up for this this thread......
jens,
this design has been validated and it works...unfortunately roland lost his files when his computer chrashed.....
jens,
this design has been validated and it works...unfortunately roland lost his files when his computer chrashed.....
Tony,
Have you been keeping up with the older group buy thread. Jens has an updated layout for the TIM amp with 12 outputs. Might be something for you to look at.
Tad
Have you been keeping up with the older group buy thread. Jens has an updated layout for the TIM amp with 12 outputs. Might be something for you to look at.
Tad
Hi,
Does anyone have any idea for the bias current for the 10 outputs versions (I am thinking of about 200mA) and what about 6 outputs version? Like my last post said, (something like a year ago already) nothing was clearly said about the setting up procedure and the old site is down now (is there a new one?).
Thanks
Does anyone have any idea for the bias current for the 10 outputs versions (I am thinking of about 200mA) and what about 6 outputs version? Like my last post said, (something like a year ago already) nothing was clearly said about the setting up procedure and the old site is down now (is there a new one?).
Thanks
The Delta-Audio site is gone, but Archive.org has it, and it appears all the Leach files are saved too:
Leach Clone
Leach Clone
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There hasn't been a definitive optimal bias study that I am aware of. You can use Self's optimum bias as a guide. I think 200 ma for 5 pair may be a bit low, but try it and see. The original Leach was biased at about 35 mA per pair with 0R33 emitter resistors - about half of Self's recommendation.
I'd suggest shooting for around 50 mA per output device pair with 0R47 emitter resistors that Jens suggested. Somewhere around 250 mA for the 10 device output stage and 150 for the 6 device. If you aren't using separate front end supplies, add 25 mA or so bringing the total to 275/175. You can easily see that I am a firm believer in precision biasing. 😉
I'd suggest shooting for around 50 mA per output device pair with 0R47 emitter resistors that Jens suggested. Somewhere around 250 mA for the 10 device output stage and 150 for the 6 device. If you aren't using separate front end supplies, add 25 mA or so bringing the total to 275/175. You can easily see that I am a firm believer in precision biasing. 😉
bigpanda,
I noticed a very definate improvement in my 10 output Leach amplifier when I raised the bias to 150 per device or .75 amp per rail. I now run a full 1 amp per rail. Until I reached the 60 -75 mark per device the bass response was almost nonexistent and the highend was slack.
I do not use the method of adjusting that is so common here at DIY audio by checking the emitter resistors because of the tight confinement. Dr. Leach suggests removing the fuse and placing your digital meter in amp mode across the fuses and checking the load on the entire rail and dividing by number of devices. This method works for me but may not be as accurate as some here would like.
I also must mention that I am using rather large heatsinks and the temperature of the outputs never gets overly warm.I have a small temperature detection device from one of my trucks at work glued to the heatsink and wired into the start relay. It has never initiated for overheat.
Tad
I noticed a very definate improvement in my 10 output Leach amplifier when I raised the bias to 150 per device or .75 amp per rail. I now run a full 1 amp per rail. Until I reached the 60 -75 mark per device the bass response was almost nonexistent and the highend was slack.
I do not use the method of adjusting that is so common here at DIY audio by checking the emitter resistors because of the tight confinement. Dr. Leach suggests removing the fuse and placing your digital meter in amp mode across the fuses and checking the load on the entire rail and dividing by number of devices. This method works for me but may not be as accurate as some here would like.
I also must mention that I am using rather large heatsinks and the temperature of the outputs never gets overly warm.I have a small temperature detection device from one of my trucks at work glued to the heatsink and wired into the start relay. It has never initiated for overheat.
Tad
Sounds ok so long as the SMD components arent too smal too handle.
I tend to stick to through hole pcb's so at least I can see the parts with my old eyes ! I use glasses and a magnifying glass to read transistor part numbers.
Some of the SMD componnets are big enough to work with but others are a real pain.
Hi,
Thanks for all inputs. I think I will start with 250mA to let it 'speak' for itself first.
tryonziess.
what is your standard of 'big', I am thinking of using 280x140x65. This always bothers : if a small pcb (mine is 4.5"x10") /w outputs is nailed to a big heatsink, does the area far from the nailing point contributes much to heat exhaustion ?
Anyway, I may have a headache for mounting the outputs to the heatsink since I am not a nice metal worker. I had some experience that I blow 1 / 2 of the tapped mounting holes and had to rework the whole set of them (if I am lucky enough to have space to shift the whole set slighty).
Thanks for all inputs. I think I will start with 250mA to let it 'speak' for itself first.
tryonziess.
what is your standard of 'big', I am thinking of using 280x140x65. This always bothers : if a small pcb (mine is 4.5"x10") /w outputs is nailed to a big heatsink, does the area far from the nailing point contributes much to heat exhaustion ?
Anyway, I may have a headache for mounting the outputs to the heatsink since I am not a nice metal worker. I had some experience that I blow 1 / 2 of the tapped mounting holes and had to rework the whole set of them (if I am lucky enough to have space to shift the whole set slighty).
happens to me too sometimes, what i do is enlarge the hole one or two sizes higher, then fill it up with "metal epoxy" with the screw on.....be sure to wrap a thin film of teflon around the screw threads so it doesn't get stuck..
bigpanda and others,
If anyone is going to drill and tap number 4-40 holes in aluminum I suggest buying a small hole saw. When you break a tap or drill you can drill it out on the circumference of the hardended tool. Then do as Tony said or tap a larger hole and insert screw and start over or grind the bit out with a diamond burr on a dremel tool. None of the above is fun.
The heatsinks on my Leach are 10x16x3 inch on each side of the amp. The real nice thing about aluminum is how it will pull the heat away from an area and spread it out. You will usually not get a confined area of high heat if everything is held together nice and tight. Barrodboss on ebay and here at this forum sells nice large heatsinks CHEAP.
There has been very little activity on this thread concerning the Superleach pcb design. I for one would really like this project to come to fruition.
Tad
If anyone is going to drill and tap number 4-40 holes in aluminum I suggest buying a small hole saw. When you break a tap or drill you can drill it out on the circumference of the hardended tool. Then do as Tony said or tap a larger hole and insert screw and start over or grind the bit out with a diamond burr on a dremel tool. None of the above is fun.
The heatsinks on my Leach are 10x16x3 inch on each side of the amp. The real nice thing about aluminum is how it will pull the heat away from an area and spread it out. You will usually not get a confined area of high heat if everything is held together nice and tight. Barrodboss on ebay and here at this forum sells nice large heatsinks CHEAP.
There has been very little activity on this thread concerning the Superleach pcb design. I for one would really like this project to come to fruition.
Tad
i use kerosene as tapping lubricant when doing aluminum, i use the screw itself to tap...i use mostly 3mm metic threaded screws....
when tapping aluminum, do not be in a hurry, tap slowly but steadily.....
it is sad that rolandong lost his gerber files due to computer crash, hope jens find the energy and time to finish this pcb layout...
when tapping aluminum, do not be in a hurry, tap slowly but steadily.....
it is sad that rolandong lost his gerber files due to computer crash, hope jens find the energy and time to finish this pcb layout...
Tony,
The super leach layout was finished and a set of proto boards was made. I can not think of the member who was doing the beta tests. If we could get the files I would be glad to put together something so we all could have a go at this. If we had 75-100 boards made it should be close to 16.00-18.00 per board. Would we need to go to a 3 oz. copper to be on the safe side? Do we need the totem-pole output with the modern 350 volt devices? A super leach cascode frontend with the conventional 16 device output should work quite nice.
We just need to find out how the beta tests turned out. Dr. Leach stated that this design could cause oscillation issues. There are very few fully tested and confirmed high output designs -- bjt-- on this forum. Most of the amps are in the 100 watt 8 ohm range.
It is also not going to be a cheap build with the parts count so deep.
Tad
The super leach layout was finished and a set of proto boards was made. I can not think of the member who was doing the beta tests. If we could get the files I would be glad to put together something so we all could have a go at this. If we had 75-100 boards made it should be close to 16.00-18.00 per board. Would we need to go to a 3 oz. copper to be on the safe side? Do we need the totem-pole output with the modern 350 volt devices? A super leach cascode frontend with the conventional 16 device output should work quite nice.
We just need to find out how the beta tests turned out. Dr. Leach stated that this design could cause oscillation issues. There are very few fully tested and confirmed high output designs -- bjt-- on this forum. Most of the amps are in the 100 watt 8 ohm range.
It is also not going to be a cheap build with the parts count so deep.
Tad
Hi,
I know it's been a bit of a long time since the last posting on that thread, but I was wondering if that project went any further.
I would be interested in such a good layout and a group buy.
I have a bunch of amps to build, for my multi-amp 4 ways project.
Leach super amp
I built this amp in the 80s. This design needs a major overhaul with up to date SIM by a real guru circuit design genius. Professor Leach was a scholar and a gentleman but design is ultra-conservative and uses too many old RCA transistors especially the 2nd stage cascode. Also a pc board needs to accommodate all the transistors including the output transistors integrated with the heatsink with minimum lead length on the output transistors. The limiter makes the amp sound un-musical and I would like to see power supply regulation of the input stages or maybe an all jfet input stage. I'd like to see someone like Scott Wurcer seriously look at this amp. Ray Hughes
I built this amp in the 80s. This design needs a major overhaul with up to date SIM by a real guru circuit design genius. Professor Leach was a scholar and a gentleman but design is ultra-conservative and uses too many old RCA transistors especially the 2nd stage cascode. Also a pc board needs to accommodate all the transistors including the output transistors integrated with the heatsink with minimum lead length on the output transistors. The limiter makes the amp sound un-musical and I would like to see power supply regulation of the input stages or maybe an all jfet input stage. I'd like to see someone like Scott Wurcer seriously look at this amp. Ray Hughes
Now that the thread has come alive again, before it die off once more...
Who has gerber files for the latest version and a component list ? are they lost+!
also, do anyone know if the the amp sounded good?
Who has gerber files for the latest version and a component list ? are they lost+!
also, do anyone know if the the amp sounded good?
It's a mirror imaged complementary bjt amp and if you are not going to match transistors to precision collector current in the both the negative and positive sides then the results will be I believe mediocre. That means you better have at least a hundred of each type of transistor to find good matches. It's difficult to find a pnp transistor that has as low a C-B capacitance as an npn transistor. So matching could be a daunting task. Mine drives sub woofers. In the mid-and hi frequencies I would rather listen to other amps but that is just my humble opinion. Ray
I was hoping to get into the group buy for your 12 output version (in the other thread). I think there is interest and we can get a good number of boards made again in a group buy, most likely over 100.
I really would like that 12 output version, but I will be satisfied with the 10 if that's what the others go for.
Can I get the gerbers from you for that 12 output? Just in case...
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