No more 60 Hz hum in a PL2000 preamp.

[George S.]

Well Joe, I don't know if I really know much more until I do some reading about this. I assume there's a powered iron toroid inside these. It'll be interesting to find out how they work and why.
Listening to the same album at same volume with the 10 VA unit. Not near as good as the 25 VA unit. Bass definition suffers and transients aren't as sharp. Midrange is muddy.
Tomorrow I'll permanently install the 25 VA unit after calculating CRC snubber values.
Hmm, wonder what ringing one of these looks like on the scope. Think I'll go look at it now.

 

[Gepetto]

Well Joe, I don't know if I really know much more until I do some reading about this. I assume there's a powered iron toroid inside these. It'll be interesting to find out how they work and why.
Listening to the same album at same volume with the 10 VA unit. Not near as good as the 25 VA unit. Bass definition suffers and transients aren't as sharp. Midrange is muddy.
Tomorrow I'll permanently install the 25 VA unit after calculating CRC snubber values.
Hmm, wonder what ringing one of these looks like on the scope. Think I'll go look at it now.

Not powdered iron at all George. A continuous strip of silicon steel wrapped into a donut. No gap like exists in all E-I cores.

 

[George S.]

Not powdered iron at all George. A continuous strip of silicon steel wrapped into a donut. No gap like exists in all E-I cores.

I have much reading to do. Silicon steel!
It rings much cleaner than the original transformer. Also adjusts to critical damping easily. I'll run back through this tomorrow before installing it and the snubbers.

 

[George S.]

A 22R gives perfect snubbing for the CRC network. More info can be found here.
https://www.diyaudio.com/community/...rmer-snubber-using-quasimodo-test-jig.243100/

 

[George S.]

Fitting the Antek AN-0212. Yes it just fits, can slide a piece of paper between it and the board and chassis flange. Since there's little left original on the unit, and I want a little more clearance, going to Dremel the board edge and gain it.

 

[J!m]

Can you stand stand it on edge?

 

[George S.]

Can you stand stand it on edge?

Could, but for simplicities sake and easy service, now have more than enough clearance for peace of mind.

 

[e30m3mon]

Fitting the Antek AN-0212. Yes it just fits, can slide a piece of paper between it and the board and chassis flange. Since there's little left original on the unit, and I want a little more clearance, going to Dremel the board edge and gain it.

You're going to have to re-brand this, you know..."George-S Linear" sounds good to me

 

[George S.]

Al, couldn't have done it without Joe, Lee, and Mark L..
Got the transformer fitted. Very happy with the added clearance.
Going to tack in the secondaries. Then use jumpers on the primaries to configure Line and Neutral connections for lowest noise on the QuantAsylum RTA.

 

[e30m3mon]

Al, couldn't have done it without Joe, Lee, and Mark L..
Got the transformer fitted. Very happy with the added clearance.
Going to tack in the secondaries. Then use jumpers on the primaries to configure Line and Neutral connections for lowest noise on the QuantAsylum RTA.

You're doing all that hands-on part, George, so without your good work none of this would be realized.
Yes - the team effort and shared expertise is what makes Phoenix a truly unique and enjoyable place to hang out. Making things better makes us all better! I can't wait to open the covers on the 2000-II (and possibly others) ... again!

 

[George S.]

I get slightly lower 60 Hz noise on the QA400 with the red primaries connected to Line, and the black primaries connected to Neutral.
Rail voltage is nicely balanced at plus and minus 16.3 VDC with NO DROPPER RESISTORS. Yahoo!
Going to take it down for a listen in the main system.
If I like it, then I'll install the snubbers and shorten the primary and secondary wiring.

 

[George S.]

I built the CRC snubbers on a old board and will transfer them over. The resistors are 22R. Each resistor is in series with a .15 uF cap. Then there is the additional .01 uF film cap.
Additionally, I have Vishay SBYV27-200 soft recovery rectifier diodes installed.
More info can be found in the PDF.

 

[George S.]

Finished. The original PL shield just fits with no trimming.

 

[gene french]

Finished. The shield just fits with no trimming.

super!!!

 

[George S.]

So was it worth it? Oh hell yes! Absolutely no hum with volume cranked, noise floor is so low I'm hearing things I've never heard before. Bass is super tight and defined. The lower frequencies are now being passed more fully to drive the subs. Transients are sharp, sharp, sharp.
Best upgrade to the PL2000 I've made so far! Thanks Joe!

 

[gene french]

So was it worth it? Oh hell yes! Absolutely no hum with volume cranked, noise floor is so low I'm hearing things I've never heard before. Bass is super tight and defined. The lower frequencies are now being passed more fully to drive the subs. Transients are sharp, sharp, sharp.
Best upgrade to the PL2000 I've made so far! Thanks Joe!

beautiful!!
its all about the music!!!

 

[George S.]

Testing the preamp on the QuantAsylum QA-400. THD is less than .003%

 

[George S.]

THD+N is less than .01% I do have a noisy room. Many computers and Allman Bros playing in the background on another system!

 

[George S.]

SNR greater than 80 dB.

 

[George S.]

Frequency Response tested with White Noise stimulus. Very similar results with Impulse, ExpoChirp, and FarinaChirp stimulus. I see a issue here that Joe has talked about in past. Close up follows.