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Old 26th May 2004, 01:32 AM   #1
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Default Transformers...which ones?

Hi-
I built my first amp last summer and used a plitron 225 VA standard toroidal transformer. I believe that it had hysteresis problems because the power had really disgusting noise on it. Looking at the scope also seemed to indicate that something was funny with the core material. So now I'm building my second amp and am wondering which transformers people find work particularly well. Given the overall positive review of plitron, I'd hazard a guess that my transformer happened to be a fluke. I'm trying to build a particularly small amp this time (to fit in a college dorm room/cell) so size is pretty important. I'm looking for something that isn't taller than 2 inches (maybe 2.5) and something on the order of 200 VA. Any suggestions? Is Vic. Mag. any good? I've heard of several other brands, but haven't been able to find any reviews. As far as price goes, roughly $50 is the range. Also, has anyone had similar experience with plitron? Thanks for your time.
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Old 26th May 2004, 05:45 PM   #2
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I have never used Plitron before, but everyone seems to like them fine. If the problem was with really with the transformer, it sounds like it may really be a fluke.

Parts Express carries Avel toroids. I've used Avels before and I like them fine, plus I've had nothing but great experiences with PE (although many say their shipping costs tend to be on the high side, I don't really have a problem there). They have the ratings and dimensions on their site, so you should be able to get pretty accurate dimensions.

As far as Victoria Magnetics goes, I have recently bought my second toroid from them and I was very satisfied with what I received. I got a 22-0-22 320VA for $63 (without shipping), but this may be more power than you need and / or more cost than you want to bear. Still, you may want to call them to see if they can provide you with one that's suited to your project. John at VM is a really nice guy and I'm sure he'll let you know if he can provide what you want.

If you want to do it on the super-duper cheap, you might call Apex Jr. to see of they have any toroids or EI transformers (usually center-tapped) for a song. Another option would be to check out the Trading Post forum-- you can get good deals there from fellow DIYers.

I'm not an expert at DIY (in fact, I just started getting into this stuff in January 2004), but the deals are out there if you're willing to look.

Can any other DIYers make additional recommendations or pick mine apart?

Kofi
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Old 1st August 2004, 06:53 PM   #3
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Default transformers...which ones?

Hello, I might be late with my answer, but anyway, your problem is not the transformer, unless is something out of real world.
More likely you have a design problem, connectivity problem or pure and simple an honest error in construction.
I used almost any transformer I've got my hands into, including ones made by myself without any sophisticated equipment, by hand.
I hope this will help. By the way check filtration and supply to amp connection.
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Old 1st August 2004, 09:38 PM   #4
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Default Re: transformers...which ones?

Quote:
Originally posted by februarie02
Hello, I might be late with my answer, but anyway, your problem is not the transformer, unless is something out of real world.
More likely you have a design problem, connectivity problem or pure and simple an honest error in construction.
I used almost any transformer I've got my hands into, including ones made by myself without any sophisticated equipment, by hand.
I hope this will help. By the way check filtration and supply to amp connection.

Yeah...one would have hoped for a design error, but with no load the secondaries were spitting out a really nasty cliped sine wave...actually I think only the + was doing it...something was *@#!ed up with it... A new one from Victoria Magnetics is coming in soon so I'll see how that compares...

Doovieman
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Old 1st August 2004, 10:11 PM   #5
Jean is offline Jean  United States
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I have ordered 6 Y23 type toroids from Avel directly and so far with no problems, cheaper than ordering from PE btw

I only wish they would do better on the outside plastic see through tape they wrap them with, as it seems to always wants to unwrap itself. Other than that, price is great and there is no mechanic hum. Great for the $ imho.
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Old 3rd August 2004, 07:07 PM   #6
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Default How close is close?

Hi all. How close physically is it permissible to install transformers to each other, with regards to RF etc. I am building a valve buffered IGC, a la Joe Rasmussen, and have a 300va 2x25v for the amps, a 30va 2x25v for the valve, and a 12va 10v for the filament. I would like to cram them into as small a space as possible.
Cheers!
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