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Old 16th September 2004, 01:59 AM   #1
ilyash is offline ilyash  United States
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Default Help with Leach Amp

Hi, Im new to the forums.

I am planning to put together the leach amp.

I read that you guys got the expensive parts for free somehow..

Can someone explain this?


Also.. does anyone have any parts they recommend other than the ones on the original parts list?


Thanks for any help, Ilya
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Old 16th September 2004, 10:52 AM   #2
djk is offline djk
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How much is your time worth?

Some here abuse the sample system for a part they can buy for $2.50, and it takes time to fill out the form.

The big money is in the case, heatsink, and power supply.
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Old 16th September 2004, 05:25 PM   #3
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http://www.onsemi.com/

Sign up for MY On, fill out the info requests. Search for ALL the parts you need from the Leach site, before exiting the system. You can get up to 25 each of the most important transistors. You need a credit card to pay for the shipping to your location. It comes FedEx next day. About $11.00 US.

The 125W Leach Amp costs at least $300 US to build even if you have access to a proper case and heat sinks at a decent price.

Avel torroid transformers suitable for your amp from partsexpress.com
at a good price.

Best to stay with the recommended parts list, they actually work as advertised.

Oh yeah, have built and use 2 300W double barreled and 4 125W Leach amps. They are sweet.

Cheers
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Old 16th September 2004, 07:53 PM   #4
ilyash is offline ilyash  United States
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Well... i read that you guys have changed some of the parts of the original leach amp.

Which parts did you switch [and for what?]

Also.. where can i get a decent chasis and heatsink?

I like the way brianGT did his..

there are many other great ones out there.

Thanks again..
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Old 21st November 2004, 03:42 AM   #5
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Default Leach am find

Hello,

I was walking in Manhattan last night and found a Leach amp model 101 in the garbage. It is in good shape, but has a few bad outputs. Does anyone know where I can find some Motorola MJ15012 output transistors and a schematic? Is there a better set of outputs anyone thinks will be better? It might be better to redo both sides.

Thanks,

Stewart.
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Old 21st November 2004, 04:06 AM   #6
djk is offline djk
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I have owned several of those.

The MJ15011/12 pair are still available from Motorola (ON Semiconductor).

Change all of them in both channels.

Change the drivers.

If any drivers are shorted, change the predrivers too.

Replace all caps made by Callins.

Replace the four 100F power supply bypass caps for the front end. Check the 100 ohm resistors that feed these from the main supply.

Replace the four 22F power supply bypass caps for the main power supply.

Replace the two 470F caps in the feedback loop to ground.

Replace the two 0.1F caps on the speaker output to ground. Use a high quility film and foil type here, as high a voltage that fits the board (250V if possible). Check the 10 ohm resistor in series with this cap.

Fire it up for the first time with a 100W lightbulb in series with one side of the line cord.

Adjust the bias.

Read the Leach info at:

http://users.ece.gatech.edu/~mleach/lowtim/

The schematic of the 101 is very close to this.

Do it right or don't bother.

If you don't want to bother, I will buy it as is.

Good luck.
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Old 21st November 2004, 08:42 PM   #7
jaycee is offline jaycee  United Kingdom
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Check eBay as you can often find toroids, filter caps and heatsinks on there that can be readily used. Also electronics junk stores are good as you may find an old amp that is toast but has a nice big pair of heatsinks, a transformer and some caps, and even a chassis you can reuse.
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Old 22nd November 2004, 01:51 AM   #8
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I have used a Carver M1.0 case heatsinks and transformer.
I like the sound of the Leach more than the Carver, but the Carver had more power.
Serosmaness
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