A teaser showing that JPS64 never rests, here is the next Yarra preamp module. This one is based on my JFET input/MOSFET source follower headphone amp which should give a very sweet sound. It will let your Yarra work as pretty nice headphone amp for driving headphones with impedances as low as 32ohms, ideally 50ohms or higher works best though. Bias current is about 125mA.
Preliminary Schematic:
Predicted FFT for 1.6Vpp into 600ohms:
Preliminary Schematic:
Predicted FFT for 1.6Vpp into 600ohms:
Attachments
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WBA18 & Yarra GB List
As I am getting ready to order the boards, please place your pre-order for the WBA18 if you are interested. Don't forget to add a note with your DIYA screen handle (name) in the order so that I can track it back to the interest list. JPS64 has the final layouts now with the larger pads around the bolts, voltage probe pins, and tented vias to reduce solder bridges.
Here is the list:
Thanks!
As I am getting ready to order the boards, please place your pre-order for the WBA18 if you are interested. Don't forget to add a note with your DIYA screen handle (name) in the order so that I can track it back to the interest list. JPS64 has the final layouts now with the larger pads around the bolts, voltage probe pins, and tented vias to reduce solder bridges.
Here is the list:
Thanks!
Attachments
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Yes, but I did not ask JPS64 to put any though holes for the 2sk170. You could just solder the legs onto the SOT23 SMT pads. I had this option actually on the Desktop Class A (DCA) amp, but no one ever used it. The BF862's are end of life, but I think you can still get them from eBay easily. I will have to check in a simulation to see if an SK209 is compatible.
So I ran a simulation on LTSpice with the 2SK209BL (readily available SOT23), and the performance is very good. Driving 1.54Vpp into a 55ohm load has 0.054%THD with a nice profile:
But requires changes to setpoint resistors:
R103+R104=2700R
R105=220R
R106=680R
Pretty simple change actually.
But requires changes to setpoint resistors:
R103+R104=2700R
R105=220R
R106=680R
Pretty simple change actually.
Attachments
JPS64 - 2 boards
xrk971 - 2 boards
Vunce - 2 boards
Roundtoit - 2 boards
Carl Huff - 2 boards
Gary S - 2 boards - Pre-order placed
Meanie - 2 boards
Big E - 2 boards
Kokanee - 2 boards + 1 Yarra MB
MD_Stryker - 2 boards
arthur - 6 boards+3 Yarra boards - Pre-order placed
afoor - 2 boards
Russellc - 2 boards
jhofland - 2 boards - Pre-order placed
Oracle1 - 2 boards
skunark - 4 boards, 1 yarra board
TungstenAudio - 2 boards
bologna1 - 2 boards - Pre-order placed
windwardmt - 2 boards
ZUM911 - 2 boards
Batty - 2 boards - Pre-order placed
bk856er - 2 boards (+ interest in a surface mount version)
Modman - 2 boards
sampsonite - 2 boards
TboneAK - 2 boards - 1 Yarra board set
BEYoung - 4 boards - Pre-order placed
mordikai - 2 boards
Asuslover- 2 Melbourne boards+ 1 Yarra board
vvs07- 4 boards + 2 Yarra boards
BDP - 2 boards - 1 Yarra board
BRN - 2 boards
xrk971 - 2 boards
Vunce - 2 boards
Roundtoit - 2 boards
Carl Huff - 2 boards
Gary S - 2 boards - Pre-order placed
Meanie - 2 boards
Big E - 2 boards
Kokanee - 2 boards + 1 Yarra MB
MD_Stryker - 2 boards
arthur - 6 boards+3 Yarra boards - Pre-order placed
afoor - 2 boards
Russellc - 2 boards
jhofland - 2 boards - Pre-order placed
Oracle1 - 2 boards
skunark - 4 boards, 1 yarra board
TungstenAudio - 2 boards
bologna1 - 2 boards - Pre-order placed
windwardmt - 2 boards
ZUM911 - 2 boards
Batty - 2 boards - Pre-order placed
bk856er - 2 boards (+ interest in a surface mount version)
Modman - 2 boards
sampsonite - 2 boards
TboneAK - 2 boards - 1 Yarra board set
BEYoung - 4 boards - Pre-order placed
mordikai - 2 boards
Asuslover- 2 Melbourne boards+ 1 Yarra board
vvs07- 4 boards + 2 Yarra boards
BDP - 2 boards - 1 Yarra board
BRN - 2 boards
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Agree with gary s - probably more folks will want to build one.
But truth be told, we ask JP to do too many things...
Presenting the Yarra v2 for GB2, now with tented vias (covered with solder mask). Also, the extra pads for the triangular holes on the rotary switch have been added, negating need for an additional and separate I/O board. These should be much easier to build and less prone to solder bridges. They do lose that cool golden porous matrix look though:
Thanks for making these boards even better JPS64!
Thanks for making these boards even better JPS64!
Attachments
I just ran simulation of 2SK170 for you Gary. It looks like if you set:
R103 + R104 = 930R
R105 = 22R
R106 = 330R
It can work really well and gives 0.060%THD with the following profile for 1.4Vpp into 51ohms:
What's interesting is that it likes a low impedance (circa 50ohms to have low THD as shown). So if driving a high impedance load, add a 50ohm load in addition. This can be done by changing the Yarra output cap load resistor from 47k to 51R.
Here is the schematic and some new renders of the PCB with tented vias.
R103 + R104 = 930R
R105 = 22R
R106 = 330R
It can work really well and gives 0.060%THD with the following profile for 1.4Vpp into 51ohms:
What's interesting is that it likes a low impedance (circa 50ohms to have low THD as shown). So if driving a high impedance load, add a 50ohm load in addition. This can be done by changing the Yarra output cap load resistor from 47k to 51R.
Here is the schematic and some new renders of the PCB with tented vias.
Attachments
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