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Valve DAC = No point in valve amp?

post #1 of 12
Thread Starter 
So, I am a happy owner of the Aune T1, with an EH6922 tube. It's the first tube product I've purchased, and I've loved it since mid last year.

For those of you who don't know, the valve sits right in the DAC stage - It's actually a regular SSD amp, with a tube DAC.

I was about to pull the trigger on a big, expensive, shiny valve headphone amplifier to go with it, but just before I did, my ever so thoughtful (and luckily, wallet-concious) girlfriend asked me:

"What's that?"

I replied "A tube amp, for my headphones"

Girlfriend: "Haven't you already got one?"

Me: "Well yeah, It has tubes, but then it's a regular amplifier after that."

Girlfriend: "But you have tube sound already. What's the benefit in more tubes?"

And then I stopped in my tracks, and realised I didn't have anything to reply with. Clever girl.

It made me think, even if the signal chain was this:

Computer -> USB -> Aune T1 tube DAC -> Line out -> Receiver -> Speakers,

Isn't the receiver technically then getting "Tube sound"?



TL;DR: What would be the benefit of getting a valve amplifier of any kind, when one can use the Line out of the AUNE T1 to give "Tube flavour" to any amplifier?
post #2 of 12
I believe you've answered your own question. There is none. The more acceptable way would be to run a tubeless source and a tube amp to flavor but then who are we......

Enjoy!
post #3 of 12

direct answer to the final question: 

 

because topology makes all the difference.  just because there is a tube in there, does not impart some kind of magical "tube sound" that any tube presence will give you. 

post #4 of 12
Thread Starter 
Could you please elaborate on that?
post #5 of 12

Well, tubes have a sound usually.  It is a coloration.  Sometimes it is preferable to full fidelity, and can trick you into thinking it is superior fidelity.  It can be enjoyable and fun to listen to which is the point of listening anyway.

 

But yes, the topology is important.  Some line level tube circuits can be fully transparent and never really display any "tube" sound.  Many pre-amps with tubes impart very little unless oddly designed to do so on purpose.  Your typical triode or ultralinear push-ull transformer coupled full power amp usually has plenty of tube sound.  As does a transformer coupled single ended amp though they sound different.  Then there is OTL tube amps.  Again some can be transparent without a noticeable sound signature, some don't. 

 

People have different preferences.  My preference is for simple push-pull transformer coupled triodes.  Single ended can be quite nice, but are too colored for my taste. I once had a single ended headphone amp that was essentially a single ended 2 watt amp that could also be connected to headphone or used as a SE sounding pre-amp.  It wasn't bad though again not quite my taste. 

 

Not familiar with your DAC, but it has a dual triode so likely just buffering each channel with half the tube.  Looking at specs, if accurate it likely wouldn't have much of a sound of its own.  My guess is the DAC/amp is the same unit with some op-amp buffering the outputs for driving headphones directly.  But this is just conjecture on my part.

 

In any case, just having a tube doesn't tell you how it will sound.  And even with tube sounding equipment they don't all sound the same.

 

To answer your question:

 

Valve DAC does not equal no point in valve amp. 


Edited by esldude - 7/9/13 at 5:54pm
post #6 of 12

You really gotta push those valves hard to get the most distortion. tongue.gif

 

For example, some single ended valve "power" amps struggle to output 10 W with less than 5% THD.


Edited by xnor - 7/10/13 at 11:13am
post #7 of 12

First off, I completely agree with esldude. I am just simply going to provide you with my experience with tube audio. 

 

 A tube amp can add more tube sound into your setup. At first I was using just a receiver with optical from my PC. Then I got the jolida fx tube dac. Just the dac alone was a pretty big difference. Meanwhile my friend has been designing my tube amp. Originally it was supposed to be a simple amp, and he made a simple proto type to test it out. The design changed into an amp and a separate tube based power supply (tube rectified). Eventually we ended up with my final amp. 

 

Every time the design changed, there were more tubes involved, and he made a new prototype for testing. Each time we tested the amp design, the new tubes definitely made a big impact on sound quality to the point where even rolling the tube rectifiers made a difference let alone the tubes on the amp. 

 

So YES, I can fully attest to there being a very good reason to get a tube amp and tube dac. 

post #8 of 12
Quote:
Originally Posted by jensy View Post

.....

Girlfriend: "But you have tube sound already. What's the benefit in more tubes?"
 

 

...ummm, the benefit is more pretty tubes...naturally!

post #9 of 12
Quote:
Originally Posted by Hi-Five View Post

 

...ummm, the benefit is more pretty tubes...naturally!

Definitely!

 

I think that's mostly it? (I'm not saying it's a bad idea, but does inyone think it just seems weird, conceptually, to use a tube in, of all things, a DAC?)

 

Side note: I kinda wish I had a preference for Tube sound... they look so much cooler...  And Tube people have so much more fun. Rolling OpAmps just isn't the same (but no cheaper... that OPA627 is pure sex)... I've never heard someone say, "OMFG you've got to hear this new NOS opamp! It's BALLER!" Or something like that.

 

Does anyone say that?  Please tell me someone has. That'd be awesome. 


Edited by Chromako - 7/12/13 at 2:41am
post #10 of 12

Can we define "tube DAC"? Is the valve being used in some sort of active filter for the DAC itself? Or is it more likely in some sort of voltage follower configuration after the digital stage?

post #11 of 12
Quote:
Originally Posted by OJNeg View Post

Can we define "tube DAC"? Is the valve being used in some sort of active filter for the DAC itself? Or is it more likely in some sort of voltage follower configuration after the digital stage?

In some dac's and depending on the topology use of various triodes is a short cut way of obtaining a flatter response compared to some solid state output stage without adding extra distortion. Yes in some cases, the valve acts as a active filter, but it comes down to it's design whether or not it's working with the digital clock on the same circuit or it's running on the output stage of the dac. This is my basic understanding.

post #12 of 12
Quote:
Originally Posted by DefQon View Post

In some dac's and depending on the topology use of various triodes is a short cut way of obtaining a flatter response compared to some solid state output stage without adding extra distortion. Yes in some cases, the valve acts as a active filter, but it comes down to it's design whether or not it's working with the digital clock on the same circuit or it's running on the output stage of the dac. This is my basic understanding.

Well, that makes no sense.  There's nothing about a triode that would result in flatter response than any solid state output stages.  Especially output stages.  The direct output impedance of a triode of any practical size is far too high to drive a transducer without a transformer. Even as a cathode follower set up for fairly low impedance, that's a loss stage, not a gain stage, and the loss is huge if you want a low source Z.  

 

Here's more than you want to know:

http://www.tubecad.com/2011/08/blog0212.htm

 

A valve as an active filter is also pointless, unless an "active filter" is to mean a first-order filter with the valve acting as an output buffer.  

 

Valves make nice high impedance input buffers, if you need that kind of thing.

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