Soekris Dam Dac

[rickmcinnis]

I am very pleased with the table. It has evolved over ten years. The tonearm over twenty years.

It is an assemblage. Using a LENCO L75 for motive force - all that is left is the motor, the platter and the idler. The motor is not connected to the plinth. It is on its own sitting atop copper plates to get the height right.

The plinth is from OSWALDS MILL and is a over-sized slab of slate - it is approx 22 inches square by two inches thick. Peter Reinders TOP PLATE and bearing along with five of TURNTABLE WEIGHTS copper "mats" to make for a very heavy rotating mass.

Tonearm: Eminent Technology 2.5 - bought this as a 2.0 when it came our and have stuck with since I like the concept and I cannot afford another! No original components remain. Everything is stripped away - the manifold is clamped directly to the plinth with pieces of ebony - none of that rickety structure that came supplied with the arm. No, I cannot easily adjust the VTA.

The manifold is low pressure/low flow for use with BIG air compressors. It needs lots of air. I have a 30 gallons air compressor on a covered deck with a copper line running from an 8 foot by 4 inches diameter tube filled with polyester that acts as a water filter and an air dampener to the arm. There is an intermediate length of PVC tubing between the final pressure gauge and the tonearm.

The "wand" is an extra long version of the carbon fiber arm tube. About an inch and one-half longer to clear the peripheral record clamp. Had this with the MERRILL table and was glad when TTWEIGHTS (now departed) offered them.

Using the Transfiguration Proteus which replaced a Temper Supreme. I am a fan of their sound.

Use PEEK screws to hold the cartridge!

The phono amp is the SALAS folded cascode. Started out sounding good but then I read this article that mentioned Mr. Yazaki of SPEC CORPORATION - very fine audio components. He, in an act of incredible generosity, right up there with you and Nigel sharing the battery/capacitor discovery, mentioned this incredible rectifier diode. He made the outlandish claim that it is as good as any valve rectifier. That of course sounds incredibly ridiculous but I could not resist. Just what if it was true? I installed this into my SALAS supply, which has nothing to do with what SALAS suggested one to use. I like Full Wave rectification with a center tap. These diodes come in a two diode package. Each channel has its own supply. It uses two old DYNACO Stereo 150 amp power transformers with a choke input (STTH6110TV is the designation for the rectifier. I use one of these in the WAVE IO power supply)

After turning the thing back on after installation I thought I was dreaming. I had never heard such an effect after changing a single component. I thought the power of suggestion had just taken complete control over me. I am hearing a sound as if one was able to use a WE 274B in a 45 volts power supply. I listen to a few records and wait for reality to set in. Could it have been the sound of an unsettled component and when it burns in the sound becomes typical of a SS rectifier. (a very sad scenario, I am trying to be funny) Yes, I know there are differences with rectifiers but so minor they are almost silly to worry about.

So after a couple of weeks of this sound I figure this thing must produce DC of great purity. I think, why use electrolytics in the filter? - I may well not need that much capacitance. I had some ASC motor run PP caps laying about so I installed 150 uF where 4700 uF had been. I figured I would lose some bass. I thought I would end up needing to get a few more of the caps but might as well give it a try.

There was nothing to be concerned about. No lack of dynamics and no running out of breath on extended low notes. Dramatic loss of grittiness in the high frequencies. General added goodness.

The phono amp has plenty of those TX2575 resistors, RELCAP PS and Vcap teflon in the Riaa and a big DUELUND as the output cap.

It is a fine circuit that deserves having money thrown at it.

Now that the digital system is working I am going to replace all of the electrolytics on the PCB. This will be a packaging challenge. I will be using those ASC PP motor runs - they are cheap and they work very well in power supplies. The circuit board will be on top of the caps (they are about eight inches high) hoping I can keep the leads to less than two inches. Will see if 60 uF can replace 470 uF. Can always tack an electrolytic to the ASCs if more is actually needed.

I suspect that is more than anyone wanted to know.

[jkeny]

Thanks Rick - great write-up

Yes, a lot of the TTs we compared to were Fran's who has a number of TTs
- a rebuilt Lenco - an L75, I think - in a DIY plinth & an air suspended tonearm - similar to a terminator arm.

That rectifier is a great find - thanks for sharing - there's a lot to be said for over-specced PSes & that diode fits the bill - for a Phono PS that diode seems to be just ticking over & would seem to have the transient speed. It reminds me of the characteristics of the LiFePO4 batteries.

[nige2000]

[nige2000]

Now that the digital system is working I am going to replace all of the electrolytics on the PCB. This will be a packaging challenge. I will be using those ASC PP motor runs - they are cheap and they work very well in power supplies. The circuit board will be on top of the caps (they are about eight inches high) hoping I can keep the leads to less than two inches. Will see if 60 uF can replace 470 uF. Can always tack an electrolytic to the ASCs if more is actually needed.

lost me here
are you talking about the dac?
should be no electrolytics on dac only bypass thin film

is the waveio powered from battery?


had one of these moments with the soekris this week

had a very very mild hum i tracked down to a fpga cap cold joint

got it sorted

[rickmcinnis]

Sorry for the confusion.

I am speaking of the phono amp which has five electrolytics; one in the shunt regulator and the remainder doing various things within the circuit on the PCB.

Forgot to mention something that has made a big difference in the sound of the table is the PHOENIX Roud Runner and Eagle combo - motor controller and tachometer. With this, the Lenco spins at 33.333_ space to signify where the numbers flicker. Opinions vary regarding absolute speed but it is obvious that speed variation is the analogue to clock errors with DACs, I assume. Absolute stability makes a tremendous difference is spatial recreation. Correct speed a welcome bonus.

That is what I was noticing last night. Got the SLAGLE autoformers installed. Then made the stupid mistake of snipping the volume control wires with the thing on and I think it corrupted the firmware. I think it defaulted to maximum volume on one channel and even the with attenuator one step from zero is was loud and distorted.

I then (finally) turn the thing off and back on and one channel is behaving normally and the other is still much louder but nothing like it was. I can balance the two channels. Now I must install the new firmware this weekend.

Now that that confession of stupidity has been made.

I installed the JCAT card in my regular computer and it does not see the card, either. I can't believe I was shipped a defective replacement. So I am still without the use of this card.

SO while listening, at this point in time, the SOEKRIS does not have the width of the phono and it does not have the extension of the sound into the room. I guess the new (dumb) buzzword is IMMERSION, but this is lacking. I do remember the first time I installed the JCAT card there was a great increase of the sense of sound coming from everywhere BUT the speakers so there is hope if ADNACO will send me another USB card. That might be what I am missing the most. REGEN does some of this but nowhere near enough. Maybe the battery will make the difference with REGEN? Another project that will have to wait until the weekend.

Please do not think I am complaining about the SOEKRIS. I figure it is as good as anything I will ever have and beyond that I know it is performing at a very high level. I am very glad I made the changes. I was hoping the differences between digital and LP would have been of a lesser magnitude. There is much left to do, I know, so the chance of narrowing this gap is good.

One thing for sure it is really neat just walking up to the machine and making a selection instead of the ritual required to play an LP. Both formats have their advantages - utilitarian and sonic. I think it is good to switch between them. Each one teaches you about the other. Even with all of the noises the LP does do something that is as hard to describe as it is to mimic with digital at this point in time. Nigel made an attempt at describing it - something about a 4D effect. There is something about the timing within each impulse of a musical note that digital does not get right. I cannot figure out if the information is misplaced or not there but it is something so intrinsic to music, so intricate, that you wonder if it can only be reproduced with a rock scraping against a jagged wall.

[nige2000]

I've no idea what your vinyl setup target sounds like
But new firmware and filters are a must
As is the 3.3v bypass battery mod on the regen
I'm not sure if the waveio would be the best for this application as with diyinhk we can bypass all regs for direct 3.3v
If its still short at that there's a bit of gain in swapping out the FPGA caps

After that were probably down to the limitations of the FPGA and programmable clock
Anyway Dont underestimate the influence of the PC USB cards and cables etc

[randytsuch]

Rick
It looks like you've removed everything on the output side of the shift registers, something I still need to do.

But, the pics still show C135 and C143 installed.

These are on the output, and imho, need to go. Easy to do, and made an improvement for me.

Nige
Speaking of the FPGA caps, I've replaced 9 of them so far, 1/4 of the way done. I'm using two soldering irons to remove them, and with this method its actually pretty easy, easier than I expected. Just need to find some time to finish.

And the more I listen to this dac, the more impressed I am. I guess these mods are scaring people off, but they really aren't that hard to do (IMHO), and the results are WELL worth it. I think this is a true audio bargain for a really good dac.

Randy

[gstew]

I am very pleased with the table. It has evolved over ten years. The tonearm over twenty years.

<SNIP>

I suspect that is more than anyone wanted to know.

Definitely not too much! Thanks for the detailed descriptions Rick. I've got an ET-2.5, an ET-2 hi-pressure, and a couple of ET-1's. I've been looking at combining one of the ET-1's with the 2.5 to get a more rigid setup. BTW, did you see the all-machined ally arm mount on the Audiogon forums?

I'd love to see pix of your ET setup Rick. Have you posted them anywhere? Or if not, can you put a link to some here or in the 'General' forum?

And also thx for your endorsement of the Road-Runner / Eagle combo... I've been watching that closely.

And the rectifier too. WOAH, that is one serious pair (so to speak....;). I was checking ST's other diodes to see if they had any comparable in different packages... these seem to be the only ones at 120A! So I have some in my Digikey cart to try on my next project!

And your Salas Folded description too. Did you post pix in Salas' thread?

And especially thx for your pix of your DAM DAC setup. I've been watching yours and Nigel's & Randy's for details. You have all taken them beyond ANYTHING anyone else has considered. I feel bad that I don't even have mine playing yet.... maybe while I am off during the holidays.

I wonder if Soren is watching here?

In any case, Rick / Nigel / Randy / Jkeny, thank for the inspiration (and often being on the BLEEDING EDGE!)

Greg in Mississippi

[nige2000]

Rick
It looks like you've removed everything on the output side of the shift registers, something I still need to do.

But, the pics still show C135 and C143 installed.

These are on the output, and imho, need to go. Easy to do, and made an improvement for me.

concur they need to go unless there's a more suitable replacement

Nige
Speaking of the FPGA caps, I've replaced 9 of them so far, 1/4 of the way done. I'm using two soldering irons to remove them, and with this method its actually pretty easy, easier than I expected. Just need to find some time to finish.

kinda like tweezers cool
think i managed to knock the first few off using one iron till i decided to try the hot air which was faster :)

And the more I listen to this dac, the more impressed I am. I guess these mods are scaring people off, but they really aren't that hard to do (IMHO), and the results are WELL worth it. I think this is a true audio bargain for a really good dac.

Randy

i think so too
sounds to have a lot of the good aspects of analog sources
with good analog sources theres no digital noise/jitter from chips switchers etc
witch pc and dac there is many possible sources of digital noise/jitter and we need to treat/ cure as many of them as possible

[jkeny]

And the more I listen to this dac, the more impressed I am. I guess these mods are scaring people off, but they really aren't that hard to do (IMHO), and the results are WELL worth it. I think this is a true audio bargain for a really good dac.

Randy

i think so too
sounds to have a lot of the good aspects of analog sources
with good analog sources theres no digital noise/jitter from chips switchers etc
witch pc and dac there is many possible sources of digital noise/jitter and we need to treat/ cure as many of them as possible

In some ways digital audio is not much different to a vinyl playback phono preamp - the voltages are in the same ballbark & therefore the possible sources of disturbance of these subtle voltages are similar. One difference is that in phono reproduction everyone agrees about the need for elimination of these elements of disturbance so consideration is given to this before phono preamp & in phono preamp (look at Rick's recent example of PS supply changes on phono stage) whereas in digital audio there is a gung-ho attitude about noise - it's of no consequence unless it's bad enough to change the bits.

This is fine in the world of communication but many don't seem to truly understand what digital audio actually is - a mixed signal environment where analogue meets digital. The gung-ho attitude towards noise on the digital side doesn't sit well with the very sensitive voltage levels being handled on the analogue side.

BTW, I'm convinced that what is being gradually uncovered in recent advances in digital audio is just how the subtly audible cues add to our sense of "realism" in the reproduced sound. I don't believe that it's the reduction in the background noise that is responsible for our perception of these subtle cues, I believe that it's a reduction in the modulation of this noise that is responsible. After all, it's reported quite extensively that vinyl & reel-to-reel tape is more convincing than most digital audio & yet the reproduced background noise is higher on these analogue sources. There may be some form of noise modulation in digital audio that fluctuates with (or is dependent on) the signal?

What we are seeing with the Soekris DAC & most discrete DACs is a better separation of the voltage reference used in the analogue side from the influences on this voltage coming from the digital processing side. This is the one major area that instantly improved in the Soekris - when this reference voltage was changed from on-board regulation to direct battery power. This is the critical point in all DACs - the conversion of bits to output voltage or current - we saw the same in the PCM1794 DAC when we improved the current reference used by the final stage that converts bits to output current.