I have been experimenting replacing the digital board in my ANK DAC2.1B with the DAM1021 R2R board from Soekris. I am primarily an analog guy, (vinyl and R2R tape), but have been enjoying streaming music from Qobus for a couple of years now. The ANK DAC2.1B, with CS8412 receiver chip and AD1865 DAC chip, is limited to 96/24 streams. Additionally the AD1865 is a 16 bit chip, designed for Redbook. I recently got a good deal on an ANK DAC4.1 Signature, so thought I would play around with the 2.1.
Physically the swap is a straight forward board switch out. I did have to put a small transformer circuit on the SPDIF RCA input, but it is quite simple. The ANK digital power supply feeds the Soekris board. The output from the DAM1021 is fed to the I/V transformers, the the 6922 tube output. to Dueland cast copper output caps. So it was really just desoldering and resoldering the various leads. The result? Well it sounds damn good. But way TOO MUCH good! The DAM1021 has a raw output of 1.4 volts and the ANK DAC a gain of approximately 28. I turned the volume way down on my preamp to get a listenable level, but decided to reduce the gain on the DAM1021 to avoid issues downstream.
The Soekris DAM1021 allows a few ways to reduce gain. One can add a pot and reduce the voltage, therefore reducing the gain. You can reduce gain via the filter files and you can reduce gain via the board system management, I tried the pot. It worked, but the new pot that I received was scratchy and has some dropouts in the resistive strip. Not wanting to battle that, and not fully understanding the system user interface, I just padded down the analog output with a voltage divider on each channel. Not elegant, not technical, but it worked.
I have been listening for a couple of weeks now. I am really enjoying the musical reproduction and the ability to listen to new music, (new to me!) on Qobuz at the higher resolution rates. Too early to do a comparison to the DAC4.1. I still need to sort the final gain solution and try different filters on the Soekris board. but this has been a fun start to the journey!!
Cheers,
Geary
Physically the swap is a straight forward board switch out. I did have to put a small transformer circuit on the SPDIF RCA input, but it is quite simple. The ANK digital power supply feeds the Soekris board. The output from the DAM1021 is fed to the I/V transformers, the the 6922 tube output. to Dueland cast copper output caps. So it was really just desoldering and resoldering the various leads. The result? Well it sounds damn good. But way TOO MUCH good! The DAM1021 has a raw output of 1.4 volts and the ANK DAC a gain of approximately 28. I turned the volume way down on my preamp to get a listenable level, but decided to reduce the gain on the DAM1021 to avoid issues downstream.
The Soekris DAM1021 allows a few ways to reduce gain. One can add a pot and reduce the voltage, therefore reducing the gain. You can reduce gain via the filter files and you can reduce gain via the board system management, I tried the pot. It worked, but the new pot that I received was scratchy and has some dropouts in the resistive strip. Not wanting to battle that, and not fully understanding the system user interface, I just padded down the analog output with a voltage divider on each channel. Not elegant, not technical, but it worked.
I have been listening for a couple of weeks now. I am really enjoying the musical reproduction and the ability to listen to new music, (new to me!) on Qobuz at the higher resolution rates. Too early to do a comparison to the DAC4.1. I still need to sort the final gain solution and try different filters on the Soekris board. but this has been a fun start to the journey!!
Cheers,
Geary
I have been running the stock filters preloaded by the designer. They are bright, crisp and detailed, with strong bass and extended highs The highs are a little forward, for me, on my system. The filters present a very different soundscape than the ANK AD1865. Not necessary better or worse, but I prefer a more relaxed presentation. I will load and listen to some "NOS" filters developed by contributors on the Soekris custom filter thread . But, just to be clear, the DAM1021 continues to impress.
The DAM does not require an I/V. I guess the transformers are just applying a pointless and distortion inducing voltage gain. Not sure if even the tube SRPP is beneficial to the DAM, but you definitely should not have both transformers and tubes. The transformers must be easy to bypass.
I/V transformer developed for (few mA) current output DAC chips (PCM63, PCM1704 etc. few ten mV input at I/V resistor)), so inappropriate to use as "output device" of Soekris R2R DACs (few Volt output).
SRPP first (lower) tube grid is direct coupled to I/V transformer secondary, so if you want to use this SRPP with DAM1021, need to use (instead of I/V transformer) any 1:1 good transformer (Cinemag CMLI 15-15B, Jensen JT-11P-1 etc.).
BTW DAM1021 has enough voltage to drive any amplifier, the whole I/V transformer - SRPP gain stage is unnecessary.
If you want to use tube stage, must to use any tube preamp stage, for example cathode follower, low gain preamp etc.
SRPP first (lower) tube grid is direct coupled to I/V transformer secondary, so if you want to use this SRPP with DAM1021, need to use (instead of I/V transformer) any 1:1 good transformer (Cinemag CMLI 15-15B, Jensen JT-11P-1 etc.).
BTW DAM1021 has enough voltage to drive any amplifier, the whole I/V transformer - SRPP gain stage is unnecessary.
If you want to use tube stage, must to use any tube preamp stage, for example cathode follower, low gain preamp etc.
I agree with both points. There is way too much gain. I plan to try the the 1021 straight out to the pre amp in a more serios evaluation mode. I initially tried the board straight out to the preamp, but it seemed to lack drive and dynamics, but I had, at that time, only the AD1865 board with which to compare. I am getting a better sense of the 1021 characteristics and will start the process to reducing stages and gain. My system is all tube amplification. The preamp has a gain of 8, so the output voltage of the 1021 is fine.
My sytem contains DAM1941 -> 801a preamp -> 300B SE.
The DAC ladder output directly connected (no IC!) to tube preamp input.
I planned to use 1:1 transformer, but it's unnecessary, the tone is very good.
Ask here, if omitting DAM1021 output bufffer IC worth it, or not.
https://www.diyaudio.com/community/...e-24-bit-384-khz.259488/page-543#post-7114121
The DAC ladder output directly connected (no IC!) to tube preamp input.
I planned to use 1:1 transformer, but it's unnecessary, the tone is very good.
Ask here, if omitting DAM1021 output bufffer IC worth it, or not.
https://www.diyaudio.com/community/...e-24-bit-384-khz.259488/page-543#post-7114121
Because you use only SPDIF (44..96kHz), the -IMHO average quality- first (FIR) filter bank within the Soekris DAC is active.
The other filters - made by members of this DIY community- would be better for 44/48kHz.
I usually use USB (SOtM output), so I scale up everything (with Roon) to 352/384 kHz, so FIR1 omitting.
The other filters - made by members of this DIY community- would be better for 44/48kHz.
I usually use USB (SOtM output), so I scale up everything (with Roon) to 352/384 kHz, so FIR1 omitting.
I have been listening to the NOS filters by @koala877. My primary reason was that the filters support hi rez. They are producing music that is quite enjoyable. The sonic signature is much closer to the AD1865 than the stock filters. The presentation of music is less frenetic, more relaxed. Imaging, soundstage and timbre are quite good.
I am still sorting out the gain. I am rapidly coming to the conclusion that the DAM1121 would be better suited for this application. The DAM1021 pulls more current from the ANK digital power supply, this also voltage differential between the voltage poles. I do not want to remove the buffered output op amps on 1021 board. Using the 1121 would allow me to reduce voltage demand and add regulation to the ANK digital power supply. I am thinking this could be done on a "motherboard" for the 1121.
I would appreciate any thoughts on the project. I am getting some interest from othe ANK DAC owners. So far my guidence has been if they do not have a need to listen to resolutions beyond 24/06, that they are probablr bot going to gain much from the conversion. But more testing/listening will help sort out my early opinion.
Cheers,
Geary
I am still sorting out the gain. I am rapidly coming to the conclusion that the DAM1121 would be better suited for this application. The DAM1021 pulls more current from the ANK digital power supply, this also voltage differential between the voltage poles. I do not want to remove the buffered output op amps on 1021 board. Using the 1121 would allow me to reduce voltage demand and add regulation to the ANK digital power supply. I am thinking this could be done on a "motherboard" for the 1121.
I would appreciate any thoughts on the project. I am getting some interest from othe ANK DAC owners. So far my guidence has been if they do not have a need to listen to resolutions beyond 24/06, that they are probablr bot going to gain much from the conversion. But more testing/listening will help sort out my early opinion.
Cheers,
Geary
I added a simple 9VDC regulated power supply to the ANK, bypassing the ANK digital power supply board. Still used the ANK mains transformer, I simply moved the leads to the new board. Nice improvement overall. Better definition, imaging and bass. Another datapoint supporting the use of the 1121, rather than the 1021. The ANK power tranny has plenty of current to maintain a solid, 5VDC regulated digital power supply. Again, I am striving for a more "quick solder and replace board swap, so utilizing as much of the original ANK componentry is a plus.