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haziz 29th April 2007 01:34 PM

Gainclone Transformers
I am building AudioSector's 3875 kit as well as Chipamp's (BrianGT) 3886 kit and will next tackle the 4780 kit. I am actually using this opportunity to gain experience in DIY. The PSU boards are AudioSector's and Chipamp's current boards which are different.

ApexJr has two Avel Lindberg amps on special:

1. Avel-Lindberg Inc.: Input: 2 X 120Vac 50-60 Hz 3 3/4" Dia X 1 1/2" Tall Output: 2 X 28.4V @ 2.67Amps over 150Va

2. Avel-Lindberg Inc: Input: 2 X 120Vac 50-60Hz 3 1/4" Dia X 1 1/2" Tall Output: 2 X 25V @ 2 Amps 100Va

I am also getting the cheap Signal transformers (Primary 230V Secondary 48VCT 7A & 28VCT 3A or Primary 115V Secondary 24VCT & 14VCT) that he has for experimentation.

Which do you recommend for the amp configured for dual mono driving 8 Ohm speakers? I may also want it to drive 4 Ohm speakers but 8 Ohm speakers are the main target. Cost is not my concern. Am I reading the instructions right that the 2x25V amp above would be a better match because of "rail voltage" and speaker impedance. I want to get the best match rather than just save a few dollars. Sorry most of the technical stuff is chinese to me, but I do want to learn.

I can also use a Plitron 300VA torroid for a stereo setup. Would this be a significant step up.




Ed LaFontaine 29th April 2007 02:15 PM

My first choice of the options you have listed would be for the #2 transformer from Apex. Use 1 for each channel.
I have several of the Signal transformers. They work fine IF you set them up for 230V giving 48vct. This means you must have the voltage from a clothes dryer or electric range type outlet. Proceed with caution.

! 1st May 2007 02:15 AM

If cost is no concern then the easy answer is none of the above, except you didn't tell us much about the 300VA option.

Generally you want about 2 x 22V / 4A or higher. The higher the current the better the regulation (all else being equal) Some people think about halving the curent when going dual mono, and it does give isolation but it also means peaks on one channel have less current reserve, more voltage depression than if it were a single transformer for both channels with double current.

150VA transformer will make a reasonable amp, but it is a bit smaller than some people use. You could use two of them but the main problem was still that to get that VA, the voltage is a little too high and the current a little too low. One x 100VA is not enough unless you aren't aiming for max output possible. IMO, you're better off having voltage a little high rather than not enough current.

At higher cost, consider this 2 x 22, 400VA

maxdd_nj 1st May 2007 02:27 AM

I use the Antek 22v+22v 400VA toroid '!' mentions in his post, in my Peter Daniel's premium 3875 amp. This thing's a hefty beast. It doesn't even get warm. The price is right too, go for it.

pjanda1 1st May 2007 03:01 AM

Avel makes a 22v+22v in several larger sizes too. Just call them up, they don't list them on their site. I use one of their 330VA 22+22's. However, I'm not sure they are any cheaper than the Antek on ebay.


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