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Abbado II NOS DAC kits

Orders now are open on Abbado II NOS DAC kits - PM me and be sure to include your payment method and location so I can quote you inclusive of fees and shipping. Abbado II is based on the work done developing 'Stack DAC' but has a much more convenient physical footprint of 100mm * 70mm using a 4 layer PCB and a single power rail of 9V. The maximum height is 20mm. Design wise, it's non-oversampling (i.e. there is no digital filter on-board) and the input format is I2S (three signal wire) at 44k1/16bits active within a 32bit frame. BCK is 64fs so 2.82MHz, no MCK is required. Output is nominally 1.3VRMS with a 6dB gain reduction option on-board and a limited range of overall level adjustment from a multi-turn trimmer. The gain reduction comes in handy when you want to use a pair of Abbados to create balanced outputs, the balanced output level can be kept the same as when unbalanced. In this configuration, the trimmer allows interchannel matching of output levels. Our I2S splitter board provides the functionality to run a pair of Abbados in balanced mode.

Preferred payment method is via Wise which typically adds a 2% fee. Our receiving currency is CNY, alternatively USD or Euro. PayPal may also be used, in USD but will attract higher fees, about 16%.

Price for an Abbado II kit : 388RMB (~$54,€50,£43)
Price for Abbado II built and tested : 568RMB

Shipping is in addition and depends on your location and speed of service. Courier (FedEx, TNT, DHL) typically takes 8 - 10 days and e-packet four to eight weeks. Not all locations can be serviced by e-packet though.

FAQs

What else is needed to turn the built up kit into a fully operational DAC?

First, you'll need a well regulated low noise power supply of 9V rated at 200mA or higher. An LM317-based board set to the correct voltage will suffice if you already have an unregulated supply (like a typical wall-wart). I don't recommend switching supplies due to issues with common-mode noise, its very hard to filter out. That disrecommendation doesn't apply though when both the DAC and amp are within the same box, in that case the CM noise isn't a worry. We can supply an LM317-based board with either DC (for unregulated DC) or AC (for a transformer) input option.

Second - you may need a digital interface card. I say 'may' because some digital sources produce I2S directly (like Raspberry Pi, dedicated SDcard players) but most sources will either output USB (like a PC or laptop) or S/PDIF coax (a CD or DVD player) or Toslink. We can supply a card for interfacing one (or more) of those sources to Abbado's I2S input. A CM6631A-based card for USB input is the premium choice as it operates under 'async USB' and offers up to 192k sample rates. Async USB has the lowest jitter however given it operates under high-speed USB it needs a fairly expensive isolator to protect your DAC and amp from common-mode noise. A TE7022-based interface has the advantage of only needing a $5 full-speed USB isolator while still offering up to 96k sample rates and is normally cheaper than a CM6631A board. For S/PDIF inputs, the board we recommend handles both coax (two inputs) and Toslink. Further, it has a switched I2S input - this can accept I2S from the USB source. A single pole switch acts as source selector, cycling through the inputs. An OLED screen is an option to indicate the selected input. This board needs a 5-12V supply, so it is fine being run direct from the DAC's 9V rail.

Third you'll be wanting some output sockets, typically RCAs so you can connect your finished DAC to your amp or preamp. We can supply these and we also have a PCB to mount them to make outputting Abbado to your system easier. XLRs would be the recommended way to output in balanced mode.

Lastly, and this is obviously optional for a DIYer, is a case. We haven't supplied cases in the past because they're so heavy (i.e. expensive to ship).

USB CM6631A card examples : https://www.aliexpress.com/item/32874113831.html www.aliexpress.com/item/1005004083748180.html
TE7022 interface example : https://www.aliexpress.com/item/1005005388553366.html
USB isolator, full speed : https://www.aliexpress.com/item/1005001369085297.html
USB isolator, high speed : https://www.aliexpress.com/item/1005001379930133.html
Multi-input S/PDIF card : https://www.aliexpress.com/item/1005002923079600.html
Coax/Toslink S/PDIF card : https://www.aliexpress.com/item/1005002772984954.html

Do I need special tools to build and test my Abbado kit?

You'll need some fine diameter solder (0.3mm is recommended), a temperature controlled soldering iron with a fine tip bit and a pair of tweezers. A magnifier comes in very handy but that depends on your eyesight. Desoldering braid is helpful for correcting mistakes. Abbado comes with many of the smaller parts already soldered down (most by machine). None of the parts to be soldered are microscopic (the smallest is 0805) and none of the ICs has pins closer together than 1.27mm. For testing you'll need a DMM (digital multimeter) which is able to read both Volts and Amps.


What's supplied in the kit?

A picture of the kit contents can be found at the bottom of this post, it contains the pre-soldered PCB plus all the components that mount on it (resistors, caps, inductors, ICs etc.). You need to solder DACs, logic, regulator and discrete transistors which are SMD parts plus various through-hole components. Input, output and power are supplied via 4pin Molex-style headers, we supply the mating half with crimped wires to these too.


What, if anything, is unique about Abbado's design?

Commercial NOS DACs typically have minimal filtering after the DAC chip itself whereas Abbado has a fairly steep (5th order) low-pass passive filter which also provides some NOS droop correction. This LC filter improves dynamics and makes the aural picture more clearly defined with acoustic instruments having a well defined position in space. Passive filters like this are extremely difficult to implement using off-the-shelf inductors as no commercially available ones have sufficiently close tolerance. So Abbado's inductors are custom, hand-wound. Having a passive filter prior to any active analog stage means the discrete buffer no longer 'sees' a step waveform out of the DAC chip, rather a continuous signal. Abbado's DAC chips are 'multibit' but they're not strictly speaking 'R2R' as internally they use no resistors. Instead, capacitors are used as elements in the DAC which have their charge constantly refreshed (similar to the DRAM in your computer) to compensate for any drift. By paralleling 16 of these devices and running them at higher current levels than typically used, the noise floor is considerably lower than with a single chip - this translates in practice to a 'warmer' sound where the acoustic ambience captured on a recording is more easily perceived. In order to achieve retrieval of these low-level ambience cues, the DACs' power rails need to be extremely clean and this is achieved through use of a pair of discrete series regulators fed from an IR LED derived reference voltage.

AbbadoII_stuffed_20230615102920.png
Abbado II rev2 Guide.jpg
 

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what do you think of Abbado compared to your other 'sons'?

Hi Guglielmo - we did a comparison of balanced Abbado (means two DACs fed by the I2S splitter) and Celibidache. I preferred balanced Abbado for its slightly warmer presentation and better instrumental separation on 'busy' parts of the music. Overall the differences were quite subtle.

What does the logic section does?

George - the logic is there to convert I2S to the right-justified (EIAJ) format that TDA1545A uses. There are a couple of shift registers which re-align the WS signal with the datastream.
 
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Got mine all mounted up and powered it up using a bench variable power supply. Yellow LED lit up. Voltages out of RCAs started in the 1-2 volt range but then drifted down to 4-5mV after 30-35 seconds or so. Waiting for a test 9V power brick to put the DAC into my test system (really thought I had a 9V wallwart/brick in my boxes somewhere...ugh!).

Cheers
 

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I've got it down on my main system. It's running using a powerbrick I bought from Amazon using Mark Johnson's SMPS filter (obviously not the cleanest way to check the Addado but more on that in a bit). First thoughts are that it's very neutral sounding. Has an airiness to it and highs are clean & contained. I've been busy with other "normal living things" so haven't had time to play music that tests bass response and soundstage and/or go back and forth using my standard DAC (AMD.org's Gamma1+2). I'm going to build AMB.org's Sigma11 PS to power it (PCB & parts will be here by Friday) to see if a clean supply alters the DACs performance. All the DACs I've had always seem to sound better when using either a linear PS, or a regulated one, as opposed to a wallwart or powerbrick.

Cheers, Pete
 
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Sounds good Pete, well done.

Obviously a clean PS can be a plus, depending on how sensitive the device is. If it sounds clean already than perhaps OK, especialy as Mark's filter is doing wonders on non to demanding DACs that need help.

It might be interesting to check on your existing system bass depth, dynamic (probably more difficult as you don't know what the device is "utterly" capable of in that regard) and image depth / 3D, as IME that's where a cleaner supply made the most immediate benefits on the DACs that were sensitive to it

Eager to read you again and again well done

Take care

Claude
 
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"Obviously a clean PS can be a plus, depending on how sensitive the device is. If it sounds clean already than perhaps OK, especialy as Mark's filter is doing wonders on non to demanding DACs that need help.

It might be interesting to check on your existing system bass depth, dynamic (probably more difficult as you don't know what the device is "utterly" capable of in that regard) and image depth / 3D, as IME that's where a cleaner supply made the most immediate benefits on the DACs that were sensitive to it."

Well, after building Ti's (AMB.org) Sigma 11 single rail PS, powered with a 25VA Talema transformer, I think the difference in what I hear is startling. It expanded the soundstage, a greater ethereal presence to my classical music appeared, violin solos were non-fatiguing, and I was able to hear delicate things happening with the musicians' instruments & in the music. The powerbrick just slightly dulled everything, even with MJs SMPS filter. The Abbado II still seems to be very neutral in nature...no coloration or warming of any of the frequency spectrum. The bottom is clean and non-muddy. I'm going to try one further step, probably superfluous, but the USB to I2S board I'm using to bring in the signal is being powered by the cellphone I use as a streaming device. I'll try powering that USB board independently of the USB connection and see if that does anything to enhance the listening experience.

Claude & Richard....in the case of this DAC I think a clean/quiet PS really is needed to appreciate its design for a silent background. I'll await other's evaluations of this DAC.
 
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The powerbrick just slightly dulled everything, even with MJs SMPS filter.

I suspect that the powerbrick is a source of common-mode noise which won't be filtered out by MJ's filter as that's a differential-mode filter. The advantage of the AMB 'linear' power supply is the absence of CM noise. I experience similar improvements myself in going from an SMPSU to a linear supply, with the SMPSU everything is 'greyer', less contrasty.

Thanks for sharing your experience Pete, appreciated(y)
 
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