[Xcalibur255]

Just one (rather geeky) question on the DAC: can it recognise CDs recorded with pre-emphasis and correct the same?

I had never even heard of this before now, and from what I just read it seems to only be a concern for some very early CDs from the 80's.

 

[CJG888]

80s and 90s. More of an issue for classical fans. It does, however, affect such august labels as BIS, Denon and Delos…

 

[whirlwind]

I had never even heard of this before now, and from what I just read it seems to only be a concern for some very early CDs from the 80's.

I have never heard of this either.....interesting.

 

[L0rdGwyn]

I am at the edge of my seat...


Which headphones are you testing with?

The usual, ZMFs

These two DACs are pretty darn close in terms of performance I would say, the differences are quite subtle actually.

Similar to what I thought when I was comparing the PCM56 DAC prototype - I think the Audial S5 gives slightly more in the way of airiness, cleanliness, staging / imaging. It is the more "clean" sounding of the two DACs. The PCM56 DAC however gives more in the way of smooth tonality, body, and perhaps sounds slightly more...natural? Maybe the term is more "analog" sounding. But again, we are talking subtle differences. Slightly lower noise floor in the PCM56 DAC, but would never be an audible problem in either one. Both NOS R2R so I expect that is contributing to the similar character, but I am still surprised given they use different chips, different power supplies, different I/V stages (active vs. passive), tube vs. transimpedance amplifier, different output coupling. The S5 though is more feature rich that my DAC - it has tons of digital I/O options and also gives you the option of cap vs. transformer output coupling. Also it has a small footprint, height-wise.

If I were to recommend one vs. the other to you, the slightly better staging of the S5 is probably more impressive for headphone use, it is a kick ass DAC. And given all of the extra features, it is more consumer friendly than my DAC. I am most likely going to keep the S5 in my headphone setup and put the PCM56 DAC in my stereo. Might A-B them there as well, but during the prototyping phase, I liked the slightly more warm tone of the PCM56 DAC in my two-channel setup. That's where I listen to vinyl too, so it will fit the theme better

Also should mention I am using the transformer coupled outputs of the S5.

 

[Zachik]

Thanks Keenan! Very helpful

 

[tubebuyer2020]

@L0rdGwyn another noob question if you don't mind: when ordering PCBs are you forced to buy a small (e.g. 50) batch or do you have a way of getting just a few?

 

[L0rdGwyn]

@L0rdGwyn another noob question if you don't mind: when ordering PCBs are you forced to buy a small (e.g. 50) batch or do you have a way of getting just a few?

I use JLCPCB, the minimum order there is 5 boards. Usually it is not much more expensive to buy duplicates (unless you are talking about a four-layer design), the cost really goes up when ordering multiple designs.

 

[L0rdGwyn]

I ended up moving the S5 to my stereo for now, want to spend some more time on headphones with the PCM56 DAC. So on my desk it stays, also doubling as a monitor stand lol. It will be fun to bring this DAC to a Head-Fi event some day, I'm really happy with the sound and especially happy about the low noise performance as I put a lot of effort into that aspect of the design.



Going back to work tomorrow, so the marathon run of DIY is coming to an end. Will be back at it on Wednesday though, the priority this week will be finishing the chassis design for Zach's 45 amplifier and getting it ordered. I have some powder coat swatches on the way for a few colors I have in mind, we'll see how they look in person, then will run the ideas by the wooden headphone master himself.

 

[tubebuyer2020]

I use JLCPCB, the minimum order there is 5 boards. Usually it is not much more expensive to buy duplicates (unless you are talking about a four-layer design), the cost really goes up when ordering multiple designs.

Interesting, thank you - not super-cheap but affordable.

 

[maxpudding]

I am a bit late in congratulating @L0rdGwyn for his new new OTL amp, it’s really nice to see new products from these great amp builders.

 

[zach915m]

I ended up moving the S5 to my stereo for now, want to spend some more time on headphones with the PCM56 DAC. So on my desk it stays, also doubling as a monitor stand lol. It will be fun to bring this DAC to a Head-Fi event some day, I'm really happy with the sound and especially happy about the low noise performance as I put a lot of effort into that aspect of the design.



Going back to work tomorrow, so the marathon run of DIY is coming to an end. Will be back at it on Wednesday though, the priority this week will be finishing the chassis design for Zach's 45 amplifier and getting it ordered. I have some powder coat swatches on the way for a few colors I have in mind, we'll see how they look in person, then will run the ideas by the wooden headphone master himself.

Heyhey don't worry too much about me, I'm just along for the ride!

DAC looks awesome! Can't wait to hear it someday!

 

[L0rdGwyn]

Heyhey don't worry too much about me, I'm just along for the ride!

DAC looks awesome! Can't wait to hear it someday!

LOL no way I'm making the final choice on color! But I have some ideas, first swatches I got didn't impress, more on the way

Maybe I can make the drive to CanJam Chicago next year if COVID allows, would be cool to bring along some of my gear for a meet!

 

[L0rdGwyn]

Gonna work on the 45 amp layout some more over the next few days.

Also, like I said, I want to try a cap coupled version of it while I have the prototype made up for future reference. Thinking ahead, this circuit could be easily adapted for 2A3 with changes to the filament supply and different output transformers, although the full power output of the 2A3 for headphones is quite a lot.

But both the 45 and 2A3 do not like to see a high DC resistance on their grids in fixed bias, especially early models with relatively poor vacuum, like 45 globes. The grid resistor loads the input stage, so using a 50K resistor (limit for 2A3) or 100K resistor (limit for 45) won't fully maximize gain and keep distortion at a minimum.

The answer to the problem for the cap-coupled version is to use a grid choke to load the stage instead - maintains a low DC resistance for the grids, but a high AC impedance to the signal due to the inductive reactance of the choke. So I've reached out to my buddy Kevin and K&K Audio (who is probably on his way to buying a vacation home with how much of my money he has gotten over the past two years LOL), going to grab a pair of Lundahl grid chokes to give this a try before taking down the prototype.

 

[whirlwind]

LOL no way I'm making the final choice on color! But I have some ideas, first swatches I got didn't impress, more on the way

Maybe I can make the drive to CanJam Chicago next year if COVID allows, would be cool to bring along some of my gear for a meet!

I would love to be able to come to this...listen to your amps and Zach's headphones and meet you guys in person and maybe I could visit some blues clubs.
This sounds like a couple of nice enjoyable days

Hopefully the world will get better as far as covid goes...I have my fingers crossed for this to be the case.

 

[L0rdGwyn]

I would love to be able to come to this...listen to your amps and Zach's headphones and meet you guys in person and maybe I could visit some blues clubs.
This sounds like a couple of nice enjoyable days

Hopefully the world will get better as far as covid goes...I have my fingers crossed for this to be the case.

Will keep my fingers crossed! Going to keep these dates circled on my calendar for next year.