redesign of leach amp pcb for integrated TO-247 output devices

[haldor]

Hi Brian,

If you place a big order, I'd take a couple of boards from you. Any idea how much you would ask for say 4 boards?

Phil

 

[herm]

Power dissipation

Has anyone calculated how much power will be dissipated
in the main sinks (per channel) with the new design?

 

[UrSv]

Jens,

Where did you get those heatsinks? They look perfect for my amp...

/UrSv

 

[JensRasmussen]

Heatsinks

I got my heatsinks from

Deltron Conelec A/S
Banemarksvej 50B
2605 Brøndby
Denmark

The Model is S245

Hope it works out for you

\Jens

 

[JensRasmussen]

Hum

Hi Brian

You are using graundplane right ?

How is R51 mounted ?? I haven't mounted it, and it seams to give a littel bit of hum. I can hert it if i the room is silent, and no signal i connected to the input.

Also the input cap seems to suffer from "mikrofonia" (If I tap it, there is a sound in the speaker). What type do you use ?

How is your ground layed out ?

\Jens

 

[jgwinner]

Jens:

>>b) The large caps<<

Right, caps at 0 voltage act pretty much like a dead short when the transformer turns on.

I'm looking at this issue now, I want to use a 1000va or 1500va amp for my 6-10 channel home theater project; I'm worried about inrush.

When looking at relays for output protection and turn on thump, I started thinking of using a capacitor bank, and then switching each set of cap's with a few relays on a timer. If I used DPDP relays, you could even use a fairly large resistor then when the caps get charged, they would self - power the relay to cut out the resistor.

On another thread there are some thermistor examples for the same thing, but I'd like to avoid the heat if possible.

Sorry for disgressing on the thread in answering the question.

The amp looks fantastic, by the way!

 

[SteveA]

Leach redesign

Brian-
I would be interested in a couple of boards, if an when they become available.
Steve

 

[BrianGT]

I have the boards ready to send off, but I am going to do more testing with the new boards first. I have tested them with a benchtop power supply, but I want to get the entire thing done before I order boards. It should not take me too long.

--
Brian

 

[jgwinner]

Doh!

Sorry about that, I was replying to the last note on page 1, after a ton of people gave answers already. Sorry for jumping in!

I will say it again, you guys have a nice looking set of amps!

 

[G]

Hi Brian,

Please let us know when your board is available. Post pics too. I think that the interest in these boards is high. Thanks for the hard work from all of us beginners. "Now where to buy the heatsinks and a chassis" he ponders out loud.

 

[BrianGT]

Sorry for the long delay in details with the board. I will get them made, but I have been distracted by my speaker and subwoofer projects. I also have been quite busy with work. I have verified that the board works, but I would like to do some more testing of the board before getting them made, comparing it to the normal leach amp. I will try to go into lab and test them soon.

Once that is done, it will take two weeks to get the boards made.

--
Brian

 

[BrianGT]

picked up a transformer for my latest leach amp... 500VA low profile 80vct for $62 ($58 if gatech student) from Victoria Magnetics. It should work good for a low profile chassis:

--
Brian

 

[BrianGT]

I also picked up a 1kVA superamp transformer 130vct. Here is a picture of both for a size comparison:

By the way, the low profile leach amp transformer is made to fit in a 1 unit high rack mount chassis:

--
Brian

 

[G]

Looking good!

 

[JensRasmussen]

Listening to a Leach amp

Hi

I'v solved the hum problem, turns out it was because of a bad ground connection.

Does anybody know what sort of Qpoint current in each transistor is the best? I have tried 30 mA and 50 mA, and the last i clearly the better. What do you use?

\Jens

 

[Toster]

I have verified that the board works, but I would like to do some more testing of the board before getting them made, comparing it to the normal leach amp. I will try to go into lab and test them soon.

Once that is done, it will take two weeks to get the boards made.

--
Brian

Hi!

Have you tested the boards and get them made?
I can't wait to get my hands on them

....and what about the price for a pair of boards?

mario

 

[jarek]

Hi ALL!
I'm going to rebuild may Leach amp with 2SC3281/2SA1943. These transistors have high Ft (>30Mhz). What do you think about omitting 'split feedback' and picking it all exactly from the output?

 

[mlloyd1]

I think you may be asking for trouble with the pair you list.
Use either the 2SC3281 and its complement (2SA1302) OR the 2SA1943 and its complement (? I don't remember). Don't mix.

mlloyd1

Hi ALL!
I'm going to rebuild may Leach amp with 2SC3281/2SA1943. These transistors have high Ft (>30Mhz). What do you think about omitting 'split feedback' and picking it all exactly from the output?

 

[jarek]

I think you may be asking for trouble with the pair you list.
Use either the 2SC3281 and its complement (2SA1302) OR the 2SA1943 and its complement (? I don't remember). Don't mix.

Sorry, my mistake. I thought about 2SA1943 and 2SC5200.

 

[JensRasmussen]

Leach feedback

Hi

Snip

What do you think about omitting 'split feedback' and picking it all exactly from the output

snip


I have tried simulating alot of different feedbackconfigurations on the Leach, how do you mean? No feedback from predriver? or short the middle of the drivers to the output?

\Jens