Thanks for your interest.
I am building a 300b amp, and am building it in two parts - PS and Amp.
The PS chassis has two power transformers (one for HT, one for Regulators), and one choke. The amp chassis has two OPTs and two chokes.
What orientation conditions do I need to consider?
On the PS chassis, do I align the two power transformers and put the choke at 90 degrees to them?
And on the amp chassis do I put the two OPTs 90 degrees to the chokes?
And should I align the chokes across both chasses as they will be close to each other, or is that not so important?
Many thanks for your help
I am building a 300b amp, and am building it in two parts - PS and Amp.
The PS chassis has two power transformers (one for HT, one for Regulators), and one choke. The amp chassis has two OPTs and two chokes.
What orientation conditions do I need to consider?
On the PS chassis, do I align the two power transformers and put the choke at 90 degrees to them?
And on the amp chassis do I put the two OPTs 90 degrees to the chokes?
And should I align the chokes across both chasses as they will be close to each other, or is that not so important?
Many thanks for your help
Bad idea to build a stereo amp. If you choose to build with two chassis, than it should be a double mono amp. Because you power a stereo amp with a separate PSU and still have only one PSU for both channels. For best channel separation, always build two separate chassis. Thats why there are double mono amps and no one will do it like your stereo amp in two boxes.
Hi
Thanks for this. But if I were to build as I have said, do you have any insight into orientation? Thanks
Thanks for this. But if I were to build as I have said, do you have any insight into orientation? Thanks
I support your plan. Several years ago I decided that it was absurd to have to build a new power supply for each new amplifier. My plan was to build a couple of universal supplies with specific current and voltage and use them to power different stereo amplifier topologies.
The results are power supplies much more robust, larger and heavier than could ever be put on an monoblock amplifier chassis. My stereo 300B amplifier power supply weighs 65 pounds with two large commercial grade low DCR inductors and a UTC commercial grade power transformer. It can output 500V at 350mA so is useful not only for a SE 300B stereo amp (90V is dropped in the 300B cathode resistor) but also a push pull 6L6 or EL34 amplifier. No electrolytic capacitors are used. Wima MKP4 caps are used instead.
So to finally answer your question: rotating transformer cores so that they are not aligned, but at 90deg. with respect to one another can greatly reduce induced coupling between them. Further reduction can be achieved by separation of the two transformers from each other.
The results are power supplies much more robust, larger and heavier than could ever be put on an monoblock amplifier chassis. My stereo 300B amplifier power supply weighs 65 pounds with two large commercial grade low DCR inductors and a UTC commercial grade power transformer. It can output 500V at 350mA so is useful not only for a SE 300B stereo amp (90V is dropped in the 300B cathode resistor) but also a push pull 6L6 or EL34 amplifier. No electrolytic capacitors are used. Wima MKP4 caps are used instead.
So to finally answer your question: rotating transformer cores so that they are not aligned, but at 90deg. with respect to one another can greatly reduce induced coupling between them. Further reduction can be achieved by separation of the two transformers from each other.
The PSU is THE most important part of an amp. So to have an oversized one isn't a bad idea at all. The best amps have double mono power PSU for best channel separation. Because every channel in a stereo system should be as independent and plays its own music.
Trans should always be 90 deg. rotated to another.
Trans should always be 90 deg. rotated to another.
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It's not a bad idea to make PSU and stereo amp. In fact the PSU doesn't need to be oversized that much as most of the time the extra energy needed doesn't happen simultaneously on both channels. So the stereo amp can count on the supply for both channels. The mono amps would require bigger PSU to achieve the same results...
Bob Carver documented this very well few decades ago using a rather powerful 6550 PP amp.
Back on topic. If the transformers are not too close it's not a big deal. Few centimetres apart is already ok to not be worried if they have the same orientation. Put the chokes 90 deg and should be fine. Usually the chokes are the more critical ones because they are supposed to filter and if they pick up noise they become almost ineffective.
Bob Carver documented this very well few decades ago using a rather powerful 6550 PP amp.
Back on topic. If the transformers are not too close it's not a big deal. Few centimetres apart is already ok to not be worried if they have the same orientation. Put the chokes 90 deg and should be fine. Usually the chokes are the more critical ones because they are supposed to filter and if they pick up noise they become almost ineffective.
Thanks for all your input.
So, as a general rule, if I put Mains transformers in one orientation, and all chokes and OPTs in the other, that sounds good to you?
So, as a general rule, if I put Mains transformers in one orientation, and all chokes and OPTs in the other, that sounds good to you?
There are three orientations, and ideally the power transformer(s), the choke(s) and the output transformers' cores should be in three different planes. And, again ideally, you'd want the center lines of the cores to line up. And, as already said, distance is your friend. Some of these ideals conflict, and all are undermined by a steel chassis. That's HIFI!
YOS,
Chris
YOS,
Chris
Be sure to put bleeder resistors in the power supply chassis.
And use bleeder resistors in the amplifier chassis, if there are more B+ filter caps there.
Otherwise, when you disconnect the umbilical cord from the power chassis to the amp chassis, and get your fingers inside . . . Ouch.
Safety First!
Prevent the "Surviving Spouse Syndrome".
And use bleeder resistors in the amplifier chassis, if there are more B+ filter caps there.
Otherwise, when you disconnect the umbilical cord from the power chassis to the amp chassis, and get your fingers inside . . . Ouch.
Safety First!
Prevent the "Surviving Spouse Syndrome".
I think its a great idea.
A class-A amplifier has a pretty constant average current drawn from the PSU, so no need to over size it too much. But of course having a stiff (over sized) PSU is always a good thing. For minimal channel L-R crosstalk, is it not enough to have separate chokes-caps after the common power transformer and rectifier?
A class-A amplifier has a pretty constant average current drawn from the PSU, so no need to over size it too much. But of course having a stiff (over sized) PSU is always a good thing. For minimal channel L-R crosstalk, is it not enough to have separate chokes-caps after the common power transformer and rectifier?
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I have had a similar idea, and I am interested in how you will link the components. How many connections do you need to the amplifiers?
If the distance is long enough, it doesn't matter anyway.
Attachments
Hi,
In terms of connections, I am going to have one cable carry HT and three earths (HT earth, signal earth, and chassis earth), another cable carrying 300b filament voltage (from Rod Coleman regulators), and another carrying driver tube heater (6.3v ac).
It would be interesting to hear your thoughts.
In terms of connections, I am going to have one cable carry HT and three earths (HT earth, signal earth, and chassis earth), another cable carrying 300b filament voltage (from Rod Coleman regulators), and another carrying driver tube heater (6.3v ac).
It would be interesting to hear your thoughts.
Why is signal earth going to the Power supply?
Is it to make the Coleman Regulators and filament circuit (like self bias network) be connected to signal earth, so that the input tube's filament/"cathode" voltage is referred to signal earth?
Consider which wires you put together into the same over-sheath.
Example, if you put the input tube earth wire and the output tube earth wire into the same over-sheath, then the higher signal current of the output stage earth will induce a voltage into the input stage earth wire.
This causes output signal to be fed back to input signal (in a phase and an unpredictable way that you do not want).
Having a separate power supply chassis and amp chassis causes more problems than it solves.
I prefer to build mono-blocks . . . still only 2 chassis for stereo.
I will find a way to afford 2 complete power supplies.
Is it to make the Coleman Regulators and filament circuit (like self bias network) be connected to signal earth, so that the input tube's filament/"cathode" voltage is referred to signal earth?
Consider which wires you put together into the same over-sheath.
Example, if you put the input tube earth wire and the output tube earth wire into the same over-sheath, then the higher signal current of the output stage earth will induce a voltage into the input stage earth wire.
This causes output signal to be fed back to input signal (in a phase and an unpredictable way that you do not want).
Having a separate power supply chassis and amp chassis causes more problems than it solves.
I prefer to build mono-blocks . . . still only 2 chassis for stereo.
I will find a way to afford 2 complete power supplies.
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I am using a star earth topology and all signal earths will connect to the star by the inputs. I need to carry that over to the power supply chassis as it needs the reference of the transformer centre tap.
I will put the signal earth and HT over one cable and the two other earths with the 6.3v ac. I think that will work ok.
I will put the signal earth and HT over one cable and the two other earths with the 6.3v ac. I think that will work ok.