Anyone familiar with the FFA200 amplifier as published in the Tech/Elektor electronics book 'Build your own High-end audio equipment'
I am building one. The power supply requires 45v-0-45v 5A toroidal transformers (according to parts list) The main line fuse is rated at 4A (F2) (according to parts list)
To calculate VA rating of the transformer:
45V+45V-1V=89V 4AX89V=356VA. My question is why 5A rating for the transformer in the parts list? Should the calculation be: 5AX89V=445VA
To calculate VA rating of the transformer:
45V+45V-1V=89V 4AX89V=356VA. My question is why 5A rating for the transformer in the parts list? Should the calculation be: 5AX89V=445VA
The line fuse is on the 240V side. The "5A" is on the 90V secondary. In a simpler world we would expect the low volt side to be 2.6 times more current than the line side.
I can't read that PDF.
*IF* this is two times 200 Watts audio output, then it is at least 660 Watts of DC. The AC/DC conversion needs about a 1.2X correction Watts DC to VA AC. So for long term FULL-power operation the transformer "should" be 750VA at least. And double that for hard work in 4 Ohms, 1500VA. Which would be 6 Amps, but this extreme is so unlikely that 5A is fine.
If you use the amp for speech/music, it will never linger at 200 Watt/channel long enough to bother the transformer. In hi-fi you can often use a much small transformer than FULL-power computations suggest. Since I doubt reliability at 4r/ch, maybe even 300VA-400VA.
Yes, the design calls for a separate toroidal transformer for each channel. 300VA to 400VA should be a safe bet.Thanks for your reply.
As the schematics is barely readable on the photo: Has this amplifier also been published in the regular magazine? If, so, when, and how did they name it?
Best regards!
Best regards!
I found a similar amplifier in the Elektor magazine two parts November/December 1991. A lower power version-150W known as the LFA150. The only difference is the current amplifier PCB layout.
The output transistors Sanken 2SA1216/2SC2922 are available locally and I believe the Elektor designs were very good.
The LFA150 was using some Toshibas not the Sanken 2SA1216/2SC2922, in the LFA - A the Sanken was used.
The 2SK146 are super-rare these days.
Jim's Audio still has a few but at a high price.
Toshiba 2SK146-GR low noise dual J-FET 1 piece New Old Stock super rare !! | eBay
Jim's Audio still has a few but at a high price.
Toshiba 2SK146-GR low noise dual J-FET 1 piece New Old Stock super rare !! | eBay
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Nothing wrong with old amp designs, even What HiFi put an original Cyrus One up against the new one, they both still have their place in the world and sound good. Some old design are better than new offerings, and Elektor have published some interesting designs over the years.
Don't be afraid to use equivalent devices. Fairchild have good equivalent output transistors like the FJL4215 and FJL4315, also sold as the new 2SC5200 and 2SA1943 parts.
Mouser stocks a range of dual jfet parts. I've substituted the through hole types with 2SK2145 SMD parts before as they are cheap. But you can get parts like the IFN401 or IFN5565 or 2N3958 and many others. They are expensive but they are unique parts these days.
Don't be afraid to use equivalent devices. Fairchild have good equivalent output transistors like the FJL4215 and FJL4315, also sold as the new 2SC5200 and 2SA1943 parts.
Mouser stocks a range of dual jfet parts. I've substituted the through hole types with 2SK2145 SMD parts before as they are cheap. But you can get parts like the IFN401 or IFN5565 or 2N3958 and many others. They are expensive but they are unique parts these days.
