Thanks for the info and links on this mod. I was considering some upgrades on my 2.1 and those I/V transformers were first on the list. Second on the list is replacing that dinky PSU for the digital board with something more substantial, powered by a separate transformer. Either by seeing if I could get a Dac 5.1 PSU board and trannie from ANK, or something like this beastie: Dual/Bipolar LV-Reg if it could be made to fit.
Judging by the link that @dogilv attached in post #39, the 330r parallel input resistors on the line board needed changing to 680r. For the Dac 3.1 in question that was R1 & R11. Looking at my Dac 2.1 board line board, it looks like that equates to R3 & R8. What's unclear to me is if any modification to the Dac board resistors is needed.
Ugh, correction, the Dac 3.1 resistors were 3300r (3K3) and got replaced with 6K8? Now I have no idea what I'm talking about.
Yes. Worked like a charm. Details covered in the thread linked in previous post. Highly recommended. I would stick in a few AN Silver Tants while your at it. It's been a while since I've done this so my memory of exact details on values etc. is a bit fuzzy, and pretty sure all the analog boards aren't the same anyway. Here's a some pictures to help the discussion although this DAC doesn't have OPT's:
You're correct there. Here is, I believe, the 3.1 analog board schematic which shows in R1 the 3.3K ohm resistor you changed to 6.8K I couldn't find an accurate schematic for the Dac 2.1 board I have, but there's this. On the current boards that 330R does not exist (and was never R3 anyway), but the 470K in the actual R3 position is now 330R. So it's a bit of a mystery to me, but I would hope that is what one would change if necessary. Did you alter the Dac board at all, do you remember?
Guys...something is super wrong with my DAC (or transport). I was listening today and the music just started fizzling out, even slowing down a little before eventually just degrading to light crackling and then nothing. The first time, a reboot brought it back, but then it happened again. All tubes are glowing and it sounds normal when it is working. I also got it working once by rebooting the transport, so it either the transport, or something between it and the line board. Now I can't get it to work at all. No sound coming out. I'm not having a good weekend with my gear. Horrible timing.
Upon further investigation, I found the power LED on my LPS-1, which powers the clean side of my transport, had a red light, which means it was not outputting power. I knew I had heard this particular fade out before, and it was when I pulled power to the clean side of the transport during play. It has a capacitor inside that slowly drains. Unplugged and reset the LPS-1 and back to a green light. Fingers crossed.
Welp, it's official, my LPS-1 is dead. Light stayed green and was playing music for maybe 20 minutes, then the same fizzle happened, I quick got up and checked...sure enough, red light. What the hell is going on and why would all of my equipment choose to take a crap during lock down? Uggggh
I think I may be able to breathe a sigh of relief. I decided to open it up to look for anything obvious on the board. Everything looked good, so I put it back together and plugged it in. Been running like 45 minutes now without issue. The extended time unplugged may have reset something. I'm guessing one of the banks of caps wasn't being switched on when the first drained.
We have 2 different AN DACs (DAC3.1 & DAC2.1) here with different output boards. the DAC3.1 has a 3.3k load resistor after the IV. the DAC2.1 (which I have) has a 330R after the IV. I have been studying the AD1865 chip datasheet a bit and also from reading in forums, most ppl are recommending I/V stage load resistor in the range of 22oR to 400R. In that ball park. These are direct loading. Using 1:1 shouldn't change that loading. 330R is in that range. Which makes sense for the I/V transformer to be 1:1. I am suspecting that the DAC3.1 I/V transformer is not a 1:1. Given that the load resistor is 3.3k, that may indicate it is a 1:10 or 1:5. And that also explain why @dogilv is able to use that particular Sowter transformer.
Oh, and also in the latest AN Kit 4.1x photos, R1/R11 have gone back to 330R. so maybe @dogilv 's unit is not the same circuit anymore. Dac 4.1x - ANK AudioKits
Some more info for the pot: From the linked post R-2R Audio Note DAC 4.1 DIY and mods it looks like @dogilv originally changed to the Sowter I/V transformers and had reduced output as a result. Hopefully it's okay that I repost the full response from Brian Sowter: --- Excellent! We have established that you must be using the Iout terminal(s) Pins 21 and 4 for the L and R channels. The DAC puts out +/- 1mA peak to peak. This equates to an rms current of 0.71 mA. Don’t worry about this point but generally is easier to work with volts and amps rms which is what you measure with a volt meter or ammeter. We have been working with DAC’s for 20 years too and we recommend a step up transformer not a 1:1! We have sold literally hundreds of step-up transformers for DACs. So the good news is that our type 1465 is the ”correct” transformer at least if you follow our recommendations. Now for the choice of I/V resistor. First you need to wire the 1465 with the primary windings in parallel and the secondary windings in parallel giving you a simple 1:5 transformer with a very high bandwidth. Connect the primary between pin 21 (or 4) and ground with NO resistor in parallel. You then connect the I/V resistor across the SECONDARY of the transformer. See attachment. Second you need to decide what voltage out you need. I suggest you go for 1.0V. Now for the calculation: 0.71 mA (=0.00071 Amps) in the primary is 0.00071 / 5 = 0.000142 Amps from the secondary. By ohms law ( R=V/I remember?) the I/V resistor you need to get 1.0 V, R = 1 / 0.000142 = 7042 Ohms. On our site we recommend 6.8K which is close enough. Hope this helps Best regards Brian --- Not sure if that helps in regard to the Dac 2.1 and its 330R though. Is the stage load resistor the one on the Dac board output or the line board input?
That helps! So it has indeed been 1:5 and the corresponding load resistor has been changed accordingly. So everything makes sense. For the DAC2.1, if someone want to use the same Sowter, then changing the 330R to 6.8k will work. Sowter also said remove the load resistor on the DAC board, which in @dogliv 's photo, is removed. (top left of the DAC board, there are 2 caps, with empty space next to it)
Hey guys, Brent isn't able to get these out for a couple weeks due to lock down. I'm obsessed and looking at Upscale Audio who appear to have the same or similar tubes to what I'm looking for. These ones say manufactured around 1970. Considering the fact that one of the tubes from Brent Jessee was made in 1970 on the nose, I'm wondering if these would be the same or close enough? @fully_articulated Can you help? Thanks Siemens A-Frame E88CC/6922
I think this is great. Here is a summary of upgrade/mods that can be done. From easy to more elaborate. - 6922 tube. Russian rockets, Siemens 6922 - decoupling capacitor. 0.47uF for the DAC2.1. Mundorf, Jupiter, Audio Note, Duelund. - I/V load resistor. Vishay Z-Foil, Audio Note Silver Tantalums (those are crazy expensive!) - I/V transformer - Sowter 1465, need a corresponding change to the load resistor, from 330R to 68k - Digital board power transformer. Currently power/mains transformer for the digital board is shared with the analog output stage. Furthermore, the power rectifier stage, digital and positive analog side of the board has a shared rectifier, on the higher end ANK DAC they are separate. ie. there are 3 of them, digital, analog+, analog-.
On one hand, I placed an order from Upscale Audio this morning and it shipped quickly. On the other hand, I’d just use your backup tubes* and chill until BJ can come through. *I’d actually use the Gold Lions over the Amperex Holland but that’s just me.
Strange, I very much disliked the Gold Lions. They sounded pretty sterile...no character, but seemed very accurate (which apparently isn't my cup of tea, lol). Thing is, I'm gonna want a spare set of these anyway since, in my opinion, it's a night and day improvement. Even if the tubes aren't identical, can I assume the ones from Upscale would be similar in characteristics, regardless?
Excellent, and quite exciting! The only other thing I wonder is how much it depends on the gain of the analog output stage. The 6.8K value is derived from having chosen a 1V output (from the transformer?), but could that be too much/little for the Dac 2.1 analog out? I not sure how relevant this is, but the new 2020 version of the Dac 2.1 manual specifies 37mV for a 1kHz test tone on the input of the analog board, and 1V on the output.
