R-2R Audio Note DAC 4.1 DIY and mods

[astrostar59]

DAC DIY (Audio Note) The story of my DAC 4.1

 

This might need to go in the DIY section, but here it is anyway, as it a DAC discussion.

 

Up to 2005 I had various DS DACs which came and went, some of which were ok, but none really grabbed me or kept me interested enough to enthuse about music much. Certainly not as much as my long gone turntable. Then I heard an Audio Note DAC 3.1 at a hifi show in the UK. It was a revelation to me. Having low budgets I had to find a way to get that sound myself. Enter Audio Note kits. I bought the (simple) DAC 1.1 kit and built it from the parts and chassis supplied. It was quite easy, and soon it was making really nice music. 4 years later they released the DAC 3.1 kit so I built that as well. This DAC was very good indeed, amazing value for the sound on offer.

 

I very quickly decided the Audio Note copper coupling caps on the line board were ok, but can be better. I changed them to V-Cap Teflons. Fitting these immediately changed the sound both in character and detail level. Also the dynamics went up a notch as did bass drive and texture. The V-Caps took 400+ hours to burn in, and that was a bit of a nightmare, as the sound is all over the place during that period. Best thing is hang in there, the goodies are coming. At 400 hours the sound was truly magical. The 2 x 5687 Tungsol NOS were singing indeed at this point.

 

The DAC after my mods.

 

Later and still having the DIY / tweaking bug I decided to start upgrading the parts in my DAC 3.1. It is what Audio Note UK do with their gear. The products are split into levels (quality and cost) and many are very similar in design, but the parts quality gets better as you go up the levels, more Blackgate (now hard to find), copper v silver wound transformers, silver wiring, etc.

 

First thing I did was upgrade the output transformers from IE-Core to C-Cores. They were not cheap but the difference was huge, taking the sound to an obviously higher level.

 

More recently I started looking at the I/V transformers, as talking the Peter Q at Audio Note UK, these play a key role in the digital to analogue section in all Audio Note DACs. The ones on the AN website are expensive, £1,800 for the Trans-496 that is fitted to the higher level DACs such as the DAC 5 Special which retails for 25K. I started scouring the web and found a guy in the Netherlands who was breaking down an Audio Note and would sell me his Trans-496. I was amazed at the increase in soundstage and depth with these transformers, it was incredible. Everything got bigger and more 3D, with even more detail.

 

Here are the bigger I/V transformers and the Duelund caps.

 

Here is the (bigger) I/V Trans-496 next to the original I/V.

I then had to change the loading on the resistors on the digital board and line board to match the Audio Note DAC 4.1 setup.

 

However, as with an increase in sound quality and as the detail goes up, there is a sonic price to pay. That detail (treble) has to sound smooth and real, not 'hi-fi' or the whole illusion is gone. I am convinced this aspect in built in to various DACs as the SQ and price goes up. You can't have total transparency if the components in that DAC are not up to it, or harsh treble and listening fatigue will result IMO. My DAC was so close to perfect at this point, I knew it was fixable. Thinking about it, and reading capacitor reviews, I began to think the V-Cap Teflons were very detailed, but were adding something else not in the music. Wanting to find out, I bought some Duelund Copper Cast for the coupling position on the line board. WOW, right away these sound so natural, almost as detailed as the V-Caps BUT really realistic and so liquid smooth (I have Stax 009s and they show everything). Now very happy indeed.

 

 

The new power supply fitted (ignore the colourful spaghetti).

 

 

A month of burning in the Duelunds, I began thinking about the power supply. It is very good being based on the Audio Note UK M2 design. The capacitors on the PCB are standard quality Rubycons (not Blackgates), and the 2 coupling caps are Mundorf Silvers which are ok. Anyway, I got a blank PCB from AN Kits and rebuilt the board but this time used Audio Note Kassai capacitors. These caps are new and are made by Rubycon specially for Audio Note UK. They are very close to the now out of production Blackgates. And for the 2 coupling caps I used V-Cap Teflons. I had to mount the Kassai off the PCB on a new mount as they were much bigger.

 

I am running them in now, and all I can say is this DAC is making incredible music, it sounds so like my old turntable, liquid and natural with incredible detail and dynamics, bass depth, but is very undigital as I hear it.

 

There are not so many tube based R-2R DACs around. Lampizator is one. Lukasz is a fan of Audio Note gear from his early articles and admits to being inspired by the AN designs. A few others are around, not to forget more exotic and high priced units like the Ypsilon made in Italy:

http://ypsilonaudio.de/Presse%20-%20Dagogo%20-%20Ypsilon%20DAC%20100%20Review.pdf

 

I would say if you are looking for a natural but very modern sound i.e. detail in spades but still sounding like real music, I would recommend looking at tubed DACs. Not only tubes in the pre-amp section, but also tube rectified. IMO they sound so natural.

 

One of the key points is if the DAC has a good line stage, you can miss out the active pre-amp. Adding a pre-amp will colour the sound as it is another unnecessary (in my case) gain stage. I read part of the magic of the TotalDAC and the CH Precision C1 is this aspect. My DAC has a transformer coupled output design with a tiny output impedance (10 ohms) thus can drive a power amplifier directly. I use a passive 42 step ladder pot to control volume with an Elna selector to drive my KGSShv or speaker amp.

 

I think the DIY route is a quite different path for those looking to get great sound out of a DAC. To me, one of the best parts to it (besides building it) is it allows you to tune the sound to suit your system synergy. I am probably an obsessive audio nut, but prior to this I did not get the sound I wanted from off the shelf products. Possibly I might have with insane budgets. I would say I have spent around £6K on my DAC, and I would do it again if I had to. It has been a very enjoyable and fruitful journey.

 

Note I am using the Bendix 6X5 equivalent for the regulation tube. It draws 50% more current but is a fabulous tube. The US Military used it in Vietnam in radio sets, and it is very rugged and sounds glorious. It takes 2 minutes to light up, but last forever. I have had over 3 years use out of these tubes. I bought a pair last year, and they actually came with the circa 1968 US Army fixing kit and instructions!

 

 

I had a custom aluminium faceplate made to finish it off.

 

Hope this inspires some folk. Now what can I tweak next? Maybe the digital power supply board?

[astrostar59]

Hello

The I/V should be 1:1 ratio. Is the Sowter a different ratio?

 

In the Audio Note UK DAC line board it is loaded as 680R in and on the digital board 680R out (near the chip).

 

In the kits is is 280R at the chip, and 3000R at R1 and R11 on the line board (so loaded). I think your line board is the kit board? I would ring Sowter and ask the loading required at both input and output. Or try changing the 3K at R1 and R11 to 680R.

 

On the AN UK DACs they also use a small cap at the output and inout of 680pFs. See the pics on the web of the DAC 4 or 5. My AN UK DAC 5 has this as well.

 

If still stuck, try asking Andy Grove at AN UK, he will know, as they used too use Sowter way back. Brian will not know I don't think, as I went through this stage with ANK, though I used the AN 496 I/Vs.

 

Good luck.

[astrostar59]

4 minutes ago, michaeltay5871 said:

Thanks for the reply ogie.  I guess the worthy upgrade maybe the digital board (to R-2R) if it is possible. Also the output trans if it will make a reasonable improvement.  I have written to AN Kit to ask them for their opinion.

I would consider building an Audio Note Kit. That is what I did and it had a great sound. It also has lots of further tweaking and upgrading that you could do to it later i.e. keep off the buying and selling DAC saga. That is what I did.

 

Your DAC4 is very old BUT original. I would sell it on AGon or HifiWigwam as intact. I believe your DAC is NOT non oversampling, that came later with the AD1865 chip. And it has filtering which Peter took out around 2006. I can see the filter caps on the digital board. And they improved the I/V conversion with transformers, then added output transformers. It really takes the sound you like right now, and injects it with everything you want, just more of all the good stuff. Funny, so many manufacturers have following (nicked) many of Peter's ideas IMO.

 

The Audio Note DACs are oddball for sure, but as I have found, they beat the pants of so many 'hi-end' DACs I have demoed over the years. I recently demoed the CH Precision C1 (R-2R) which is 21K and it beat that as well, also the Esoteric K-01, the Naim 555, it goes on. You don't get fancy casework, or DSD (who wants that?) but what you do get is Redbook to die for, a superb smooth sound and fatigue free real music. Reminds me of my vinyl rig. If you want 'hifi' sound look elsewhere.....

 

Talk to Brian. I know him well, he will give you more advice and sort you out. The 4.1 Kit is the one I would go for.

[astrostar59]

I was thinking about this. The Kits never used the Sowter I/Vs, but the UK DACs did way back. The loading on the kit DACs is very different to the UK DACs, as I spoke to Andy Grove about this very subject when I was doing my mods. The AN UK DAC has a 680R at the chip and 680R at the input to the line board, thus the I/V is balanced same load each end. The kits however have 330R at the chip and 3KR at the line board input. Thus the kit is 10 times the resistance at the input end on the line board. Quite possibly the kit I/Vs are very different, and this would explain your signal drop.

 

I fitted 680Rs both ends on my Kit DAC with the 496 I/V and it worked perfectly.

[astrostar59]

The AN UK Copper caps are sluggish, thick in the lower mids and generally lumpy, no details. I had them in my `conquest MBs, AN pre-amp and DACs. Even the AN DAC 5 had them in. I think they are really poor. Needless to say I replaced all of them, with the resulting increase in speed, transparency, bass extension and texture. Basically waking up each unit.

 

The V-Caps Teflons are too much detail, and it comes with a price, cold and harshness. The V-Caps Coppers are better, nearly as detailed more realistic tone so way better than the AN Coppers at this point. The Duelunds are heavenly. If the V-Caps Coppers are 7 I would say the Duelunds are 9. I put them in my DAC 5 and wow, different machine completely. The AN Silvers are supposed to be close to the Duelunds, and even more money, but a buddy of mine tried them and sold them, saying they were cold for hours, i.e. took half a day to charge up and sound balanced, and didn't get to the Duelund levels anyway.

 

The coupling caps in many tube amps and Dacs are the single most component to change the sound, so IMO it is best to view them as critical, even though it can get pricy. It is easy to change them yourself with a steady hand, maybe 30 minutes tops.

 

So my score is:

AN Copper 3 (poor)

V-Caps Teflon 5 (detailed, fast but too cold)

V-Caps Copper 7 (very good, could stop hear if money is an issue)

Duelund Copper Cast 9 (amazing, heavenly)

Duelund Copper with Silver bypass 10 (perfect) 

 

[astrostar59]

My goodness, I can't quite believe what I have read....

 

So, by my own ears and experimentations I am wrong, and am basing my judgement on price v performance? I just recommended the V-Caps Coppers as a good alternative to the Duelunds. On silver by-pass, I think you will find many do this in finished products, such as Lampizator Golden Gate for example. The bypass as cheap so possible to try it out.

 

On Kasei caps, they are not for coupling duties, they are in the PS and are electrolytics. The BGs being better, maybe, but the BG thing is over blown IMO.

 

In this case, and the original question, I would say try the V-Caps coppers, no big deal if they don't work, can sell them and low loss after. BUT I would bet they will blow the AN copper out of the water, that is unless you like muddy sluggish and coloured sound?

[astrostar59]

Good reply thank you. Sorry if we had a 'thing' there. AN UK, could say lots about Peter Q, but won't go there. All I will say is do the research....

 

The kits, different story. Really good value and great sound, realistic for the money, take from that what you will re AN UK the and their pricing strategy.

[astrostar59]

8 minutes ago, Orangecrush said:

Ok, I went with the CuFT's. (Thanks Astrostar.) Even though I got a good deal on the Kit, it was still and stretch and can't justify the Duelunds at double the price. I think the Jupiter Coppers would have been good as well from all I have read, but I am pretty confident the CuFT's will be the best for the money in this application. I think squeezing allowing as much resolution and transparency out from this vintage chip is important. 

 

One (dumb) question I have is are the choice of caps less critical being that the 4.1 is transformer coupled? Someone told me that, but it doesn't make sense to me. As long as there are caps in the signal line, they will have an effect on the sound, right?  

 

 

Nice choice Orangecrush. You will be happy I am sure of it. The V-Caps Coppers are close to the Duelunds, and have the fast bass and dynamics of the Teflons, but less cold and bright, more natural balance. Blow the crappy AN Copper out of the water Ha Ha.

 

On the Transfomer outputs, you are still massively effected by the coupling caps on the line board. So don't think you have wasted your money on those caps. The C-Cores lower the output impedance right down to drive the next stage amongst other benefits.

 

When you get the DAC be aware the V-Caps need about 500 hours!!! to run in, so be patient. The DAC will sound flat and constricted for a week or so, then up and down a bit for a while. It should reach full performance at 500 hours. I would leave it on 24/7 and run some tunes on repeat overnight (with your power amp tuned off of volume down).

 

When it is run in, you can upgrade the line board tubes to some nice Tungsol NOS which I find really good, and then a Bendix in the 6X5 slot, and a Mullard NOS for the ECL82, or go for an NOS Telefunken or NOS RCA if you find you want more detail. Avoid new tubes, they are rubbish.

 

Good luck my friend!

[astrostar59]

Yes Raytheon, but the Tungsols are famous for being a great 5687, maybe the best ever and not too expensive.

[astrostar59]

I would fit a BNC in the extra socket on the back so you have the option to use either, and fit the switch to select them. Or bypass the switch and simply connect one or the other. Loosing RCA is not so good, especially if you decide to sell it.

[astrostar59]

If you end up with the same connections in the DAC, I don't see the difference. Audio Note use RCA in to the Fifth Element from the Fifth Force....

[astrostar59]

There is MORE...

 

You can further improve the PS board with oversized Kassai caps. I mounted mine on a separate board at the front. It is a squeeze but will fit. The bass and bass control improves with this upgrade.

 

The digital board is the kit version. The AN UK DAC 4.1 and 5 board is much better, has decent regulation on it. I got a blank PCB and built mine up. It can run off the kit reg board as well. Sounds much better than the kit digital board which is really the original 1.1 kit board.

 

The best tubes are the Bendix on the PS. Peter Q says don't use that, but everyone does, inc on his DAC 5 and M5/M6 pre amps. The Mullard ECL82 is the best reg for the same board. On the line board I liked the Tungsol 5685 best, NOS 1950s.

 

The I/V connections to the digital board and line board needs to be loaded correctly, AN UK use a different loading to ANK Canada. I used the AN UK loading with 680pf caps and 220k tantalums. The tants on the line board can be 2 waters, or better the new ceramic ones from AN UK.

 

Hope this helps.

[astrostar59]

More thoughts on this

 

Agreed, the AN UK copper caps are bad, really poor and lumpy bass, rolled of treble. No idea why Peter Q uses those in the AN UK DAC 5 Special I had, but they are rubbish. Possibly to keep the DAC 5 Signature sounding better by simply changing the caps?

 

I also don't buy into the silver transformers and such which cost a packet and claim to sound so much better. It is the same circuit, yet the Signature costs 15K more! 15K for 2 x 'better' output trans and 2 'better' I/V trans. Ridiculous. Peter can sell ice to the eskimo's....

 

The AN DACs are old now, way overpriced and can be bettered. Things have moved on IMO. But the Kit 4.1 tweaked up is a sweet spot. I have kept mine and will never sell it, and use it in a second headphone system. My main DAC is the Aries Cerat Kassadra which does everything much better than the AN UK DAC 5 did, MUCH better. Bigger dynamics, incredible detail yet super smooth with it, massive soundstage, bass of the scale good and fast. The AN DACs are sow, and get confused quickly as things hot up. I believe the caps and power supply can't cope, it all needs to be bigger IMO. And the digital board is the old AN UK DAC 4 board going back to 2004. Are they really saying they can't improve it? Don't believe it. I could say more but will stop short.

 

I would recommend the Kassandra and at 18K euros is a bargain v the AN DAC 5. I have tried many DACs now, and the Kassadra is the end game for me, as good a the best TTs IMO.

 

PM me if you are in Spain and want to hear it.

 

Hope this helps.