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Old 18th September 2001, 10:59 PM   #31
Super is offline Super  United States
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Thanks for the advice. I haven't yet determined what values to use for the voltage supply rails, but it'll probably be more in the area 32v with a 1000 va torroid, to give me about 25 watts output. This would also allow safe operation with 50v caps. I just want to keep it somewhere in the range of 25-30 watts each. As far as heatsinks go, I'm not objectionable to using a fan to cool the amp, as long as I can find one that's nearly silent, which seems to be easier said than done. Theres also a possibility that I can have the heatsinks made by a machinist friend, so I'm not to concerned in that area. I've got plenty of time to source things out anyways. If you have any suggestions as to where I can find inexpensive new or surplus 1000 va torroids, let me know. Likewise with the 50v caps.

Oh, one more question, can someone explain the purpose of a rectifier bridge?

Thanks again
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Old 19th September 2001, 12:30 AM   #32
paulb is offline paulb  Canada
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Aieee! You're thinking of building a 1 KW power supply, and you don't know what a bridge rectifier is for?
Super, I recommend you start with something a little smaller. Call it a prototype. Maybe one of the headphone amplifiers at headwize.com.
There are some excellent articles on basic electronics at:
http://sound.westhost.com/articles.htm
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Old 19th September 2001, 12:52 AM   #33
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Bryan,
A bridge rectifier is a diode circuit to convert AC to DC. If you think of each diode as a one-way street, then look at a schematic of a bridge, you'll be able to see that no matter whether the AC is 'coming' or 'going' it will be able to pass on as a pulse of DC, which in turn charges the caps that come after the bridge.
If you're looking at a +-32V rail situation, 35V caps will do. The 20% extra mentioned earlier is excessive. It won't hurt anything, mind you...it's just a waste of money. Just for reference, my old Thresholds have +-76V rails on 80V caps. I just tickled my calculator's tummy and it tells me that's on the order of 5%. Note also that caps frequently will have a "surge" rating, meaning what voltage they can take over their rated voltage over a short time period, such as a blip on the AC line.

Grey
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Old 19th September 2001, 02:49 AM   #34
PassFan is offline PassFan  United States
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Lightbulb Fancy parts and wire

Also Super:
My first two prototypes were built with basic components and run of the mill wire. This circuit just flat out sounds good . Building with common components also allows you to do upgrading and listening tests at a later date. Some people actually enjoy this as a method of hearing for themselves the different components utilized in the upgrades to form their own opinions. Its all just part of the hobby
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Old 19th September 2001, 03:46 AM   #35
Super is offline Super  United States
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Paul: Just to let you know, this isn't going to be a one man effort. I have 2 experienced electronic technicians helping me, and this isn't going to happen right off the back. This is just the learning/part sourcing phase. I'll have played around with some electronic circuits by the time building time comes around.

Pass: Sounds like a good idea, but again, this is all cash permitting. If I can get some stuff with a company or bulk discount, then sure, I'll pick up a batch of components with equivalent or slightly different ratings and see how things go. However, since some of the components would be much less likely to come heatsinked, this would mean changes in the chassis and heatsinks which may become a pain in the butt. The wire I can do, however. I'll gladly experiment between standard ofc copper, higher quality copper, maybe some braided geometry, and most importantly, conductor type. I'm curious to see how, say, internal wiring with silver litzwire would vary from copper. The one I can think of off the top of my head would be a brighter, more defined sound with the silver and a darker, more laid back sound with the copper. Or how about silver plated copper? One can only wonder if it would yield similar results to changing interconnects and speaker wire. But hey, thats what DIY and tweaking is all about
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Old 19th September 2001, 05:14 AM   #36
paulb is offline paulb  Canada
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Thanks for letting me know, I think I can sleep now. Have fun!
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Old 22nd September 2001, 01:12 AM   #37
Super is offline Super  United States
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Default Time to tinker!

My dad surprised me and picked up an older pair of Meridian 105 monoblock amplifiers in working condition off of e-bay for about $300. As soon as they come, its tinkering time. Without having to think twice, I know they're getting a new set of binding posts, some new RCA jacks, and a much heavier power cord. I have some questions though. What are some of the things I should try swapping on the inside? Internal wiring is one thing I can think of. Also, I know that the BNC connector type is far superior to that of RCA plugs. Could I simply replace the existing RCA jacks and use BNC connectors instead? Or could I somehow use XLR inputs? (Note: My current preamp has RCA outputs, but I'm not going to touch it, because it's still under warranty). I contacted David Hall of Meridian, and he is going to photocopy the schematics and all the information he can dig up on the amps, so I should have all the parts values and layout. Any suggestions would be greatly appreciated. As always, thanks again.
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Old 22nd September 2001, 02:50 AM   #38
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Bryan,
Yes, you can substitute BNC connectors directly for RCA jacks. No problem, there. If you're in that mode of thinking, consider also Camac connectors.
XLR connectors are primarily for balanced signals. They have three pins: ground, positive, and negative. Unless the Meridian is a balanced circuit, there's not much point in using them.
If you're looking for a grab-bag of ideas for mods, there's always the ever-popular adding of capacitors (either electrolytic, or film, or both) to the power supply. If you're going to have the schematics, perhaps other things will occur to you once you have them in hand.

Grey
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Old 22nd September 2001, 04:05 AM   #39
Super is offline Super  United States
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The camac connectors look pretty good, but they sure are pricey! ($10 a piece!) I've only seen one source for them so far, and thats from Fischer. I also haven't seen any gold plated BNC connectors. Does anyone know any good sources for either of these connectors?

By the way, I'm definitely looking for a grab bag of ideas
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Old 22nd September 2001, 03:53 PM   #40
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Bryan, Bryan, Bryan...
*Exasperated Sigh*
Haven't you figured it out yet? The entire *purpose* of a hobby is to keep you poor! Of course the Camacs are expensive. They wouldn't be fulfilling their function if they weren't. The purpose of a hobby is to keep people suffering from an excess of enthusiasm off the streets and out of trouble. Can you imagine what would happen if all the pent-up energy represented by the folks on this site were to be unleashed upon an unsuspecting world? Chaos! Overnight, things would change, and the hoi polloi don't like change, so they invent traps to keep us caged. I mean, sheesh, I know you're only fifteen, but I thought you were onto that part of the program...ahem...
As for a source for Camacs, try:
http://www.bainbridge.net/percyaudio
I know he used to carry them. Others may as well.
Ideas...dunno. Without seeing either the schematics or the unit itself, all I can do is suggest The Usual Suspects: caps, connectors, and wire. Depending on build quality, you could consider going through and upgrading the resistors and caps in the circuit, but it's expensive and tedious. Sometimes worth it, sometimes not. Honestly, I'd tend to advise against it.

Grey
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