I used a 10K stepped attenuator first then switched to an Academy Audio muses. Difference was more than huge. Succes met bouwen!
A question for Jim or Wayne, finally getting around to building this pre, I got an early kit that has 2SK209GR grade Jfets supplied, but I notice the latest schematic in the store page is showing 2SK209BL grade. Had a quick scan of the thread,but did not see any posts on this.
What is the correct Idss grade for the Toshiba 2SK209 for this design?
Thanks in advance guys.
What is the correct Idss grade for the Toshiba 2SK209 for this design?
Thanks in advance guys.
For me it's not clear how to connect the psu. I have this new toroidal transformer that I never used. It has 2 x 15 volt AC. Actually the voltage is a bit higher, 17 volt. So I need a rectifiers for DC power. How do I go from 2 x AC to 2 x DC with 3 cables (one for ground)? Most images here I can't follow the cables. I should take the ground from the case? Do I need a ground protector loopback?
Bert:
I assume the photo you posted is just an example; the toroid's label indicates the secondaries are 25V. Using that toroid as an example, though, the red and black wires are the primaries -- they would be connected to the 230V AC live (after the fuse and switch) and neutral connections. The orange and yellow wires constitute one secondary and the brown and blue wires are the second secondary. The secondaries are also AC; they need to be connected to rectifiers (e.g., two bridge rectifiers) to convert the voltage from AC to DC. You need a capacitor bank for your power supply, and by properly connecting the DC output from the rectifiers to that capacitor bank you will end up with +DC voltage, Ground and -DC voltage, which is then connected to the two sets of power inputs on the BA2018 pcb.
Keep at it -- you're going to to be very pleased when you've completed your BA2018.
Regards,
Scott
I assume the photo you posted is just an example; the toroid's label indicates the secondaries are 25V. Using that toroid as an example, though, the red and black wires are the primaries -- they would be connected to the 230V AC live (after the fuse and switch) and neutral connections. The orange and yellow wires constitute one secondary and the brown and blue wires are the second secondary. The secondaries are also AC; they need to be connected to rectifiers (e.g., two bridge rectifiers) to convert the voltage from AC to DC. You need a capacitor bank for your power supply, and by properly connecting the DC output from the rectifiers to that capacitor bank you will end up with +DC voltage, Ground and -DC voltage, which is then connected to the two sets of power inputs on the BA2018 pcb.
Keep at it -- you're going to to be very pleased when you've completed your BA2018.
Regards,
Scott
You need a power supply board to give you rectified, DC filtered power. That isn’t part of the diyAudio store kit.
No, the red and black are not the primary on the pictured transformer. The Brown and Blue are the primary wires. As per the label on the transformer and conventional wire colours for mains.
I'll follow up SRMcGee by suggesting that an easier route might be to use a different transformer, one that is AC in and DC out. For instance, the Antek AS-0518 is popular for the BA2018 build. https://www.antekinc.com/as-0518-50va-18v-transformer/ just in case.
Also, for that Vigortronix transformer, here is the spec sheet:
https://www.vigortronix.com/wp-cont...146-xxx-1xx-D0009-Single-Primary-Toroidal.pdf
Also, for that Vigortronix transformer, here is the spec sheet:
https://www.vigortronix.com/wp-cont...146-xxx-1xx-D0009-Single-Primary-Toroidal.pdf
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Bert, Your transformer is fine for the preamp. As others have said, you need a power supply circuit to convert AC to DC. A good one to use is the VRDN bipolar power supply by Mark Johnson:
https://www.diyaudio.com/community/...l-ckts-11v-to-20v-1-5a-with-de-noiser.355883/
Mark has included a zip file of the Gerber files for the manufacture of the pcb:
https://www.diyaudio.com/community/attachments/tzptr7_a_vrdn_regulator_rev_a-zip.852117/
https://www.diyaudio.com/community/...l-ckts-11v-to-20v-1-5a-with-de-noiser.355883/
Mark has included a zip file of the Gerber files for the manufacture of the pcb:
https://www.diyaudio.com/community/attachments/tzptr7_a_vrdn_regulator_rev_a-zip.852117/