Valve based Digital Analogue Converter

[tomtidswell]

How about it?

I have 4 optical output sources, an iRiver (nonApple mp3 player), a CD player, a DVD player and an Apple Laptop. Having a valve based optical digital to analogue converter would be ideal (and even save on an upgrade of the CD player).

Tomtidswell

[pre65]

Hi-what about a valve buffer and DAC ? (as 2 separate components)

It has been said a valve buffer can give a CD player a more "analogue" sound and even improve the "drive" of a passive pre.


Philip

[NickW]

Originally Posted by pre65

Hi-what about a valve buffer and DAC ? (as 2 separate components)

It has been said a valve buffer can give a CD player a more "analogue" sound and even improve the "drive" of a passive pre.


Philip

Hi Philip,

I've heard the same but surely all the added valve buffer can do is "alter" or mask what is going into it (?). I started to build my own DAC with valve output stage some time ago, but got hoplessly diverted in building the WD88 and Pre3/Phono3 etc, etc. However, that phase is coming to an end, and I'm looking to resurrect the DAC project.

I had baselined the Burr Brown PCM1704, being the last word in parallel multibit DAC technology. I got as far as getting the basic DAC functioning, but not the valve output stage. Since then, up-sampling techniques seem to have come along with some favourable reviews. The hybrid BB PCM1794 DAC also seems to have been widely accepted. The next challenge is then to have a properly integrated valve output stage in place of the traditional op-amps.

The point of this reply is that I would agree that a DAC kit would be really good to have, but "specing" it might be quite challenging. Some will want no oversampling, others will want bells and whistles.

Nick

[robinhelen]

Hi,
Why have an output stage???
I use a TDA1543 NOS DAC using 12 stacked chips. This provides plenty of output using passive I/V i.e. 2 resistors. This is connected straight to my amp input with no coupling capacitor (as the amp input uses one). I originally thought about a valve buffer, and with just 1 chip it would be necessary I think, but 12 chips does the trick perfectly. Virtually nothing in the signal path, no oversampling, no filtering = very good sound it seems. The DAC came as a modular kit and you can have as many multiples of 12 chips as you like. The more chips the greater the effective bitrate achieved.
Rob

[Dik Dolan]

Why use chips.... how about a fully valve dac? How hard could it be?=)





*That just proves my ignorance*

[david beard]

I'd be interested for sure!

didn't HFW do avalve DAC years back - I seem to remember something along such lines - does anyone else remember this and better still have any details of what it was all about?

Cheers
Dave

[little eddy]

I'm all for this. My AN DAC kit has always bettered any intergrated valve output CD player that I have tried in the past, (although I have not tried any of the newer entrants). The power supply, descrete component and valve options available together with an appropriate DAC that a new kit could consider and offer, should prove to be a very impressive performing unit.

What about including an AES/EBU input given the increasing number of US equipment supporting balanced digital outputs? Even my old modest Cambridge Audio DiscMagic transport has a balanced output and from the listening tests I did, this was preferred to the unbalanced RCA output, (possible because my AN DAC has switchable RCA and XLR inputs).

Although not of interest to me, AN DAC kit also has a USB input option.

[Black Stuart]

Robinhelen,
have you had a look at NOS DAC thread on diyaudio, fascinating and that Dutchman takes on board all suggestions. The intensity of investigating all possibilities is mind blowing. BTW he also sells a PCB which is supposed to be top class.

[Tourmaline]

Originally Posted by Black Stuart

Robinhelen,
have you had a look at NOS DAC thread on diyaudio, fascinating and that Dutchman takes on board all suggestions. The intensity of investigating all possibilities is mind blowing. BTW he also sells a PCB which is supposed to be top class.

I heard the audio note NOS dacs in action; no harshness whatsoever and very lifelike, touchable sound. Now is that a trade mark of audio note but i can imagine that most NOS dacs share that common feature...

I also read that alot of people comming from multi sampling dacs/oversamplings dacs cannot go back once they took the step to go NOS.
The other side i hear is that NOS dacs might not as detailed as the oversampling/multi sampling dacs.

In the end, it's all about preference and taste.

[NickW]

Hi all,

Just to add to the debate....I recently ordered a RAKK DAC-2 with passive output board. It uses the BB PCM1794 DAC with asynchronous upsampling - the modern school I believe? - and the opposite end of the spectrum to the NOS DACs with zero upsampling/reclocking (?).

I have to say it blows my old Meridian 606 DAC out of the water!, and I had thought that the 606 (coupled with the 602 transport) was pretty good. I'm told an active valve output stage will make things even better, but I can't stretch that far yet. However, all in all, the passive output RAKK DAC-2 has more "music", detail, etc than anything other than the best CD player I've heard to date which was/is the Krell Evolution 505 at ~ £9k at Oxford Audio Consultants in the the process of buying near speakers.

The RAKK DAC-2 has so far cost me ~ £350 (the current US Dollar rate really helps), and I'm chuffed to bits with it. It works really well with the Meridian 602 transport, but I suspect any other transports would be ok too due to the asynchronous upsampling.

Ok, I shall now keep my head down amidst the barrage of offended Forum readers that truly believe the NOS side is best.....

NickW