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Old 7th February 2018, 02:17 PM   #21
audiowize is offline audiowize  United States
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Quote:
Originally Posted by soulmerchant View Post
Output Impedance :
Tube 22K
Solid State 10K
I'm not sure which of those numbers is less impressive!
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Old 7th February 2018, 03:05 PM   #22
Flaxxer is offline Flaxxer  United States
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Quote:
Originally Posted by Lingwendil View Post
What did you modify in it to "fix" the issues?
I have a list somewhere of everything I did to it. I will find that, and post back here. I cab tell you if you never heard the DAC with the Silverplate from Siemens, it made a HUGE difference. I mean HUGE. I tried rolling other tubes, like CV, Mullard, etc, etc ... But the DAC remained closed in and dark. The Silverplate with mods made it come alive. Ryan, from Vapor Aadio heard it, and thought it was as good as he had heard at the time for under several thousand.

One last thing ... A lot of people on this thread are commenting on the tube I asked about, with opinions on it, and you are not saying you have ever heard the tube in question. Posting specs means nothing. Absolutely nothing.
Listen to it, and then you will know why it is considered special. Knocking something just because you are not agreeing with the current going rates on something, does not change that items value or performance. Especially when you were not the buyer or seller.

Grab one and listen. Best of tube richness, without any freq roll off. Very open and dynamic. It was very worth it in the EE Minimax for sure.
Have a great day everyone!
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Old 7th February 2018, 03:08 PM   #23
audiowize is offline audiowize  United States
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Specs do matter. A tube stage with 22K output impedance isn't suitable for driving much more than 6" of cable, and certainly not up to the job of driving the volume pot of a preamp (you pretty much have to pray that it's a 100K-500K pot, not a 50K or below).

So opinions of a tube's performance in a poorly designed piece of gear isn't going to mean a whole lot.
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Old 7th February 2018, 03:09 PM   #24
Flaxxer is offline Flaxxer  United States
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And one more thing ... I made a post on the DAC sub forum, and asked for advice on more recent DACs which have bettered the EE DAC, without spending any more than the $750 I paid for the EE DAC.

I could NOT have garnered a reply to that thread, if I had have said I was a naked supermodel in a hot tub full of warm oil, ready to video chat about DACs!!!!!!

So please ... instead of talking down the DAC, offer newer suggestions which are now considered better. I need a new DAC soon.
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Old 7th February 2018, 03:10 PM   #25
Flaxxer is offline Flaxxer  United States
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Quote:
Originally Posted by audiowize View Post
Specs do matter. A tube stage with 22K output impedance isn't suitable for driving much more than 6" of cable, and certainly not up to the job of driving the volume pot of a preamp (you pretty much have to pray that it's a 100K-500K pot, not a 50K or below).

So opinions of a tube's performance in a poorly designed piece of gear isn't going to mean a whole lot.
What did the DAC sound like when you listened to it ?
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Old 7th February 2018, 03:17 PM   #26
audiowize is offline audiowize  United States
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I searched your username and didn't find the thread you mentioned...

When we see 20K of output impedance, it's very easy to determine that the tube output was grafted on without any consideration. The designer could have just added a tubed cathode follower instead of a voltage gain stage and the output impedance would've dropped to a useful level (well below the solid state output even!).

I did get to compare the Minimax and the old Cal Audio Sigma from the 90s late last year in my system. There wasn't any comparison, and now knowing that the output impedance of the MM is 20K and my preamp attenuator is 25K, I can understand why the top end sounded a bit rolled off (wasn't the only problem though).

There's a Cal Audio Alpha on eBay for $500, it's a bit better than the Sigma, and that's well under $750. (It looks like there are two Gammas on there too, I haven't listened to one of those)
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Old 7th February 2018, 03:27 PM   #27
w5jag is offline w5jag  United States
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Quote:
... What I do know, is this tube must be hard to get. Because I was just contacted, and sold my tube with dampening device for $150. ...
Dang.

I pulled one of those out of an Eico VTVM that I robbed the power transformer from; had not seen plates like that before. It was unmarked, so I just assumed it was another Mullard.

I tested it in a modified Tubelab SSE and found that it was an average performer from a THD / IMD standpoint; certainly nothing special. Just another 12AU7.

But, who am I to argue with audiophiles. If it is a $150 tube, I could certainly use the pocket money for other projects. I have a tub full of 12AU7's, maybe there are more of them in there ....

Win W5JAG
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Old 7th February 2018, 04:03 PM   #28
Lingwendil is offline Lingwendil  United States
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Value of this tube ?
Quote:
Originally Posted by Flaxxer View Post
I have a list somewhere of everything I did to it. I will find that, and post back here. I cab tell you if you never heard the DAC with the Silverplate from Siemens, it made a HUGE difference. I mean HUGE. I tried rolling other tubes, like CV, Mullard, etc, etc ... But the DAC remained closed in and dark. The Silverplate with mods made it come alive. Ryan, from Vapor Aadio heard it, and thought it was as good as he had heard at the time for under several thousand.

One last thing ... A lot of people on this thread are commenting on the tube I asked about, with opinions on it, and you are not saying you have ever heard the tube in question. Posting specs means nothing. Absolutely nothing.
Listen to it, and then you will know why it is considered special. Knocking something just because you are not agreeing with the current going rates on something, does not change that items value or performance. Especially when you were not the buyer or seller.

Grab one and listen. Best of tube richness, without any freq roll off. Very open and dynamic. It was very worth it in the EE Minimax for sure.
Have a great day everyone!
A buddy at work has a MiniMax DAC, I don't think it sounds all that nice for the price honestly. It almost sounds compressed to me, no matter what tubes he rolls, or amplifier he uses. I'm curious as to why, that's all. I've given a few tubes from my stash for him to play with in it.

Oh, believe me. I've heard the tube in question

I'm not looking to buy or sell anything either.

I have I think five left, along with a bunch of fancy clear top (which given a choice, I prefer) varieties. That having been said, I've always preferred any 6CG7 or 6SN7 type to even the fanciest 12AU7 types. I only use the 12AU7 for guitar applications these days, as they don't usually measure or sound as well to me in circuits without high degeneration. I used to use a bunch back in my headphone amp days, but once I found the better results from the other options I wasn't very into them anymore.

I think a worthwhile modification would be rewiring the DAC for a 6 volt heater and running the 6CG7, as it's a nice little-bottle 6SN7. This also opens the possibilities of many of the better 6 volt heater tubes, which would be a very nice way to go. There are a few fantastic similar spec Russian tubes that would work well too.

Quote:
Originally Posted by Flaxxer View Post
So please ... instead of talking down the DAC, offer newer suggestions which are now considered better. I need a new DAC soon.
I personally meant no offense, although it sure seems that way, and I apologize.

You looking to build or buy?

I'm getting ready to do a dual mono PCM1794 build, with tube based differential IV stage based on the Russian subminiature 6N16B tubes, although it could just as easily use the 6SN7, 6N1P, or 12AU7 types of tubes. I used to play around a ton with the PCM1794, and really, really like them. The Twisted Pear COD boards are affordable and versatile for building them up. Just add a USB/SPDIF to I2S type of input and go. Reasonably user friendly builds.
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Last edited by Lingwendil; 7th February 2018 at 04:10 PM.
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Old 7th February 2018, 04:32 PM   #29
Flaxxer is offline Flaxxer  United States
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To begin, here is my original DAC thread, where I wanted advice:

ES9018 DAC advice

As far as the 22k output ... All I know, is it was used three different preamps. As a preamp itself with at least 7 or more amplifiers. And I bypassed the volume control completely, when I rewired the DAC with Mundorf wire. I used this straight from the USB on my computer. And EVERY way I used it, there was more than enough gain and headroom. It was never any issue with any system. So, I dunno.

Next, I am not offended one bit. I was just surprised at how the thread went. I originally posted, to try and QUICKLY see what the tube was worth now. I only remembered it was supposedly special. After the first response, I figured I had better just look into it again. Then I did a computer search, and found a saved email in a folder. So next, I thought I would be nice, and post up what I THOUGHT was great info about a rare special tube. No biggie to me, as it makes no difference, since the tube had already sold. I was just surprised at the seemingly downward direction some seem to want to take it.

Maybe again, it was the combination of all of the mods I did, instead of more the tube, which brought about such change in the DAC.

Lasty, I'm about to go to work. But someone once told me that DACs have gained huge advances since my DAC came out. He said modern DACs that cost $200 can best it now. So I was looking for info about what is the new great things in DACs now.

I love posting here, and wish EVERYONE a great day, or night !
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Old 7th February 2018, 04:39 PM   #30
audiowize is offline audiowize  United States
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Yeah, you're running up against a wall of opposition that is in response to the following progression of events that play out here and often times elsewhere on other forums:

1. Someone buys something inexpensive and poorly engineered from China.
2. They listen to it, and it's not great.
3. They change the:
A. Capacitors
B. Tubes
C. Potentiometer
D. Wire
E. Jacks/hardware
4. The piece of equipment with fatal engineering flaws is now magically perfect (proud papa syndrome).
5. Those aware of the underlying sources of the original flaws (usually an issue with poor circuit design, poor build quality, or poor transformer design) are annoyed.


You are correct that there are some excellent inexpensive DACs available, but I wouldn't bother buying a kit (you'll need an ESD safe working surface for starters). I'd recommend starting with a Firefly or something from SMSL.

(the output impedance issue on your tube DAC could be remedied by adding feedback to the existing circuit or using the 12AU7 as a cathode follower fed from the solid state output).

Last edited by audiowize; 7th February 2018 at 04:41 PM.
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