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Old 7th February 2018, 06:22 PM   #31
Lingwendil is offline Lingwendil  United States
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Value of this tube ?
Quote:
Originally Posted by audiowize View Post
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.
Nothing wrong with buying something affordable and fooling with it until you like it, but I agree much of the improvement that one perceives can definitely be attributed to the Proud Papa syndrome. Other aspects are easy to measure and compare.


Quote:
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).
There are some really nice DAC modules for some attractive prices lately. I've seen some complete dual mono modules with the PCM1794 as cheap as $40 shipped lately, and they use some decent components too. Some opamp replacement and power supply work would be all it takes to get a really nice rig for not much fuss. Good way to go for the guy that isn't necessarily interested in doing a completely scratch built design, and likes to tinker. Just pick out your USB/SPDIF to I2S of choice (I'm liking the looks of the ministreamer lately) and put it all in a nice box. Everything after that is just lashing up wire to the periphery.
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Old 8th February 2018, 12:26 AM   #32
FullRangeMan is offline FullRangeMan  Brazil
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Gentlemen await my new video on YT: How to Spot a Rare GM70 Tube.
They should cost at least $500 each graphite, copper $900 each$$$
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Old 8th February 2018, 09:43 PM   #33
Wavebourn is offline Wavebourn  United States
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Value of this tube ?
Quote:
Originally Posted by soulmerchant View Post
Whenever I hear "rich midrange" or "very extended lows and highs" etc. I immediately think one thing - the curcuit must be rubbish.
Is not it obvious?

Quote:
This "Minimax DAC" is easy to find using a search engine:

MiniMax DAC

Looking at their quoted specs, check the output impedance values:

Output Impedance :
Tube 22K
Solid State 10K

So now I think to myself.... wow, how did they ever manage to get Solid State ouput impedance THAT high?

Maybe I should consider a career in marketing?
You already have failed your Marketing interview.
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