Hi!
I'm building a power supply for a preamp and a phono riaa circuit using 2 10000µF filter caps and 3 Superteddyregs. I'm looking for a transformer ith 2 separate 27v-0-27v windings but have no idea what kind of current capabilities I should be looking for. I'm guessing that the preamp stage doesn't require much current but nore do the regulators but what about the inrush current caused by the filter caps.
On acoustica.org.uk (Modifying and building audio power supplies) they are going for a 500VA R-core which seems impossible to find or even get custom build. Are those 500VA really necessary or would something less powerful be enough ? BTW if anyone knows where to get custom build r-core or even El-core transformers that would be great
.
Thanks!
I'm building a power supply for a preamp and a phono riaa circuit using 2 10000µF filter caps and 3 Superteddyregs. I'm looking for a transformer ith 2 separate 27v-0-27v windings but have no idea what kind of current capabilities I should be looking for. I'm guessing that the preamp stage doesn't require much current but nore do the regulators but what about the inrush current caused by the filter caps.
On acoustica.org.uk (Modifying and building audio power supplies) they are going for a 500VA R-core which seems impossible to find or even get custom build. Are those 500VA really necessary or would something less powerful be enough ? BTW if anyone knows where to get custom build r-core or even El-core transformers that would be great
.Thanks!
500VA is very, very unlikely to be necessary for line-level functions. You really do need to know the current demands of your preamps to select the best fit transformer, but they're very unlikely to need more than a 50VA. You have no need to be concerned about inrush current to the caps as transformers are thermally limited and inrush spikes barely warm them up at all even though they may draw more than the current rating for a few tens of mS.
Hi Abraxalito.
That would be a great relief because with those power ratings, things get really expensive. It's a NAC152xs clone, hard to find any information on the power consumption of those but if the pictures aren't lying fully built versions available on ebay seem to use something like 50VA r-core transformers. So I could for example go for a 100VA to stay safe. Is there any benefit that would explain why they are using a 500VA except for keeping it very cool ?
That would be a great relief because with those power ratings, things get really expensive. It's a NAC152xs clone, hard to find any information on the power consumption of those but if the pictures aren't lying fully built versions available on ebay seem to use something like 50VA r-core transformers. So I could for example go for a 100VA to stay safe. Is there any benefit that would explain why they are using a 500VA except for keeping it very cool ?
I think the benefit might be psychological, there's a school of thought in audiophilia that says that 'oversized' transformers sound better than ones designed on engineering terms. But I reckon there's a sweet spot - going bigger than necessary just increases your capacitance to mains and hence heightens your susceptibility to mains-borne noise.
If it were me building this power supply I'd spend the extra money on series chokes rather than on transformer steel and copper
If it were me building this power supply I'd spend the extra money on series chokes rather than on transformer steel and copper
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I see, that does seem to make a lot of sense. My finances thank you for this answer. As this is my first build I don't want to go too crazy.
With what I read about the regulators I will use they are extremely silent, I don't even know if chokes will be necessary here. Aren't they usually used on tube gear ?
With what I read about the regulators I will use they are extremely silent, I don't even know if chokes will be necessary here. Aren't they usually used on tube gear ?
Yeah, often valve designs will use 'choke input' power supplies, however those are only much use on classA amps. But you can get considerable benefit in reducing supply noise, in my experience, through using CLC filtering with much less bulky (and less expensive) chokes than are needed for choke input designs.
Another idea that may be appreciated by your finances: Go to your local "dechetterie" (sort of dump yard), find a small rather old (Japanese) amplifier on the pile and get permission to remove the transformer (eventually also the big electrolytics) for educational purposes.
The transformers used, in the past, to be symmetrical (bridged amplifiers were too expensive) and the secondary voltages are often around 27-0-27V. Power typically some 100VA.
Probably quicker, but at least cheaper.
The transformers used, in the past, to be symmetrical (bridged amplifiers were too expensive) and the secondary voltages are often around 27-0-27V. Power typically some 100VA.
Probably quicker, but at least cheaper.
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I don't know where you live but I've been to a few déchetteries and either people don't throw this stuff away any more or everyone has the same idea and line up at opening hours to get it all out .
I've been collecting and repairing old japanese solid state amps for a few years and never (I might not always have checked) came across a transformer with double 27-0-27v secondary windings. If you have a model in mind please share.
.I've been collecting and repairing old japanese solid state amps for a few years and never (I might not always have checked) came across a transformer with double 27-0-27v secondary windings. If you have a model in mind please share
.Hello.
The must for any class is power regulated ( Mosfet drived by TL431 for example), but there's loss and output voltage is less.
For preamp and any low power circuit it's the best solution, there's many low noise regulators IC.
CLC is very good with class A and must be adjusted for intensity.
The must for any class is power regulated ( Mosfet drived by TL431 for example), but there's loss and output voltage is less.
For preamp and any low power circuit it's the best solution, there's many low noise regulators IC.
For the preamp stage I will be using the superteddyregs (SuperTeddyReg | DIY | TeddyPardo), I've read some great things about them. Aren't most older model power amps a mix of regulated and unregulated (for the driver and output stage) ?
If I remember correctly the quad 303 for one has a regulated power supply, even if they actually regulate the 0v rail. And if I look at the schematic of for example the sansui au-999 it has regulated supplies all the way and just the rails coming from the main filter caps directly to the output transistors. Maybe our definition of "older" isn't the same
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