[manbear]

  Hey guys. I have a Aune T1 with a 6922 tube. I am pairing with AKG Q701 headphones. I want to pick up a really warm tube, I think that will pair well with the headphones and I prefer a warm sound over harsh or "crisp" treble. What kind of tube would you guys suggest, the socket is the 6 pin circle (the socket name escapes me). 

You only hear the tube when you connect the Aune's DAC out to a separate amp. If you are plugging the Q701 into the Aune, your DAC/ amp is entirely solid state and you aren't using the tube at all. So save your money and don't buy a tube. 

 

[IamLoki]

Where is your proof on that, this is marketed and designed as a tube usb DAC. Every output on the amp is run through the tube as stated in the manual and product specs. If you remove the tube the amp no longer works. You can even plug the tube back in when on and the sound will slowly come back as you see the tube warm up. That would be quite the smoke show to even program a sound delay when the tube is plugged in.

 

[manbear]

  Where is your proof on that, this is marketed and designed as a tube usb DAC. Every output on the amp is run through the tube as stated in the manual and product specs. If you remove the tube the amp no longer works. You can even plug the tube back in when on and the sound will slowly come back as you see the tube warm up. That would be quite the smoke show to even program a sound delay when the tube is plugged in.

Hmm, I thought I read that you only hear the tube on the RCA outs, but I must have misinterpreted. Silly me 

 
 In the Q&A section of the first post: http://www.head-fi.org/t/633006/aune-t1-usb-tube-dac-amp-discussion-thread-see-first-post-for-faq
 
"Q: Does the Aune T1 DAC utilize the tube, does the T1 headphone amp section use the tube, or do they both use the tube?
A: The Aune T1 is a USB tube DAC with a solid state headphone amp. What this means is that if you want the benefits of the tube, you must use the USB Input of the T1.  The amp section of the T1 does not use the tube by itself. Technically, you could bypass the DAC of the T1 and just use the amp but this type of use is not really what the T1 is for. One thing you can do is use the T1 USB input then hook up a different amp to the RCA out of the T1. This will give you the benefits of the tube and allow you to try a different/more powerful amp (though I think the amp in the T1 is quite good).  I personally have a speaker amp hooked up this way so I can use my headphones and some bookshelf speakers at the same time from one source."

 

[IamLoki]

No problem friend. I bought the Aune T1 solely because of the reason that is uses the tube with the DAC, I wanted to be able to tube roll and tailor my sound for my headphones. 
 
Honestly I am just not very happy with my Q701s. They have an awesome sound space but they just dont seem to deliver any respectable or realistic bottom end. I dont need thumbing bass but if my shure se215 IEM sound better then my headphones double the price I think there might be a problem. But these have been my affordable dream headphones for years so I am willing to give them all the chances to have them sound right. Right now I want a warmer sound. 

 

[manbear]

I owned the Q701 for a while. I used them with a Little Dot tube amp and experimented with tube rolling. About tube rolling -- it's fun to try and I recommend giving it a shot if the tubes are cheap. However, and this is just me, I lost faith in tube rolling after a certain experience -- I had some supposedly warm tubes and some supposedly bright tubes. I thought that I had the warm tubes in, and I was listening and focusing on how the mids seemed so rich and the highs seemed so smooth. But then I looked and I actually had the bright tubes in. After that, I no longer heard any difference in the tubes. But you should try for yourself. 

As far as bass goes, the only time I really appreciated the bass on the Q701 was when I was listening to songs that had major bass in the recording. The Q701 do a good job with really deep bass. The problem is that songs without that deep bass just didn't sound impressive. 

There are a few possible fixes I'd recommend. The easiest is to use EQ and increase the bass. Some people have an aversion to EQ because they think it's going to compromise sound quality. In my experience, it doesn't at all (unless you are going crazy with it and causing distortion). Just think of how much EQ the mastering engineers who made the recording used. Most music has already been through EQ before you even play it. 

A more complicated, but potentially more satisfying option is to do the bass port mod on the Q701. It is explained in the Q701 appreciation thread. Basically, it involves taking apart the outer cups and peeling off a little sticker that is covering a hole on the driver's internal housing. I have not tried it, since I was trying to sell my Q701 by the time I found out about it and didn't want to take them apart, but those who have say that it greatly improves the bass. Just be careful and take your time if you decide to do it. 

EDIT: Here is one thread about the mod: http://www.head-fi.org/t/660408/reversible-akg-k701-bass-mod
There is more in the Q701 appreciation thread.

 

[bbmiller]

Where are the benefits of tubes and tube rolling best effective?

Hello
I have been thinking of purchasing the aforementioned  Aune T1 but I am not sure because of a few reasons.
 
Our tubes and tube rolling most effectual in the DAC or the headphone amplifier? I fear I can only afford the expense of getting tubes for one of these and will have to go solid-state for the other. Aune T1 is already a vacuum tube DAC and a solid-state amplifier so it meets the bill of being an economical good low-cost purchase. But that where is the best place to have one tube you can afford question still confounds me 
 
 
Another thing that nags on me in regard to considering the Aune T1 is how suited it is to a do-it-yourself improvement project? On another thread I started I asked the question
 
 
Can a USB powered DAC, headphone amplifier, etc. filter out power supply noise from the USB line?    
 
One of the responders tomb gave an answer which might be pertinent to whether or not the  Aune T1 might be a good bet for me. I quote him below

 
The iFi device is a linear-regulated supply, but it's extremely expensive.  HiFimeDIY has a USB isolator that they claim has an improved power supply, but it is not powered externally, so performance can't be dependable.  There is an inexpensive DIY solution in the works, but I'd be accused of shilling if I spoke about it in detail.  There is information in the DIY section.  Another user on Head-Fi - mcandmar built his own device awhile back with proven results.  Other than these, I'm not aware of another truly audiophile solution.
 
Switching power supplies are often very noisy.  They claim to have "pushed" the noise well above the audible threshold, but there are many artifacts, phase distortions, etc., that cause harmonics into the audible band.  Let me emphasize, however, that "noise" in the power supply is rarely something that's heard.  Instead, it's a general lack of quality in sound: maybe a glare in the high-end, a general loss of dynamics, sloppy bass, etc.  It simply causes effects that result in sounding blah vs. GREAT.  Only extreme examples - not worthy of any consideration at all - result in noise that's directly audible in the sound signal.
 
Also, switching power supplies can sometimes be used with amplifiers (including headphone amplifiers) with good success.  However, every amplifier circuit has a calculated property known as PSRR - Power Supply Rejection Ratio.  It's a measure of how much noise in a power supply will affect the amplifier circuit itself.  Good circuits have very high PSRR's.  However, powering a source such as a DAC does not qualify.  Once noise is introduced, it'll propagate throughout the signal stream.

 
The iFi device is a linear-regulated supply, but it's extremely expensive.  HiFimeDIY has a USB isolator that they claim has an improved power supply, but it is not powered externally, so performance can't be dependable.  There is an inexpensive DIY solution in the works, but I'd be accused of shilling if I spoke about it in detail.  There is information in the DIY section.  Another user on Head-Fi - mcandmar built his own device awhile back with proven results.  Other than these, I'm not aware of another truly audiophile solution.
 
Switching power supplies are often very noisy.  They claim to have "pushed" the noise well above the audible threshold, but there are many artifacts, phase distortions, etc., that cause harmonics into the audible band.  Let me emphasize, however, that "noise" in the power supply is rarely something that's heard.  Instead, it's a general lack of quality in sound: maybe a glare in the high-end, a general loss of dynamics, sloppy bass, etc.  It simply causes effects that result in sounding blah vs. GREAT.  Only extreme examples - not worthy of any consideration at all - result in noise that's directly audible in the sound signal.
 
Also, switching power supplies can sometimes be used with amplifiers (including headphone amplifiers) with good success.  However, every amplifier circuit has a calculated property known as PSRR - Power Supply Rejection Ratio.  It's a measure of how much noise in a power supply will affect the amplifier circuit itself.  Good circuits have very high PSRR's.  However, powering a source such as a DAC does not qualify.  Once noise is introduced, it'll propagate throughout the signal stream.
 
 

Material that offended tomb in the response below has been removed.

 

[tomb]

1. That post is very confusing the way you quoted me.  I didn't post that pic, the blue line above it, or anything below it - yet, it's contained in the field that supposedly defines my quote.
 
2. Tubes in a DAC are a pipe dream.  If one is in there, it's only "flavoring" the solid-state I2S output or the solid-state buffer.  It's not really functioning in the DAC process.
 
3. It's probably best to start small with an inexpensive DIY DAC and work up.  DIY-ing a commercial DAC by modifying it in some way is a small-return/high-risk scenario.  I wouldn't do it.  Either you like the DAC you bought or you should sell it and buy a different one.
 
JMHO.

 

[bbmiller]

OK
How my a edit the above post so it becomes on the offensive to you? I haven't bought that DAC I gather is not real and just flavors the output. So what might be recommended as possibly the lowest cost real tube rolling unit or where in these forms my I go to research that?

 

[tomb]

Thanks!
 
I'm curious, though, why is this in the "Sound Science" forum?  Seems like the amplifier section would be the appropriate place and would not attract the trolls.

 

 

[Claritas]

Reading very old threads on this topic, I came across this short comparison: http://spectrum.ieee.org/consumer-electronics/audiovideo/the-cool-sound-of-tubes/distortion.
 
Summary:
 
- Transistors operating on low-voltage supplies tend to have higher spectral distortion components than tubes.
 
- If we go to high-voltage transistors, operating on supplies comparable to those of the tubes, the distortion products are less objectionable. Unfortunately, the noise floor of such devices is much higher.
 
- No other active device possesses both the low distortion products and the low noise floor of the medium-mu triode.
 
- The distortion products of transformers are much lower than those of active devices, yet quite different in character.
 
What do you think?

 

[elmoe]

  Reading very old threads on this topic, I came across this short comparison: http://spectrum.ieee.org/consumer-electronics/audiovideo/the-cool-sound-of-tubes/distortion.
 
Summary:
 
- Transistors operating on low-voltage supplies tend to have higher spectral distortion components than tubes.
 
- If we go to high-voltage transistors, operating on supplies comparable to those of the tubes, the distortion products are less objectionable. Unfortunately, the noise floor of such devices is much higher.
 
- No other active device possesses both the low distortion products and the low noise floor of the medium-mu triode.
 
- The distortion products of transformers are much lower than those of active devices, yet quite different in character.
 
What do you think?

 
Interesting that noone's answered any of this yet.

 

[Eternal Schism]

Thanks!

I'm curious, though, why is this in the "Sound Science" forum?  Seems like the amplifier section would be the appropriate place and would not attract the trolls.  

By trolls you must mean people who have taken the time to become educated enough not to be deluded with placebo and heresay by people who would be unable back up their claims in a scientific controlled test. Yep we are definitely the trolls here!

 

[proton007]

   
Interesting that noone's answered any of this yet.

 
Read the comments on the same page where this article was posted. There's quite some information in the replies.
 
The gist of the problem as I notice is that transistor based amps allow for designs that aren't just possible with tubes (Tubes inherently allow for a class A/AB amp design).
Now, these 'other' transistor based designs may perform worse than tubes, but they're a lot cheaper and smaller and less power hungry, and if that's your design objective then it works for you.
 
Another factor listed is that op-amps have improved over the years, while tubes have stayed where they are. Moreover, nothing's stopping anyone from creating a good design using transistors. You can find a class A/AB solid state amp, and chances are it'll have better specs than tube amps.
 
Lastly the article is from 1998, 16 years old. I'd say that electronics have been continuously been improved, and chances are most of the initial problems of op-amps have been contained.

 

[elmoe]

   
Read the comments on the same page where this article was posted. There's quite some information in the replies.
 
The gist of the problem as I notice is that transistor based amps allow for designs that aren't just possible with tubes (Tubes inherently allow for a class A/AB amp design).
Now, these 'other' transistor based designs may perform worse than tubes, but they're a lot cheaper and smaller and less power hungry, and if that's your design objective then it works for you.
 
Another factor listed is that op-amps have improved over the years, while tubes have stayed where they are. Moreover, nothing's stopping anyone from creating a good design using transistors. You can find a class A/AB solid state amp, and chances are it'll have better specs than tube amps.
 
Lastly the article is from 1998, 16 years old. I'd say that electronics have been continuously been improved, and chances are most of the initial problems of op-amps have been contained.

 
So basically, the only argument against tubes is a cheaper design (which isn't necessarily true nowadays in this hobby, when you want a good design). I'm a skeptic by nature but some of these comments are suggesting that double blind testing shows listeners can't tell solid state and tubes apart. That's a bit of a stretch to say the least.

 

[proton007]

So basically, the only argument against tubes is a cheaper design (which isn't necessarily true nowadays in this hobby, when you want a good design). I'm a skeptic by nature but some of these comments are suggesting that double blind testing shows listeners can't tell solid state and tubes apart. That's a bit of a stretch to say the least.

You'll be surprised by the variety of applications amplifiers have.
Audio is just a portion of that whole pie. A number of devices wouldn't even exist without solid state amps; the cost, reliability and form factor of solid state makes that possible.

I'm skeptical with regards to the blind testing statement as well, but it's due to the fact that a good tube amp will very likely have lower specs than a good solid state amp, and at best can match them.

Another theme I could notice in that discussion was guitar amps. Maybe there are some aspects of tubes that suit a guitar amp, but then it becomes application dependent.

I mean, if one *wants* to hear that vintage sound, there's no harm in using a tube amp, but then it's just a preference issue, not a technical one.