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Getting the best out of Allo.com's new Katana DAC...
Getting the best out of Allo.com's new Katana DAC...
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Old 17th November 2018, 08:55 PM   #21
Markw4 is offline Markw4  United States
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Greg, You do a good job of describing the conventional thinking about power supplies for top notch audio. However, things are starting to change, although most audio product designers haven't figured it out yet. For example, Benchmark DAC-3 uses a SMPS, followed by what look like some LDOs, lots of SMD ceramic caps, and quite a few small electrolytics.

The SMPS can be seen in the upper right corner in the pic attached below.

DAC-3 is on the Stereophile A+ recommended equipment list. It sounds better than Katana ever could, as it uses external interpolation filtering and also some techniques to keep jitter very low while maintaining the benefits of ASRC. Just goes to show there are other ways to do such things, and although DAC-3 is not cheap, it is the least expensive on the Stereophile A+ list.

Another thing to possibly consider is that a lot of power supply problems come from the line rather than the load. For that reason I use a (discontinued) Monster HTPS 7000 Mk II power conditioner. That works for everything in the audio rack, and considerably reduces the requirements for power supplies in individual pieces of equipment. Although the power conditioner is no longer made they can still be found on ebay, and are extremely worthwhile. Most stereo systems sound much better immediately when plugged into one. The sudden improvement in sound is a dramatic effect.

When I do listening tests here, including for Katana, all devices are powered through the conditioner. It helps a lot.
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Last edited by Markw4; 17th November 2018 at 08:58 PM.
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Old 17th November 2018, 11:36 PM   #22
Bigun is offline Bigun  Canada
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Getting the best out of Allo.com's new Katana DAC...
Thanks Greg!
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Old 18th November 2018, 12:45 AM   #23
Greg Stewart is offline Greg Stewart  United States
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@Markw4,

First, thanks. AND welcome, @Bigun.

Mark, please don't take my comments as being a blanket condemnation of SMPSs. I know some highly-regarded gear, such as the DAC3, the Mytek Brooklyn, the iFi Pro iDSD, Emperical Audio, Devalet, Berning, Bruno Putzeys work, and many others use them to very good effect. Of the amps I've used in the last 12 years, 4 had SMPSs and only 1 had linear supplies. 2 of the SMPS-powered ones were my best amps for their time and one has a good chance of being my best amps in the future. AND my personal experience with SMPSs powering source components and some reviews I've read have suggested that for some of those units they can be improved with very good linear supplies... at a price. Both ideas co-exist for me... that SMPSs can be good and compete with and better linear supplies... and that in some situations SMPSs can be bettered by linear supplies. I'm just pointing out my experiences and some that I've seen that are similar.

Thanks for the interior pix of the DAC3. My unprofessional assessment is that they have implemented a more extensive than typical power filtering regime with a number of inductors in addition to the LDOs and MLCC. Allo does similar, but generally has less real-estate available, so less-extensive. I'm sure what Benchmark did there is a key element of the SQ of the DAC. And the internal pix of the Mytek Brooklyn seen in the 6Moons Audio review (here: http://www.6moons.com/audioreviews2/mytek4/4_big.jpg), seem to show less extensive filtering than the Benchmark unit. It was one of the DACs that was improved by using an external linear supply. Draw what conclusions one may from that.

Still, finding a good set of SMPSs for the Katana may be a lift with the current offerings. That's why I'm watching the Nirvana closely. BUT as Allo has indicated, getting the quality they want from a unit able of a 5V/3A output has been challenging. That's why I have latched onto Allo's suggestion that adding a +-15V supply as part of the base 'getting the best quality' configuration, along adding an isolator which requires a third 5V supply for the RPi. This all lowers the current requirements for the 2 supplies powering the DAC / isolator and the Microprocessor board and broaden the good choices out there.

Back to the DAC3, I do like that Benchmark implemented their own filter regime. While the current generation of ESS DAC chips have significantly improved filters than the previous generations, they still are limited by the DAC chip real-estate AND the need to push specs as far as they reasonably can. Many suggest that much of the sonic signature of the Ayre DACs is also due to their proprietary filtering. AND companies like Chord are deeply wedded to their digital filtering techniques. Hopefully Allo can move that direction with a future incarnation of the Kali and/or Katana.

Finally, I don't know if you saw my comments about my AC filtering regime over in the main Allo thread. If not, go check them out. We are in violent agreement on the need for significant AC line filtering. I have an extensive 'defense in depth' approach with distributed parallel passive filters around our entire house, passive filtering and active regeneration on my main audio gear, and I though I didn't mention these there, auxilary linear power supplies (for things like switches, music server, FMC's, etc) with some tweaks to lower the measurable noise fed back into the AC lines and optical networking links between the digital source gear and the final playback gear along with local isolation at the DAC input. All worthwhile.

Finally, I have another comment to add to my previous post on whether the Katana is a well-engineered product. In another realm from power supplies, I suspect a large portion of what people hear from the unit is due to the 6 Sparkos Lab discrete opamps in the output stages. At $80 for a dual version of that device, Allo has packed in the equivalent of $240 of output stage components into their $260 DAC. That makes it an even more incredible bargain!

Not that I'm trying to sell them (nope, no financial interest in Allo here!). BUT that thought just blew my mind.

Later!

Greg in Mississippi
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Old 18th November 2018, 01:18 AM   #24
Markw4 is offline Markw4  United States
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Quote:
Originally Posted by Greg Stewart View Post
... please don't take my comments as being a blanket condemnation of SMPSs...
Of course not! Just didn't want people who don't know as much about it as you who might be reading along to get the idea extensive linear supplies are the only way to go to get good results. However, designing good SMPS still remains more of a specialist activity. Anyway, probably enough has been said about it by now to last the whole thread.
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Old 18th November 2018, 02:23 AM   #25
ktham is offline ktham  Canada
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[QUOTE=Greg Stewart;5604588]@Markw4,


Finally, I have another comment to add to my previous post on whether the Katana is a well-engineered product. In another realm from power supplies, I suspect a large portion of what people hear from the unit is due to the 6 Sparkos Lab discrete opamps in the output stages.



@ Greg Stewart
The Sparkos Labs discrete opamps have made a positive difference in my modified Quad 44 preamp. I made the changes while I was waiting for Katana Ver1.2 to arrive in October. Consistent with the changes I had to adjust for the increase in load current to my shunt regulated power supply and resizing the heat sinks. Sometimes being the minimalist has its downfall! But then, isn't that what a DIY'er does which is to look for any excuse to tweak, experiment, build and enjoy the music?
Using the discrete Sparkos op amps I hear the darkness between tracks which is quite pronounced at normal listening levels. Hopefully this week I will get to hear the new Katana with this setup once the external +/- 15V supplies have been assembled and tested.
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Old 18th November 2018, 04:22 AM   #26
xx3stksm is online now xx3stksm  Japan
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Getting the best out of Allo.com's new Katana DAC...
@Markw4,

I would say the PCB of DAC-3 has an interesting structure which most tens of dollars DACs can't have. There are few traces on the component side in spite of several QFPs. This is because it has internal layers for routing traces, power plane, and a ground plane. A ground plane with no split line is mandatory for a DA converter to guarantee excellent SNR. Cheap DACs don't and can't use multi-layer PCB. I don't think high-speed DAC like ESS can do the job without an inner ground plane. This is not personal likeness but physical low in electronics.

DAC-3 probably avoids laying traces on the component side not only to prevent from reverse engineering but also to have good noise immunity. If their target is RF, this is not a good idea. It may result in many vias and impedance mismatching. But this is the best layer structure for an audio DAC, IMHO. I also prefer to use the same one as DAC-3. The component side is parts and ground plane for shielding, where there are no high-speed traces. I guess the 1st inner layer has necessary signal traces and the 2nd is a ground plane. The solder side is power rail. I'm sure their PCB is more critical than DAC chip itself for good SQ though I haven't listened DAC-3 so far.
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Old 19th November 2018, 12:23 PM   #27
Dimdim is offline Dimdim  Greece
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I'm pretty sure I read somewhere that the DAC-3 has a 6 layer PCB.
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Old 20th November 2018, 02:39 AM   #28
Greg Stewart is offline Greg Stewart  United States
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Getting the best out of Allo.com's new Katana DAC...
To keep the conversation going, here's some details of the Katana end of my +-15V supply that anyone with moderate DIY experience can to use to duplicate (or better!). ALSO, be kind, this was a 1-evening Q&D build... it is not pretty nor was it intended to be!

1. To compliment the Sparkos Opamps used in the output stage, I used +-15V Sparkos regulators (that have served me well in other builds/mods).

2. To keep the paths short, I cut a piece of perf-board to match the RPi DAC HAT outline and built the reg point-to-point on top.

3. To minimize the contacts, I fed the outputs directly into the +-15V input on the Opamp board via a pair of 3-position sockets (with only one contact used on each). I used another 3-position socket to engage the ground connection. I used those sockets to match the pins on the Opamps stage board and make it easy to mate correctly.

4. Raw DC was +-23V from the supply I described earlier in this thread. That's higher than needed. With a good stiff supply feeding the Sparkos +-18V should suffice, +-19V gives a bit of margin.

5. I used a pair of 3900uF/25V United ChemiCon KYB series caps as local filter caps on the inputs. A pair of 680uF/16V KYB are on the outputs.

6. I added small-ish heatsinks. Even with the current draw and the overly-high input voltage, they don't feel over-hot. I'll measure at some point.

7. It's all connected to the raw +-23V DC supply via 18G wire. The output of the raw DC terminates in a 7-pin Hirose connector (7-pin so that I can someday go to dual-mono raw DC supplies). There's also a pair of 2-pin high-current Deans Connectors (from the model airplane/model car world) to allow me to try different output regulator setups. Better to have just 1 connector, but those Hirose are expensive (and EOL now, so harder to get).

I've been prodding Allo to consider producing a generic +-15V regulator stage printed circuit board that would mount on top of the Katana stack the same as mine and have pads to support 7815/7915 pinout regulators (Sparkos or others). It would be cool if they could configure it for LM317/LM337 and LT1963/LT3015 regs, but that would likely lead to wiring mistakes and burnt regulators and/or Katanas. Better to do 2-3 different board versions... might be a good community project here for a group buy? I don't have board design chops, but I bet some reading this do.

Alternative higher-end regulators to consider are Belleson and the new Dexa discrete regulators. I have used both of these before in other projects with similar good results. But input and output filter cap requirements may be different... read and follow the datasheets.

AND of course, Salas might be some of the best you can use here, but they won't fit on top of the Katana as these series regulators do.

Other alternatives?

Greg in Mississippi
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Old 20th November 2018, 03:02 PM   #29
soundcheck is offline soundcheck  Germany
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I think all this here goes way over the top for most of the people.

I'd say. First things first. Or better the easy wins first.

1. I'd start with what RPI and what OS and what OS setup to use
2. I'd discuss how to get rid of this awful USB-C powering scheme
3. I'd discuss removing these cheap RCA sockets
4. I'd discuss what grounding scheme to apply

And there's more.

For sure I consider a $1000 power approach as one of the 1st things to do nonsene.

My 2 cents.
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Old 20th November 2018, 04:25 PM   #30
ernesternest is offline ernesternest  Europe
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Yepp, this easily goes the wrong direction. BUT the thread title gives us an idea of that direction. I'd rather be happy about an effective way of powering the Katana in order to get 92.5 percent out of it using a decent, medium priced, rather simple PSU. Just my 2 cents.

Thank you for all your efforts and entertainment.
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