Because of the bad weather here in the Netherlands i had time to do a project with i want to do for a long time. It is the riaa phono preamp from Triode Dick.
I used the 2014 schematic and ad an other powersupply and a impedance selector. Further I collected some parts I liked from the past, like Amtrans resistors, Obligato capacitors, silver mica capacitors, Bendix 2C51 tubes and JAN 5755 tubes.
Next week I shall start with the PCB.
I used the 2014 schematic and ad an other powersupply and a impedance selector. Further I collected some parts I liked from the past, like Amtrans resistors, Obligato capacitors, silver mica capacitors, Bendix 2C51 tubes and JAN 5755 tubes.
Next week I shall start with the PCB.
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Another rainy afternoon. I made the pcb with toner transfer method.
Just laserprint the pcb design on glossy paper.
Used my wives iron to transfer the toner from the print to the copper of the pcb.
Remove the paper with warm water and ready to etch.
After etching drill the holes and spray some solderlack on it.
Just laserprint the pcb design on glossy paper.
Used my wives iron to transfer the toner from the print to the copper of the pcb.
Remove the paper with warm water and ready to etch.
After etching drill the holes and spray some solderlack on it.
Attachments
As build schematic.
Added 5U4 tube with heater transformer for softstart.
Added 470nf capacitor between ground heater and ground anode supply.
Changed some input impedance resistors.
Total cost about € 450,-. If using less expensive parts the cost will be about € 300,-.
Added 5U4 tube with heater transformer for softstart.
Added 470nf capacitor between ground heater and ground anode supply.
Changed some input impedance resistors.
Total cost about € 450,-. If using less expensive parts the cost will be about € 300,-.
Attachments
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I have a question about the 5755 tube. Looking at its data sheet, it seems it has the high anode resistance, low transconductance, but high amplification factor similar to the ECC83/12AX7. Is there a particular reason to use the 5755? From what I can tell, its Cmiller won't be very different from an ECC83/12AX7. Maybe a bit lower, but still 200pF or higher, even without the cable capacitance.
Incidentally, that's a beautiful looking build!
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Incidentally, that's a beautiful looking build!
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