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Old 21st September 2013, 02:37 PM   #61
diyAudio Member
Join Date: Sep 2013
Okay so does sharing one big transformer across multiple channels have disadvantages?

If i go all mono I think either of these will be my cheapest option, not really sure what the difference is though?

Option 1:

25 + 25 160VA Toroidal Transformer | PHOTONAGE

Option 2:

Ebay Item Number: 281158053035

Sure, if doesn't start you crying and you want to go the whole dual-mono way.
No matter what I do it will make me and my wallet cry but i really don't want a failed project so im happy (read: sad) to spend a bit extra if its gonna make it worth my while more.

EDIT: Just saw your reply AudioSan. I guess what you say is true, even high end amplifiers only use one transformer. Will there be a noticeable difference if i just use one transformer?
Also, If i have a high VA rated transformer and I am only running three channels off it wont that overload those channels??

Last edited by cjflis; 21st September 2013 at 02:50 PM. Reason: Didnt notice AudioSan's Commment
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Old 21st September 2013, 02:52 PM   #62
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Join Date: Feb 2009
if you go for 2*25V transformers, then i would only use the amp with 8ohm speakers. without heavy dips. you are better off going down to 2*20V if you want to use 4ohm speakers.
mine will be a single 400VA 2*18V transformer(giving me +/-25V) and a 60.000uF cap bank. that will give me 50Wrms pr ch at 4ohm.
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Old 21st September 2013, 03:07 PM   #63
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Join Date: Sep 2013
Thanks AudioSan but my speakers are 8 ohm so thats fine

Originally Posted by cjflis View Post
Will there be a noticeable difference if i just use one transformer?
Also, If i have a high VA rated transformer and I am only running three channels off it wont that overload those channels??
Also, what do you think about this?
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Old 21st September 2013, 03:40 PM   #64
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Join Date: Feb 2009
you can run all 3 ch from one single transformer. BUT, then all 3 ch must share a common PSU also.
you can have as big transformers as you like.
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Old 23rd September 2013, 03:44 AM   #65
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Join Date: Sep 2013
But should I go with seperate transformers? I like the idea of having modular channels so if one PSU or transformer fails i can tell straight away. But if there is no sound difference i will not.
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Old 23rd September 2013, 11:47 AM   #66
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Join Date: Apr 2010
Location: Coffs Harbour
At the beginning stages of DIY, the serious questions are about the initial cost which will be high for all the gear needed to get started. The benefit of many options that sound like a good idea won't mean a thing for some time to come, when you have other gear that is comparable to your project.

If transformers are available here fairly cheaply, I'd buy just one 120VA type and assemble 2 stereo amplifiers - get them working absolutely A1 and then think about expansion with a second transformer and power supply for as many extras and dollars as you care to throw at it. Some options that are really just principles of design, but pan out as no improvement at all - just a nice theory that worked for someone else. Don't get fixed on too many possibilities. Get it started and working. That may yet be quite an undertaking on its own.

The key to fun is success - don't spoil your chances by setting goals too high, too expensive or just too complex to reach easily in one project. You did realise you need fairly good soldering gear (don't assume safe and lead-free solder is good to use though. It's a bummer without perfect flux temp. and technique.) You'll also need lengths of heavy gauge hookup wire in colours suited to your power leads, speakers and shielded wire for the input leads, volume control perhaps, as you'll see in many project pics here. You may go for spade connectors or screw connector blocks to enable you to separate your assemblies. Take care to use a size compatible with the boards- 1/4" spades are enormous.

All you may have to purchase from Chipamp in the future is the tiny PCBs, so postage costs shouldn't be prohibitive for a couple of extra boards. Don't fret about not buying everything at once, which will keep you dithering for months.

Last edited by Ian Finch; 23rd September 2013 at 12:02 PM.
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Old 23rd September 2013, 12:26 PM   #67
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Join Date: Nov 2006
Location: Adelaide, South Australia
Blog Entries: 46
I understand you are in Australia. From what I read you would best go to either ALTRONICS or JAYCAR and get yourself a kit.

Their kits are all pretty good, and have been built by a zillion people in Aus/NZ.

A couple of suggestions are ALTRONICS (you can phone in an order): K5130 $79.95. This gets you:
- The rectifier and power supply
- +/-15VDC supplies for the preamp
- TWO channels of LM3886
- A pair of heatsinks (75mm tall if I recall) will fit your 80mm high case.
- In summary this is a "one board does it all for you" approach --> maximum fun minimum fuss for a first build for you

You could build this and be off and running with minimum risk of things going pear shaped. You also avoid the hassle of sourcing a bunch of bits, which for a first project is probably more of a worry than you want.

It will just work for you too.

If you want to go to JAYCAR instead I am not sue they sell that "integrated" board, but you can buy the functional parts:
- Cat KC5150 (an LM3876 50W amplifier), $30 - you need TWO of these
- ZR1314 bridge rectifier (OK this gets a tiny bit technical)
- RE6241 2,200/50V electro caps x 2 (Again a bit of wiring to do here)

My advice - get onto the ALTRONICS website and get into a good simple thing to get you started.

Have fun, build some stuff and see what it takes to make it work, and to blow it up. Just keep well clear of 240VAC.

Last edited by googlyone; 23rd September 2013 at 12:29 PM. Reason: typo
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