UcD400, in summary.

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deandob

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Joined 2002
Interesting that these are hard to find, I didn't have any trouble at the time when I was looking for them (which is unusual, I usually pick the hard to get parts!).

A CRD is actually just a JFET with a resistor on the gate that regulates the saturation current. It is possible just to use a normal JFET and setup a test rig to find matching pairs.

Check out this article for more options and a good background on this method.
Bias OpAmps for Class A

Regards,
Dean
 
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deandob

Member
Joined 2002
Yes, they have a good range but expensive. Also not too far from home so good for pickup if needing a part quickly.

There are probably alternative parts that could be purchased at Mouser or Digikey but would need more research, and there are other places that findchips has found but they have high order quantities. Maybe someone in the US who knows the US parts market better can give you a better indication.

Regards.
Dean
 
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Ric Schultz

Member
Joined 2002
tweakaudio.com
On the scope you could see a very slight increase of wiggle on the sine wave. So, slightly more RF....nothing like Nuforce looking waveforms....now there is some serious RF. Sound is better...slightly better imaging....not seriously better, but noticeable....probably not worth it unless you are really tweaky...many things I did made more difference....putting the transformer up on one half inch plywood and using bronze (non magnetic) hardware makes way more difference, for instance. Really, you need to get rid of those silly steel plates and bolts on your trannies.....open up the sound! Lift them off the chassis with wood.....yes, works. Use tie wraps to hold them down....I use bronze bolts because I have epoxied center.....if you have big round hole then 4 large tie wraps will hold it down fine....maybe not for cross country shipping.....but fine.....a large tie wrap can handle 50lbs. each....four of them...now you are talking 200lbs....how much does your transformer weigh?
Happy tweaking!
 
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Ric Schultz

Member
Joined 2002
tweakaudio.com
Rather than thinking about physics....just listen...very easy to do mod....if you hear a difference and you like it great....if you don't, not much time or money spent. Just do it! And tell us what you hear! Transformers seem to like to breath...like us all. They sound closed down with steel and even aluminum next to them....take the steel bolts out of the center of your diode bridges too....use bronze or brass.....better sound....and while your tweaking get rid of LEDs....now they really mess up the sound. Listen...listen...listen and learn....and enjoy. Of course, you will want to damp the ringing heatsinks....mucho bad...those ringing heatsinks.
 
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LTK

Member
Joined 2003
My transformers are heavy 650vA, epoxy filled centre so no top plates are needed, they are screened and have a damping pad attached to the bottom.
They are not the normal off the shelf types
My bridge rectifiers are discrete
Are you sure some of these tweaks are not the placebo effect
 
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Ric Schultz

Member
Joined 2002
tweakaudio.com
Ever hear of Jimmy Hughes?

He is on of your British reviewers.....he is the one that turned me on to the LED distortion thing in the mid eighties....he said he removed the LEDs from a Threshold amp and some preamp and noticed a more pure sound....I had no LEDs then, so for years just stored the info in my bio computer and when I had my first DAC (Stax Talent) I was modding it and removed the LEDs on the front panel and realized how right he was. So, this hocus pocus about LEDs comes from that Island we all love. The British started all this "listening to stuff".....I blame them. Actually, very grateful for the knowledge and better sound. Thank you listeners.......LEDs add some kind of distortion/noise to the power supply that modulates the signal....at least that is what I hear.

Yes, spin the volume control twice counterclockwise before pointing it towards magnetic north (in the northern hemisphere)......he he.

It is so much fun to post here about sound differences....there are so many here that share my enthusiasm for better sound! he he I am sure there will be hundreds of posts from those that will be doing these tweaks and reporting back. Well, maybe not hundreds...he he... but if just one person benefits from this info.....great....they have better sound for essentially nothing. Happy tweaking!
 
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