[JakeJ]

Sorry, I was under the impression this was about tube arcing, not tube rolling.

[Dracule1]

You're correct.  This thread is about rectifier tube arcing.  I started a different thread on different rectifier tube recommendations on tube-ophile.

[Dracule1]

  Correction, I looked closer at the 37 capacitors in the digital section of my tube DAC.  They are 22,000 microFarads each, not picoFarads. So there are total of 814,000 microFarads for the digital section.   I don't know why the digital section needs so much capacitance , but it makes it sound more dynamic with better bass extension according to the designer. The tube analogue section has its own power suppy, but I haven't opened it up yet to see how many capacitors are there.  According to my DAC designer, it is the power supply in the tube analogue section that is probably causing the rectifier tube arcing.  He is going to install a resistor to prevent this.  All I can say so far, it has the most amazing clarity. My dynamic speakers now have electrostatic clarity, but with macrodynamics electrostats can only dream about.

[Quiet Earth]

I'm glad that you confirmed the 37 caps are not directly after the tube rectifier and are not part of your arching problem.

The tube analogue section has its own power suppy, but I haven't opened it up yet to see how many capacitors are there.

If you do open it up, you will have to look carefully to see which (and how many) capacitors are actually wired directly after the tube rectifier. In other words, you can't just count up all the caps and assume they are wired in parallel, and are wired directly after the rectifier. This is where a schematic diagram comes in handy. 

According to my DAC designer, it is the power supply in the tube analogue section that is probably causing the rectifier tube arcing. He is going to install a resistor to prevent this.

Glad you got that sorted out. Let us know how the repair turns out and if the DAC still sounds the same, better or worse. Also, your DAC sounds very interesting. Can you tell us who makes it and which model it is? Or is it a prototype and a secret?

[Dracule1]

I would have to kill ya if you knew which DAC I have.  Seriously, I know I'm being vague but I will reveal all when all the kinks are worked out and the DAC is fully broken in.  Suffice it to say it is a 4 chassis hi rez DAC using two TI/BB 1792A chips, single ended output using a single 6SN7 tube with tube rectification.  It accepts SPDIF via XLR, BNC, RCA or toslink.  I'm using Audiophilleo to convert my USB signal from my MAC Mini to SPDIF via BNC.

[JohnR]

They are 22,000 microFarads each, not picoFarads.

Are you sure they aren't 22 microFarads? (A picture would sort it out )

[Dracule1]

[srb]

Aha!  Now I can see what DAC it is from the picture!  When you said "These are electrolytic caps a little bigger than the size of a D cell battery", I figured they would have to be 22,000uF.  Regardless of what series/parallel configuration they are wired in or where they are used, I can't think of too many components of any type that have that much capacitance.  Many large brutish power amplifiers have only 100,000uF to 200,000uF capacitance per channel.
 
Hopefully at some future point in time, the mystery will be revealed along with a nice interior photo of this DAC-beast.
 
Steve

[Steve]

Aha!  Now I can see what DAC it is from the picture!  When you said "These are electrolytic caps a little bigger than the size of a D cell battery", I figured they would have to be 22,000uF.  Regardless of what series/parallel configuration they are wired in or where they are used, I can't think of too many components of any type that have that much capacitance.  Many large brutish power amplifiers have only 100,000uF to 200,000uF capacitance per channel.
 
Hopefully at some future point in time, the mystery will be revealed along with a nice interior photo of this DAC-beast.
 
Steve

Hi Steve,

Not unheard of. Over at AudioKarma, there is a guy that claimed 11,000uf in his Cd player and 150,000uf in his preamplifier. Either he or another uses two 50 lb power transformers in a preamplifier. Go figure.

Cheers.

[srb]

Not unheard of. Over at AudioKarma, there is a guy that claimed 11,000uf in his Cd player and 150,000uf in his preamplifier. Either he or another uses two 50 lb power transformers in a preamplifier. Go figure.

Sure, I didn't say unheard of, just that I didn't know of too many.  I knew Wyred 4 Sound used 88,000uF in the power supply of their DAC and 164,560uF in the power supply of their STP-SE preamplifier (both not terribly expensive components), but 814,000uF - I gotta see this thing!
 
Steve

[Dracule1]

Looks like I miscounted the number of caps in the digital section.  There are total of 44, so 968,000 microF total .  Isn't 1 Farad enough to bring down an elephant ?  Can anyone explain why or what the electrical advantage of having such high capacitance in the digital section?

[JohnR]

To be honest, I'd say that is poor engineering. Maybe it's just marketing, bigger is better etc Not meaning to get anyone's nose out of joint.

[Dracule1]

I doubt it's a marketing ploy.  This guy really does not advertise...seems like most people know him through word of mouth.  As for poor engineering, you're entitled to your opinion.  That's fine, but can you explain why you think it's poor engineering?  Poor engineering implies you are going to get crappy sound, but this is the best DAC I have heard, and I have heard DACs costing in tens of thousands, albeit not in a direct side by side comparison.  It easily beats my Tranquility SE which I thought was the best sounding DAC under $4K by a large margin.  BTW, the designer has a full time job in the aerospace industry and for decades has been making tube amps (mostly SETs) for consumers and custom ones for some very highly regarded speaker manufacturers and has been building DACs for the past 20 years. He does have some controversial ideas about DACs (eg, he doesn't buy into the current bandwagon of blaming most of the ills of digital audio on jitter).  The fact that he didn't foresee rectifier tube arcing from the analogue power supply is somewhat puzzling and a little annoying, but arcing seems to only occur with directly heated rectifier tubes.  The indirectly heated rectifier tubes seem to work fine, but doesn't sound good at least the one's I've tried so far.   I have seen some of the most highly regarded audio designers make mistakes that you would think should have been foreseen.

[JohnR]

Well, as you yourself said, a Farad should be enough to bring down an elephant.

Not sure what you're asking...

[Quiet Earth]

I think it's a lot of capacitance too, but I won't slam the idea (or the designer) based on one picture and a vague description of how it might be put together.

The fact that he didn't foresee rectifier tube arcing from the analogue power supply is somewhat puzzling and a little annoying,

Yes it's annoying, but since this is a prototype built by someone who is trying out new ideas or still learning, then it's really not a big shock,,,, no pun intended.    Also, I would reserve the term "poor engineering" for when someone calls themself a company and ships out a product that isn't quite ready for production. But that's just me.

He does have some controversial ideas about DACs (eg, he doesn't buy into the current bandwagon of blaming most of the ills of digital audio on jitter).

Neither do I, so you certainly have my attention. When you are ready to reveal  the name of the DAC (or what it is and how it works) I will be interested to learn about it. You said that it sounds as good as those costing in the tens of thousands. Which pricey DACs have you heard that did not sound as good? Just curious.

[Steve]

Sure, I didn't say unheard of, just that I didn't know of too many.  I knew Wyred 4 Sound used 88,000uF in the power supply of their DAC and 164,560uF in the power supply of their STP-SE preamplifier (both not terribly expensive components), but 814,000uF - I gotta see this thing!
 
Steve

No harm meant Steve.

Cheers.

[Steve]

To be honest, I'd say that is poor engineering. Maybe it's just marketing, bigger is better etc Not meaning to get anyone's nose out of joint.

I agree with John, probably marketing hype. Take a look at the two 50 lb power transformers in a guy's preamplifier. Gets attention, "lots of iron". If he ever sold it commercially, lots of money and profit. For every dollar cost, probably .75 to a dollar in profits. Certainly an incentive for marketing twist and large, high cost parts. 

Cheers.

[Dracule1]

I still don't understand why some of you call this poor engineering. Is this bad for the circuit...cause damage to the DAC?  The arcing was found to be related to the power supply in the analogue section, not digital.  Apparently my unit is the only one that has had this problem. I think he built at least 7 like mine but no arcing with those.

Because of some of your skeptical comments regarding the high capacitance,  I took the capacitor bank out of the digital section which cuts the capacitance by half.  I was somewhat taken by surprise the audible degradation in the drive/dynamics, low end punch, refinement, and the spaciousness.  It was still better than any DAC I auditioned in recent memory, but the effect was audible.   So the designer did this for a purpose.  I find it amusing people will prematurely inject there opinion but not provide a reasonable explanation as to why they think it's bad engineering...unless they really don't know what they are talking about.

[Dracule1]

As to other very expensive DACs I have auditioned but not in direct comparion to this DAC, the full dCS stack (over $70k I think), Meitner unit (~$20k),  Playback design ($15k), Esoteric P05, top Marantz SACD/CD player, Audio Research top of the line digital, and Zanden DAC.  All of these have their signature sound, but for my taste the DAC I have now has given me the most musical enjoyment.  But take this with a grain of salt,  I have not made direct comparison because it would be impossible for me to do.   

[Dracule1]

Steve,  I respect your opinion but marketing hype would imply he advertises and pushes the extra capacitance as something special that makes it unique compared to other DACs.  Mine just came with it.  He didnt make anything special of this extra capacitance.  I didn't know about until I bought the unit.  Like I said, he's a low key guy.  He doesn't have any extensive white sheet on his technology.  I dont know why it works, but the extra capacitance in the digital section does make an audible difference so I know it not some baseless marketing hype.  Unless you've tried it yourself, why dismiss the idea?