Several Chapters Tonight:
Chapter One: The Meaning of Life for Delta Sigma DACs
This one is something I never have addressed seriously so I suppose it is time. What opinions and background constructing delta sigma (ds) based dacs do I have? I should begin by compartmentalizing the building blocks of a DAC. Basically, there is an input section, a digital to analog engine, and an analog output section, the three sections of all DACs, no matter how much they cost or how well they are regarded. The input section routes, handles, and formats digital audio signals to send them to the digital engine. The analog output section processes the converted analog signals to the rest of the audio system after the DAC. The digital to analog engine changes the digital data to analog (the way audio/sound occurs in nature)
A bit of a digression to surround sound decoders reveals that if one disregards the video section in the SS decoders, the same same three sections are involved, with more analog output sections (channels). In the digital to analog engine are also proprietary processes to separate audio into said analog sections. I am a bit out of date, but there are only a few digital engines designed for SS decoders which are available to the licensed SS decoder maker. Now, I know of few audiophiles who buy surround sound processors as a two channel vehicle. Surround sound decoders decode audio in support of video, and use delta sigma conversion engines. Another application is gaming where you have audio in support of gaming, and use delta sigma conversion engines. Yet another would be audio in support of convenience (smart phones), again utilizing delta sigma conversion engines. What surround sound decoders have in common with gaming devices and smart phones is that there are few audiophiles who would choose such devices as a primary audio device; further, they all sport delta sigma engines.Let’s explore the Eight main advantages of delta sigma conversion engines: 1) They are cheap – 2) They measure very well for distortion, noise, etc – 3) They are very cheap – 4) They are very well documented, usually with a copy me please and design me in data sheet, or sometimes even with example circuit boards for a cheap to copy me example. This makes it simple for non-digital designers (which are many or most of all of the designers of higher end audio equipment) to build delta sigma engined converters. - 5) They are extremely cheap - 6) There are so many of these chips available from so many chip makers that they allow you to plagiarize their circuits and use their physical circuits for free as a competitive necessity. - 7) The good old’ boys and the chipmakers who sponsor them at the AES just love delta sigma; low prices = high volume and low chip fab cost. The suits just love that Schiit. - 8) And lest I forget – they are so cheap as to be almost free, particularly since you get a complementary design. Now what do I mean for free? I consider it a waste of money to spend over 4 bucks on a delta sigma engine, with half of that being a norm. In contrast, the Schiit multibit engines: a Yggy Engine is $340, for Gungnir $150, and Bifrost $80.
So what conclusion do I draw from this? Delta sigma engines have a place in life for devices where the best audio is not the primary purpose, but only a secondary purpose, such as: surround sound devices, gaming devices, or cell phones – OR as well as when a product absolutely, positively needs to be cheap. After all, I put in the Modi 3, and Jason put them in his least expensive digital options for various amps as well as the Fulla. It still is a cheap Bifrost option, but probably not for long, based upon client interest. Let me say this again. Delta sigma is for hardware designs where audio is secondary to a greater function OR when it needs to be cheap.
After that digression through surround sound decoders, gaming rigs, and phones let me return to the three building blocks of digital to analog converter boxes. The first was digital input selection, formatting, and routing circuits. This where the digital input signal gets picked, converted to I2S or BWD or whatever the engine requires, and de-jittered in a more sophisticated design. To properly execute this, an engineer should be very conversant with digital theory and if clever will analyze the analog characteristics of the digital signal. Many of the delta sigma data sheets have mundane input/switching circuits which are frequently found plagiarized in the wild, along with the accompanying engine. Since there are only a few manufacturers who actually produce their own engines, this is where you find digital variations more audible, not just as a result of the engine, but as a result of the digital input circuit as well.
So we arrive at the analog section. This is where the experience level and component/circuit preferences of the designers are far more varied than the digital sections, but generally skewed higher. Here is where the modern designer, who more often than not, functions as an audio design artist, tuning the sound of his converter as he likes. This is where enormous amounts of money can be added to the design, from five dollar resistors to 40 dollar capacitors, specialized solid state devices or tubes, and the power supply to support them $$$. In addition, the speciality designer may add custom machined enclosures $$$$.
As those familiar with my designs know, my designs are not “tuned”. They are designed to be reproducers of recorded music which once existed in the acoustic wild, NOT a sonic canvas which have painted to some aesthetic construct.
Chapter Two: USB Questions
Now that we have a USB input section of our own design in solid beta for the Schiit line, what about the USB host (output) section?
Are we working on it? Yes!
Is it complete? No, still pre-alpha.
For what application(s)? Well, initially the Schiit transport.
Will you make a card for PCs with this host circuit? Nope, never. Even if I thought it were brilliant to enable competitors’ gear it would be a nightmare to support.
What is the oldest Linux kernel version which will support the Unison (Schiit) USB board. messed if I know – the oldest working kernel I have personally compiled and verified is 4.19. If I had infinite time I would build them all backwards until failure. I suspect any kernel incorporating UAC2 should work.
Chapter Three: Turntable Questions
Note I have seen only one question on this thread and more than a few on other threads; if you do have a question you want answered please post it here, as it is difficult for me to follow other threads just looking for TT questions. Much of this chapter has been posted elsewhere, but deserves to be addressed here where the question was asked. That question is:
Now that Sol is (almost) here, what cartridges do you recommend? And are there any to avoid at all costs? Thanks!
Let me reply with a series of generalizations and four specifics. There are two major classes of cartridges – moving magnet and moving coil. Moving magnet are the most prevalent, both in terms of numbers sold and models available. Moving coils are fewer and more expensive. The users with the $60,000 turntables tend to have the $5000 and up moving coils. Then they invite all both of their audiopile friends to stare, gape, and take photos of the vinyl rig before they play their two vinyl LPs. The MM (moving magnet) cartridges tend to have better compliance (ability to track and move with the LP groove) as they get pricier. This is important because the cartridge needle cannot move, the vinyl gets worn. The MM frequency domain is relative flatness up to 2-500Hz or so, then a plateaued dip until 2-3K or so, then a tendency to again be relatively flat until right before the final peak at 15-20KHz before it drops off to nothing. As the cart gets more expensive, the frequency domain gets better; the midrange dip gets better the high end peak gets higher up and less pronounced, etc. (Generally.)
Moving coil carts tend to have a less dipped midrange, but then a rising hi frequency response that can start as soon as 3-5K or so. They can be 10-15 db up at 20K! No kidding! They tend to have quite good compliance and therefore low distortion, albeit with the treble control turned up. Then the MC lovers talk about what wonderful detail their phono system has. (Albeit usually with great compliance!)
Before I go into hiding from MC lovers, a brief note on stylus shapes. The commoner ones are conical, elliptical, shibata, and a few other more even more pointy at the edges of the needle in contact with the record. In that listed order, the shapes of the edges of the needle get sharper and sharper, and let us not forget, pricier and pricier. A bigger problem is that as the radius of the groove decreases (Huh? Get’s closer and closer to the center of the record) the sharper the edge of the needle in contact with the groove, the more the high end rises, that is brighter and brighter as it gets to the center of the record. It seems the old scully lathes cut records to be at their flattest with conical syli (Needles). But wait, you say, weren’t those record master cutters equipped with sharp edged cutters?? Yup, you bet, but they are cutters, NOT designed for playback.
Now I have left off a few odd types of cartridges (strain gauge, FM oscillator modulators, variable reluctance, of which Deccas are a subtype, and others I may forget for the moment.)
Now, I seldom endorse any other maker’s anything – but I really love a Decca Plum (Now called Maroon) cartridge. I know, I know, they cost more than our turntable. They do everything right: conical stylus, completely made by hand, track at 3 grams, absolutely no cantilever, directly scans at stylus; everything right and perfect in the frequency domain; in your face just like a multibit DAC! Yeah! Forget the Gold, get the Maroon!!
Failing that the two hundred buckish Denon 103R and the 100 hundred buckish Nagaoka ain’t bad. You could probably even find a conical stylus for it, since Nagaoka is primarily in the styli biz.
I realize my conical/spherical preference flies in the face of not just current but classical audio press wisdom. It is easy to try for yourself, and if you get a Sol, you will sooner or later be trying other carts. It is an entirely new barbed-wire lined rabbit hole.
Anyway, enough on carts/turntables for now. Any more questions, please post them here.