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Old 29th October 2003, 09:19 AM   #101
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Hi all,

The thing is alive

I now need to sort out the top and front

\Jens
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Old 29th October 2003, 09:20 AM   #102
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The back
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Old 29th October 2003, 09:21 AM   #103
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From the top
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Old 20th September 2004, 08:56 PM   #104
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Hello all,

I have had several requests for my version of the Leach Amp, but lost my original layout some time ago due to a hard disk failure (I will now be making weekly backups).

Anyway I have remade the layout on one board with room for 5 sets of output transistors and 10000uF 100V rail caps. (40mm diameter)

Let me know if anybody is interested in a group order for these, and also if you have any requests regarding the PCB.

The PDF pic contains the layout, witch measures 120xx250 mm

\Jens
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Old 21st September 2004, 12:20 PM   #105
arasuk is offline arasuk  India
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Wink modified leach amp

Hi JENs,

Your version of leach amp looks good , can I request you to provide me the pdf files of the leach amp so I can do this amp. (of course this is my dream amp).

1. you have used 5 pairs of Output pairs, what was the purpose, can it increase the power or you have done this to handle loads down to 2ohms.

2. what is the max voltage rail you recommend.
3. can I use 2sa1943 & 2sc5200 pairs.

4. can you provide some details of your modified version.

Thanks
Arasuk
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Old 21st September 2004, 01:11 PM   #106
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Hi Arasuk,

>1. you have used 5 pairs of Output pairs, what was the purpose, can it increase the power or you have done this to handle loads down to 2ohms.

I have done this to be able to play into smaller loads and to increase the rail voltages while keeping a decent SOA for the output devices.

>2. what is the max voltage rail you recommend.

So far I have only tested it with +-55V, but Iíll be making tests with +-68V when I get the proto PCBs

>3. can I use 2sa1943 & 2sc5200 pairs.

YES! And MJL4281/4302

>4. can you provide some details of your modified version.

Small signal transistors are BC546/556
Vas and pre driver are MJE340/350
Drivers are MJE15034/15035

Extra decoupling caps on board along with zobel network and fuses.

The rest of the components are more or less the original, I'll be making a BOM later when everything is tested

\Jens
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Old 21st September 2004, 02:16 PM   #107
Jean is offline Jean  United States
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Looks good!
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Old 21st September 2004, 06:27 PM   #108
arasuk is offline arasuk  India
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Smile Modified leach amp!!

Hi Jens,

Thanks for the reply,

1. I remember Mr.Leach pointing out that +/- 58v is the best possible rail voltage. do you think Increasing it will lead for SOA problem.

2. Then using BC546/556 would not be probably better ???

3. About the short ckt prot what values do you reccomend,and have you tested with these values.

4.Does the "diode array" need to be implemented on the heat sinks??? can I replace them with some To220 type diodes or with an BJT.

thanks

Arasuk
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Old 21st September 2004, 06:40 PM   #109
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>1. I remember Mr.Leach pointing out that +/- 58v is the best possible rail voltage. do you think Increasing it will lead for SOA problem.

I think he means for the setup with two transistors.

>2. Then using BC546/556 would not be probably better ???

I don't understand what you mean, please explain

>3. About the short ckt prot what values do you reccomend,and have you tested with these values.

I have tested them using +-55V, they need to be recalculated with +-68V!

>4.Does the "diode array" need to be implemented on the heat sinks??? can I replace them with some To220 type diodes or with an BJT.

You must place the diodes on the heatsink!! TO220 diodes could work well, for thermal tracking, not sure how the added cap to heatsink will influence the thing though

\Jens
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Old 22nd September 2004, 05:22 PM   #110
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Sweet! Now how's about boards, docs, price? Except for plate thru, I can make my own 2 sided board. Foil pattern price?

Prosit
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