Apr 052012

I wondered how long it might be after Deltec Precision Audio had returned to the audio market that they once again had a DAC as part of their product portfolio. Not that long as it has turned out and its a real blast from the past, looking identical to some of their1990’s range of Digital To Analogue Converters. Of course if you look on its back, the presence of a USB input leaves the viewer in no doubt that this is a bang up to date design and no vintage piece of digital kit.

This is an interesting item for me to have a look at, because being honest back in the day I was not a fan of the original Deltec DAC’s. Now in saying that I need to make it very clear that I am talking about their designs that used 1BIT/DAC 7 Bitstream Digital to Analogue Converter technology (the PDM3 does not as it uses a AK4397 32-bit DAC chip at its heart), such as the Little Bit, Bigger Bit. Frankly I found the sound of those designs (and others like the Meridian 203 DAC) to lack dynamic range and pace compared to designs using multi-bit DACs such as the ubiquitous TDA 1541 (1) I much preferred the sound of CD players and DACs that had multibit technology at their heart.

I was quite excited to see this DAC (having been aware that Deltec were working on a DAC but I had been sworn to secrecy, so I had to keep stum about it) at last years National Audio Show at Whittelbury and even more excited to get hold of a sample for a listen. Before looking at the PDM3 in more detail, it is very much worth while taking a bit of time to remind ourselves of the historic position Deltec hold in the development of Digital audio technology in the UK in the 90’s.


From the early 90’s Deltec Precision Audio had a wide range of DACs from the DPA – PDM1, which used a Philips’ SAA7320 bitream DAC/ decoder and the analogue stage was based around a DH-0A32 discrete opamps. The next DAC the PDM1.2 was similar to their first one but used a SAA7322 decoder and the next one PDM1.3 used the much heralded (at the time 1993) DAC7 module or SAA7350. These were all expensive items but none as expensive as the two box PDM2, which was a high end design, designed to extract every morsal of performance from the SAA7350 Philips DAC.

I don’t think there are too many who would argue that Deltec Precision Audio  in the early to mid 90’s were leading the way among UK audio companies who produced DACs, and the then addition of a series of more budget DACs the Little Bit and Bigger Bit gave Deltec a huge slice of the UK specialist audio market. In 1994 they introduced a radical new design in the form of the PDM1024, which was Deltec’s first ever implementation of their Current-Pulse Conversion technology: direct bitstream conversion not based on commercial DAC chips. This particular product sold at the time in 1994 for £6000. Despite all this success Deltec Precision Audio closed their doors in 1997.

In 2011 rumours suggested that the new Deltec were cooking up a new DAC and at the National Audio Show held at Whittelbury Hall in September 2011 those rumours were confirmed by the appearance of a prototype version of the DAC I have sitting on my audio rack as I type these words.

Technical Details

The PDM3 was designed by Deltec Precision Audio’s Dave Clarke and has three priority selected inputs, USB, optical SPDIF and coaxial SPDIF, with sample rates from 44.1KHz/16 bit to 96KHz/24bit. At the neart of the design is the AK4397 32-bit DAC chip, which is able to accept digital signals up to 192kHz. The USB receiver is an iso-synchronous type that only accepts signals up to 48kHz. The PDM3 is also a non upsampling design.

Deltec have this to say about their design

‘The Deltec PDM3 is a true high end performancedigital to analogue convertor. It has been designed to keep the signal path as simple and direct as possible. Digital integrity is maintainedby not using potentially corruptingup-sampling or DSP(Digital Signal Processing)before the converter.Following the converter our reconstruction filter is formed around our uniquehybrid voltage amplifier. Together these enable the PDM3 to have exceptional transparencyand instrument separation.’

As with the recent Calyx DAC review (more or less done at the same time as this review) I did not use the USB input as I don’t support computer based audio. Ludite you may think, and I am proud to be so in this matter.


The Deltec Precision Audio PDM3 comes in a compact case 230 wide by 100 high by 330mm long with a nicely made curved front cap (with only a single light and logo adorning it) which finishes of a case that is constructed from a u shaped formed sheet which is secured to a base plate. I have to say though that this case was quite resonant and indeed amplified the hum of an internal transformer. During use (once I had introduced this item to the system ) I ended up placing the DPA Power RF Filter (identical shaped case just different colour) on top which damped the loud hum to an inaudible level.

On the back panel there is a single pair of RCA analogue outputs (no balanced outputs on this design) a USB input, RCA Coax digital input, a Fibre Optic input and a Deltran Clock link input (2)

As the DAC had a security seal underneath I did not open it to take photos of the internals but Deltec have been kind enough to provided a photo that gives an opportunity to see under the hood.

Review System

The system I used for this review was the same as the one I used during the Calyx DAC review, except that I used the Deltec Power RF (3) filter as well, to power the DAC and the Transports I used. I don’t normally employ such a device during my reviews but I made an exception in this case because using it with the PDM3, and either the Micromega Data or Audiomeca Mephisto transports, well the improvement in performance was quite marked.

Sources were my Moon Andromeda CD player, Audiomca Mephisto and Micromega Data CD transports and an Olive4HD for HD tracks.  Amplification was via a Chapter Audio Signature pre-amplifier and Couplet power-amplifier, with Anthony Gallo Reference 3.5 speakers. All equipment was housed on Clearlight Audio Aspekt racks, with the CD  transports and Olive4HD used on a Ginko Cloud Isolation platform (4) Signal cabling was TrusoundZ Revelation, Atlas Mavros with speaker cable Atlas Mavros. Mains cabling was TrusoundZ , Audience AU24 and Analysis Plus Power Oval 2.


Nitin Sawhney – Broken Skin

The Dali Demo CD

Jazz Side of the Moon – The Music of Pink Floyd

Initial Impressions

It has been a very long time since I had a Deltec Precision Audio Digital to Analogue Converter in any system I have owned in say nearly twenty odd years and as I indicated earlier in my introduction to this review I was not a fan of those early experiences. However from the off listening to the PDM3 was not what I had expected and despite the unit having just been powered up my initial listening encouraged me to put away my past prejudices; yep even audio reviewers can have both positive and negative bias re the products they encounter. So putting all my negativity re past encounters away, I am glad I took the time to listen to the PDM3 but  if I say much more at this point I will be getting ahead of myself.

The unit I had in for review had been run in, but it did still benefit from being powered up over a period of about a week, during this time music played via the PDM3 opened up and the presentation became somewhat sweeter and more musical.

Having also been supplied with a Deltec Power cord I listened extensively to the Deltec DAC initially with it and then with one of the TrusoundZ TSZ-0966 power cords I had been reviewing recently and in the context of my system I preferred the DAC with that particular mains cable fitted. Using the TrusoundZ cable gave me a slightly more open, detailed and focussed sound, with a little bit more definition and extension in the bass.

As I also had the Deltec ‘The Power Plus’ mains RF unit to hand as well and I hooked it up to the DAC and noticed an immediate gain along similar lines to those I had obtained from the Trusoundz TSZ – 0966 mains cable but taking that improvement in sound quality even further. Trying the Power Plus with a Deltec Power cord and then a TrusoundZ one feeding it from the mains supply after a few swap arounds I found myself again preferring the TrusoundZ cable as the input feed cable.

As I had no TrusoundZ female to male IEC equipped cables (not even sure if TrusoundZ make such an item) I stuck with Deltec’s, but during the review, being honest, there were times when I wondered if I could have pushed the envelope by using TrusoundZ power cables throughout. The bottom line though, regardless of the mainscables used, was that the Deltec DAC took a big leap forward in performance when hooked up to the Deltec Power; as did any of the transports I used during the review period.

Initially I used my Micromega Data transport but after quite a bit of comparison I once again was confronted with the ‘not all transports are equal equation’ and it was very clear that my Audiomeca Mephisto transport offered superior sound over the Micromega Classic Data. I used the TrusoundZ TSZ-0015 RCA to RCA digital cable for data transfer duties, preferring it to any of the others I had to hand, including the Perfect Wave cable Deltec provide with the DAC; which while good should really only be viewed in the context of a ‘get you started’ item.

I also used a set of the new Deltec Black slink cables as well, at the start of the review, and while they were very good (subject of their own review soon) I ultimately decided to stick with my own Atlas Mavros RCA to RCA cables as I was using Mavros XLR cables during comparisons with my Moon Andromeda CD player. To have used another cable make would, I felt have been to  add too many more variables into the listening process.

One new item to my system that I did use during this time was a Ginko Cloud isolation platform (4), an item I have wanted to try out for many years since reading about them in the pages of Stereophile. I will be doing a little mini review on this item soon.

I used my usual reference albums during this review but also many others as well. The unit was well run in before hand. Only bug bear was a huming transformer which still buzzed even with the Power hooked up, in fact the only way to stop this was to place the power on top of the DAC, a less than ideal solution. This noise is I am pretty sure was due to the shape of the case amplifying the transformers buzzing within; as damping the case reduced the hum massively.

Now I think it only fair to say at this stage that the Deltec PDM3 DAC is equipped with a clock sync facility, which Deltec calls Deltran-link and they will equip your CD player with this facility at a very reasonable cost. However as I had no access to a suitably equipped transport  to avail of  this feature, one that should significantly raise the bar of performance from the PDM3; I would encourage a prospective owner of the DAC to consider having this fitted to their transport. However not having access to a Deltran equipped transport I decided to review this DAC in the way someone might if buying it to upgrade an older CD player and perhaps play computer files through it; though I did not do that, as I am very old school and have yet to seriously consider going down this road. However I did play HD 24 bit 192 tracks through the Deltec from the coax digital output on my Olive 4HD which would give me some idea of the performance one might gain by availing of Hi Resolution computer sourced files.


As I said above it has been a very long time since I had heard a Deltec DAC and in the main my dislike of those earlier DACs was down to the technology they used; i.e Bit Stream. I much preferred the more open, dynamic and pacy sound of CD players and DACs using the Philips Multi Bit DACs, such as the TDA 1541. I always felt that Bitstream DACs sounded mushy and a tad slow; well this new DAC from Deltec is anything but as it is: open, detailed, fast and very musical but achieves all this with a presentation of music which is very neutral; lying just to the slightly leaner side of things. Its not bright or forward as such just highly focussed.

Bass is very good but in comparison to my Moon Andromeda was leaner, less full and as such lacked a bit of weight, scale and drive on some of the Dance/Electronica tracks I used while reviewing it. Please don’t get me wrong though, this DAC had plenty of bass just it was tighter and slightly less extended than the Moon but it was every bit as nuanced as the Andromeda.

I used the Moon Andromeda as it is my day to day reference digital source, though it would have been both nice and useful to have had a similarly priced DAC from another company as a comparison aid as well. However comparing to more up market items is always useful to.

Using Nitin Sawheny’s wonderful album Broken Skin with the Audiomeca Mephisto the sound was was beautifully nuanced, detailed, delicate and yet powerful and driven when the music contained such elements. Vocals were nicely placed within a wide deep soundstage (these aspects were narrower and shallower with the Micromega Data used as transport) and very much had their own space within the acoustic. During the track Tides the piano had a very solid real presence within the room and all the percussion elements also had their own space, focus and decay were reproduced well and any shortcomings were only obvious when listening to the same tracks via the Moon Andromeda which had greater transparency, focus, detail weight, scale and better timing but this is to be expected from a £10000 CD player in my book.

Listening to Stimela from Hugh Masekela on the Mephisto Deltec DAC combination was a very pleasant experience as the music ebbed and flowed, rose up and down with all the nuances that I know and love present. However listening to the same track on the Moon showed that its greater weight and scale benefited the acoustic, timing and textures of the underpinning bass and drums. Some drum and bass detail was much reduced via the Deltec DAC a good example of this is the drum strike at 7 mins and 56 seconds as the decay and impact of the stick on the skin had greater reality, dimension and decay via the Andromeda, with the same sounding more recessed and less dimensional via the Deltec Mephisto combination. However in saying that it was only via doing the comparison that it became obvious that the PDM3 was lacking in this area. Was it fair to do the comparison? Possibly not but reference components are there to be used to assess the ultimate performance levels of those items in for review and as such I found it useful to compare the PDM3 to the DAC section of the Andromeda and also the Mephisto/PDM3 combination against the Andromeda while used as an all in one CD player.

Red book CDs and I played many through the Mephisto/PDM3 combination always sounded engaging, musical, detailed, nuanced and not lacking in much except if compared directly to the Andromeda. I was curious to see how the PDM3 sounded with HD tracks played through it and to assess this I next turned to using an Olive 4HD via a feed from its coax digital output and still using a TrusoundZ TSZ-0015 digital interconnect.

Using the Olive 4HD as the source and playing the 24 bit track Money from Jazz Side of the Moon the quality of music reproduction via this DAC was simply stunning, with a vast wide deep acoustic and excellent information retrieval. Every nuance of the music and the interplay between the musicians was presented in an open and detailed way but without etch or hardness. At the beginning of the track the drums stood solid and three dimensional, very much in their own space and the acoustic was deep, silent and dark in the middle and left side until the organ began playing again presented in its own space. Interplay was also very good as was the timing between musicians.

Comparing the higher spec (except possibly in the context of its Coax input?) Calyx DAC to the Deltec on HD tracks the Deltec DAC was quite a bit better, with the Calyx sounding less real and dimensional. Keep in mind that this result is on the basis of results obtained via the coax inputs and not USB.

This particular DAC was marked down in a recent review re its ability to convey timing well and during the course of this review, whether it was being feed Red Book CD or HD I did not feel this was an area that particularly stood out as a failing of the Deltec DAC in the context of my system. In fact I felt it played tunes really well and had very good timing. It was bettered by the more expensive Moon Andromeda used as a DAC or in CD mode but that in my experience, so far, to date has always been the case with no other CD player or DAC that I have either reviewed or had the loan of bettering it; please note I say so far.


I still sort of feel this is only really two thirds of a review, as I have not tried the USB input, but as I have yet to embrace computer audio (not sure if I will unless I have no choice) I will leave others to cover that aspect of its performance. What I have done is to check its abilities out as an upgrade to an older CD player and as in past experience I have found that the better the transport the better the performance, which somewhat puts paid to the notion put forward by those who say any old cheap transport or even a DVD player will be good enough.

While I was not able to check out the DeltranLink facility which ‘should’ offer a significant performance increase the marked difference between the Micromega Data and the Audiomeca Mephisto (something I have heard many times before with the Mephisto always being the best in any comparison) and the Olive 4HD as transport playing red book CDs ripped to its internal Hard Drive being better than the Data but still not as good as the Mephisto. The Deltec DAC also showed a marked jump forward in performace while being feed a 24bit/192 HD tracks from the RCA digital output of the Olive 4HD. Now whether this was as good as it would have been if feed via the USB input or not I am not sure as that was untested but the Deltec feed 24/192 music was quite significantly better than the Moon Andromeda.

So in the round I was impressed by the Deltec Precision Audio PDM3, any old negative bias swept away by the sound of music reproduced via this new design. I would however like to remind readers that the PDM3 was used with the Deltec Power Plus (as such turning it into a two box design) and the results I have written about were obtained from that combination. Using the PDM3 without it in the context of my set up did not quite give the same result, as such, I think that using the two together should be considered mandatory. If you can’t stretch to both at the same time, then certainly the Power Plus should be bought at a latter date and your integrated CD player used as a transport, or a dedicated transport, will also benefit from being hooked up to it.

Welcome back Deltec Precision Audio to digital music reproduction; your return was long overdue but it was worth the wait.



Maker/Supplier: Deltec Precision Audio, Swindon – England, Tel: 01793 239085, International: +441793238085


Model Number PDM3

Retail Price £2650

Weight: 2.6kg

Dimensions:(WXHXD) 230x100x330mm
Features: Digital inputs:coaxial, TOSLINK, optical, USB B • Analogue outputs: RCA phono• Deltran clock link• 32-bit DAC• High-quality digital cable supplied.

(1) This link will take you to a paper focussed on the TDA1541 –


This link contains a run down of early DAC technology –


(2) Deltec were also one of the very first companies  to realise the benefits of slaving the CD transport to the conversion clock in the DAC; which reduces jitter a major issue when using a separate transport and DAC. Basically if the signal is not perfectly in sync the digital signal ends up having an almost ghost image; much like a TV picture, via an aerial (remember those). That is a somewhat over simplified description of ‘jitter’ but the signal becomes less clear once you send the raw ones and zeroes out of the CD player/transport, up an interconnect which may or may not be 75ohms, through connectors that most definitely are not unless they are BNC ones. Once the signal reaches the DAC then it has to try and reconstruct the signal and deal with the fact that it may well  be less than ideal now.

I think it fair to say that most early DAC designers did not fully understand the effect that jitter had on the music and DPA were one of the first to realise the importance of dealing with jitter and they achieved this with using a Deltran Clock Link in their own transports which  feed this data to the DAC via a fibre optic link. As mentioned in the main body of the review Deltec will fit a DeltranLink to your own CD player/transport to get the most out of the PDM3.

This excellent article in Stereophile explains jitter much better and fuller than I can so have a read here –


(3) DPA The Power Plus RF Filter Triple Package with single power slink input cable and three power slink output cables £1098 (UK only price) I plan on reviewing this item in its own right soon.

Specification Input 115VAC/230VAC (factory set) 10A max Output 115VAC/230VAC total load 10A max Earth Leakage less than 2.5mA Size 110x230x310 (HxWxD mm)Weight 2.2Kg

(4) Ginko Cloud 11 Isolation Platform $499

Just before beginning this review I was lent a Ginko Cloud 11 to play with by a friend. Having read a fair bit about these in the pages of Stereophile and The Absolute Sound magazines I was pretty excited to get my hands on one and despite an inclination towards being slightly skeptical after getting my hands on it I was soon impressed enough to use it during this and the Calyx review.

I will assess it fully in its own stand alone review in the very near future.

You can find more info here http://www.gingkoaudio.com/

© Text and Photos Copyright 2012 Adventures in High Fidelity Audio…..except for Deltec Precision Audio  product photos and album covers. Copyright belongs with their original publishers.

NB No part or portion of this article may be reproduced or quoted without written permission.

 Posted by at 9:48 pm

Sorry, the comment form is closed at this time.