• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Kofi Annan in: "Kofi's Baby Huey"

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Sheldon

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Joined 2003
Bas Horneman said:
Yes you are correct of course. I knew that. But just wanted to demonstrate clearly the branching after the choke. :)
Click to expand...

Problem is, it doesn't demonstrate the correct outcome, and it doesn't properly represent the branching. To accomplish both, it would be better to model as summed parallel branches, and have a separate (not in PSUD) schematic. This applies to parallel chokes too (which would be modeled as 1/2 the value).

BTW, if you add series resistance as shown, and it is followed by a good sized cap, your supply impedance will be largely determined by the final cap, providing it big enough to deliver current at all audio frequencies. Film cap should go there if you've got a good sized one.

Sheldon
 
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boywonder

boywonder

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Joined 2008
Sheldon said:
BTW, if you add series resistance as shown, and it is followed by a good sized cap, your supply impedance will be largely determined by the final cap, providing it's big enough to deliver current at all audio frequencies.
Sheldon
Click to expand...

Never thought of it that way......good to know.........So if the final cap can provide the juice, the PS output impedance is essentially the ESR of the final cap? How do you know when it's big enough?
 
S

Sheldon

Member
Joined 2003
boywonder said:
Never thought of it that way......good to know.........So if the final cap can provide the juice, the PS output impedance is essentially the ESR of the final cap? How do you know when it's big enough?
Click to expand...

Good question. The best way to do that without the math background would be to model it in spice.

But I think you can look at it like any other RC circuit. Consider the final supply cap and the following impedance to form a high pass filter. Simplifying: the reflected load through the transformer would represent R in the high pass circuit. So if your transformer is 5k, and your final cap is 40uF, the -3dB point would be around 1Hz. But that's about 37% ripple. Of course, at 20Hz it will be much lower, so I'm guessing that it's in a good ballpark, but I'm not sure of the correct way to calculate the ripple at that frequency. And the preceding resistor and circuit will interact, as will variations in speaker impedance. Maybe someone can come up with a good rule of thumb. But even if it's simmed, you still need to decide how much ripple is acceptable.

Sheldon
 
chrish

chrish

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Joined 2003
Sounds interesting Kofi. I have had my Baby Huey for a while now with the Edcor output transformers. I am in the process of building a pair of PP 6L6 amps with Tamura output iron. I have my speakers set up with active crossovers, so when I put my 6L6 amps in the system I am either going to ditch the active crossover and have the new amps power the both drivers, or tweak the Baby Huey for tweeter duty. For this purpose I was thinking of upgrading the output transformers, so would be very interested in the specification you ordered through electra-print and if you are able to, an indication of the price.

Regards,

Chris
 
Kofi Annan

Kofi Annan

Member
Joined 2004
homepage.mac.com/jasonandpatti/PhotoAlbum1.html
chrish said:
...would be very interested in the specification you ordered through electra-print and if you are able to, an indication of the price.

Regards,

Chris
Click to expand...

Sure.

OPT: 100mA / 44% UL taps / 8K primary / 8-ohm secondary / 15W / $115.00 each plus shipping

Power: 200mA / 275-0-275 / 5V @ 3A / 6.3V @ 6A / $130.00 for M19 laminations, $172.00 for M6 (M6 runs cooler, according to Jack).

Hope this helps.

Kofi
 
Kofi Annan

Kofi Annan

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Joined 2004
homepage.mac.com/jasonandpatti/PhotoAlbum1.html
Two bias blocks completed. Two to go.

Yeah!

Kofi!
 

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Kofi Annan

Kofi Annan

Member
Joined 2004
homepage.mac.com/jasonandpatti/PhotoAlbum1.html
Got some 20K resistors, so I'll use those...

I know its been a while, but the top plate is now dry and I'm ready to start the serious soldering.

First question of the day-- what's the best way to test the bias blocks and CCSssessses? Can i put a resistor across them and test before they come in contact with the rest of the circuit? If so, what value resistor would be best?

Pictures coming...

Kofi
 
Kofi Annan

Kofi Annan

Member
Joined 2004
homepage.mac.com/jasonandpatti/PhotoAlbum1.html
AAARRRGGGGHHH!!!!

So, I was clipping a lead today on the PSU side and the little bastard bounced around the chassis top and went into the MOTHERFATHER HOLE in the MOTHERFATHER TRANNY on the primary side.

Anyone got any good ideas on how to get this out? Do I need to pull the transformer apart or can I sigh it out somehow?

FFFUUUUDDDGGGGEEE!!!

KKKOOOFFFIII!!!
 
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