Hiten's CNC Phono Build - Courtesy Sachin :-)

[Hari Iyer]

Hi all,
Finally assembled power supply for this Phono Preamplifier. Some pictures. What a beautiful PCB design and circuit. I am turning in to big fan of Sachin and Oms work. I hope someday they make SE tube amp kit.
The Power supply is half finished (I envy those who work 'fatafat' and make beautiful amps, speakers etc.(In other words I am Lazy ) I need 12-0-12 transformer for this. I did visited Lamington Road and transformer was well made (Rs. 250) But total negative marks for finishing. Need good finish like this. The metal casing will be good (Though it doesn't sheild magnetic flux from spreading) OR will go for R Core transformer. Any pointers are welcome for R Core OR Well made + finished EI transformer.
Thanks and regards.

I am not sure why you need such high value filter capacitors on your powersupply where the current demand is so low. These high value capacitance make your phono preamplifier sound very sterile. For a musical sounding phonopreamp the capacitance should be less. Also remove all capacitors from, Opamp power supply pins it's not needed. A simple 10nF will do.

Reduce capacitance to not more than 300uF and bypass capacitor to not more than 10nf. Check Texas instrument bypass capacitor data manual for proper implementation.

 

[Hiten]

Haribhai,
I am no expert in circuit design. Designer must have thought about that. One reason I can find is this is universal power supply and may be used with tone controls or other circuits which may require current. About main RIAA board also if you are talking about 0.1 uf film capacitors the designer must have decided its use. One thing I can think is as this kit may be used in different environment with lots on noise and interference, from external to internal. I have seen lots of diyers putting power supply in separate chassis and PS wire running to phono board which may pick up interference.
I have heard this Phono Preamplifier (first build five years a go) and it sounds excellent . Though strange as it may seem I build things in my capacity just for love of electronics.
Regards.

 

[Hari Iyer]

Haribhai,
I am no expert in circuit design. Designer must have thought about that. One reason I can find is this is universal power supply and may be used with tone controls or other circuits which may require current. About main RIAA board also if you are talking about 0.1 uf film capacitors the designer must have decided its use. One thing I can think is as this kit may be used in different environment with lots on noise and interference, from external to internal. I have seen lots of diyers putting power supply in separate chassis and PS wire running to phono board which may pick up interference.
I have heard this Phono Preamplifier (first build five years a go) and it sounds excellent . Though strange as it may seem I build things in my capacity just for love of electronics.
Regards.

I have used 300uF in my powersupply and just 10nf as bypass capacitors. I removed the 100uf and 0.1uF bypass from my opamp pins and put just a 10nf on them too. My wiring is not neat like yours and it's all point to point wiring everywhere, yet it's super silent.

 

[Hiten]

Sachin has pointed out Input capacitor position (Black 1.5uf) on my board. Following picture has correct position.