"old" DAC wanted - any suggestions?

[nat8808]

There's one of these on Fleabay at the moment (http://cgi.ebay.co.uk/ws/eBayISAPI.d...ht_2529wt_1141) and he's got a DPA power supply. I've done a bit of googling and they still seem to be highly rated but comments about mucho RF noise production.

Must say I'm tempted - they do look tasty and vintage/aesthetics wise would go well with the Quads.

Steve

Hi Steve - can I chip in and say that I have a DPA PDM 2 for sale.. for a fair amount less than Emporium Hifi (that's been for sale on Ebay for over 6 months, originally at £650). I've mine advertised around the place (can't remember if I advertised it here..) for £450.

It is currently the DAC I listen to (but I've plans for modifying others that I want to get on with) and have never heard any RF problems. Indeed, from reading the reviews, I don't think the reviewers did either.. it came out in their measurements but didn't seem to effect their conclusion.

Mine has a higher serial number than the Emporium one, so perhaps it did have the RF problem sorted out by then?

Did you also know that DPA has reformed and is again offering their CD transport clocking modification called 'Deltran'? The PDM 2 has a clock output that is then fed to the transport via DPA's add-on board and locks the clocks of both DAC and transport together to eliminate clock jitter. Always wanted to try it myself.

Maybe you could try it out for a bit if you're not too far?

[worrasf]

Hi Steve - can I chip in and say that I have a DPA PDM 2 for sale.. for a fair amount less than Emporium Hifi (that's been for sale on Ebay for over 6 months, originally at £650). I've mine advertised around the place (can't remember if I advertised it here..) for £450.

Drat I just ordered a new REGA dac as I just couldn't make my mind up but had decided to give the Emporium unit a miss - just got bad vibes. Otherwise I would definitely have bought yours - thanks for the offer though.
Regards
Steve

[roob]

Did you also know that DPA has reformed and is again offering their CD transport clocking modification called 'Deltran'? The PDM 2 has a clock output that is then fed to the transport via DPA's add-on board and locks the clocks of both DAC and transport together to eliminate clock jitter. Always wanted to try it myself.

Andy
Chevron Audio should be able to offer this service, they clock linked my dac to my transport and it is a really good upgrade far better than the normal cdp upgrades on offer. They also modify the power supplies of DPA dacs for another performance boost.

[Yomanze]

Drat I just ordered a new REGA dac as I just couldn't make my mind up but had decided to give the Emporium unit a miss - just got bad vibes. Otherwise I would definitely have bought yours - thanks for the offer though.
Regards
Steve

For £400 you could do the following mods to your Quad 67:

Clock Upgrade
Output stage mod as described earlier
Capacitors upgrade around DAC in particular
Dedicated regulators for DAC

I know Brenton does similar mods: http://www.fidelityaudio.co.uk/quad.html

Just think that this player has the potential to wipe the Rega DAC out...

[worrasf]

Hi Steve, I'd be willing to do that mod for you. It seems pretty straight forward based on what it says in the datasheet but the the level of complexity will depend on how much space there is in the CDP and the layout etc. I can certainly have a look and let you know whether I feel I could manage it. PM if you're interested.

Dave (HiFidelityGuy) has worked wonders on the Quad 67 and it's sounding superb so respect is due to him.

Far more dynamic and punchy, more detail and control, more "airy and open" but amazingly there is still the "lush" Quad sound underneath - strange but true.


Steve

[HighFidelityGuy]

Stop, I'm blushing.
For those interested I simply bypassed the active output stage as suggested earlier in the thread. I used the Vishay MKP-1837 caps recommended by Neil (Yomanze) and some lovely Shinkoh Tantalum resistors. I also replaced the PCB mounted phono sockets with some Neutrik chassis mounted sockets.

To allow the best to be obtained out of the passive output (and prevent high frequency roll-off) I also made up a custom interconnect cable made out of DNM solid core ultra low capacitance cable terminated with Neutrik Profi connectors at one end and a gold plated Neutrik 5-pin DIN plug at the other end to allow connection to Steve's modded Quad 33 preamp.

I was really quite surprised at the improvement the mod made. It's not subtle and definitely worth doing.

Thanks Steve, happy listening.

[Marco]

From the Grave

A chance for some folks to benefit from the advice offered here, who may not have read it first time round…..

Marco.

[Barry]

The Quad 67 player always was a very good design and a significant improvement over the earlier 66 model. I doubt if much improvement would be made in using an external DAC, since as has been noted, the internal DAC chipset used in the 67 is already very good.

The simplification of the output circuitry as described by Yomanze is very sensible advice - and it would appear, has been proven in practice by one happy user.

Any component that appears in the audio signal path needs to be of the highest quality, so choose carefully. If it were doing it, I would experiment with Vishay Z-film types, or other high quality metal film resistors. Avoid carbon and carbon-film types.

[StanleyB]

The Quad 67 player always was a very good design and a significant improvement over the earlier 66 model. I doubt if much improvement would be made in using an external DAC, since as has been noted, the internal DAC chipset used in the 67 is already very good.

The DAC chipset makes up only a fraction of the total that contributes to the overall sound. Within a CDP there are loads of sources of noise that can affect the performance of the decoded signal. Whirling motors, displays, etc all go towards creating a noisy environment. An external DAC does not have those bagage, and stands a better chance of sounding far better than a CDP.

[Barry]

The DAC chipset makes up only a fraction of the total that contributes to the overall sound. Within a CDP there are loads of sources of noise that can affect the performance of the decoded signal. Whirling motors, displays, etc all go towards creating a noisy environment. An external DAC does not have those bagage, and stands a better chance of sounding far better than a CDP.

Well I haven't seen inside a Quad 67, but would assume they had done the right thing in providing adequate screening and separate power supplies for the transport and digital circuitry.

I have experimented with using external DACs with my Sony CDP XB930QS player. I found the changes were small; a difference rather than improvement in SQ. Deciding that the fewer boxes the better, I have returned to using the internal DAC of the Sony. Of course that is not to say that an improvement could not me made, but based on my findings I am, at the moment, quite happy with the current arrangement.