Transformer for a tube amp question

[A3rd.Zero]

Yeah, its alot like the Morgan Jones on headwize but it differs in a few ways. It is the HAP-03 made by RADII out of China. Its a real POS but if you can get it to work it sounds really nice with Senn HD-600's. Ill be using mostly High ohm cans so I think that I can keep the Output Cap low, if not however Ill just add it to the headphone jack.

Thanks

Milo

[fdegrove]

Hi,

I plan to use 4 FREDS for the fullwave rectifier, each is rated to 12A and 1200V so even if I parallel the winding I won't be heating up the FREDS. Is there a problem with supplying twice the amperage to the amp, or will it only draw what it needs anyway?

Someone once advised against the use of HEXFRED diodes, I forgot why exactly but I suppose they were misbehaving.

Either way, if you can't get Schottkys to do the job I'd put some snubber caps across the diodes.
12A is way too much but it'll only hurt the bank, I suppose.

The preamp will only draw whatever it need, so while it's overkill it won't do any damage.

Cheers,

[A3rd.Zero]

I thought that was the way it was with current. So do I need to rectify each side of the 220V winding seperatly or is there a way that I can rectify it at the same time and still get 110V with twice the current? Basically do I need to buy 4 more freds? The 12A ones were the same price as the 6A ones and I figured that it will just keep the heat down so what the hey. What would you recommend as snubber caps, type, rating? I know that that is an absurdly broad question but I only know enough to know that the question is broad not what I should use.

He he, at least im not asking "What is the best capacitor ever?"

Thanks,

Milo

[A3rd.Zero]

CHOKY

Im interested in that solution but im still to new at this. could you draw me a picture. Ill post it on my refridgerator

Thanks

Milo

[Zen Mod]

Originally posted by A3rd.Zero
CHOKY

Im interested in that solution but im still to new at this. could you draw me a picture. Ill post it on my refridgerator

Thanks

Milo

[A3rd.Zero]

oooo fancy!

So I gather that the schematic has good PS noise rejection right? Thats why you can get away with just using a full wave rather than a bridge rectifier. Or am i missing the point.

Thanks for the help.

Milo

[fdegrove]

Hi,

Thats why you can get away with just using a full wave rather than a bridge rectifier. Or am i missing the point.

Both the graetz bridge and the FW rectifiers are errr...FW rectifiers.
It's just that the bridge is much more efficient, something you don't want here.

Both need to be filtered adequately just the same.

Cheers,

[A3rd.Zero]

Thanks Fdegrove,

Could you explain the efficienty issues? Why dont i want the more efficient solution?

Thanks

Milo

[fdegrove]

Hi,

Why dont i want the more efficient solution?

Efficient in the sense that it would put out a higher voltage, since you said in your opening post that you only need 110V I assume
there's little point in turning excess voltage into heat.

You'll already see close to 125 VDC max on the filter caps.

Using a FW bridge and NOT grounding the CT would give you twice as much volts in theory.

If that's what you want then that's fine by me.

Cheers,

[A3rd.Zero]

I dont know if the powersupply section calls for delivery of 110V or if that is just the winding of the transformer that they used (the schematic is a little unclear because they never give voltages at test points). If I were to construct a powersupply as below, wouldnt I have basically 110V (not taking into account RMS due to the rectifier or the caps) and just twice the amperage that each side of the winding could produce? Again sorry if I'm totally missing something.

Thanks,

Milo