A couple more 5f1 questions

[Duke]

I'm still working on my 5f1. I've changed the rectifier to a 5v4 and I really like the change. I just received my new Weber output tranny...check this out:

The old one in the chassis is a Triode Electronics OT specifically for a tweed champ. It's about 25% the size of the new Weber on the right. The damned Weber is so big it won't mount on the chassis with both bolts. Anyone else use one of these?

I get some 60 Hz hum and notice when I add the negative feedback cap, it's much worse. Can someone explain that? It sound super with the strat as is.

I can't wait to install the new OT and see what happens.

I just finished a 1x12 cabinet and loaded it with a WGS Veteran 30. I'll send finished pics once I get the tweaking settled. Until then, here's the cab:

[Duke]

I'll reply to my own post. I installed the new Weber OT. It has more range; deep bottom end compared to the Triad OT. The 16 ohm tap was nice too. The 60 hz hum is still there, but not as noticable. I have not tried the negative feedback resistor yet. Here is the chassis with the new OT mounted. You can see how I had to mod the mounting.

[tubeswell]

You probably will find that putting a choke in the filter would be beneficial for getting rid of the hum

[Duke]

Originally Posted by tubeswell

You probably will find that putting a choke in the filter would be beneficial for getting rid of the hum

I put the neg feedback on a switch today. Every time I turned it on, the hum was unbearable. I suspected I had attached it to the wrong side of the output jack, so I checked the layout and found something even simpler. The output jack wasn't grounded. I had put isolation washers on it and hadn't attached a ground. I removed the washers and the neg feedback is fine now. It still has a low 60 hz hum, but I can live with it.

[tubeswell]

There is generally always some residual ripple in the B+ when you use a CRC filter. But one of the reasons that SE amps tend to be hummier than PP, is that there is no phase cancellation in the OT that otherwise occurs in the primary winding of OTs in PP amps, which otherwise cancels this residual ripple: so if you don't like it, you need another way of getting rid of it. A CLC filter between the rectifier and the OT supply node will get rid of virtually all of that hum (if you decide to change your mind and take if further at some stage). In this regard, a choke provides superior ripple cancellation. The EMF that surrounds the choke iron (when a current is running through the choke winding) acts to stabilise and regulate the current (which in turn stabilises the voltage). The little 4H 150R standard small fender choke http://www.triodestore.com/22707.html is all you need for a SE 6V6 amp like that. Run a 10-20uF filter cap and then the choke in front of the 'normal' OT supply node cap - see suggestion

[Duke]

Originally Posted by tubeswell

There is generally always some residual ripple in the B+ when you use a CRC filter. But one of the reasons that SE amps tend to be hummier than PP, is that there is no phase cancellation in the OT that otherwise occurs in the primary winding of OTs in PP amps, which otherwise cancels this residual ripple: so if you don't like it, you need another way of getting rid of it. A CLC filter between the rectifier and the OT supply node will get rid of virtually all of that hum (if you decide to change your mind and take if further at some stage). In this regard, a choke provides superior ripple cancellation. The EMF that surrounds the choke iron (when a current is running through the choke winding) acts to stabilise and regulate the current (which in turn stabilises the voltage). The little 4H 150R standard small fender choke http://www.triodestore.com/22707.html is all you need for a SE 6V6 amp like that. Run a 10-20uF filter cap and then the choke in front of the 'normal' OT supply node cap - see suggestion

Thanks man, that's really helpful and it looks simple. I need to figure out where to place the choke on the chassis. Any suggestions?

[tubeswell]

wherever it will fit. Those little chokes are pretty small. Might be able to get it right on the end there, or between the two trannies

[celeste]

Originally Posted by tubeswell

wherever it will fit. Those little chokes are pretty small. Might be able to get it right on the end there, or between the two trannies

Chokes have one major problem, noise pickup. Placement can be very important when it comes to elimination noise. You might want to play with placement and orientation before you drill the mounting holes

[MikeMurray]

Originally Posted by celeste

Chokes have one major problem, noise pickup. Placement can be very important when it comes to elimination noise. You might want to play with placement and orientation before you drill the mounting holes

Interesting - thanks.

[Duke]

Another question has "popped" up. I put the cathode bypass cap on a switch. When I turn the switch on to bypass mode, there is an audiple POP sound. Right now I'm running the cap directly from the board to the switch and then a wire to ground. Would it make a difference to run the current from my board to the switch, and then the cap from the switch to ground? I'm guessing the pop may be from stored current in the cap being released when switched on. Experts? BTW, thanks for all the help getting this thing dialed in.

[tubeswell]

Originally Posted by Duke

Another question has "popped" up. I put the cathode bypass cap on a switch. When I turn the switch on to bypass mode, there is an audiple POP sound. Right now I'm running the cap directly from the board to the switch and then a wire to ground. Would it make a difference to run the current from my board to the switch, and then the cap from the switch to ground? I'm guessing the pop may be from stored current in the cap being released when switched on. Experts? BTW, thanks for all the help getting this thing dialed in.

The pop is the cap charging. If you put a high value (2M2 +) resistor across the switch so that the switch shorts the resistor when engaged, it should help eliminate the pop. And when the switch is open, the high value of the resistor effectively means that no current is getting into the bypass cap anyway - so the cathode resistor is effectively un-bypassed - see concept