I'm starting a 300B PP amp build and looking for a power transformer. At this point I'm going tube rectification, and a separate 5v ct filament transformer. Probably looking for 500v-0-500v or more. It also needs to supply the driver tubes, likely ECC99 or some variant. Still debating monoblocks or stereo, and that obviously makes a difference in the power requirements.
Where should I look? Hammond? Edcor? what else? I don't know much about them from a quality standpoint.
My current amp uses an original ST-70 transformer, and that is probably overworked, but I don't have any problems with it either.
And since I'm asking, what about output transformers? I want something nice there, but don't want to break the bank either.
Where should I look? Hammond? Edcor? what else? I don't know much about them from a quality standpoint.
My current amp uses an original ST-70 transformer, and that is probably overworked, but I don't have any problems with it either.
And since I'm asking, what about output transformers? I want something nice there, but don't want to break the bank either.
Go for monoblocks. With a standard stereo chassis you will not have comfortable room for anything but the most rudimentary circuit and power supply. And the thing will be HEAVY. I now realize that a chassis with plenty of spare room is one of the great luxuries of life. And lifting a stoopid heavy amp will hurt your back.
The pwr former requirements will be determined by the type of filter.
Cap input or choke input.
Hand drawn schematics of mine below. Drew theses in 2003 when I built the amps. Still playing music today.
My power supply parts and design came from Altec PA booster amps. Sadly one transformer shorted so I had some custom units built by Heyboer Transformer. The Altec chokes buzzed so I ended up with Hammonds.
Both built into the orig Altec housings.
I recently added the 6AU4 damper tube to drop the volts a tad and to add a nice slow turn on. Works excellent.
Ron
Cap input or choke input.
Hand drawn schematics of mine below. Drew theses in 2003 when I built the amps. Still playing music today.
My power supply parts and design came from Altec PA booster amps. Sadly one transformer shorted so I had some custom units built by Heyboer Transformer. The Altec chokes buzzed so I ended up with Hammonds.
Both built into the orig Altec housings.
I recently added the 6AU4 damper tube to drop the volts a tad and to add a nice slow turn on. Works excellent.
Ron
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FWIW, I take a dim view of vacuum rectification in a new power amp build. High PIV Schottky diodes are every bit as quiet as vacuum rectifiers, while providing great flexibility.
A look at a 300B operating conditions chart suggests you are thinking about choke I/P filtration. That can get expensive. SS rectification allows for large value cap. I/P filters that are reasonably well regulated, at lower cost. Check the archives for my posts about "hash" filters.
AnTek offers highly affordable toroidal power trafos.
I think the consensus is that Edcor O/P "iron" is, at least, as good as Hammond, while costing somewhat less. Cost will rise, if you order from 1 of "the usual suspects".
I was looking at the Amity. I've wanted to build it for years, but other things, like kids and college and an old house that always needed something got in the way. It's been such a long time since that was posted that the transformers specified are not available anymore, or at least not that I can find. And it isn't as if they have to be those specific ones anyway. I already have Lundahl interstage transformers on hand, bought them at a huge discount on eBay. If only I could score a quad of WE 300B's at a huge discount. 
I'm looking at either JJ or Genalex instead. 4x300B = OUCH.
Eli, was it you that had offered me the driver end for the Amity 10 years ago? It was somebody local. I've been using my 6B4G modded ST-70 for all of these years, and frankly, I don't have any issues with it. But there is always something better. I've heard it up against SE amps, but I like the sound of PP DHT.
Maybe I should look again at what Kevin Carter offers for PS kits. I'm not wedded to the idea of wiring it all up when a pcb kit from someone that knows what they are doing would be better.
I'm looking at either JJ or Genalex instead. 4x300B = OUCH. Eli, was it you that had offered me the driver end for the Amity 10 years ago? It was somebody local. I've been using my 6B4G modded ST-70 for all of these years, and frankly, I don't have any issues with it. But there is always something better. I've heard it up against SE amps, but I like the sound of PP DHT.
Maybe I should look again at what Kevin Carter offers for PS kits. I'm not wedded to the idea of wiring it all up when a pcb kit from someone that knows what they are doing would be better.
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