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Cheapest power supply transformers?

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  • #31
    Originally posted by R.G. View Post
    In most tube amps, the power transformer is the single most expensive part in the amp. The output transformer is often a close second. The resistors, caps, tube sockets, etc. are almost negligible. Chassis, enclosure, speakers, controls and switches are also bigger ticket items.

    Then there's the cost of safety. It's important to remember that even one consultation with a lawyer about why this widow or parent is suing you will cost a lot more than you'd make on an amp. So it's really crucial to know how to be sure that anything you ever give/sell to anyone else is made with safety rated parts and wired correctly to not let the high voltage AC and DC in the amp get loose and either kill someone or start a fire.

    Little amps seem safe enough - but that AC power line coming into it hooks to a power station capable of starting fires all day long and not even breaking a sweat; and it only takes about 20ma of 60 cycle AC current to sent some hearts into fibrillation.
    Although times are a little tough right now and I've only built about 73-75 amps this year, and some of those were little 5 watters too....by far the most expensive part of the equation is the damn cabinetry and speaker combo!!
    I'm paying as much as $350.00 for a finished 3x10 cabinet these days and that is without the speakers!
    $140-$160 for a full trio of 20w to 50w transformers is a bargain with respect to the importance of the total project.
    Bruce

    Mission Amps
    Denver, CO. 80022
    www.missionamps.com
    303-955-2412

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    • #32
      That's great! Where was this from?

      Originally posted by Zozobra View Post
      I suppose to put it into perspective I priced up 2x and 4xKT88 PTs

      Spec 1 (2X ~ 250VA):
      400V @ 550mA
      6.3V @ 5A
      41 euros

      Spec 2 (4x ~ 410VA):
      400V @ 900mA
      6.3V @ 8A
      49 euros

      Bear in mind the HT secondary doesn't include power factor but thats a lot of bang for buck! They offer a shrouded 'audio grade' PT option where were 58 euros and 75 euros respectively but I can't see it making a lick of difference to the performance. Also adding additional secondaries wasn't too bad either. I'll probably specify a bias winding when I'm ready to order some bits.

      Certainly the HT requirement you've spec'd there is only 100VA and the heaters will only be another 20-30VA or so on top of that. Certainly sticking the whole thing on a 200VA core will probably be fine (although it always pays to do the maths ) and it should be quite compact and cheap too.

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      • #33
        Originally posted by Enzo View Post
        The original poster, starting this thread, opened with the statement he planned to sell them and make some money, $50 in his example. Absolutely nothing wrong with making them for fun, giving them away, selling them just to cover parts, whatever. But when the stated purpose is to make money at it, I figure those are legitimate things to consider - return on parts investment and labor compensation.
        And also lets not forget what RG said which I'm not sure was taken to heart totally. These days there are people out there that are looking for a reason to sue somebody which is why most Amp Co's and Pro Gear for that matter get their equipment CE Certified or comparable and now the FCC has strict regulations on emissions for transformers and there are some people out there that know these are required and will be looking for you if you don't have them. CE is not cheap by any means and unless you get into mass production not really worth it so while it's cool to make a few bucks amongst maybe some friends around the neighborhood do some research before you go putting this out where gremlins can eat you up.
        KB

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        • #34
          Originally posted by Hellhammer View Post
          That's great! Where was this from?
          TOROIDY.PL Transformatory Toroidalne Producent, Audio, Separacyjne, Trójfazowe, 230/110V, 110/230V, Na zamówienie

          I must stress that I haven't ordered one yet but they've been great to shoot specs with by email. I think a few people on AX84 have used them and I should hopefully have one of the PTs in an amp before the year is out.

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          • #35
            Ok, thanks mate!

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            • #36
              This guy gets transformers made in China. He does the design. Seems like he knows what he's doing but I've never bought from him.

              PP Output Transformers, Tube Power Transformers items in Musical Power Supplies store on eBay!
              WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
              REMEMBER: Everybody knows that smokin' ain't allowed in school !

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              • #37
                Originally posted by jazbo8 View Post
                A cheap DC-DC SMPS with a laptop PS could work, e.g., 12V 4-5A PS could easily power bunch of tubes, and the SMPS takes care of the HV (also powered from the laptop PS). I recently rig one up just to see if the SMPS would be noisy as many have claimed... Alas, it worked just fine, and it was not noisy. For both the SMPS and laptop PS (bought them brand new), I paid <$10 (in China, don't know if the same could be had elsewhere). Anyway, if you have some old laptop power bricks laying around, give them a try.

                Jaz
                How do you get HV out of the laptop PS? You change the transformer? What is the reason all the established guitar amps don't use switchers?

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                • #38
                  More and more amps ARE using SMPS. One reason many do not it that a simple linear supply has fewer hurdles in noise radiation. The law restricts what your product can spew back into the power grid. SMPS can of course be designed to meet all current regulations, but it is not trivial. The most basic skilled designer can put together a linear supply.
                  Education is what you're left with after you have forgotten what you have learned.

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                  • #39
                    Originally posted by Alan0354 View Post
                    How do you get HV out of the laptop PS? You change the transformer? What is the reason all the established guitar amps don't use switchers?
                    A desktop computer power supply will be easier to modify. Lots of dead ones lying around. Trouble shooting tip: If the fan kicks off but the supply shuts down, check/replace the 5V (or 3V) rectifiers. If the fan doesn't kick off, replace the inverter transistors. That will fix about 80% of the dead supplys you find.
                    WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
                    REMEMBER: Everybody knows that smokin' ain't allowed in school !

                    Comment


                    • #40
                      How many volts can I get from a modded laptop supply? Or a desktop supply for that matter? They are smps too right? My primary concern is that they are easy to fry. Transformers are very tough in comparison... I always thought it would be fun and a neat excercise to build a more bullet proof smps from tubes like a 6080... It might be a silly idea but if you short out a tube it may survive where as a transistor would likely die instantly.

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                      • #41
                        Loud/Crate did issue 2 SMPS Tube Amps, a 50W and a 100W one.
                        Both had to be pulled out because constant breakdown and warranty replacement was a financial black hole.
                        The otherwise excellent Power Block was pulled out by the same reason.
                        SMPS *can* be well made, but not everybody is up to it. (yet).
                        In a few years they will be as reliable as iron ones and still much cheaper.
                        Juan Manuel Fahey

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                        • #42
                          These days most SMPS are designed by engineers that specialize in their design. Most work for semiconductor companies. It's very complicated, even for a wall wart size supply or a CFL light bulb. If you need power factor correction, it's more complicated. International Rectifier makes a Power Factor Correction chip. You can't see the data sheet online, it says "consult factory". They'll design it in for you if the quantities are high enough, but then you are stuck using their chip.

                          Messing with SMPS is not a job for the novice. You need the right equipment and a lot of experience. You can get just about any voltage if you can wind enough turns on the core. Every part needs to be scrutinized. Capacitor ripple current, diode switching time are things that can't be overlooked.

                          The real limit is the number of Watts. A 100 Watt guitar amp would require at least a 300 Watt SMPS. Momentary overload equals shutdown or failure.
                          WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
                          REMEMBER: Everybody knows that smokin' ain't allowed in school !

                          Comment


                          • #43
                            Originally posted by loudthud View Post
                            A 100 Watt guitar amp would require at least a 300 Watt SMPS. Momentary overload equals shutdown or failure.
                            I don't know much about it but this is what I've read is the real drawback as to their application in musical instrument amplifiers in general. Bass amps with SMPS power supplies have less whollop, etc. I've read this a few times. So, could a 300W or 400W SMPS supply be built for a 100W application AND still be cheaper than the standard power supplies that have been used in such 100W amps???
                            "Take two placebos, works twice as well." Enzo

                            "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                            "If you're not interested in opinions and the experience of others, why even start a thread?
                            You can't just expect consent." Helmholtz

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                            • #44
                              Sure. You can put a whole lot of small parts together for the cost of an SVT sized iron transformer.


                              The problem with blanket statements like SMPS bass amps lack whollop is that what they are really hearing is that the particular bass amps with SMPS they HEARD lacked whallop. I'd wager it isn't the SMPS-ness of the amp that is the problem, but rather than underdesigned SMPS. They hear an amp they don't like, see that it has an SMPS, and decide the SMPS is at fault just for being an SMPS.

                              If we were used to good old linear solid state 1000 watt bass rigs and heard a 100 watt tube bass amp for the first time, we might be tempted to say tube bass amps lack oomph.. But no, underpowered tube bass amps lack the oomph.

                              After all, we have 3000 watt PA amps with SMPS and they work fine
                              Education is what you're left with after you have forgotten what you have learned.

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                              • #45
                                Why dont you wind your own transformers? It's not hard. A stack of iron, some wire and a bobbin... and the up side is you get just what you want not a big bundle of compromise.

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