Ceriatone Prinzetone Clone

[milkyBK370]

Hi, I'm currently building a Princeton-inspired amp based on Ceriatone's layout and design. I'm having real trouble laying my hand on a 47 Ohm, 3 watt CC resistor that's used for the NFB control. I had a look at my parts inventory and I have a metal film resistor which matches the resistance and power values. My question is, how much affect will using a metal film resistor, rather than the CC resistor, cause? Do you think there would be an audible difference? Are there any other factors I should be aware of?

I'm using this layout.. http://ceriatone.com/images/layoutPic/f ... iatone.jpg

And this is the MF resistor I'm proposing to use.

http://uk.mouser.com/ProductDetail/IRC/ ... jweQ%3d%3d

Mouser and Farnell don't seem to have a CC resistor @47r, 3w.

Any help/advise would be greatly appreciated.

[Reeltarded]

Just a guess: it won't hiss as much.

Cheers!

[diagrammatiks]

there's really no reason why that has to be a 3 watt resistor.

[Jana]

And there will be no audible difference between a MF and a CC in that position. None, nada, zilch, zero.

[NickC]

there's really no reason why that has to be a 3 watt resistor.

Maybe it was done that way following conventional wisdom that with Carbon Composition resistors, one should go high wattage for lower noise?

As Jana said though, it matters not in that NFB position.

[milkyBK370]

This is why I love this forum. No BS, just good advice when its needed. Thanks very much.

[diagrammatiks]

there's really no reason why that has to be a 3 watt resistor.

Maybe it was done that way following conventional wisdom that with Carbon Composition resistors, one should go high wattage for lower noise?

As Jana said though, it matters not in that NFB position.

it doesn't matter in that position. There's the nfb pot and even if that pot was shorted there's still the 6k8 resistor forming a voltage divider with the 47ohm resistor. There's almost no voltage drop there.

Also higher resistances are more susceptible to noise.

If noise was a concern then the 6k8 should be 3 watts as well.

But, it's just a tiny amount of nfb that the resistor type there shouldn't matter at all.

[milkyBK370]

OK, so I have another stupid question but I'm gonna embarrass myself and ask it anyway.

The PT I have is the Hammond 290AEX (UK 240v primary). I have a question relating to the data sheet below:

http://www.hammondmfg.com/pdf/EDB290AEX.pdf

Using this layout...

http://ceriatone.com/images/layoutPic/f ... iatone.jpg

There are two black primary wires on the PT. Does it matter which of these I connect to the Neutral pin of the IEC and which to the power switch? The layout is clearly marked 0 volts to the neutral IEC socket pin and the other wire to the switch. There is no way to tell the two black wires on the PT apart so I can connect them either way. Right?

[martin manning]

Correct, no polarity to worry about.

[milkyBK370]

Thanks mate. The pdf needs to be more specific for a n00b like me!

[milkyBK370]

Oh, one more thing. The layout screen/shield on the layout. I don't seem to have a wire from the pt for that. I have the red/yellow wire grounded but have everything connected now. No 'E' as referred to in the layout.

[martin manning]

That PT just doesn't have a shield ground wire, so just ground the red-yellow HV CT. I see there is no CT on the 6.3V winding either, so you'll want to add two 100R resistors to ground, one from each side of the heater circuit for a ground reference, or it will hum. If your layout looks like the C-tone, you can put one from pin 7 on the left-most 6V6 to the nearby ground lug with the 1R on it, and the other one from pin 2 on the other 6V6 to the ground lug over there.

[milkyBK370]

OK. Thanks for the advice.