No more 60 Hz hum in a PL2000 preamp.

It's back in the system running on the original transformer. It's very quiet with no hum. But it's lost the punch and bass definition it had with the Hammond transformer.
The difference is really noticable. These preamps definitely need a larger transformer.
Going to finish listening to side 2 of the album. Then download the datasheet for the Antek, and make some paper cutouts to make sure it'll fit.
12 deg F. outside, turned on the 8 Lava Lamps to heat up the room some. It'll probably take about 4 hours for the big one to get going.
 
They'll fit easily. Ordered 2. I've never worked with a toroidal transformer before, but the datasheet looks like the wiring is a non-issue. Looks like I join the primary connections and join a single green and blue secondary to create the center tap.
 
The nice thing about toroidal transformers are their lower "hum field". You might also consider mumetal shielding around it. Cured a problem I was having although steel will work too. It's a function of the strength of the field.
 
I'm cheap so I just remove the offender from the area...

The phono preamp has been successfully built MANY times with the switch mode PS right next to the amp boards, but I moved mine out anyway.

In that case the "filter board" was specifically designed and tailored to filter that specific power supply. The filter board I mounted in the main cabinet, but the A/C line filter and SMPS were outboard, with low voltage DC going up to the main cabinet only, into the filter board (tucked in a corner inside a steel box) and then onward to the power switch and amp boards.
 
BlueCrab said:
Maybe this:

Toroidal shield
Click to expand...
Jim BC, I do have a good size sheet of mumetal left over from a past project, but that cover is the bomb. Going to open up a preamp and find a cover that fits. My mumetal has adhesive on it, so I can always stick it on the cover if needed. Thanks! I will have to revisit the rules for bonding mumetal to ground if it's needed.
 
J!m said:
I'm cheap so I just remove the offender from the area...

The phono preamp has been successfully built MANY times with the switch mode PS right next to the amp boards, but I moved mine out anyway.

In that case the "filter board" was specifically designed and tailored to filter that specific power supply. The filter board I mounted in the main cabinet, but the A/C line filter and SMPS were outboard, with low voltage DC going up to the main cabinet only, into the filter board (tucked in a corner inside a steel box) and then onward to the power switch and amp boards.
Click to expand...
Jim, yup, understood. As last resort I'll put the transformer in it's own enclosure. That would simplify matters, but I'm going to try to keep it self contained if possible.
 
AnTek also makes those covers. Time to revisit the site and find the one for that transformer.
 
Well, the cover for the AN-0212 transformer is a CA-002. Not listed on the website, but it is in their eBay store. Too big, won't fit the available room in the chassis. None the less, I have two of those 25VA on the way.
The next smaller size is the AN-0112, a 10VA unit. This one takes a CA-001 cover which will fit the available space.
So, also ordered the smaller units and covers.
We'll see how this sorts out once the stuff arrives and I can get to it.
Lee once said "We need a great sounding PL preamp".
That's the goal.
 
J!m said:
Maybe put the Aragon guts inside the PL box?

Or a WOPL preamp? Joe?
Click to expand...
I started to clone a Acurus L10 for the PL2000 chassis. Even have enough NOS Toshiba transistors for several builds. But quality switches that fit the chassis and faceplate are a issue. I'll get back to it once I retire and can keep from getting sidetracked.
Given all the different preamps built, there's probably no way to make a preamp retrofit board profitable.
Easier just to buy a Acurus or whatever and call it done.
 
George S. said:
Well, the cover for the AN-0212 transformer is a CA-002. Not listed on the website, but it is in their eBay store. Too big, won't fit the available room in the chassis. None the less, I have two of those 25VA on the way.
The next smaller size is the AN-0112, a 10VA unit. This one takes a CA-001 cover which will fit the available space.
So, also ordered the smaller units and covers.
We'll see how this sorts out once the stuff arrives and I can get to it.
Lee once said "We need a great sounding PL preamp".
That's the goal.
Click to expand...

Amen George!!
 
Hopefully it fixes your issue George. You may also learn some new tidbits about leakage flux
 
Gepetto said:
Hopefully it fixes your issue George. You may also learn some new tidbits about leakage flux
Click to expand...
Yes. And if I do have to remote mount it, I'll have options. After hearing it with the upgraded transformer, it's depressing to listen to it now. It made such a huge difference.
 
Got the toroidal transformers in. The big one just fits without a cover, the small one just fits with a cover.
The small one has epoxy potting compound in the center. Hole needs enlarged to fit the mounting stud.
Going to try them both.
 

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Testing the big one with no shield, the AN-0212, a 25 VA unit. Pretty damn amazing! Absolutely no hum with the volume cranked. It's sitting on top of the stack with both top and bottom covers off, and it's dead silent in all input modes.
The extended and defined bass is back, the meters on the 700 Pro driving the stereo subs are back to dancing. Channel separation and balance are also better defined. And this is with a old Steve Miller album and Shure M91ED.
It really shouldn't sound this good with a LP and the background be this quiet.
And, I'm back to feeling the bass sound pressure at a very moderate volume.
Going to test the smaller 10 VA unit with the cover on it.
Damn I'm happy this is going to work as a self contained unit. Thanks Joe!
 

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George S. said:
Testing the big one with no shield, the AN-0212, a 25 VA unit. Pretty damn amazing! Absolutely no hum with the volume cranked. It's sitting on top of the stack with both top and bottom covers off, and it's dead silent in all input modes.
The extended and defined bass is back, the meters on the 700 Pro driving the stereo subs are back to dancing. Channel separation and balance are also better defined. And this is with a old Steve Miller album and Shure M91ED.
It really shouldn't sound this good with a LP and the background be this quiet.
And, I'm back to feeling the bass sound pressure at a very moderate volume.
Going to test the smaller 10 VA unit with the cover on it.
Damn I'm happy this is going to work as a self contained unit. Thanks Joe!
Click to expand...
And now you know some important things about leakage flux George
 
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