Jens Rasmussen Leach clone group buy

[tryonziess]

We are up to about 25 boards at this point. I think that is enough to get an order started. I should be getting some quotes back early this week. Thanks Tad

[BobEllis]

Originally posted by Dougie085
What kind of output is the 10 transistor version capable of? And these are full class a arent they? Also anyone know roughly what the parts cost to fill these boards are?

The Leach amp is a class AB amp. You can bias it higher within limits depending on your heat sinks and number of output devices.

The six transistor version is roughly equivalent to the standard Leach amp - good for around 125W/8R with ~58V rails.

The ten transistor version would be better suited to operation into low impedance loads or at higher voltage rails with the proper component ratings. Run it up to 70 volt rails and you should have a nice 200W+ amp.

[farl]

....please count me also for one set.

Farl

[BobEllis]

WIKI HERE to help Tad track interest.

Thanks Tad.

[Dougie085]

I'm down for at least 2, possibly 7 though depending on board costs.

[Dougie085]

How big of heatsinks do these require? I'm trying to figure out if its possible to fit 7 of these in one chassis.

[Damon]

Go to the bottom of this page...

http://delta-audio.com/Leach_pics.htm

Have a look around while there; Jens provides a lot more info on the Leach.

[jacco vermeulen]

The minimum heatsink size is 10" in length and 5" high due to the size of the board. (12" long for a 10-device board)

Overhere, 12" is a standard size, 10" is not.
With 200 watt devices, such heatsinks will place the max dissipation at 150 to 170 watts (25C safety margin).
Means you'll not have to worry about your amp overheating, even not if you fancy fullrange ribbons.
Also means the minimum space requirement for a single channel is a 10"x4"x5" (L/W/H) block, depending on the lytic height used.
Tightly squeezing 7 amp units close to eachother is not recommendable, there's a risk of heat build-up between the modules.
You'll also need adequate space for 2KVA or more transformer volume, first Q would be how large you allow the case to become.

[BobEllis]

How about turning the boards on end - 10h x 5w with the fins vertical? Then you could make the sides of the case out of three channels and put one on the rear. There was/may still be a guy on eBay selling appropriate sinks.

You'd end up with something like 20" x 20" x 10" with plenty of room for power transformer(s) and lots of big caps inside.

If you really want to pack them in tight, You might be able to get away with sinks smaller than the boards that allow you to mount the filter caps on the bottom of the board, making each channel around 2" thick. Just don't expect to push them too hard and be reliable.

[tryonziess]

I have one quote in so far of 12 dollars per board with 2.5 oz copper and .062 thickness. These are huge boards. Any input on surface finish, silver, color would be useful. Thanks Tad