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Balanced to unbalanced board


sbelyo

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30 minutes ago, mypasswordis said:

2ff58d7b41.png

A little breakout board for the AD5254 digital potentiometer... so I can dynamically bias the Dynalo through my phone (through a uC). 256 step resolution but lowest full wiper resistance seems to be 1k so 3.9 ohm per step. 

Very nice! i have been looking for something like this.

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if you are going thru all that effort (and its a good idea) might as well add some hall effect devices on the power rails to monitor the bias current.

something I did in the uberamp quite a while ago and that made the bias super stable, set it to what you want and it works. then if you want to get super silly, add dynamic bias

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  • 1 month later...

Very slowly coming along... just noting the size difference.

What is everyone using for the right angle headers? I bought some 4 pin headers for the main 4 pins but ground pin is off to the side, maybe just airwire that one? Also are you socketing the headers or directly soldering? If socketing what are you using?

20170708_013406.jpg

Edited by mypasswordis
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So I did end up using a female header socket and air wiring the ground. The part number for the 4 pin right angle header is 68016-404hlf. The leds I used are extremely bright orange-red, glad once i case it up it will be harder to see. I am measuring about 3.95ma after a few minutes warm up but the thing lights up like a Christmas tree. Will do further testing hopefully over the weekend 

20170712_174555.jpg

20170712_211501.jpg

Edit: the diamond buffer boards are getting really toasty

Edited by mypasswordis
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I have a discrete opamp that is unity gain stable that sounds quite nice. Once you get this up and running and familiar with the sound, I would appreciate a comparison. Will send samples for positive review only though. K thx bye.

 

Actually, it would be a PITA - mine are dual opamps on a single board. So, would probably need a new board.

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Got some old RPi heatsinks I can stick on if need be. Gotta check with temperature probe 

19 hours ago, luvdunhill said:

I have a discrete opamp that is unity gain stable that sounds quite nice. Once you get this up and running and familiar with the sound, I would appreciate a comparison. Will send samples for positive review only though. K thx bye.

 

Actually, it would be a PITA - mine are dual opamps on a single board. So, would probably need a new board.

Okay let me know whenever!

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Put a heatsink on the back of the buffers

 Could you be persuaded to modify the board? Basically would need a SIP-10 pinout for the dual opamp and usual external resistors.

 

Pinout would be:

 

1 - signal ground

2 - OUT_A

3 - -IN_A

4 - +IN_A

5 - -23V

6 - +IN_B

7 - -IN_B

8 - OUT_B

9 - +23V

10 - psu ground

 

Drop-in replacement for something like NJM4558E, pin 1 and pin 10 are omitted (one of the advantages to a discrete opamp is handling ground properly/differently/carefully)

 

http://akizukidenshi.com/download/NJM4558.pdf

 

Also, would need to note changes to the external circuit for slightly higher rails.

 

 

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So I did end up using a female header socket and air wiring the ground. The part number for the 4 pin right angle header is 68016-404hlf. The leds I used are extremely bright orange-red, glad once i case it up it will be harder to see. I am measuring about 3.95ma after a few minutes warm up but the thing lights up like a Christmas tree. Will do further testing hopefully over
Edit: the diamond buffer boards are getting really toasty

A few questions:
1) The air wires I presume are grounds? Ground(s) aren't accommodated in the connector pin pattern? (I didn't look at my boards obviously)
2) How did you attach the heat sinks?

Thanks!


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You'll know once you look at the boards, there is a gap between ground and the other 4 pins. If it's just a standard 2.54mm gap then potentially you could use a 6 pin header (if you cut the end off the gap header), though the socket end would still need to be 4 and 1, and the unused gap header would just be dangling. 

The RPi heatsinks already have some 3M adhesive squares so just stick them on. :) I wasn't sure if they were electrically insulating so just to be safe, I avoided the vias on the bottom of the boards. 

Edited by mypasswordis
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