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Old 21st September 2018, 03:14 PM   #171
ichiban is offline ichiban  United States
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Introducing Mercury - Achieving escape velocity.
I believe when the Mercury was released, Brian or Russ indicated the schematic would be released. Is that still true or considered too proprietary?
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Old 21st September 2018, 03:38 PM   #172
Russ White is offline Russ White  United States
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hmm - no - I wouldn't have indicated that. I may decide to release it at some point - but it is not intended to be public at the moment.
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Old 21st September 2018, 03:59 PM   #173
Russ White is offline Russ White  United States
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I will be very open about it's method of operation however - and I don't mind answering specific questions. I just don't plan on releasing the whole schematic right now. Possibly in the future.
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Old 21st September 2018, 04:17 PM   #174
metalman is offline metalman  Canada
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Quote:
Originally Posted by Russ White View Post
I believe it would work fine - but I must warn that I have not tested it.

I have used IVY for COD and it works really well!

My one concern with using Mercury for COD is I am not sure how that DAc chip would do with the self leveling input bias. It may be that that chip needs the input to sit at or close to GND - not to center at the DAC outputs... I have not tested that scenario and I am not setup to test it at the moment - so if you want to try it it would have to be at your own risk. That said - I am inclined to think it would work fine. I would use something like 390R to start - increasing that value if the output is not high enough for you.


Cheers!
Russ
Iíve played around with different I/V stages for the Burr Brown 179X series DAC chips, and while the Mercury should work, this DAC chip family is designed to output into a low impedance virtual ground. As the I/V stage input moves away from gound the sound quality begins to degrade. I found that as a general rule of thumb the I/V input needs to stay within 50mV of ground with an input impedance off less than 10 ohms to get best performance.

Terry
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Old 21st September 2018, 10:00 PM   #175
Russ White is offline Russ White  United States
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Hi Terry!

Nice to see you around!

Yeah input impedance will be very near zero up to the Mhz region on the Merc

I suspect we might get a bit better results with a fully symmetrical front end like that of the mercury?

The input will basically just float to the mid point of the current bias of the DAC.

I would not try it with a conventional I/V stage (dual trans-impedance stages) - but I suspect the super symmetrical nature of this circuit might fare better.

In any case - I can't say - I have not tried it. It would be fun to give it a go and measure it. BTW it would be pretty trivial to reference the Merc's common mode input to GND for testing purposes.

Cheers!
Russ
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Old 22nd September 2018, 01:51 AM   #176
metalman is offline metalman  Canada
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Quote:
Originally Posted by Russ White View Post
Hi Terry!

Nice to see you around!

Yeah input impedance will be very near zero up to the Mhz region on the Merc

...

The input will basically just float to the mid point of the current bias of the DAC
Russ, itís been awhile, but Iíve been ghosting around, and recently starting to play back in DIY again. Nice to see Iím still remembered.

Floating at the bias midpoint could work here. I see what you mean now.

I hope to make a venture into Buffalo / Mercury territory in the future, but right now I donít have the time or cash flow to make that a reality. Big props for what you have accomplished with Twisted Pear! Youíve gone waaaay beyond the humble beginnings of the designs I had a finger in. Well done indeed!

Terry
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Old 29th September 2018, 03:20 AM   #177
itsikhefez is offline itsikhefez  United States
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Introducing Mercury - Achieving escape velocity.
Curious if anyone here has tried the Mercury as a headphone amp directly? Specifically I'm interested in some of the Sennheisser's, such as HD650, HD700 or HD800s?
What are your thoughts?
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Old 29th September 2018, 06:11 AM   #178
itsikhefez is offline itsikhefez  United States
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Introducing Mercury - Achieving escape velocity.
Quote:
Originally Posted by itsikhefez View Post
Curious if anyone here has tried the Mercury as a headphone amp directly? Specifically I'm interested in some of the Sennheisser's, such as HD650, HD700 or HD800s?
What are your thoughts?
A few questions before I try this myself:
1) What is the correct wiring for a 4 pin XLR socket from the balanced outputs?
2) Can I connect both 4 pin XLR for headphone and dual XLR's for active monitors?
3) I have already installed the resistors for 4V output... do I need to change this?

I plan on driving the above mentioned headphones.

Thanks for the help!
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Old 8th October 2018, 07:34 PM   #179
stephen1212b is offline stephen1212b  United States
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Love the Mercury but just a heads up one of the LME49600 was not flush to the board and two pins needed to be soldered to make proper connection. This has only been the case once out of several boards but I though to mention it in case someone else has a dead channel when first assembling.
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