factory! I would love to try a quad of his 300b tubes, but they cost serious money. Maybe one day.... I bet they are really good though. |
@charles1dad Well, let's just say I have experimented and know which I prefer:) The 300b amps have a dedicated 5V regulated DC supply for each 300b tube and a 6.3V DC regulated supply for the drivers and input tube. The preamp has a 6.3 V regulated DC supply for the pair of 6SN7 tubes. I value blackness between notes:) |
Regulated high voltage supplies are also a very hot button issue. I know what I prefer from having built the same circuit with multiple power supply topologies and critically listened to each. The way I do it costs more money and certainly has to be worked out so that it is very reliable, but once you get to that point.... As I said, I value absolute blackness between notes and very fast transient response delivered by supplies that are grossly over rated for what they have to deliver. Other people value other things..... to each their own path. |
@alexberger Hi. I just tried schottky diodes maybe 5 or 6 years ago and I liked the sound. They have a fast recovery time. They also have very low voltage drop so are good for small filament supplies, but the main reason is the fast recovery. I didn't hear any difference compared to the super high priced hexfreds or other types in the sort of supply I build. The automotive schottky diodes are not expensive and they are available in voltage and current ratings that far exceed requirements of the circuits I am building so there is plenty of headroom, and you can get to-220 versions that fit everywhere. So basically, they work well, sound really good, and are readily available. |
We all apply sound engineering practice. We overbuild all power supplies and over spec all parts. But there are choices that affect the sound. If you need a 1 watt 1K resistor you can use any type on a cathode, but different types have different sounds. The cathode bypass cap might need to be 100 uF. Different 100 uF caps sound very different. All will satisfy engineering standards, but parts and layout choices have profound effect on the final sound. We make these choices to achieve the sound we desire. There might be 2 or 3 different tube types that would be appropriate for a place in a design, but can have very different sounds. I can build an amp with entirely different parts and wire and have it be exactly the same from an engineering standpoint, but have a very different sonic presentation. I believe that is what Lynn is alluding to. |
@atmasphere First off, this thread was started by a fellow who has a rough first prototype of a zero feedback push pull 300b amp, so of course we are discussing that. I agree that in that circuit you hear everything. I will tell you that even in circuits with feedback I will not use electrolytic caps in the signal path. I also do not use them in my power supplies, but only in the filament supplies. In my experience electrolytic caps make circuits sound grey and hazy compared to a very top quality film cap. You can wait forever for a lytic to run in, you can bypass it with small film caps, and whatever else. When I replace them with a very good film cap I hear the difference. To each their own. I also hear differences between resistor types in key spots in circuits, whether the circuit has feedback or not. Again, my experience, so I build amps with the parts types that I favor. |
Yes, we are pretty much back to an updated Karna circuit with more modern power supply topology, and custom wound iron everywhere. I listened to every possible variant of the circuit and it is obvious that removing all coupling caps and going with all transformer coupling walks all over any other variant in pretty much every way. We are now using custom wound Monolith Magnetics iron for power and output transformers, and Cinemag interstage transformers. The chassis is much wider than the shoebox amps displayed at the Pacific Audio Fest in Seattle. Spatial will change the look slightly, but the layout and size will be the same. There are reasons for the layout, which makes for very short signal path at all sections and also has complete isolation of the power supply from the signal part of the amp. They are just about ready to build in quantity and I would expect them to be available in November or December if all the vendors meet their production schedules for parts. I will say that I cannot listen to anything else now. I am spoiled..... everything else sounds dull and coloured to me now and I have pretty much cleared my house of all other amps and preamps. We shall see what others think! I cannot seem to post a photo of the final prototype, but will upload to my old website and see if I can post a link to that photo eventually.
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I managed to update my ancient website with the beginnings of 300b project page. There is a photo of the final prototype of the Blackbird 300b monoblock amp at the bottom of this page. Spatial will change the look a bit, but dimensions and layout will be the same. The amps are optimized for sonics and short signal path. |
@alexberger Spatial Audio Lab will be in charge of presentation at shows. I know we are returning to the Pacific Audio Fest in Seattle again next summer. Beyond that I don't know. We are focusing on getting the preamp and amps into production by year end. They are also finishing work on their Q series speaker. A prototype of that was shown in Seattle and they expect to release that by the end of the year. So lots going on. Spring shows may be a bit soon. Given they are in Salt Lake City, I suspect they will focus on American shows though, so probably not Montreal. You never know though:) |
The regulated filament supplies for each 300b can deliver 3 amps, and the tubes draw 1.2 amps, so they are coasting along, like the B+ supplies. As Lynn described, the amp is lightning fast. I would love to audition the Elrog 300b in it. I have to admit the Linlai replica WE300b is just superb though. I cannot imagine it needing more slam, but my speakers are 97 dB and an easy load, so the amp is just cruising along and is really not stressed. Whitestix told me he tried a pair of Dynaudio C1 on his shoebox earlier edition amps and they drove them with no trouble at all in his smaller room. That is the third or fourth time someone has put a more difficult speaker on the mere 27 watt amps and they had no trouble. I don't suggest you power some horribly inefficient speaker with these amps, but don't let the 27 watt rating fool you. Any rational speaker load is fine. |
No, the comparison isn't really fair. The little Chinese amp is a nice value for the money, but it is a single ended design made of, shall we say, "cost effective" parts. It probably makes 7 or 8 watts per channel. The mono 300b amps are built with cost no object parts and custom wound transformers, with state of the art power supplies, and they really are about 27 watts/ch. They cost multiple times what the Willsenton does. The Willsenton has a chance on efficient speakers. It doesn't have a prayer on a speaker presenting an inefficient and difficult load. |
Which is why, on my highly resolving system, I could clearly hear the differences between CCS loaded RC coupled, choke loaded RC coupled, and interstage coupled versions of essentially the exact same amplifier. IT coupling won hands down in all areas and is the way these amps are built. The preamp too. No RC coupling anywhere in the signal path.... Of course you need really good transformers.....which has taken a year. |
@tuckia08 Thanks for your comments. I have heard a number of 300b now, but not the new WE 300b and I have not heard the European expensive tubes. When I tried the Linlai WE300b copy I stopped looking. I can get them for about $750 a quad from my supplier and so far the 4 or 5 quads have all been perfect with no issues. As for sound.. well they stomped all over all the $400-500 per quad tubes from China, and the Gold Lion reissue, which is a nice tube, very well made, but just cannot match the clarity of the Linlai WE300b copy in this push pull Blackbird. The Monolith OPT is based on their standard summit series core. I don't want nano or amorphous. The amps have incredible micro detail and the tonality and timbre of instruments and vocals are spot on to my ear. They are rich and full sounding. I am happy with the summit cores. I was playing records last night because I am burning in a phono stage for a customer and shipping it today. I had not used phono with this final version of the amps and I have to say that I heard subtle details in the familiar records that I had not heard before, even with earlier prototypes of these amps. The summit series transformers do it for me:) I too will be interested in user comments. We hope to be making them in November! Yes, the Lampi Pacific is outstanding. Mine is modded a bit and I am considering sending it in for their upgrade. They will put the Horizon digital engine in there for about $4K, and do a few other things. Spendy. Once the 300b project is off the ground maybe I will gamble the $4K:) But the Pacific is just stunning as it is. I run a quad of NOS 46 tubes with adapters, so they are essentially a 45. The clarity is astounding. I wish we had this quad at the Pacific Audio Fest in that Pacific that Fred, the NA distributor for Lampi loaned us. Anyway, enjoy your Horizon. An end game source no doubt! Once you get a DAC that good... you cannot go back.
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The Blackbird amps are running the 300b tubes at about 400V B+ (plate - cathode voltage), and just a wee bit under 80 mA. About 31.5 watts at idle. They sound wonderful and should last a very long time. The tubes each have their own independent regulated filament supply and are right at 5 volts. I have measured a lot of them and it is always 4.99 - 5.01 volts. All the supplies are regulated so the tubes stay at that operating point. It seems to be a sweet spot for the 300b tubes, although I suspect that dialing the operating point up a bit for the Euro super tubes would be an option. The supplies are run very conservatively and could easily handle the extra current. |
Yes, these amps sound very good after 10-15 minutes and are very consistent. They sound the same every day. I have the preamp and amps plugged into a Puritan supply, which does clean up grunge in the AC line. Basically, you turn them on and they sound quite good as soon as they can play music in 30 secs or so, but in 15 minutes or so the tubes are all warm and then they are pretty much on song until you turn them off. They may sound a wee bit better after 30+ minutes, but really 15 gets you almost all of it. Plus they run quite cool. You can leave your hand on the transformers or anywhere on the top panel even after the amps have been on for an hour. No, it is not a class D amp that barely warms, but they run quite cool for a class A tube amp.
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This has been an interesting thread. I didn't start it, nor did I expect it to have this long a life. It is very clear that there are many ways to build amps and preamps. I just want to restate my goal for this project. I am semi-retired. I wanted to build the best sounding preamp and amp combination that I could. A setup that I can happily listen to the rest of my days and that will drive a reasonable subset of the speakers out there. Within reason, I didn't care at all what it cost. Once done it will be produced by a partner and priced according to what it actually costs to build plus enough to cover their labor and margin to stay in business. It will be sold directly to customers though with no distributor markup. But it costs what it costs to build because the main goal of the project was to produce the best sounding preamp and amp that was possible without have some four chassis amp or gold plated case and $50,000 starting point. The thread has shown why we made the design choices we did and where it led us based on a combined (gasp) probably 70 years of experience with amplifier design and builds between Lynn and I. He is the historian as well, and I have rebuilt literally hundreds upon hundreds of pieces of classic tube gear, so I guess that makes me sort of a hands on historian. At any rate, I thank everyone for their civility and free discussion of audio ideas that has made the thread enjoyable. I hope to meet a few more of you next year at the Pacific Audio Fest when I will be there with actually production versions of these for you to hear. Trust me, they are FAR better than the prototypes shown this past June. |
@gladmo Spatial Audio Lab will be making the amps and preamp. All parts are ordered and I hope to be going to Salt Lake City in early November to train them on the builds: https://www.spatialaudiolab.com/news/september-2023-update If you have interest, then contact them.
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The thing about the transformer coupling is that once done correctly, it just works. It will not fail. It protects against a tube that may develop a grid short. Rare in smaller signal tubes like the 6SN7, but I have seen it. So for a commercial amp I just want something that works and the owner never has to worry about. If he or she gets a hum or odd noise from the system, a quick tube change will most likely solve the issue. Direct coupling has the chance for a tube failure to propagate to the next stage. Very rare, and if it was just my own amp that I could repair, then I probably wouldn't worry about it. But if you put 100 amps out into the world....sooner or later a rogue tube will appear. Lynn's point about servo circuits is also valid. It adds complexity and again, a possible failure point. If my own amp in my living room, then fine. I can fix anything. But if I put 100 amps into the world I don't want to see one fail. My business philosophy would be to immediately take care of the problem for the customer, but I would rather just avoid the issue entirely. Every component and coupling method has a sound. I found the well designed transformer to have less of a sound than any other method, plus it is totally reliable. I find it more transparent than any other method as well, with subtle detail more audible. It has less coloration than anything else. I think transformers get a bad name because there are a lot a mediocre ones out in the world and that is what most people have heard. If you go all in on good ones they are quite spectacular. So that is the way we went. As to Lynn's comments about capacitors, yes, I have heard a very large subset of the best caps available, bypassed and unbypassed, etc... You can happily live with many of the best ones, but the transformer coupling kills them all to my ear in this circuit. Once you hear the really good IT you realize that none of the caps can produce the tonality of the transformer. The instruments all sound just a little wrong with the caps. The transformer does the "piano is in the room" thing a LOT better in this circuit built this way. You may have a different experience in a different circuit built with a different power supply. RC coupling is certainly easy. LC coupling a little more difficult because you need a good anode choke and you have to physically find room for one. Direct coupling has advantages, but again, there are failure modes and colorations. The hallmark of this circuit is the absolute transparency and I just found the transformer sounded best, once a really good one was wound, and it will be trouble-free. |
@stephenr First off, thanks for you polite post on this thread. I bet your 12B4 preamp sounds great. I have tried removing the Raven preamp and going direct to the amps from the Lampi Pacific DAC via xlr. It sounds very good. It doesn’t sound nearly as good as with the Raven active preamp in the chain though. Over the years I have experimented with various passive preamps built with top notch volume controls and none were as satisfying as a really high end active tube preamp in my system to my ear. As for the direct coupling, no I didn’t experiment with it in this project. I have heard it in other amps. As Lynn has described above, there were reasons for avoiding it in this particular project. I am sure you can make it work well in your amp though and I suspect it sounds very good. |
I see Lynn has spilled the beans on the driver tube change. I have listened to the 6L6 (Russian 6P3S-E), the KT66 (Shuguang black treasure KT66), and the KT88 (My stash of a quad of the now unobtanium Shuguang WEKT88). Of course I have spent almost two years listening to the 6V6 as the driver before this. In my system the KT88 wins hands down. It has midrange and bass that hits you in the chest at moderate listening levels. That is in a good way. It is vibrant and rich and tonally correct. It has all the highs of the other tubes, but sounds less thin. If you put any of these tubes, including the original 6V6 in this amp and had never heard any other driver, you would still think it was the best or one of the best amps you had ever heard anywhere. But the KT88 is just superb. That doesn't mean that in someone else's system they wouldn't prefer a KT66. I also have EL34 to try, but haven't bothered because I think it the worst of the octal output tubes of that ilk and never understood why anyone liked them. Mine are Mullards too.... Let's just say that with the KT88 you FEEL the music in a way you do not with any of the other driver tubes. You sort of LIVE the performance. It is quite striking, and the larger chassis of the final design, coupled with the very conservatively designed power supply, allows for the amps to easliy handle the roughly 14 watt dissipation of the drivers vs. the 7 watts of the original 6V6. It still runs very cool for a class A 25 watt tube amp. What I will say is the output section is basically a supercharged amplifier of the driver section sonics. You clearly hear the nature of the driver tubes. This is of course true in other amps, but I have never heard the effect like this. Usually a driver tube change is audible, but not night and day. Imagine all the things you love about your classic KT88 amp with far less distortion and that KT88 rich full sound on steroids. You are inside the music in a way that none of the other drivers do in my system, in my living room. You get that KT88 sound without all the nonsense of feedback, RC coupling, whatever. Instead you get an effortless, breathless, KT88 rich sound with lightning fast transient response. This is related to slew rate and I will let Lynn discuss that if he chooses. What matters is how it sounds:) So now you have an amp with all large plate tubes, no feedback, that is lightning fast and will produce 25 watts all day long with tons of current. The previous 6V6 version has easily driven 85 dB speakers. The KT88 version... :) Just to be clear, this is my system so those of you wanting to get a feel for it can know what I am using: Lampizator Pacific DAC with 46 DHT tubes run XLR. Dac is modded to eliminate a cap between DAC board and output stage resulting in a very slight pop when it changes resolution at the beginning of a track. I find this benign, and the clarity is increased. Just saying so you know this is better than a stock Pacific. This drives the Raven preamp and Blackbird amps, cabled with Paul's best Anticable XLR v. 5 something..... Speakers are Spatial audio X5 with seriously updated crossovers. I never heard the X5 wake up like this....
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@tinear123 Hi.. write Cloud Sessions at Spatial audio lab and he will know what is in the crossover. I am sure they can build something for you. |
I just cannot resist. This is a poor photo of the square wave on the Blackbird interstage transformer between the 6V6 and the 300b at 1 KHz and about 30% power (7 or 8 watts). There are NO grid resistors or grid stoppers or networks of any kind. The primary of the transformer is wired directly to the driver plates and the secondary is wired directed to the 300b grids. The KT88 looks as good or better.... Lynn and I were quite impressed. Dave Geren at Cinemag knows what he is doing..... This is an all tube amp with no feedback anywhere. Yeah, it sounds like it looks.....
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@alexberger Please report back on the sonic diff between the A-107 and RC coupling. Completely different amps, but I much preferred all IT coupling. Curious to hear your impression |
@tinear123 No. Production starts in late November when I go to Salt Lake and teach the guys at Spatial the builds. I would expect a review by late spring and perhaps an audio show in the west somewhere next summer. That is kind of going to be the schedule I think. There will be a review pair that could potentially end up at a show in the east next year, but that would be Spatial Audio Lab's call. I really wish that folks could hear what I am listening to in my living room. It would be fun to have any of you over. There will be a complete setup in Salt Lake City area by January and I am sure audition arrangements could be made for anyone who wants to hear it along with a top end Spatial Audio Lab speaker. Of course this doesn't help any of you out East.... It is definitely the plan to have a review setup of both preamp and amps and have it reviewed by legitimate reviewers next year as early as possible. Perhaps sometime next year we can have them appear at a show in the east somewhere. |
Well... Lynn has lots of wild ideas, but the thing is that they are very well thought out, and they are based on years of technical experience with Tektronix. I learned many years ago in academia, and as part of my main career in forest ecology research, to listen to really smart people with wild ideas. Many of them were simply ahead of the mainstream thinking. The mainstream often ends up there.....eventually. Lynn suggests improvements and where practical, I try them. We finally ended up with a larger chassis that could accommodate all the things we wished to try. They are still under 19 inches so they fit any rack, since 19 inch is the traditional rack width. To my ear, it worked beautifully.... The final touch was the addition of old school gas VR tubes to further isolate the input tube supply from the drivers, and of course the move to KT66/6L6 or KT88 drivers. I think we are done finally. |
Actually I have rebuilt 3 or 4 of the ST70 amps. The best version is to skip the 7199 or 6GH8 types and to one install of the octal driver replacement boards. I really liked the 3 6sn7 tube version that tubes4hifi used to sell and perhaps still does. It makes the amp considerably better. Really in every way. That said, they still run out of steam under load because the power supply is only adequate and there is no room in that tiny chassis to install a better supply. They are great amps for the money. But they are still not particularly great. However, there is little else you will find at that price point to touch it. |
@alexberger Fine is a relative term. If you improve the power supply in a citation II the amp is greatly improved. That is why the KT88 amps I used to build have FAR better power supplies than vintage amps. If you build a vintage amp with the sort of power supply you are using in your SET that vintage amp would sound much better. |
Actually, the Kootenay, and the the Valhalla amps use a similar circuit for input and drivers (with judicious use of a CCS), and the power supplies are the basis for what we used in the Blackbird 300b amps. We improved the power supply design for the Blackbird, but the same basic ideas are in the Kootenay KT88 power amp and Valhalla 6L6 integrated amps. Long tailed pair with CCS and really good power supplies and iron. As Lynn said, it makes for a really good tube amp. Not the level of the 300b project, but very nice indeed. |
The octal boards for ST70 are direct fit and do not stress the power supply. You can use the diode replacement for rectifiers, but it sounds different. Basically, the amp is not bad, and a great deal for the money when restored and updated. A decent preamp and some reasonably efficient speakers and a person can have a very pleasing stereo. That said, an ST70 is nothing special because there really isn't room to make it special. I think we agree on that. You might as well start over and do it right without the compromises. |
@pindac that will be up to Spatial Audio Lab. I am going there in late Nov to teach them the builds of amps and matching preamp. There will be a review pair made that will spend some time in the USA next year. After that we shall see. It is not hard at all to spec power transformers with dual windings and make a 220-240 VAC input version and source a proper IEC connector. While I expect both these pieces to be very reliable, the problem with supporting European and Asian markets is shipping cost, and if the customer has a problem of any sort, the shipping costs are enormous to help them out with any warranty issues. If you make 100 units of anything, no matter how reliable, one will either be damaged by a reckless carrier, or some weird problem may arise. The important thing in that case is to immediately take care of the customer, and that is expensive outside of N America. So that will be Spatial's call. It is much more expensive to support markets outside the USA and Canada. |
@pindac Would it require a 240 VAC version or have most of the ones you have heard been US market 120VAC ones that someone was using a step up transformer with on your side of the pond? I will say that I have the pair of prototype amps that will go into production other than some cosmetic changes to the cases and panels. The circuit and power supply will not change as they are done. I abuse the amps regularly, putting them on the bench and tweaking something and turning them on and off 10 times in 30 minutes. Nothing has fazed them in 3 or 4 months since their birth. So I am pretty darn confident if they arrive undamaged they will simply just work and be very reliable. I/we wouldn't sell them if they were not very reliable. But shipping overseas is always dicey, even with good packing. |
I have a thorough dislike of working with lead-free solder. Nothing flows in a point to point build like a good 2% silver solder. Lately I have been using Wonder Solder for the past year or two and it is just wonderful to work with. Of course, one could use lead-free solder, and pass all the hurdles and build things for shipping in large numbers to the EU. First you get the product off the ground in N. America. We have pretty much free-trade between Canada and the USA, and it is quite easy to make things in either country and ship to the other, duty and tariff-free. My main point above was that it is very expensive to deal with customer support across the pond. If you ship 100 things to 100 people, about 1% of the time something happens. For example, UPS will admit that they have a 4% claims rate. Things happen. No matter how robust you make something, and how thoroughly you test it and the tube set before you ship it, things happen a very small percentage of the time. Or a customer plugs a tube you didn't sell them in there and it grid shorts. This gear is quite robust against serious damage when that happens because in all these years of building things, I have seen all sorts of failures. When a bad tube kills something, I improve designs so that will only blow a fuse instead next time. So these things are quite stable, but still, every now and then things happen. When they happen in N. America it is far cheaper to sort out. You always take care of the customer. It is much more expensive to do so overseas..... |
The gear could easily be wired for 220-240 VAC 50Hz. Everything we use supports it except for ordering multiple primaries on the power transformers. Again, the project must get off the ground in the USA/Canada. If they are selling, and people from Europe are inquiring, then perhaps Spatial may be interested in that market. Hard to say. If demand is outstripping supply there is no reason to make your life difficult dealing with markets outside N America. Down the road......maybe |
Just a note that Spatial will be at the SW Audio Fest in Dallas, March 15-17. They will have the final production versions of the Raven preamp and Blackbird mono 300b amps driving their speakers. I will be there all day Friday and Saturday, and a bit on Sunday morning. So if you are in the general vicinity and want to hear this gear please stop by! We will have tons of music on a hard drive, and if internet Gods are willing we will have Tidal and Qobuz available to queue up requests.
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I just returned from Dallas, and I have to tell you that our room was one of the top two or three in the show. Danny Ritchie (GR Research) came by and told us our room was his pick for best sound of the show. Sam Whitt, the speaker designer at Spatial, just completely nailed that new Q3 speaker. It is superb.... Of course the preamp and amps driving it didn't hurt either:) |
I believe the preamp is $5500. Search for spatial audio lab, find the site and look at the revelation series and preamp and you will find it. On the preamp, it is fully balanced and transformer coupled to output. Pin 1 is shield and grounded to chassis, pin 2 is XLR + phase and pin 3 is XLR - phase. It will drive any power amp with XLR connections, and will happily drive a 10K amp input impedance. |
Hi. It is a very subtle change that I find inaudible, but on paper it is slightly better. The xlr inputs now go directly to the Attenuator and the rca go through a 1:1 transformer to convert to xlr. The previous version ran all inputs through the 1:1 transformer. Honestly, the Cinemag 1:1 transformer is so good that it has something like .25 degree phase shift at 20 Hz. You cannot see it on the oscilloscope and it is sonically transparent. So running the xlr through it was not an issue, but I figured out how to go direct in for the xlr. Again, I changed my preamp and I really cannot tell much difference on the xlr between input transformer coupled and direct. I doubt I could reliably tell in a blind test. The transformer is that good. So if you are using predominantly rca inputs to the preamp there is no change. If you are using the xlr inputs, then there is a change on paper, but you would be hard pressed to hear the difference. |
That is the first thing you notice when you hear our 300b PP. The bass is amazing. It is not over emphasized at all, but if there is bass energy on the recording you hear it all. Most importantly, it is the quality of the bass, not the quantity. When I built the prototype I had never heard anything like it. The resonance in the body of instruments, the attack and decay of bass notes. Then we spent over two years improving the amps by eliminating cap coupling, improving power supply designs, working with Dave Geren through several iterations of custom interstage transformers, moving to Monolith output transformers, etc... Now the bass is otherworldly. So I can imagine a well designed PP 300b is going to have those qualities with a good field coil speaker and make people take notice. |
