Holo Audio – SPRING 3 DAC level 1 (R2R – DSD1024)

SPRING MODELS

Three versions of the Spring 2 DAC. Below are the three levels, and KTE being our no compromise model with all options:

SPRING GEN 3 LEVEL 1

(The base model is quite good all by itself and priced so competitively it’s impossible to beat the performance/price ratio.) This model has basic caps for the PSU, and does not include a CNC remote. It has standard Red label 5N Copper Otype Transformer, round wire type copper wiring. Considered the base model however packs a mean punch for price per dollar performance ratio. (no remote control in this version)

”OPTIONAL upgrade – Preamp Module” – Fully discrete and balanced relay controlled volume control. Controls all the digital inputs volume with precision. This has trickle down technology from our popular flagship Preamp the Serene. Using 4 amp modules and hundreds of transistors.

This DAC was carefully implemented with some of the finest components. 

TECHNICAL SPECIFICATIONS

DSD is natively supported for the first time on this Discrete Resistor Ladder DAC

HoloAudio is the world’s first to support DSD natively on Resistor Ladder DAC, so far the only one. This is not the DSD converted to PCM before digital-analog converter, but directly by the discrete components of the DSD digital to analog converter. Supported currently on MAC (DOP)and Linux (DOP), and Windows/PC (Direct Native and DOP). Please note, the word ‘R2R’ is the name of a kind of architecture of resistor ladders. This architecture requires less resistors yet still is capable to deliver more than acceptable performance. Most DACs in the industry use this architecture. The DSD module of Spring3 does not use R2R architecture for the DSD, more specifically it uses a very specific architecture which is optimized to perform DSD to analog. So to be entirely accurate the DSD part of Spring is using resistor ladders, not R2R..

Spring3 DAC R2R structure and design + Input/output Stage

Modern and popular delta-sigma type DAC differs from R2R within one clock analog value can recover a sampling point, and the delta-sigma is used to represent an analog signal after passing through oversampling and high-speed digital switching 0 and 1. In comparison, the conversion structure of R2R is most direct and pure, but delta-sigma is essentially a digital chip, high-speed digital signals 0 and 1 switch to the low-pass filter to process the analog signal and this process is prone to various problems, produce digital sound (digititus) and also in the super-sampling process will inevitably cause some ringing and distortion. But DAC R2R structure requires high-precision resistor network which the cost can be very expensive. And the digital delta-sigma DAC chip in comparison is very low cost. Patented R2R technology. This is the first discrete DAC that has Linear compensation and this allows for ultimate music reproduction accuracy. Dual R2R ladder network with advanced architecture for PCM, and Dual Resistor Ladder network with optimized architecture for DSD!

I/O stages: There is an Op Amp used for input stage and discrete component used for the output stage. The discrete output stage is working in pure class A.  The output voltage is 2.9 Vrms for single ended output and 5.8 Vrms for balanced output (dsd playback is half these voltages). The single ended is RCA. Balanced is XLR. They both use the same output stage. It’s BiPolar Junction Transistors, direct coupled. The big MKP capacitor you can see in the output stage is for the power supply, not for signal coupling. And the output impedance is 200 Ohm. 

A common question we get…” Why do you use an Op amp at the input of the DAC?”  

The input stage with an opamp is a good choice. It has a paired transistor input by the nature it is manufactured. But an opamp for the output stage is limited due to it’s size and the thermal capability. Also, no one will offer an opamp with class A output as it’s efficiency is so low. So an opamp used as input and discrete output combined together will have an advantage. It doesn’t mean that all discrete is not good. Actually, if we need to achieve enough low distortion. It needs at least 30-40 transistors. Which not only will it be huge and waste of space but it will also be too costly. I mean, to beat the opamp’s performance, a simple discrete architecture is not possible, although an all discrete design looks beautiful.

The true balanced circuit design

These two pictures can explain the true balanced design quite well. The bottom side has the same resistor ladders as top side. The dac module is a pure 24bit discrete R2R design (PCM) and discrete Ladder Dac optimized architecture (DSD).

What are the Spring 3’s sound characteristics?

One of the strong points of the spring is the spatial sounds stage presentation. It’s very wide and precise. It never sounds congested like many DACs. The high end is very detailed and never harsh sounding. It has the R2R goodness that many have come to know and love. R2R has almost a cult like following and this DAC will surely become a sought after DAC.  Everything comes effortlessly for this DAC. Bass is layered and textures, quite full and present without ever masking over the sweet mid tones that are produced. One special thing about the Spring is its amazing voltage regulation circuitry that better than 0.2uV output noise! This along with the O-core transformer helps regulate the purest power which translates to audio clarity and accurate reproduction. It must be heard to appreciate and come to love its sound.

Jeff Zhu comment on the Spring3

Spring3 PLL is nearly the same design as our flagship dac, the May. The main difference between Spring3 and May is that May uses our latest technology and cost is no object, therefore has better components. For Spring3, it uses the latest technology as May. But the main goal is to get high performance at reasonable cost, and I believe we absolutely achieved this goal. Although it’s price is higher than Spring2. I think the performance/cost ratio is higher than Spring2. It’s not much behind May! The pre-amp module inside is a very decent way to control volume, really one of the best ways. I think the digital volume is terrible, especially for this level of DAC. So I never added digital volume control on Spring and May, only on Cyan which is our entry level product. Digital volume is very easy and has very low cost added, albeit compromised. The reason we don’t use it is that ‘free digital volume’ will lead customer to use it and not realize it is not ideal for use with our higher end dacs. I don’t want misguide the user to use our DAC is that way. I think they will be most pleased with our fully balanced, discrete analog volume control for a low optional upgrade price.

Jeff Zhu – HoloAudio Explains his patented R2R technology

There are ways to improve the performance, the segment+R2R is one way. Trimming is another way. There is an additional R2R ladder in Spring, it compensate the main R2R ladder. It works like trimming, but trimming is to change the resistor value. This additional R2R ladder are digital controlled and is to compensate the resistor tolerance. For example, the MSB of 16 bits should have the value of 32768, but due to tolerance, it represent 32700 in real world. Then that additional R2R ladder will compensate 68 into it. Then it became 32700+68=32768.

Actually there are other ways to improve performance, I just told you two stories. There are more stories behind the design. It is really hard. I must count every via holes in layout, every PCB wire has it’s impedance and must put attention on it. A via hole can be 50 m Ohm, it is 1/20000 of 1 kilo-ohm, and you see, it covers 32768 which is the MSB of 16bits. Also the switches has self-impedance which is about several ohms to 30 ohms. If you find this issue. Maybe you will go crazy, it seems to be an impossible mission. But a good designer will overcome all these problems. It’s our value at HOLO Audio.

All the resistor tolerance, switch impedance, line impedance, via hole impedance, finally reflect as linearity. There is a chart that shows Spring’s linearity, it’s excellent. But I suggest you to look at THD performance. Bad linearity must result a bad THD performance. But good linearity doesn’t mean there will be good THD performance. THD is dynamic performance, more critical than linearity which is a static performance.

If you look at the THD performance, you will find Spring to maybe the best among those competitors. I’m applying a patent which contribute a lot of that performance. But I can’t tell you how. It’s confidential now.

R2R LINEAR COMPENSATION

There’s an additional R2R ladder in the Spring DAC, it compensates the main R2R ladder. It works like trimming, but trimming is to change the resistor value. This additional R2R ladder is digitally controlled and will accurately compensate the resistor tolerance. For example, the MSB of 16 bits should have the value of 32768, but due to tolerance, it represents 32700 in real world results. Then that additional R2R ladder will compensate 68 into it. Thus it now becomes 32700 + 68 = 32768. What this means is that it’s likely the most precise Discrete DAC on the market with near flawless linearity, lowest THD and highest SNR of any NOS DAC. The sound is simply something you must experience to fully realize how special this DAC is. It’s a patented technology exclusive to Holo Audio.