Another Super High End Phono Stage! No expense spared...

I upgraded a turntable PSU to use active regulation instead of a simple zener shunt+capacitor and I cut the capacitance downstream of the regulator by 10x because it simply wasn't necessary with the active regulator on the job.

There may be some advantage to having the regulators on a separate board from a noise standpoint. With the regulators on a separate board you don't have any of the unregulated voltages present on your audio PCB. At a minimum I'd want the rectifier + it's capacitor bank/chokes/pi filters on a separate board if possible.
 
A high value of capacitance may cause the regulators to struggle - but probably not. There's no advantage in having having electrolytics with a much higher voltage rating than is required. About 10% over is plenty in my opinion.
I see lots of phonostages where "the audio circuit" is on one PCB and "the power supply" is on another, with the voltage regulators on the power supply PCB. To me it makes more sense to have the regulators on the audio PCB so they are close to the circuit it they're meant to be supplying regulated voltage to.

Thank You for the info,
The last preamp i designed i made it a mono board, one per channel. and each with its own power rectifier, regulator transistor circuit and capacitors. All on the same pcb, but that only has a gain of 5 or so. I thought it might be best keeping the power rectifier and regulator separate this time due to the really sensitive nature of the phono.
I may lower the capacitors a bit to a higher voltage and lower capacitance keeping there current size.
I have switched my parts list to use cheap ceramic 100nf caps also, apart from price is there a benefit to using them over poly caps? apart from cost.
 
Actually, doing some reading at diyaudio it seems that even X7R ceramics are a good choice for power supply decoupling. It seems the additional high frequency ESR can damp ringing at MHz frequencies that aren't nice to opamps.
 
Actually, doing some reading at diyaudio it seems that even X7R ceramics are a good choice for power supply decoupling. It seems the additional high frequency ESR can damp ringing at MHz frequencies that aren't nice to opamps.
Yes that is interesting about the caps, the NPO ones are a bit more costly actually.
What do you think would work best,
Wima poly, NPO ceramic or the cheapest X7R ceramic?
Or would it not make much of a difference.
The X7R is cheapest by far
 
My board after a few changes. In case you haven't noticed, I like to take things to the extreme. That includes my noise filtering with capacitors.
Should i leave my input resistors at 300R or change them back to 2.2K, or not use it?
Also is 100R for both my front and back end gain control resistors ok, or is it asking for trouble gainwise?
I am also thinking of using the AD823 chips since i really like the fet sound, i build alot of Nelson pass Class A Mosfet designs.
CNC PHONO BOARD, not finished.PNG
 
With the regulators on a separate board you don't have any of the unregulated voltages present on your audio PCB. At a minimum I'd want the rectifier + it's capacitor bank/chokes/pi filters on a separate board if possible.
Yes, it's not a bad idea to have the rectifier well away from the audio because rectifiers can radiate RF, though a small capacitor is parallel with each diode in the bridge is a common way to suppress it.
With a typical chip regulator the voltage is only regulated directly at its pins. It would be possible to have perfect regulation at the pins and far-from-perfect regulation at a remotely located PCB, hence the suggestion to have the regulators close to the audio circuit - it's standard practice in many branches of electronics.
 
Should i leave my input resistors at 300R or change them back to 2.2K, or not use it?
As mentioned a few posts ago, the "input resistor" can be used for RF filtering, but only if it is followed by a capacitor. Without the capacitor the filtering is dubious. Its other purpose of limiting bias current is extremely dubious since bias current doesn't depend on that resistor anyway.
 
Thank you Skrodahl, i can see how the 100nf poly caps ill be using are best for noise suppression as close to the power pins as possible.
Is there no benefit to having extra on board capacitance, or is it a draw back, or does it not matter?
As for the ground plane i've not had problems soldering because of it before, except for components coupling to it need extra heat. i have good temp controlled solder stations that make it easy.
I will play around with inversing the circuit also.

rothwellaudio said it, they may cause the regulators to struggle. I've even used DC-DC converters and switch-mode power supplies (feel free to shudder :)). These will most likely struggle because of the added capacitance.

100 nF poly caps will work in many instances. Use multilayer (monolithic) ceramic caps to be extra certain, since they are better at higher frequencies. See this article from Rod Elliott for more info:
http://sound.whsites.net/dwopa.htm#s32

All boards where I've had the ground fill on the bottom layer require approx 20 deg C higher temperature or longer soldering time on my Weller WT-1/WTP90 with high thermal mass tip to avoid the odd cold joint. It's almost no effort, and it'll make your life just a little bit easier. Of course, that depends on what temperature you're starting with.
 
With a 2-layer PCB, if the ground plane is on the top layer, is the connection reliant on the through hole plating or does the solder need to reach through the hole to hit the pad on the topside of the board?
 
With a 2-layer PCB, if the ground plane is on the top layer, is the connection reliant on the through hole plating or does the solder need to reach through the hole to hit the pad on the topside of the board?

It's only reliant on the through hole plating, you'd like to have at least some solder flowing into the hole (and optimally all the way through) for best connectivity and for structural integrity.

@Lllewellyn: I've crossed out the caps that I would leave out. They really aren't needed. You can keep the footprints in there, just in case, but you don't need to mount the actual caps:

upload_2018-10-31_15-0-15.png

You could even use my input impedance calculator (box.com) to choose other values for the input impedance resistors.
 

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It's only reliant on the through hole plating, you'd like to have at least some solder flowing into the hole (and optimally all the way through) for best connectivity and for structural integrity.

@Lllewellyn: I've crossed out the caps that I would leave out. They really aren't needed. You can keep the footprints in there, just in case, but you don't need to mount the actual caps:

View attachment 1319232

You could even use my input impedance calculator (box.com) to choose other values for the input impedance resistors.

Thankyou, i will leave a lot of the foot prints in and use the all if i feel like it needs it as an option, i like to over do my cap filtering most times.
I will have the board made with through hole connected and all pads gold plated.
It is quite cheap now to get boards made.
Ill make a few, I'm sure some of my friends will want a board also.

Thankyou very much for the calculation sheet, this will make things very easy indeed.

Ive only just taught myself how to use eagleabout a month ago, but have been practicing alot.
There are still lots of functions i need to discover. Im completely self taught in electronics.
 
You've made lot of progress over a month, and even mastered the ground fill which takes a lot of people a long time to learn. Well done!

There are probably more things to be said about the layout, but you seem to have a plan that you've stuck to. Do you have specific RIAA filter caps in mind? Their footprints could probably be reviewed again. Also, you should really add a rather large resistor to GND (R3: 100k ohms or so) at the output end of both your Janzen caps which is currently missing. It completes the high pass filter on the output.

upload_2018-10-31_23-54-37.png

The resistor R4, which should be a low value to avoid adding extra noise, can be added as a protection against shorting the output. Most of the op amps we've discussed here have over-current protection, so you won't be doing anything awfully wrong by leaving it out.
 
You've made lot of progress over a month, and even mastered the ground fill which takes a lot of people a long time to learn. Well done!

There are probably more things to be said about the layout, but you seem to have a plan that you've stuck to. Do you have specific RIAA filter caps in mind? Their footprints could probably be reviewed again. Also, you should really add a rather large resistor to GND (R3: 100k ohms or so) at the output end of both your Janzen caps which is currently missing. It completes the high pass filter on the output.

The resistor R4, which should be a low value to avoid adding extra noise, can be added as a protection against shorting the output. Most of the op amps we've discussed here have over-current protection, so you won't be doing anything awfully wrong by leaving it out.

Thank You,
I've not thought about RIAA cap values, i've only copied others work and am not experienced enough to change them. Should i change the values?
I am using wima poly style caps for the capacitors. How important is there type and size?
Should i make provision for them to be larger audio caps?
Thank you i'll add the 100K resistors to ground on the output.

CNC PHONO BOARD, not finished.PNG
 
Do you have specific RIAA filter caps in mind? Their footprints could probably be reviewed again.

Thank you, i have taken your advice and made my own multi cap footprints, so i now will have a choice of 3 different sizes for each in case my parts change.

CNC PHONO BOARD, not finished.PNG
 
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The resistor R4, which should be a low value to avoid adding extra noise, can be added as a protection against shorting the output. Most of the op amps we've discussed here have over-current protection, so you won't be doing anything awfully wrong by leaving it out.
Yes, that resistor would protect the op-amp from short circuits but it also has another purpose - to protect the op-amp from capacitive loads which might cause instability. In a domestic hi-fi with 1m interconnects it probably doesn't do much but in a studio or concert environment where much longer cable runs might be in use the capacitive load on the op-amp would be considerably higher and including the resistor is good practice.
 
I am sorry for asking so many questions, Im not sure ill get this power board made, i may just make it myself at home on blank pcb. Does this simple circuit look like it will work? I realise 25vac is quite high but the small teriodal is very cheap.

15v mini power board.PNG
 
With a typical chip regulator the voltage is only regulated directly at its pins. It would be possible to have perfect regulation at the pins and far-from-perfect regulation at a remotely located PCB, hence the suggestion to have the regulators close to the audio circuit - it's standard practice in many branches of electronics.

Yes that is something i will still consider having it on the same pcb as the phono, i was testing out a regulator circuit theory i had which may work, but am unsure if i did my resistor values correctly.
 
Zener regulation isn't particularly sophisticated, even with a pass transistor. Is there a reason why you aren't using a regulator IC?
Of course, that PCB is only for a single rail power supply and your audio circuit is designed for a split rail supply, but I presume you realise that.
 
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