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Jens Rasmussen Leach clone group buy

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#345
Jen's, Where do we stand at this moment on the new layout. How long before the gerbers might be ready to go to the pcb manufacturer. I believe we have enough people on the Wiki to make a group buy feasible.
I for one would also like to see a layout for a seperate regulated front end for this amplifier design on this go round. Thanks Tad
 
#347
tryonziess said:
Jen's, Where do we stand at this moment on the new layout. How long before the gerbers might be ready to go to the pcb manufacturer. I believe we have enough people on the Wiki to make a group buy feasible.
I for one would also like to see a layout for a seperate regulated front end for this amplifier design on this go round. Thanks Tad
Click to expand...


AFAIKT noone desided what layout they want.... I'm sort of waiting for more to put forward their thoughts.

Btw, my name is Jens, and not Jen!!

\\\Jens🙂
 
#349
Layout opinion

Jens,
I would like to see the new boards setup like the second round of the KSA50 boards, with the output boards separate. Having all 10(5 pairs) of the output devices that close to each other doesn't give you much chance to utilize your available heatsinking very efficiently.
Looking at tryonziess's amp up above shows that he is effectively using one third of the total amount of heatsinking available on that amp. The other two thirds are there just for show. It would be nice to be able to place the main/driver PCB internal, and all of the output devices spread evenly on the heatsink.
Let me know your thoughts on this.
Thanks,
Donovan
 
#350
Landoctor, One of the strange things about this amp design is I cannot for the life of me get anything to heat up. Driving full volume into a 6 ohm speaker load the output transistors and the heatsink barely climb past ambient. Is this a good thing or not.
All in all I am quite happy with the results of this build. Pushing 73 volts on each rail and no appreciable overheat is nice. I wish all of my projects turned out this good. Tad
 
#352
Where to cut

Hi

There seems to be more and more builders that would like the amp to be split into two boards.
To do this cleanly, I think that the drivers and pre-driver for the output should use the same (higher) supply voltage as the input and voltage amplifier section of the amp.

These changes means that:
1) The two big fuses, caps, zobel and output section will be separated from the rest of the amp.
2) I must rearrange the protection circuit to better use the PCB area.
3) R1 and R23 will be deleted.

The total PCB area for the amp will be bigger = more expensive.

If these changes are made the amp will be less rugged since the mechanical requirements for the heatsink is now only dictated by the output stage size – the builders will have to be satisfied with less freedom to choose the rail voltages.
Is this ok with everyone?

Best regards
Jens
 
#354
What do you mean "less rugged"? You would still need to use appropriately sized heatsinks for your output power, so I don't see how separating the outputs would change anything.
I think the rail voltages available would suit just about anyone wanting to build this amp. If they were after something different, then they could choose to build the Super Amp, or any of the million other models out there.
Just my .02.
Thanks,
Donovan
 
#356
By less rugged, Jens means that there is a possibility that the builder may use smaller (maybe undersized) heat sinks than a one piece board requires. The one piece board is a means of "idiot proofing" and relieves Jens of at least one repeating question about his boards - "Is this heat sink big enough?"

That said, the heat sinks that Professor Leach recommended for the original are a bit on the small side. That so many have enjoyed the amp implies that people will either use the amps well below their capability or use proper heat sinks. I believe that we will be reasonable in our heat sink selection.

If we go with split boards, we should make a "Building Jens' version of the Leach Amp" WIKI page including sections on proper heat sinking and protection circuit value selection.

my :2c:
 
#358
Separating the final output stage from the others as Jens suggests is an excellent idea. This will give builders far greater flexibility to use any heat sink and any case output transistor they wish to. This is clearly a more universal and useful choice for all involved. Furthermore, Jens' suggestion of increasing the voltage for the two first two stages of the current gain stage will mean that this arrangement will produce slightly more output power than the existing Leach design (assuming that the driver clips first). This is a very good idea. Bob Ellis has seconded this configuration. I would like to add another vote for this also. A superior design is evolving. --- HK
 
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