[JoshK]

I'd like to try to slave the transport off the DACs clock and make the reclocking synchronous, but that is a more ambitious mod.

I'm curious how you'd go about that. Wouldn't it be easier to just put in I2S?

Well John Swenson was kind enough to share me his I2S input scheme and it sounds doable, so I might have to try that out.  This is going to be some time in the future though when I have enough time to devote to testing.  I think I will have to make up a pcb board to accomodate it though...not sure.

[brj]

Josh, I know of two kit based USB->I2S input modules that you might consider as well:

1) Scott Nixon's USB->I2S module
2) Doede Douma's USB->I2S module (Danny Richie just pointed me to this one the other day.)

If you or others have comments on how they compare to each other (or John's implementation), I'd be curious to hear them.

[Bequerel]

It looks like you did a great job on modding.  Most of your mods are really straight forward and I think most DIY'ers here could tackle them.  It looks like to eeked out uber performance with simple mods.   Any comments on the sound before and after?

This cheap unit is actually very good before modding... if you replace the tubes with good NOS. The mods I did widened the soundstage a lot. The transparency also gained a lot from the mods. The result was actually so good that I have sold two units with a little bit simpler mods to local audiophiles.
Since I did the whole package at once, I cannot comment on the incremental improvements.

[JoshK]

Josh, I know of two kit based USB->I2S input modules that you might consider as well:

1) Scott Nixon's USB->I2S module
2) Doede Douma's USB->I2S module (Danny Richie just pointed me to this one the other day.)

If you or others have comments on how they compare to each other (or John's implementation), I'd be curious to hear them.

Thanks Brian, however, I am really not interested in a USB input, basically because I like the SB interface with remote pc. 

[brj]

Thanks Brian, however, I am really not interested in a USB input, basically because I like the SB interface with remote pc.

No problem.  I'm shooting for something similar, as I'm looking at a remote PC wirelessly feeding a USB DAC and controlled via PDA.  (The SB interface seems pretty good, but I like the idea of dropping in whatever software I prefer.)  All of the pieces are dangerously close to being available...

[JoshK]

If you want help figuring it out, I'll be happy to, just that I'm not interested in doing it myself. 

[MarkM]

I can't remember all of the mods off hand that I made to my Dac 60.

Basic mods that yielded good results.

1) 4 Fred bridges.  PS, DF supply and DAC feeds.  This was very worthwhile!
2) All Power supply caps and added a choke.  Also did the supply caps that feed the DA.
3) added .1uf Film caps on some of the other Silmic.
4) upgraded jacks
5) tubes
6) Upgraded the Output caps and some resistors

Stock, the Dac 60 is a fine performer for the $$, modded, resolution is kicked up.  Finally through in the towel and said enough.  I did flirt with upgrading the regulators though and with winter approaching, might be worth investigating.

[JoshK]

An elegant solution (and likely inexpensive) to improving the low voltage regulation inside the DAC.  finesse

[LeChuck]

1) 4 Fred bridges.  PS, DF supply and DAC feeds.  This was very worthwhile!

I'm curious about this. Can you post a picture of it, and maybe a brief explanation of how you did it (I'm not a DIY guru)? I'm also wondering what the "worthwhile" improvements you heard were.

[JoshK]

Got my DAC60 tonight. TOok a look under the hood.  Looks very modable.

BTW, did some more digging and a CCS loaded grounded cathode stage isn't necessarily a better option but a grounded grid stage would be (current amp is what is called for with I/V). 

[audioengr]

Here is what I see....
From the digital side, I see U1, your receiver, U2 is your digital filter, and U3 & U4 are your left and right channel DACs.  From my quick glance they don't look to be balanced dacs, somehow I thought the 1704s were....not that that is a bad thing mind you. 
X1 is the local clock, but I am clueless as to what clocking scheme is employed.  I just see it is fed into the receiver and passed from there to DF & dacs.  Is it really a 6.1Mhz clock or is this a typo?  I thought clocks were typically 11, 16, 33Mhz.

Ok, after some more reading, I realize that it is indeed a 6.1Mhz clock.  Multibit dacs make less demand of the speed of a DAC (thus creating less jitter). This is a good thing.  The reclocking is asynchronous which is more flexible with different sources but less ideal for 44.1Khz.  I'd like to try to slave the transport off the DACs clock and make the reclocking synchronous, but that is a more ambitious mod.  First things first....

BTW, if I am loosing anyone, just holler and I'll take a couple steps back and try to explain.

I think the key elements to tackle are regulation of the various circuits.  All the low voltage regulators are the very pedestrian LM317.  I think we can improve on this and empirically determine whether this matters...I am only guessing it does.  DC coupling caps on the outputs have been done here already.  What type of diodes are used on the B+?  If they are low quality then high speed soft recovery type would be a nice improvement.

I am definitely going to look at changing the tube section to ccs loaded grounded cathode from the SRPP current.  That should be a nice step up and not too hard to do. 

the 6.1MHz clock is only used for decoding the sample-rate, not for any kind of upsampling or reclocking.  Changing it will have no effect on the audio.

Steve N.

[persolo]

Hello, guys.

Did anyone get any good results out of their adventures? I have now received a replacement pcb, which is working after putting everything back together. Now I'm just waiting to get home and start playing. I guess my first "mod" is switching the stock valves with some Golden Dragon. I hope it works more than 12 hours this time 

[F-100]

Which tubes are you folks using with your DAC-60?
Currently, I'm using NOS RCA 6922 Gold pins (Made in Germany) but want to do some tube rolling. aa

[persolo]

I am currently using some Golden Dragon tubes. These gives me a much improved response in the lower end over the included Sovtek.
I'm hoping to get some Sonicaps soon and eventually I will try to get hold of some Siemens CCA golden ones or maybe Philips Holland/Mullard NOS from the 60s. I'm not quite sure yet. Any input would be appreciated