GB for bare PCBs - Status Update
Dear All,
The boards have been ordered and will be here by next Friday.
At that time I will be able to ship to all of you with the exception of who request to solder the SMD parts of the Buffer circuit. Please ask to carlsors to send your parts to me.
If you don't sent the payment yet, please do it and add in the paypal notes you DIYAudio nickname, so I can understand who pay what
Best Regards,
Enrico
Dear All,
The boards have been ordered and will be here by next Friday.
At that time I will be able to ship to all of you with the exception of who request to solder the SMD parts of the Buffer circuit. Please ask to carlsors to send your parts to me.
If you don't sent the payment yet, please do it and add in the paypal notes you DIYAudio nickname, so I can understand who pay what
Best Regards,
Enrico
Forget to mention... somebody ask me by PM if the parts are included in the payment.
With the exception of the VHC for the 1/2 Clock Delay circuit (including the SMD resistor) ALL the other parts are to be payed separately to carlsors and you will receive the parts from him.
Regards,
Enrico
With the exception of the VHC for the 1/2 Clock Delay circuit (including the SMD resistor) ALL the other parts are to be payed separately to carlsors and you will receive the parts from him.
Regards,
Enrico
CCS matched sets with resistor pairs not needing pot
There has been some interest in installing resistors that equal the resistance needed to achieve 0.40ma without a pot as inspired by stjn001.
Now that I'm mostly done measuring and sorting 2SK208's I can provide a few 2SK208's sets matched at 0.40ma with a +/- 1 ohm resistance range. Smaller 805 Susumu RG resistor pairs are available to provide the total resistance needed without a pot. I will be ordering BF862 buffer Jfets and CCS resistors soon so PM me ASAP if you want to risk trying these. Cost will be a bit higher. No guarantees these will make the DACs run exactly at 2.7V, but you can always replace the smaller value ohm SMDs with trimmer pots if this doesn't work to your expectation.
I plan to ship SMD parts next Monday to those who ordered only CCS SMD parts.
Ross
There has been some interest in installing resistors that equal the resistance needed to achieve 0.40ma without a pot as inspired by stjn001.
Now that I'm mostly done measuring and sorting 2SK208's I can provide a few 2SK208's sets matched at 0.40ma with a +/- 1 ohm resistance range. Smaller 805 Susumu RG resistor pairs are available to provide the total resistance needed without a pot. I will be ordering BF862 buffer Jfets and CCS resistors soon so PM me ASAP if you want to risk trying these. Cost will be a bit higher. No guarantees these will make the DACs run exactly at 2.7V, but you can always replace the smaller value ohm SMDs with trimmer pots if this doesn't work to your expectation.
I plan to ship SMD parts next Monday to those who ordered only CCS SMD parts.
Ross
CCS JFET solder test
I wondered how much a 2SK208 might change from the heat of soldering so I did a test. After measuring the resistance needed for 0.40ma in my SOT-23 test socket I soldered it on a SOT-23 adaptor board and measured it again. The current using the same 691 ohms source resistance changed to 0.3993ma - a change of less than 0.2%. This would change a 2.700V Rload to 2.695V. This is close enough for me.
Those who want EXACTLY 2.70000000 volts should use the pot and NOT order matched value resistor sets. The 2SK208 matched sets vary +/- 1 ohm which can also introduce an additional error of less than 0.2%. The total error for soldering heat plus 2SK208 resistance variation could introduce RLoad Voltage variations of +/- 0.01 volts. These variations will NOT affect the differential voltage offset because the + & - differential outputs use the same CCS board.
IMO this variation is inaudible. Matched 2SK208 sets with matched resistor value sets still seem like a workable alternative to the resistor plus trimmer pot configuration as long as the 2SK208 is not FRIED during installation.
I wondered how much a 2SK208 might change from the heat of soldering so I did a test. After measuring the resistance needed for 0.40ma in my SOT-23 test socket I soldered it on a SOT-23 adaptor board and measured it again. The current using the same 691 ohms source resistance changed to 0.3993ma - a change of less than 0.2%. This would change a 2.700V Rload to 2.695V. This is close enough for me.
Those who want EXACTLY 2.70000000 volts should use the pot and NOT order matched value resistor sets. The 2SK208 matched sets vary +/- 1 ohm which can also introduce an additional error of less than 0.2%. The total error for soldering heat plus 2SK208 resistance variation could introduce RLoad Voltage variations of +/- 0.01 volts. These variations will NOT affect the differential voltage offset because the + & - differential outputs use the same CCS board.
IMO this variation is inaudible. Matched 2SK208 sets with matched resistor value sets still seem like a workable alternative to the resistor plus trimmer pot configuration as long as the 2SK208 is not FRIED during installation.
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Definetly better performance using a single precision resistor without a pot for CCS
I thought I had mentioned it somewhere
Real World CCS resistor posibilities
Nige2000
In a perfect world there would be a Susumu RG resistor that matches the resistance needed by every 2SK208 JFET. These combinations are rarely found in the real world - trust me. More possibilities exist if two resistors are used in combination which IMO would not be an audible compromise. Combining a trimmer pot with a resistor isn't ideal, but it guarantees adjustment to exact voltages/currents needed and sounds much better than the 6K resistor. Another compromise to find more resistor value possibilities is to substitute other SMD resistors for the Susumu RG which may not sound as good.
All my test 2SK208/2SK246 CCS boards used trimmer pots and sounded great.
Nige2000
In a perfect world there would be a Susumu RG resistor that matches the resistance needed by every 2SK208 JFET. These combinations are rarely found in the real world - trust me. More possibilities exist if two resistors are used in combination which IMO would not be an audible compromise. Combining a trimmer pot with a resistor isn't ideal, but it guarantees adjustment to exact voltages/currents needed and sounds much better than the 6K resistor. Another compromise to find more resistor value possibilities is to substitute other SMD resistors for the Susumu RG which may not sound as good.
All my test 2SK208/2SK246 CCS boards used trimmer pots and sounded great.
Carlsor, alternative approach to overcome the variation due to soldering heat to the JFET's is to measure, R set value afterwards, which is what i did. Still a little heat when soldering the resistors odf-course..
Btw, my question with regards to output voltage spread with the standard 6K resistors in the meain thread, was never answered. But I suspect, since 6K R's used are 1% accurate, fluctuation around 2.7V will be higher then what you are aiming for here.
Btw, my question with regards to output voltage spread with the standard 6K resistors in the meain thread, was never answered. But I suspect, since 6K R's used are 1% accurate, fluctuation around 2.7V will be higher then what you are aiming for here.
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theres 180 ohm in my 2sk208 r ccs
in digikey theres susumu 165,169,178,180,200 and 220 ohm resistors
id be happy enough anywhere between 2.5 and 2.7v on the outputs
all seems very possible to me
GB for bare PCBs - Status Update
Dear All,
As promised I get the boards today
Tomorrow I will start to prepare all the envelopes and Monday morning I will send your boards with the exception of the following people that requested the Buffer SMD parts to be soldered by me:
- Myint67
- Brumjam
- pdb
- tods
I hope that you already ask to carlsors to send me your parts
I will advise again when the shipment is done.
Best Regards,
Enrico
Dear All,
As promised I get the boards today
Tomorrow I will start to prepare all the envelopes and Monday morning I will send your boards with the exception of the following people that requested the Buffer SMD parts to be soldered by me:
- Myint67
- Brumjam
- pdb
- tods
I hope that you already ask to carlsors to send me your parts
I will advise again when the shipment is done.
Best Regards,
Enrico
Attachments
Dear All,
As promised I get the boards today
Tomorrow I will start to prepare all the envelopes and Monday morning I will send your boards with the exception of the following people that requested the Buffer SMD parts to be soldered by me:
- Myint67
- Brumjam
- pdb
- tods
I hope that you already ask to carlsors to send me your parts
I will advise again when the shipment is done.
Hi Enrico,
I asked you to solder the SMP parts too (real name David Coe) so I should be added to your list. Carlsor is sending my bits to you.
Thanks
David
Best Regards,
Enrico