| spa317 |
I have a two box DPA (Deltec) PDM2 dac, which was their top model back in the early 90's.
As I dont have a chance to compare it with todays newer models, I wonder how well my PDM2 compares to current digital offerings - Has digital sound come a long way since the PDM2, or has my unit stood the test of time well (and should I keep it!)
I use the PDM2 with a CEC TL5100 belt drive transport.
I wonder how my combo would compare to a one box unit like the Consonance Ref 2.2 player....am I still better off with seperates?
Thanks, Mark. |
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| JohnW |
Mark,
The PDM2 was a good DAC for its day – the combination of SAA7350 & dual DAC7 being very hard to beat even today. The weakness in the design is the very poor PCB layout & decoupling of the supply lines.
DPA / Deltec products can sound very bright and hard mainly due to there MASSIVE RF output levels. Ironically one of the bigger causes of RF emissions from Deltec / DPA designs is the output Mute relay, who’s energising coil is powered from the RF noisy digital sections. As these are after the LPF and have no decoupling capacitor on the coil, they do a fine job of coupling RF noise from the digital 5V rails to the audio outputs. I see this flaw on many DAC designs.
In addition, the Yamaha YM3414 (not 100% certain of the part#) digital filter is poor, the later YM210??? 22Bit filter is still one of the best I’m aware off - bettered only by the PMD100 in my humble opinion.
I would be very weary of an “Up-Grade”, the PDM2 is a very good DAC – if your thinking of selling it cheap I would be happy to buy it from you.
John |
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| spa317 |
John,
Thanks for the reassuring feedback.
When I have the dac on, I get quite a bit of RF interference on my tv in another room, so what you say rings true.
Should I consider having any upgrades done on the PDM2, or is it best to leave and enjoy as is? I am not a tech guy, so would have to get someone to do this for me. If it is worth doing some upgrades on, would you need the schematics? I believe there is an RF filter that was made by DPA, I think it was more of a mains filter box. I might be able to pick up one of these, but I already use a power filter in my system anyway.
Thanks,
Mark |
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| JohnW |
Mark,
I once had a friend whose neighbours complained about their television picture breaking up when he power-up his Deltec DAC - in the end he was forced to sell it.
The major RF emissions are from the Audio outputs & Coax inputs, there’s little that can be done to these externally that will not adversely affect the sound. Simply placing 10nF ceramic capacitors across the relay coils can help, but the PCB ground plane design is so poor that this is not always guaranteed.
Upgrading the digital filter is not a simple affair. A worthwhile upgrade is to use the Deltran (the external clock sync feature) – maybe a competent engineer could add a 256fs clock input to your CEC transport. If your ever over in Prague or HK I could modify your unit for you. If your interested I could post a circuit design for this - I believe the CEC uses a 384Fs Master clock. |
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| spa317 |
John,
My CEC transport has had a G&D Transforms (US) clock upgrade done, which apparently reduces jitter.
I guess this might have already covered what the Deltran clock upgrade does...?
Sounds like I should just keep enjoying what I have for now, and not worry too much until the unit expires! I think the dac chip for my PDM2, the TDA1547, is very hard to get replaced these days as it is no longer made.
Thanks again,
Mark |
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| JohnW |
Mark,
I should be able to find some spare TDA1547's if you ever in need of one - its very unlikely they will fail, the most comman failure with DPA / Deltec designs is the Coax input buffer the DS9637 which gets zapped by 110V mains leakage currents due to the SPDIF RCA center pin making circuit contact before the RCA Ground connection.
Upgradeing the clock inside the transport will not offer much benfit. Using the Deltran option Enables a low phase noise clock inside the PDM2 digital section - bypassing the VERY poor (Jitter) YM3623B SPDIF decoders Clock output.
I'm not sure of anyone offering a Deltran upgrade these days, however I good engineer should be able to fit a 256Fs clock input to your CEC - this will have to be converted internally to provide 384Fs for the CEC. |
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| adlanar |
hi,
check out chevin audio from the uk. http://www.chevinaudio.co.uk/index.htm
i think they do dletan conversion of standard cd players / transports. it's in the upgrades section of the website. |
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| spa317 |
| Thanks for that info, but not really practical for me to consider as I live in Australia.....good to see that someone in the UK offers upgrades,etc for the DPA gear! |
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| Jules |
Just read this thread and thought my thoughts may be of interest.
I have owned a Pdm2 for about 10 yrs and recently aquired a Musical Fidelity Tri-vista dac.
The perfect dac would be a mix of both, as they both have their strengths and weakness, but the point is that the DPA isn't outclassed in this company.
Haven't been plagued with excessive brightness from the DPA,
sounds very smooth to these ears.
The only problem I've had is about 5 mins of splats on the output when powering up from cold, it's not really a problem as both boxes are left on, so the problem only arises when moving kit from room to room, and the splats disappear when the unit warms up ( 5 mins or so).
One day I'll get round to tracking down the cause, and finishing off my bass guitar I made, and painting the house, and mowing the lawn, etc, etc |
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| spa317 |
Jules,
Cheers for that comment on the PDM2! It is reassuring to know that it can still hold its own in comparison with modern offerings. Maybe digital hasnt advanced as far as I might have expected, even hoped (well, without stratosphere type prices at least).
Think I will hang on to the trusty old PDM2 for a while longer yet, till something comes along that will noticeably surpass it (and spend any upgradeitis money on cd's!)
Thanks,
Mark |
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| Jules |
Hi Mark, don't know much about your transport, but that's where I've done my recent tweaks, I'm using a Pioneer stable platter PDS904 with the dac section removed, and an Audiocom superclock 2 fitted, the superclock is preceeded by one of their invisus super regulators, itself powered by an outboard Coutant (ex broadcast) power supply.
I've also fitted a 5v Invisus to feed the digital stages, again this is fed from an external supply.
All the improvements from these tweaks were readily apparent through the PDM2. |
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