Avoid entering AC in the phono box, it can introduce some harmonic noise unless twisted and shielded, then again still possible. You could terminate the DC umbilical with a 4700uF like the one in the supply near the DCin connector of the phono so to have some kind of lower impedance like having the PSU near.
There is good EI and some good variety of toroidal also, potted, shielded etc. Usually by specialists.
Congratulations. After all you invested much care into making yours a very good build.
So DC it is. Any real drawback in not using such a capacitor near the dc in? I was trying to avoid having components outside the pcb's, but if there is a real advantage I'll do it.
Me I kept it basic in those aspects just to confirm its good enough on simplest arrangement. And it was. Not that more stuff can be detrimental per se. Alex added much stuff PSU side and he is even happier now for example. You could try for yourself and leave out any extras if not making much difference in your system.
This is mine
A two box setup with the raw DC supply and transformers in a seperate box to the folded phono stage.
It's very quiet, possibly the quietest phono stage I've ever owned. Setting the bias for the Jfets is not easy, the temperature inside the box has a large affect on the bias voltage.
I've yet to find a good way to get it right. Despite the ventilation slots opening the lid of the box causes the bias voltage to change rapidly. How critical is the bias voltage?
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
A two box setup with the raw DC supply and transformers in a seperate box to the folded phono stage.
It's very quiet, possibly the quietest phono stage I've ever owned. Setting the bias for the Jfets is not easy, the temperature inside the box has a large affect on the bias voltage.
I've yet to find a good way to get it right. Despite the ventilation slots opening the lid of the box causes the bias voltage to change rapidly. How critical is the bias voltage?
Clean, simple, effectively quiet build. Congrats. Its the high gain one I suppose (I see two Jfets on minisinks I think). For which cart model? Any listening sessions done yet? Hovlands? The test points level around the input stage can vary +/-1V after settled with warm up. Say 30mins. Not that critical. Use crocks to monitor with lid closed.
Yes high gain version with two Jfets on mini-sinks. Cart is Koetsu Black Goldline running into 100ohm load setting, arm is 12" Jelco 750, TT Palmer 2.5.
Been listening to it most of the day today. I'm not sure about the Hovlands, I used them previously in my valve phono stage. I might swap them out with Russian FT2 teflon 0.1uf and Russian KBG 2.2uf PIO.
Thanks Salas. Yes certainly in that ball park. What coupling caps would you suggest over the Hovlands?
I will try with 200 ohms. I have tried 200 and 100 ohm resistive loading with my old setup before and I can't tell any difference to be honest. I was using a Salas design Jfet head amp (2x 2SK170) into a valve phono stage (WD phono II) 5751 & ECC83 in the cathode follower.
Seeing that unused spot for a resistor on the PS board
made me wonder if there could be a little gained by using a resistor after the rectifiers. Not having looked closely I assumed it goes from the rectifier to the cap but now that I think about it I doubt that is the case and some mild board surgery would be needed.
I plugged in the basic supply into DUNCAN AMPS TOOLS PS simulator and with a 29R resistor there would be halving of ripple. Of course, I have no idea how accurate this is but it does seem it could dampen pulses from the diodes.
As you go higher you get a tiny reduction in ripple but the graph looks funny. When you get to around 40R the ripple begins to increase. At 100R you are back where you started.
I do not think we have to worry about efficiency too much with this circuit.
Knowing that this is a post from someone with no fundamental knowledge of power supplies or electronics in general (I can follow the instructions and make vain attempts at synthesizing what I have seen from other circuits) I would appreciate the opinion of someone who knows.
Thanks,
made me wonder if there could be a little gained by using a resistor after the rectifiers. Not having looked closely I assumed it goes from the rectifier to the cap but now that I think about it I doubt that is the case and some mild board surgery would be needed.
I plugged in the basic supply into DUNCAN AMPS TOOLS PS simulator and with a 29R resistor there would be halving of ripple. Of course, I have no idea how accurate this is but it does seem it could dampen pulses from the diodes.
As you go higher you get a tiny reduction in ripple but the graph looks funny. When you get to around 40R the ripple begins to increase. At 100R you are back where you started.
I do not think we have to worry about efficiency too much with this circuit.
Knowing that this is a post from someone with no fundamental knowledge of power supplies or electronics in general (I can follow the instructions and make vain attempts at synthesizing what I have seen from other circuits) I would appreciate the opinion of someone who knows.
Thanks,