I want to build a stand-alone power supply chassis. It will have multiple transformers so that I can regulate the input stage independently, give the outputs their own winding etc. etc.
I want to physically isolate it from the amp chassis (maybe half a metre).
I will regulate at least one of the heater windings and use AC for the others.
I am tentatively planning to make a ground star point on the power supply chassis. To this point I will connect the filter and regulator output grounds and the heater floating circuitry.
I then plan to run a single ground to the amp chassis and star this to all ground points there.
Does this sound good?
Would the heaters be OK referenced all the way back at the power supply chassis?
Should I be running separate ground cables from the ps chassis for the various stages?
I want to physically isolate it from the amp chassis (maybe half a metre).
I will regulate at least one of the heater windings and use AC for the others.
I am tentatively planning to make a ground star point on the power supply chassis. To this point I will connect the filter and regulator output grounds and the heater floating circuitry.
I then plan to run a single ground to the amp chassis and star this to all ground points there.
Does this sound good?
Would the heaters be OK referenced all the way back at the power supply chassis?
Should I be running separate ground cables from the ps chassis for the various stages?
Hi,
I think I understand where you are going to.
It might help if you renamed your grounds.
Audio ground (including speaker return, decoupling etc).
Power common.
Safety earth.
Signal ground.
Each does a different job and should be thought of (and designed separately), then combined at a convenient reference location.
Your heater supply is floating but then you talk about a reference, which?
I think I understand where you are going to.
It might help if you renamed your grounds.
Audio ground (including speaker return, decoupling etc).
Power common.
Safety earth.
Signal ground.
Each does a different job and should be thought of (and designed separately), then combined at a convenient reference location.
Your heater supply is floating but then you talk about a reference, which?
There are couple of things which you may be at risk of confusing. I mean gronding as in 0v returns, and 'grounding' as in connecting a conductive case to your mains supply ground for safety. View these ase two separate, though related exercises.
You really want every independant supply to have its own 0v return to the the raw supply, otherwise currents flowing in the shared , common impedance of the 0v return will corrupt them all. It's certainly not ideal for the regulated lines; the common impedance back to the regulators ground in the PSU box will degrade regulation, possibly quite severely. The datasheet for the LM117 is worth a read on this point alone. Ideally, you keep a regulator right next to the ciruit it is serving; if this is not practical (heat load/ space availability etc), consider using separate sense and power leads (4 terminal' or 'kelvin' sensing') for the very best performance eg 'front end' regs.
All this means more pins in your umbilical cable(s), but without you are really compromising the benefit of an offboard supply
As to safety grounding that's easy, if you use a metallic case it must bbe connected to the 'ground' of the incomming supply unless directed otherwise by electrical codes where you live. Whether or not you choose to connect the circuit 0v to this ground also is a consideration taken in light of the rest of your system, which should connect circuit 0v to 'ground' once and once only.
Hope this helps!
You really want every independant supply to have its own 0v return to the the raw supply, otherwise currents flowing in the shared , common impedance of the 0v return will corrupt them all. It's certainly not ideal for the regulated lines; the common impedance back to the regulators ground in the PSU box will degrade regulation, possibly quite severely. The datasheet for the LM117 is worth a read on this point alone. Ideally, you keep a regulator right next to the ciruit it is serving; if this is not practical (heat load/ space availability etc), consider using separate sense and power leads (4 terminal' or 'kelvin' sensing') for the very best performance eg 'front end' regs.
All this means more pins in your umbilical cable(s), but without you are really compromising the benefit of an offboard supply
As to safety grounding that's easy, if you use a metallic case it must bbe connected to the 'ground' of the incomming supply unless directed otherwise by electrical codes where you live. Whether or not you choose to connect the circuit 0v to this ground also is a consideration taken in light of the rest of your system, which should connect circuit 0v to 'ground' once and once only.
Hope this helps!
I will need heaters at B+ for the HT reg, some at 1/2 B+ for upper mu stage devices, some at 40-60V and some at B- (driver stage). I would like to reference them using an active voltage divider, for a low impedance reference.AndrewT said:
I plan to connect the safety ground to the chassis, and to one point on the circuit. I don't see this as a difficult decision. (though it could be tricky, it's neither here nor there)
I think I'm tackling two problems at once here: physical separation and multiple transformers.
Normally, I collect the ground connections from a single stage (Rg, Rk etc) to a single point and return that to the star at the first filter cap.
I am a little confused as I see Rk as being both power and signal. I also am having trouble understanding the need to differentiate decoupling from power.
By this I assume that my normal practice of returning each stage to the star point is warranted, and I should consider only one star point in the entire design.martin clark said:
Thanks.martin clark said:
If acceptable, I could put the regulator onto the amp board and run the HT as AC from the power chassis to the amp chassis.martin clark said:
- Status
- Not open for further replies.