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Old 17th March 2003, 01:26 AM   #21
jwb is offline jwb  United States
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Great thread starter Harry. I especially liked page 72 of the Linear app note.

None of the articles I read cover the basics, and audio hobbyists may not be well acquainted with the underlying physics. Everyone should read up on the subject of oscillating systems, either from the electrical angle of LC tank circuits, or from the mechanical approach of spring-mass oscillators. Of special importance are the concepts of underdamped, critically-damped, and underdamped oscillators. Critically damped systems settle to the desired level in the shortest possible time. Underdamped systems oscillate before reaching the desired level. This is seen as circuit noise, EMI, etc. Overdamped systems reach the desired level very slowly, and can be the cause of too high impedance in a circuit.

Without understanding this you cannot design a damper!

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jwb
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Old 17th March 2003, 04:43 AM   #22
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Default It's easy to talk about specs, but it's hard to find a good sounding diode

No, it is not easy to talk about specs and interpret them. What constitutes a good sounding diode may be dependent on the circuit in which it is used. I started this whole dialog to address some common questions that seem to resurface from time to time. For example:

Are shottkys a better choice than fast recovery diodes?

How do snubber circuits work?

Will putting a snubber circuit on a conventional diode bridge work as well as a bridge made from fast recovery diodes?

Is putting a capacitor across each diode and/or the transformer windings a good idea?

What makes a good sounding fast recovery diode how do I pick one with having to listen to them all?

Are 30 Amp diodes better sounding than 8 Amp diodes?

What diodes sound best for digital supplies?

Will snubber circuits work with fast recovery diodes?

There are dozens of FRED type diodes, and listening to all of them is not practical or economical for most people. There seems to be a diode of the week syndrome that is very frustrating to many people. I believe that many of the fast recovery diodes chosen are not the best ones to use. There are many new types coming out with optimization of other parameters than the fastest reverse recovery times. The idea is to turn this into a little more engineering and a lot less mysticism. There are dozens of fast recovery diodes that might be worth listening to and hundreds of permutations of snubber circuits or parallel
capacitors that could be tried. Anyone have a few hundred hours to do this entirely by listening test alone. I have been messing with this diode stuff for about 10 years and still have a lot questions. I have also done a lot of work on EMI reduction in telecom and have some new perspective on diode noise and RFI suppression. I used the IXYS diodes, based on a little research, long before their word of mouth reputation spread. Those who wish to do all this based only on listening test else are free to ignore this thread. For those willing to study the literature, measure, model, AND LISTEN; I welcome and need your input. I would really read the references in this thread as you will have no idea what is being discussed without doing so.


A tutorial on resonant circuits and critical damping (those who call it dampening are all wet) can be found here:

http://www.ee.surrey.ac.uk/Teaching...circuit-theory/

The applet at: http://www.ee.surrey.ac.uk/Teaching...ampedcases.html
is very interesting to see the effect of damping factor on a resonant circuit.
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Old 17th March 2003, 08:17 AM   #23
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Fred,
dunno what happened, but your last links seem to be wrong (at least for me). I think you meant this one for theory, and pointed here for the applet. Right ?
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Old 17th March 2003, 08:36 AM   #24
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Glad to have you back, Fred!
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Old 17th March 2003, 11:06 AM   #25
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Default Gaincard Diodes

Quote:
Originally posted by vladimir



It seems that original Gaincard use FE5D fast recovery diodes: one single bridge. Has anyone tried it ?
http://db.audioasylum.com/scripts/t....ks&m=60943

Hi Vladimir, You brought up a very interesting link for adepts to the gainclone showing the inwards of the Gaincard and clues to the construction of the Power Humpty.
The FE5D is a nick-name for the General Semiconductor BYV28-200 diode. Datasheet now at www.vishay.com (200V 3.5A )
http://www.vishay.com/search?query=byv28-200

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Old 17th March 2003, 12:16 PM   #26
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Default applets and oranges

The correct URL for the damping applet is at:

http://www.ee.surrey.ac.uk/Teaching/...mpedcases.html

Be sure to read the previous sections. It takes one from the definition of resistance, inductance, and capacitance to describing phasors, complex impedance, and finally to the RCL circuit and damping. It is a good intro or refresher to the concept of reactance and resonance.

Some people have remarked on the difficulty of measuring rf ringing in a power circuit and I will agree. The combination of scope and an RF detection and rectification circuit is probably the
best approach. An RF "sniffer" circuit can be constructed and a simple circuit is at:

http://sound.westhost.com/project74.htm
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Old 17th March 2003, 12:41 PM   #27
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Default The FE5D is a nick-name for the General Semiconductor BYV28-200 diode.

Actually these are not the same type diodes. One is a 5 amp diode and the other a 3.5 amp diode. Their reverse recovery time is also different. They do share the same DO-204AP package and are similar but not identical.
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Old 17th March 2003, 01:22 PM   #28
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Cool Re: The FE5D is a nick-name for the General Semiconductor BYV28-200 diode.

Quote:
Originally posted by Fred Dieckmann
Actually these are not the same type diodes. One is a 5 amp diode and the other a 3.5 amp diode. Their reverse recovery time is also different. They do share the same DO-204AP package and are similar but not identical.
Hi fred,
Yes you are absolutely right. I looked in the wrong column.
Datasheet of the FE5D is here:
http://www.vishay.com/search?query=fe5d
So it IS a 5A diode.
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Old 17th March 2003, 01:49 PM   #29
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Default Diode dilema

I based my comparison on the data sheets from Vishay and will do some further reseach. I didn't mean to blow it out of proportion since they do appear to very similar even with the differences stated in the data sheet. I am also doing further investigation into snubber networks and their optimization with various diode types. Reading further articles on EMI generation from diodes reverse recovery effects has uncovered even more knowledge on this subject. I will try to conduct some Spice modeling and measurements to go along with the theory and diode data sheet numbers. The topic is really worth investigating since RFI in audio equipment can very much effect the sound. The noise from the rectifier bridge may be a major contributer to this RFI noise.

I have also invited alfsch to share his measurement results with us from the post in the "replacement diodes for 1N4007" thread:

replacement diodes for 1N4007
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Old 17th March 2003, 01:54 PM   #30
massimo is offline massimo  Italy
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Default Re: McCormack strategy...

Quote:
Originally posted by Tube_Dude
MackCormack strategy...for the two schools of thougt been happy.(fast versus regular diodes)...they use boths!!

D3,4,5,6---Fast

D7 ....to....D14 ---regular 1N4007...

So the best of both wolds!

We can called it...new hibrid rectification!!!
I strongly suspect that D7 to D14 aren't "regular" 1N4007
They look like Telefunken (now Vishay) SF4007 "Super Fast Soft Recovery Rectifier" 1000V/1A according from the Sintered Glass Case SOD 57.
They are also sold by Partsconnexion at 50 cents each.

Thus Mc Cormak takes the best from ONE world....
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