Board count
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
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
Dougie085 said:
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.
How big of heatsinks do these require? I'm trying to figure out if its possible to fit 7 of these in one chassis.
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.
http://delta-audio.com/Leach_pics.htm
Have a look around while there; Jens provides a lot more info on the Leach.
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.
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.
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.
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.
preliminary quote
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
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
IIRC, the last buy was .090 thick, 2 oz. copper. Advanced Circuits got ~$11.50 per at 125 pieces. The price of copper has gone up though.
I'm fine with standard green/white/silver plating. I think a thicker board should be considered given the size, though.
I'm fine with standard green/white/silver plating. I think a thicker board should be considered given the size, though.
Yeah I have some of those Ebay heatsinks for an Aleph project. I just didn't think these would be generating as much heat as the aleph because they are Class A/B. 20x20x10 is huge 🙂 I'd rather do like 2 chassis I probably don't need 7 channels could do 5 or 6. Would it be bad if the fins were going horizontal? I know its not ideal but these heatsinks are quite large.
You shouldn't have a problem with horizontal fins in normal home use. Pass uses horizontal sinks on the XA60.5 and others-
I have a 4 channel Leach on the Apex jr tunnels horizontally running without a fan. They stay reasonably cool at sane listening levels, although one amp on each side is just powering the tweeters. You sinks have more surface area.
An externally hosted image should be here but it was not working when we last tested it.
I have a 4 channel Leach on the Apex jr tunnels horizontally running without a fan. They stay reasonably cool at sane listening levels, although one amp on each side is just powering the tweeters. You sinks have more surface area.
Hi,
while testing my bare uncased Leach, running 3pair @ 210mA total bias from +-58Vdc, I laid the sink flat with fins pointing down.
The 200mm by 130mm by 40mm sink became far too hot to touch within about twenty minutes. During this overheating the multiplier had reduced the bias significantly below the 210mA but fully recovered within thirty minutes of standing it back up properly.
In the upright position the sink runs at about 10C above ambient. I guess it ran @ >30C above ambient laid flat and with much reduced bias.
If these quesses are about right, then Rth s-a went from 0.5C/W to 2C/W due to orientation.
while testing my bare uncased Leach, running 3pair @ 210mA total bias from +-58Vdc, I laid the sink flat with fins pointing down.
The 200mm by 130mm by 40mm sink became far too hot to touch within about twenty minutes. During this overheating the multiplier had reduced the bias significantly below the 210mA but fully recovered within thirty minutes of standing it back up properly.
In the upright position the sink runs at about 10C above ambient. I guess it ran @ >30C above ambient laid flat and with much reduced bias.
If these quesses are about right, then Rth s-a went from 0.5C/W to 2C/W due to orientation.
If the output devices were detatchable I could make the amp much smaller quite easily. So I'd say I'm interested in the seperate output model. And 6 amp boards.
i wonder if advanced circuits still has the original information for the last group buy. where are they located. i will give them a call and see if they can do the same deal. the like the thick board idea myself. i will order the heaviest copper, within reason, that they offer. thanks for the input tad