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#1
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Fast Recovery Diodes
I've built several pieces of electronic gear from kits and I can read
schematics. I have a factory guitar amplifier and I've been told that if I add FRED's that I will get better note separation on chords and better low end. I have a schematic of the amp. Where do I put the FRED's? Are they inline between certain components or are they added as bypass to components. Should I look for any diodes anywhere in the circuit and just replace those? And here is the big question. DANGEROUS VOLTAGES! The two tube amps I have built I did so from parts and when I plugged them in they worked so there was no trouble shooting and any trimming was safe. With this tube guitar amp unplugged and installing these FRED's am I playing with fire? Do I have to drain all the caps prior to doing work? How do I do that safely and is there anything else? Thanks. Also - if I get the go ahead to proceed with this mod who makes the best FRED's? |
#2
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You are trying to follow some type of myth. There are many of these around.
Fast Recovery Diodes are used in specific types of switching power supply designs, and in specific applications where high speed polarized damping of high speed pulses are required, as such in the flyback and or scan circuits. The damper diode in a TV high voltage section is a fast recovery type diode These are mainly used in TV equipment. FRD's have specific specification ranges to fit the applications that they are to be fitted to. I would guess that they can be used as expensive rectifiers in your tube amp, but this would be a waste, and may not perform as well as the standard type of diodes. When the AC from the main power transformer is being rectified, it is best to use a soft type of rectifier, such as a tube rectifier that is normal for a tube amplifier. Standard silicon diodes may be used, but damping resistors, with some added small bypass caps should be used. The choice of the diodes, and related parts are very dependent on the required specs for the design. This has to do with noise factors, and the current pull of the supply section that is being handled. In a tube amplifier, running the tube heaters on DC may help to keep some of the AC background hum or line noise down to a bit of a lower level. This is not as simple as putting rectifiers, and large filter caps to drive the tube heaters. A full blown adequate DC supply would be required. I remember seeing in many tube amplifiers a hum bucking type of configuration being used in the heater design, using a type of balance pot to keep the ground reference balanced between the heaters. A simple form of this is to have the heater source floating from ground, and feeding the tube heaters. A wirewound variable resistor of a few Watts rated is wired to each side of the heater supply, and the centre is put to ground. This control is mounted on the chassis preferably at the rear of the amp, and set up as a service adjustment. This control is to obtain the best hum balance. Going by memory this control was generally a 100 ohm linear, wire wound, 2 Watt control. The procedure was to set this control for the minimum amount of background hum. In many amplifiers, it was not critical. But at some locations, where there were electrical grounding problems, this adjustment helped out. One thing you can also do in the wiring of a tube amplifier, is that the heaters should all be wired back to a central distribution for the heater supply. Even though they are wired in parallel in these amplifiers, it is best to have them all in a star or spoke like configuration for the heater supply distribution. I have seen tube heaters wired in a sort of daisy chain parallel affair. This is not a good way to do it. In the lower cost amplifiers, I have seen one side of the tube heaters connected directly to ground. Then the supply side is wired in a sort of daisy chain from the source all the way to the last tube. This is not a balanced heater supply, and can be susceptible to have more hum and noise radiated back from the heaters. I hope this all helped to set you a bit straighter with this. -- Another big rip-off I see these days, are the very expensive AC cords for amplifiers and electronic equipment. All of this equipment uses DC after the power supply for the operation where the sound is processed. As long as an AC cord that is rated for the current pull of the device is used, there is no difference if it is made of gold, silver, or whatever! If you were to see the wiring from the AC outlet, to the breaker panel, and then to the wires to power utility company's distribution, your nice cheap AC cord looks a lot better! As long as the AC has a distortion of less than about 5% with no serious spiking, it is good enough to run any electronic equipment. What is important is that the proper supply volts are present, and that the current source is adequate to be stable. -- Jerry G. ====== "Terrified" wrote in message ... I've built several pieces of electronic gear from kits and I can read schematics. I have a factory guitar amplifier and I've been told that if I add FRED's that I will get better note separation on chords and better low end. I have a schematic of the amp. Where do I put the FRED's? Are they inline between certain components or are they added as bypass to components. Should I look for any diodes anywhere in the circuit and just replace those? And here is the big question. DANGEROUS VOLTAGES! The two tube amps I have built I did so from parts and when I plugged them in they worked so there was no trouble shooting and any trimming was safe. With this tube guitar amp unplugged and installing these FRED's am I playing with fire? Do I have to drain all the caps prior to doing work? How do I do that safely and is there anything else? Thanks. Also - if I get the go ahead to proceed with this mod who makes the best FRED's? |
#3
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"Jerry G." wrote in message ... Another big rip-off I see these days, are the very expensive AC cords for amplifiers and electronic equipment. All of this equipment uses DC after the power supply for the operation where the sound is processed. As long as an AC cord that is rated for the current pull of the device is used, there is no difference if it is made of gold, silver, or whatever! If you were to see the wiring from the AC outlet, to the breaker panel, and then to the wires to power utility company's distribution, your nice cheap AC cord looks a lot better! As long as the AC has a distortion of less than about 5% with no serious spiking, it is good enough to run any electronic equipment. What is important is that the proper supply volts are present, and that the current source is adequate to be stable. Have you seen the expensive duplex outlets? I would love to be a mouse in the telephone room of the power company billing office when someone calls and wants the service wiring upgraded to OFC pole to home. Some company's already sell "updated" ring wiring for homes! I feel fortunate to live in a rural comunity, I have my very own pole pig, pretty clean power. |
#4
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Jerry G. wrote:
You are trying to follow some type of myth. There are many of these around. Fast Recovery Diodes are used in specific types of switching power supply designs, and in specific applications where high speed polarized damping of SNIP Here is the link for reference as to what I now know is HYPE http://vacuumtube.com/Products.htm##...overy%20Diodes Scroll to the bottom last mod offered Fast Recovery Diodes (FREDs) and Schottky Diodes |
#5
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On Wed, 23 Feb 2005 12:21:35 -0500, Terrified wrote:
Jerry G. wrote: You are trying to follow some type of myth. There are many of these around. Fast Recovery Diodes are used in specific types of switching power supply designs, and in specific applications where high speed polarized damping of SNIP Here is the link for reference as to what I now know is HYPE http://vacuumtube.com/Products.htm##...overy%20Diodes Scroll to the bottom last mod offered Fast Recovery Diodes (FREDs) and Schottky Diodes By all means experiment. That is what all this is about! Be very careful though, playing with valve (tube for those of you on the other side of the big pond...) amps can be fatal - literally. You must *always* follow safety precautions when working on high voltages or in situations where high voltages could possibly occur. You only get one life... If your amp has a valve rectifier and you change it to any solid state type then you must be fully aware of what will happen. Unless you make other changes the high voltage rail will go much higher due to the lower voltage drop in the rec. This will, in many cases, damage things like capacitors and may even damage some output valves in some cases! The diode "myth" isn't complete twaddle. It has some basis in truth as the effect on rectification can be seen on a scope trace. Whether anyone can genuinely *hear* the difference in types of diodes is something else! -- Mick (no M$ software on here... :-) ) Web: http://www.nascom.info Web: http://projectedsound.tk |
#6
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"Terrified" wrote in message ... Jerry G. wrote: You are trying to follow some type of myth. There are many of these around. Fast Recovery Diodes are used in specific types of switching power supply designs, and in specific applications where high speed polarized damping of SNIP Here is the link for reference as to what I now know is HYPE http://vacuumtube.com/Products.htm##...overy%20Diodes Scroll to the bottom last mod offered Fast Recovery Diodes (FREDs) and Schottky Diodes It is just breathtaking to think that people are that mercenary to take such advantage of ignorant tube-heads. Maybe it is their own fault for not studying how the real electronics work. |
#7
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From: "Arny Krueger" Subject: Fast Recovery Diodes Date: Wednesday, February 25, 2004 11:52 AM "Terrified" wrote in message I've built several pieces of electronic gear from kits and I can read schematics. I have a factory guitar amplifier and I've been told that if I add FRED's that I will get better note separation on chords and better low end. My wife was told that if she wore a copper bracelet, her arthritis would go away. Guess what? There's a common gambit in audio where people are told weird things that they don't realize is the technical equivalent of perpetual motion. In audio, its possible to convince yourself that doing anything or nothing makes something sound a little better, at least for a while. |
#8
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Terrified wrote in :
I've built several pieces of electronic gear from kits and I can read schematics. I have a factory guitar amplifier and I've been told By another musician, a friend, an audiophile? that if I add FRED's that I will get better note separation on chords No you won't. and better low end. No you won't. I have a schematic of the amp. Where do I put the FRED's? Are they inline between certain components or are they added as bypass to components. Should I look for any diodes anywhere in the circuit and just replace those? This says you are not qusalified to do this. Stop before you permanently damage your equipment or yourself. |
#9
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"Arny Krueger" wrote in message ... From: "Arny Krueger" Subject: Fast Recovery Diodes Date: Wednesday, February 25, 2004 11:52 AM "Terrified" wrote in message I've built several pieces of electronic gear from kits and I can read schematics. I have a factory guitar amplifier and I've been told that if I add FRED's that I will get better note separation on chords and better low end. My wife was told that if she wore a copper bracelet, her arthritis would go away. Guess what? There's a common gambit in audio where people are told weird things that they don't realize is the technical equivalent of perpetual motion. In audio, its possible to convince yourself that doing anything or nothing makes something sound a little better, at least for a while. Junk science is just new age superstition. |
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