I do not need another DAC

[Sligolad]

Bulk of the components for the DAC and Power Supply arrived today...fun starts soon!

[Fran]

We have been busy prototyping the output stage on this DAC. One of the key sonic signatures of the DAC will be the current to voltage converter and output stage. We have been looking at both valve and solid state options here. I had 2 different stages that I had ordered quite a while back from Aliexpress for messing about with the output of a CD player, so I went to examine could they be used for this DAC as well. The classic one for current output DACs is what is now popularly known as the Lampizator stage - a 6n2 SRPP circuit. This gives lots of gain, is a really well developed stage and the valves are excellent, plentiful and cheap.

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The only thing that was needed to get it functional is a transformer with the appropriate voltages. Surprisingly the stage powered up perfectly, is perfectly quiet (always a bonus) although there are a few bits that were needed to make it safe and practical (earthing and a bleed resistor). Sound from this is lovely, theres lots of gain, so volume knobs will be turned down, but its clean, deep, lots of detail and loads of impact.

The second curiosity was another valve stage from Aliexpress, this time using a really oddball radio valve from the 40s (and when I say radio, I mean battery powered valve radios from the 40s).

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This caught my eye because these valves are directly heated triodes - like those 10Y, VT45, 300B and plenty of others that valve afficionados gush about. The price was so low, and it came as a built unit, it seemed a no brainer. Well, the thing is that from first turn on, this unit has been a struggle. Because it they are DHT valves, the filament supply is critical - get it wrong and you will have hum, and I don't mean background low level type hum either. So I ran it from some batteries to start with, and there was certainly enough promise to make me struggle on. The next bit was to improve my cobbled together power supply. The high voltage supply went to a much improved one, with a regulator system. Likewise, the filament heaters were also regulated, and then there were a few other minor tweaks to wrong the best out of it. The sound here is sublime to my ears and I am very happy with it and tbh, could just box this up now and call it done.

But this spurs us on more - because there are more stages to try out yet and much promise in them!! Hopefully we can start getting together in the coming months to get some critical evaluations done, and comparisons.

[tony]

I am hoping to get a listen/loan next week of one of the trial iterations of this dac. Looking forward to the silky sounds.

[Fran]

Its been a while since we posted - but experiments are continuing. A lot of the work at present is focussed on the output stage still, and as something is built there is usually a bit of troubleshooting or at least optimisation. There is one valve based unit up and running very well, and sounding pretty good (Tony can comment here maybe), and I have another solid state (jfet) unit running here that also sounds very good. It carries some disadvantages though as it really uses a battery power supply which is always a bit of a pain unless there is recharging built in. That is not easy to implement in this case.

Its really very interesting to see how they develop....


Fran

[Sligolad]

Another one running here all week and it is definitely the best sound I have ever heard from a DAC.
Feeding the DAC through the Lampizator Tube Output stage with very high quality clocks in the chain burning in at the moment.

All very heath robinson but still working on tweaks and configurations....honestly though just too lazy to break it down and tidy it up yet as I am compelled to listen to as much music as I can given the amazing sounds coming out of this kit.

[Diapason]

Never mind the sound, it's the WAF that makes it!

All most intriguing, gentlemen.

[tony]

Met Fran covertly on the covid border between Kildare and Dublin. It was all very clandestine, lurking around in a garden centre checking the coast was clear and we were not being watched.

Got the MDF board home after being given the instructions from Fran. It would not self destruct after 30 seconds once I avoided touching certain parts.

First thing is this version of the Dac although it has valve output is really neat and tidily put together. It is way more simple to look at compared to the groupbuy dac that is packed full of parts. Maybe if the dac is shoe horned into a smaller case it wouldn't appear that way. Don't get me wrong I wouldn't have a clue how to put it together but from working on the other dac (Under instruction) this looked much easier to pull together to my eyes.

Got to spend a couple of hours on Thursday comparing the group buy dac to this new one and picked a variety of tracks and switched over and back.
My conclusion was similar to what Derek had reported on the whatsapp group and I think he has posted on it here. This Dac has more warmth and beautiful tone to it. Derek used the word heft and I agree it just gives a really meaty sound. I found that I could crank up the volume with this dac and it never got too much. I tried a Dave Brubeck track from Concord on a Summer Night (Black and Blue). The group buy dac sounded just a bit more shrill at high volume levels compared to the new dac.

The decay on instruments like cymbals is just magical and for my ears definitely a lot more defined, subtle and audible compared to the group buy dac.
I listened to a variety of tracks the first night. A lot of them were Talking Heads tracks I will admit but that was the initial SD card I choose and I couldn't draw myself away from trying a few more tracks. I know the tracks too well but it was so much easier for a first time listener to hear all the multiple guitar grooves, clear crisp cymbals of the drumming and the hypnotic bass lines often permeating these tracks. Vocals just had a real tone to them and the backing singers on live tracks can nearly be placed on stage.

I settled in last night for a few hours listen but it went on for nearly 5 hours. Didn't bother switching in the groupdac I was just going to enjoy my time with this new dac. Switched in another SD card with tons of the usual favourites and a variety of different types of tracks including classical stuff with Netrebko and Garancha, Just a little loving, Johnny Cash, Oscar Peterson, LCD soundsystem, Radiohead, Bjork, Koln Concert, The Cars first album , Down by the River, Joy Division (Atrocity Exhibition), AC/DC Live She's got the Jack(It's great early Bon Scott) and a few Miles Davis tracks. All well recorded jazz music sounded sublime and Garancha's voice sounds magical. It all just sounds so natural. I found myself just letting the tracks roll on till I had to give up due to the hour. There are elements in all those tracks I could bang on about but best for people to hear the dac themselves and draw their own conclusions.

Have the in-laws calling for a garden visit at lunch time today so hoping to retire to the bedroom later to try the dac out on the group buy amp and 63's.

Unless Fran or Pearse pull some more magic from the hat I think I will be going for this version of the dac. Covid has thrown up a silver lining as Fran probably wouldn't have started this and progressed it so far so quickly in normal times.

[Fran]

This is another output stage that we have been working on - its a very neat current mirror stage, and sounds excellent in the testing so far (this one was kindly facilitated by a friend over on DIYaudio who is the genius behind the circuit and helped us in making it). In fact its good enough for us to have made one for each of us. The picture doesn't really convey how small it is - the blue board you see on the piece of alu angle in the photo is about half the size of an SD card (about 20mm square). There are 6 dual transistors and 12 resistors on each one. Each stereo pair is then mounted on that piece of alu which acts as a heatsink for the devices - and keeping them all thermally coupled helps keep everything working smoothly. This output stage needs an excellent power supply, and luckily we have that in the DAC already, although we will be looking at options for it for sure.

When its contrasted with the valves, it is just so tiny its laughable - but of any component I've ever had here in the system, this one goes lower than any of them. I didn't think my speakers could go that low.

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[Fran]

It's been a while since the last post, but we haven't been idle. At this point we have now tested out and gotten first impressions on 2 X valve output stages and 2x solid state output stages. I might summarise it by saying that all sound as variations on good. The DHT stage is a bit more lush while one of the solid state stages is more neutral with the others in between.

Many of us have more than one source, so it would be nice to have one DAC with 2 sources on a switch. So we've done some work on just that and the photo shows where we've got to - this one unit takes 2 sets of inputs and one output and then reclocks that immediately before it gets to the DAC and all runs off a single supply. The idea here is that doing it this way removes a lot of loose wiring and this means more stability and long term reliability.

[Fran]

Its been a while since I updated the thread here, but things have been moving along slowly but surely. Experiments are still underway with output stages, and the more we listen to them, the more it turns out that people prefer different ones. Funny how that goes.

My own build has taken a turn for the better, and I have set it up with a DHT triode output stage which I think sounds lovely. I want to finish the functional build now by adding a second source (USB to accompany the SD card player I already have). Whether I'll ever put it all in a box is another matter!!