DAC + tube amp showdown!

[PaulyT]

Yep it's the upgraded version. Strange that optical input is all I use and it's never given me any grief. Nonetheless I will check it when you send it back and if something is amiss Schiit will repair it for free.

Okay, that's good to know, thanks. So my DA8 still beats the Uber Bifrost... :teasing-neener:

What I would LOVE to evaluate is the Benchmark DAC2, but that's ~twice the price of the already high $$ I paid for my DA8, so that's probably not gonna happen anytime soon, or ever. But Waldrep (Dr. AIX) goes on and on and on about how awesome that DAC is, it'd be interesting to compare. On paper, the specs of my DA8 are actually quite similar to the Benchmark DAC2.

 

[PaulyT]

Another thing you can try would be a different tube in the crack. If you have a TS 5998 it makes a huge difference.

Ha! Actually, I do, as a matter of fact. It was one of the tubes I rolled with my Jade. So that's a drop-in replacement for the one you sent with the Crack?

What about a 6AS7G? I have a Chatham 6AS7G in my Jade, which ultimately I preferred over the Tung-Sol 5998. I wonder if that would work as well?

What's the small tube in the Bottlehead? I may have replacements for that as well...

Huh, from some online reading it seems the crack takes pretty much exactly the same tubes as the Jade. Interesting. So I may try my TS 5998 and Chatham 6AS7G, along with my various 5751 tubes which are in the same family as the 12AU7.

 

[malsackj]

When looking at the tube data sheets between a 6AS7G for use as a regulator tube in DC power supply units

Amplification factor is 2

the 5998 is Amplifiction factor is 6

The 5998 is intended for use as a series tube in regulated rectifier circuits.


The 5771 is a tube designed for rough service. sturdy vibration-resistant tube. amplification factor is 70

 

[malsackj]

12au7 has amplification factor of 20.

 

[PaulyT]

Ok, time for some rolling!

First I tried the Bottlehead with my Chatham 6AS7G, and my Raytheon 5751 (which is the combo I preferred on my Jade). No go, lots of distortion. Same thing with a Sylvania 5751, so I don't think it's just my tube.

However, the combo of Walls's 12AU7 (GE? Not sure what brand it is as the label is mostly worn off...) with my 6AS7G was really quite nice! Huge improvement over Walls's 6080. No perceptible hum even with volume all the way up. Still not quite up to the level of the WA6 in terms of "three-dimensionality" (my term for breadth and especially depth of the soundstage), but it's now in the same ballpark. And considering it's ~half the price, nice little amp. The WA6 has a very slightly warmer tone, to my ears, which I like better. I've found that that can sometimes be adjusted a bit with different tubes (I know Flint's cringing now ) but I don't have other 12AU7 tubes to try.

However, with all combinations of tubes, I still have the issue of hum with low settings on the crack's volume knob. As I was changing tubes, I checked the wiring very carefully for anything loose or suspicious, but everything looked fine visually.

 

[PaulyT]

So I dusted off (literally, it'd been on a bottom shelf for years) my Audiotailor Jade, and plugged in the Chatham 6AS7G and Raytheon 5751 (the famous "windmill getter" model). I need to go back to the Bottlehead again, and will in a bit, but I think I have to give the nod to the Bottlehead on this one. Just slightly better imaging and resolution. The Jade does have a somewhat warmer tone, somewhere between the Bottlehead and the WA6, which I generally prefer for extended listening.

I think I paid $200 for the Jade, so it's on par with the Bottlehead; definitely spent more on tubes than the amp in this case. :?

 

[PaulyT]

Just for kicks, I tried Walls's 12AU7 with the Jade (along with the 6AS7G). That is, the exact same tubes I liked with the Bottlehead. And... definite improvement, now the Jade is pretty much on par with the Bottlehead. In fact I'd be hard-pressed to express a preference between the two. I think maybe overall I like the slightly more "tubey" warmth of the Jade, while there are a few tracks I preferred on the Bottlehead. Tiny differences, I won't swear by them.

It's interesting that the Jade works fine with the 5751 while the Bottlehead clearly does not (with my headphones). So while they're apparently similar amps, both OTL, and can use the same tubes, there's obviously some design difference. But I don't know nearly enough about tube amp circuitry to guess why that is.

When I was using the 5751 in the Jade, it was primarily with my Denons; it seems that with the T1, the lower gain of the 12AU7 is more appropriate. I will use this opportunity to once again point out the huge swing in impedance between different models of headphones (20 - 600 ohm), vs speakers (basically 4 - 8 ohm). This makes matching of an amp with headphones not as straightforward as amps with speakers, in my experience. Though I suppose both speakers and amps can vary a lot in sensitivity, as well, yet another factor.

 

[malsackj]

http://tdsl.duncanamps.com/show.php?des=5751

So you can substitute CK5751, CV4017, CV8312

or with changes in output.

12AX7, 12AX7A, 12AX7R, 12AX7S, 12AX7WA, 5751WA, 6057, 6681, 6L13, 7025, 7382, 7494, 7729, B339, CV10319, CV4004, CV492, CV8156, CV8222, E2164, E83CC, ECC803, ECC803S, ECC83, ECC863, M8137, QB339

all of these tubes will work in the soccet for the 5751, A guitar player can also do the same for his 12ax7 in his amp.

 

[PaulyT]

Thanks. Yeah the Jade originally came with a (cheapo) 12AX7, I believe. With my headphones at the time, I found I liked the 5751 better. Right, the 12AU7 is dramatically lower gain, but interestingly still works well in the Jade. The Bottlehead Crack is designed for the 12AU7.

 

[PaulyT]

Walls, I'll be getting ready to ship your stuff back to you soon. But you might get more than you bargained for.

If you're interested, I can also send you the Jade to try out.

 

[walls]

LOL!!!

I would love to play with the Jade, send the Bifrost but keep the Crack because I am going to mail off the HD650's. I really want to hear your impression of them vs the T1 with the crack.

I have a couple things to comment on but will have to later as I am pressed for time right now.

 

[PaulyT]

'k, cool. I've never actually spent time with the 650, looking forward to it. I'll get the jade and the bifrost in the mail before too long...

 

[walls]

Sending out the 640's tomorrow. They come in a case like the t1's so not sure what the shipping will cost but I don't want to cram them in a pre paid box. Lol

 

[walls]

*650's

 

[malsackj]

According to my guide from tung sol you can change the 5998 with 6as7g.

The tubes sound is based on the make up of the plates, heaters, and grids. They will change based on the chemical treatments ,

capacitance of the various parts and the spacing of the parts. These are variable with some being slightly off 5 to 10 percent ?
This is why most tubes sound close but are up to differences because the manufacture is not .0001 accurate.

If there is hum in the system it would be from possibly the heater for the tube is AC or not filtered enough to keep out the hum.

The phones actually are RFI and hit most audio devices if close enough. even the balanced mic lines on PA.

My substitute guide says 5998 5692 6as7g 6as7ga 65L7gt 6042 22 total items .