Deltec / DPA

[Arkless Electronics]

Hmmm... I've got a PDM1 series 2... may have to fettle it some day!

 

[Svein]

The PDM1-2 user guide, it's a printout with some measurements of the dac too.

 

[Arkless Electronics]

Incredibly bad advice there to leave it powered on!! That explains why every DPA DAC I've seen (4) has had completely knackered and leaking electrolytics!

 

[Svein]

Incredibly bad advice there to leave it powered on!! That explains why every DPA DAC I've seen (4) has had completely knackered and leaking electrolytics!

Tom/DPA_Service also recommend to switch the units off when not in use. I have replaced the electrolytic psu-caps on 4(!) DPA-dacs and all of them were almost perfect in capacitance and ESR values.

 

[Arkless Electronics]

Tom/DPA_Service also recommended to switch the units off when not in use. I have replaced the electrolytic psu-caps on 4(!) DPA-dacs and all of them were almost perfect in capacitance and ESR values.

In the case of 2 of the 4 I have worked on they didn't even work due to knackered caps...

 

[Svein]

 

[martin clark]

Nice job

Also highlights the basic problem - the original parts were both marginal (85degC/2000hrs rated at best, running right-up to their voltage ratings) - and then located very-close by small transformers that run towards 60degC simply because they are small transformers, and have high iron/copper losses. So useful life of the caps was inherently limited.

Use modern 105degC/+ longer-lifed parts as you have @Svein - the problem goes away.

 

[davidsrsb]

The DPA power supply assumed 240 V meant 230 V to 240 V. Many of us have very high mains, which makes these small transformers cook.
A bucking transformer is the solution.

 

[Arkless Electronics]

That looks familiar....
I only heard my PDM 1.2 for about an hour then it died on me....
Got it free, found open circuit and leaking PSU caps and replaced them, now seemed to work but stuck in mute. Bypassed relay... great it works! For about an hour (if that) then it made noises like a faulty DAC IC and died a few minutes later... I haven't looked at it since! My Little Bit (with better op amps and caps etc) sounds so good I've had no inclination to do anything further on the DAC front...
My very much first impressions of the PDM 1.2, obviously based on hearing just a few tracks before it died, was that it was not as good as the Little Bit... Probably not a fair comparison with an about to die DAC and hadn't been used in years!

 

[Svein]

I use the PDM1-2 as the main source and miss absolutely nothing. The amplifier is an Avondale system with 821+/Snaps TPR4 pre and fantastic dual-mono Qudos power amplifier i bought from LesW some months ago. With Avondale amplifier the PDM1-2 stand out as the best - and it's really, really good. With (old) Naim amplifiers the result is different and the Bigger Bit/DX32 may give a better impression of pace and speed than with the PDM1-2, but don't even hint at what the Avondaled system can do.

The printout of the measured parameters:

 

[Svein]

The Bigger Bit after replacing the psu-caps with Suncon/Sanyo capacitors. They have very long life and of the same mark as the original caps.

DX32/Enlightenment:

 

[Svein]

Digital replay in 1994.

 

[sq5ebo]

I have a DPA DAC DX32, I replaced all electrolytic capacitors because a few were already damaged. I added heat sinks to the hottest LM317, LM337 stabilizers. Now I wonder if it makes sense to replace the operational amplifiers from NE5534 to OPA627? Do you have any experience in this topic? Thank you in advance for any suggestions.
Tomasz

 

[martin clark]

Hi Tomasz,

I'd would leave them as NE5534; the output stage is designed and compensated for stability around these devices. Substituting much 'faster' opamps like the OPA627 when it is exposed to a lot of HF noise from the PDM output can end in worse results, not better. It would take a fair amount of test equipment and time to ensure all was well.

 

[Copperjacket]

I have a dpa 50 phono stage which I am currently using with a Shure M75 which I am thinking of replacing. Can anyone recommend any cartridges that will have a good synergy with it please?

 

[martin clark]

The DSP50 is a very, very rare thing indeed! I don't have any factory data or printed reviews on it - sorry.

I do know it is basically the same as inbuilt phono stage included in the early iteration (onebox, PSU onboard) DPA50 preamp; the last/third version of this preamp has an off board PS;U and to go with it - the Phono stage was 'done properly' in its own case to stand alongside as an accessory.

So I strongly suspect the loading & choices are exactly the same as the early DPA50 pre: I own an example of that. The MC input is 100R/ 1nF; the MM input is 47K / 330pF;

NB this also was the same in the Deltec DSP200 Phono stage of 1994 (of which I've a couple of photos of the innards.)

That's about all I know - sorry!

 

[Copperjacket]

Thank you very much Martin.

It sounds pretty amazing on it’s MM settings and on the basis that my existing Shure needs tlc I thought I would look at MC cartridges. What are you using with yours please?

Incidentally, how are you feeding your second power amp from your pre?

 

[martin clark]

I don't have a turntable(!)

re: the power amps - I completely disabled (internally, invasive diy) one channel in each, and use them as monoblocks; one XLR to each from the preamp (the late, 3rd version, plain pre- with outboard PSU) - quite simple.

 

[Copperjacket]

Wow! I didn’t see that coming. Did one amp have a damaged channel? What speakers are you using with them?

 

[NeilK]

When I had my 50S I used a Goldring 1024 to good effect - it worked very well, better than a Nagaoka MP11 or a Grado - the designation escapes me. I did not try MC with the 50S.