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Balanced to unbalanced board


sbelyo
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  • 2 weeks later...

Thanks Kevin and spritzer for your help. If any group buy for the FET version happens, I will definitely take part in. Otherwise I will also be happy to order PCB to use for myself if Kevin permits.

I have one more question, what is your favorite PSU for buffer stage? I have a Walt Jung PSU with AD586 / AD797, is it good enough?

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  • 4 weeks later...

I took a stab at Mouser BOMs for the diamond_buffer and unbal_2_bal SMD boards.  Can someone kindly enough to check and correct the BOMs?  Many thanks!

**** Edit ****
The below lists hadd these changes (thanks to mypasswordis!):
LED from 2V to 1.9V
300-Ohm LED resistors from 250-Ohm
0.1uf C2/C3/C7/C8 caps to 0603 package
10uF C1/C4 to X7R
Other note: OP27G U1/U2 can be changed to other op-amp
**************

Unbal_2_bal SMD
Mouser #                            Description                                                                                                  Order Qty.

757-2SC3324BLTE85LF   Bipolar Transistors - BJT Audio Freq Low Audio Freq Low                      7
757-2SA1312BLTE85LF    Bipolar Transistors - BJT PNP Trans -0.1A LN -120V VCEO                     7
284-APC1206B1K00N       Thin Film Resistors - SMD 1KOhm 0.1% 1206 25 PPM                             4
667-ERA-8AEB103V           Thin Film Resistors - SMD 1206 10Kohm 0.1% 25ppm                             12
667-ERA-8AEB132V           Thin Film Resistors - SMD 1206 1.3Kohm 0.1% 25ppm                            2
647-UWX1E101MCL1        Aluminum Electrolytic Capacitors - SMD 25volts 100uF 8x5.4 20%        2
584-OP27GSZ-R                  Precision Amplifiers LOW-NOISE PREC IC 2.8V/uS                                    2
581-06033C104K4T4A      Multilayer Ceramic Capacitors MLCC - SMD/SMT 25V .1uF X7R             4
710-885012209028            Multilayer Ceramic Capacitors MLCC - SMD/SMT                                      2
710-150120SS75000         Standard LEDs - SMD WL-SMCW SMDMono TpVw Waterclr 1206           4
603-RT1206BRD07300RL Thin Film Resistors - SMD 1/4W 300 ohm .1% 25ppm                                6

Diamond_buffer SMD

Mouser #                             Description                                                                                                    Order Qty.
649-68016-404HLF            Headers & Wire Housings 4POS R/A HDR SnPb                                           1
279-CPF1206B10RE1        Thin Film Resistors - SMD CPF 1206 10R 0.1% 25PPM 1K RL                   4
279-CPF1206B24R9E1      Thin Film Resistors - SMD CPF 1206 24R9 0.1% 25PPM 1K RL                 2
756-PCF1206R-20KBT1     Thin Film Resistors - SMD .125W 20K ohm 0.1% 25ppm                            1

757-2SC3324BLTE85LF     Bipolar Transistors - BJT Audio Freq Low Audio Freq Low                        4
757-2SA1312BLTE85LF      Bipolar Transistors - BJT PNP Trans -0.1A LN -120V VCEO                       4
710-150120SS75000          Standard LEDs - SMD WL-SMCW SMDMono TpVw Waterclr 1206            2
603-RT1206BRD07300RL   Thin Film Resistors - SMD 1/4W 300 ohm .1% 25ppm                                6

Edited by Skooby
parts updates
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Opamp caps are 0603 package and use 300 ohm resistors for 2V LEDs (actual in circuit voltage will be more like 1.9). You need to at least somewhat match the LEDs before soldering them in so buy some extras

Edit: Y5V caps aren't good, if you are bothering with .1% resistors then get X8R/NP0 or at least X7R

Edited by mypasswordis
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^ yup, and the resistors for the current sources still should be changed to 300 ohms from 250 given the 2V LEDs which run at ~1.9 in circuit. Everywhere in the circuit you see a current source like this, replace with 300 ohms:

4e7ebb0fc2.png

Really it's more for the diamond buffer boards than anything else as IIRC I measured about 52 C on the PCB (also using 2V LEDs and 300 ohm resistors) and this was after I added heatsinks

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  • 3 weeks later...
  • 1 month later...
On 8/31/2017 at 9:01 PM, Skooby said:

I took a stab at Mouser BOMs for the diamond_buffer and unbal_2_bal SMD boards.  Can someone kindly enough to check and correct the BOMs?  Many thanks!

**** Edit ****
The below lists hadd these changes (thanks to mypasswordis!):
LED from 2V to 1.9V
300-Ohm LED resistors from 250-Ohm
0.1uf C2/C3/C7/C8 caps to 0603 package
10uF C1/C4 to X7R
Other note: OP27G U1/U2 can be changed to other op-amp
**************

Unbal_2_bal SMD
Mouser #                            Description                                                                                                  Order Qty.
757-2SC3324GRTE85LF   Bipolar Transistors - BJT Audio Freq Low Audio Freq Low                      7
757-2SA1312BLTE85LF    Bipolar Transistors - BJT PNP Trans -0.1A LN -120V VCEO                     7
284-APC1206B1K00N       Thin Film Resistors - SMD 1KOhm 0.1% 1206 25 PPM                             4
667-ERA-8AEB103V           Thin Film Resistors - SMD 1206 10Kohm 0.1% 25ppm                             12
667-ERA-8AEB132V           Thin Film Resistors - SMD 1206 1.3Kohm 0.1% 25ppm                            2
647-UWX1E101MCL1        Aluminum Electrolytic Capacitors - SMD 25volts 100uF 8x5.4 20%        2
584-OP27GSZ-R                  Precision Amplifiers LOW-NOISE PREC IC 2.8V/uS                                    2
581-06033C104K4T4A      Multilayer Ceramic Capacitors MLCC - SMD/SMT 25V .1uF X7R             4
710-885012209028            Multilayer Ceramic Capacitors MLCC - SMD/SMT                                      2
710-150120SS75000         Standard LEDs - SMD WL-SMCW SMDMono TpVw Waterclr 1206           4
603-RT1206BRD07300RL Thin Film Resistors - SMD 1/4W 300 ohm .1% 25ppm                                6

Diamond_buffer SMD

Mouser #                             Description                                                                                                    Order Qty.
649-68016-404HLF            Headers & Wire Housings 4POS R/A HDR SnPb                                           1
279-CPF1206B10RE1        Thin Film Resistors - SMD CPF 1206 10R 0.1% 25PPM 1K RL                   4
279-CPF1206B24R9E1      Thin Film Resistors - SMD CPF 1206 24R9 0.1% 25PPM 1K RL                 2
756-PCF1206R-20KBT1     Thin Film Resistors - SMD .125W 20K ohm 0.1% 25ppm                            1
757-2SC3324GRTE85LF     Bipolar Transistors - BJT Audio Freq Low Audio Freq Low                        4
757-2SA1312BLTE85LF      Bipolar Transistors - BJT PNP Trans -0.1A LN -120V VCEO                       4
710-150120SS75000          Standard LEDs - SMD WL-SMCW SMDMono TpVw Waterclr 1206            2
603-RT1206BRD07300RL   Thin Film Resistors - SMD 1/4W 300 ohm .1% 25ppm                                6

 

Another edit to your BOM. The transistors should be the BL type, not the GR. So the 2SC3324 transistor should have mouser part 757-2SC3324BLTE85LF

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Digikey says that 2SC3324/2SA1312 is NRND and is recommending 2SC2713/2SA1163 as a substitute. Any reason why I wouldn't be able to use the 2SC2713/2SA1163 transistors for the unbalanced/balanced board and diamond buffer?

Comparing the datasheets for 2SC3324 and 2SC2713 it seems like the 2SC3324 has a lower noise figure, but otherwise have identical specs. 0.2dB and 1dB max vs 1dB vs 10dB max respectively. Seems like I should go for the original pair while I still can. Too bad it's backordered on Mouser until March.

Edited by cspirou
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  • 5 weeks later...

cspirou: I would add an input resistor to ground as well. You can match Q1 to Q3 and Q5 to Q7, but I don’t think matching is all that useful here. If you want to try another small SMD buffer, let me know. I have just ordered some boards now that I have verified their performance versus sims.

 

I can include matched Toshiba JFETs and the other dual package BJTs are available at Mouser.

 

0cab7578d0cbcbcf4e6f6b8699ba265d.jpg

 

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