Hi Guys
I don't believe there is any confusion about what a "super leach amp" is - just that it _can_ be many things.
The original Leach amp outlined in the Audio articles was the "Low TIM " amp. This has comp diff inputs, comp VAS, and comp parallel EF output. He revised this several times, cascoding the input stage but no other part of it.
The "Double Barrel" has a cascoded output stage to allow higher peak power into 8R.
If there was also a "Super" amp from leach, I have not heard of it - maybe it is a colloquial reference to the DB?
My suggestions above are to highlight the difference of options we have today that Leach did not have back in the early 1970s. There are lots of benefits to having a large output stage with several parallel current paths, but... How much peak power do you really need?
If you have a large room and power hungry speakers, then you need lots of power to achieve a high SPL. Personally, I prefer to be able to actually hear all the music and value my hearing, so <80db is more to my taste and I never suffer from listening fatigue. For me, the large output stage running at much lower voltage works fine. There is a linearity advantage to having more voltage headroom than you actually use, along with energy storage benefits in the supply, so a compromise is found between keeping everything appropriate to your situation and wanting more than you need just because it costs hardly anything to have.
As an aside, to drive ESLs directly you need an amp that can drive a 90-degree load. An easy thing to do if you design the output stage to handle the dissipation caused by full current into a dead short.
Have fun
Kevin O'Connor
I don't believe there is any confusion about what a "super leach amp" is - just that it _can_ be many things.
The original Leach amp outlined in the Audio articles was the "Low TIM " amp. This has comp diff inputs, comp VAS, and comp parallel EF output. He revised this several times, cascoding the input stage but no other part of it.
The "Double Barrel" has a cascoded output stage to allow higher peak power into 8R.
If there was also a "Super" amp from leach, I have not heard of it - maybe it is a colloquial reference to the DB?
My suggestions above are to highlight the difference of options we have today that Leach did not have back in the early 1970s. There are lots of benefits to having a large output stage with several parallel current paths, but... How much peak power do you really need?
If you have a large room and power hungry speakers, then you need lots of power to achieve a high SPL. Personally, I prefer to be able to actually hear all the music and value my hearing, so <80db is more to my taste and I never suffer from listening fatigue. For me, the large output stage running at much lower voltage works fine. There is a linearity advantage to having more voltage headroom than you actually use, along with energy storage benefits in the supply, so a compromise is found between keeping everything appropriate to your situation and wanting more than you need just because it costs hardly anything to have.
As an aside, to drive ESLs directly you need an amp that can drive a 90-degree load. An easy thing to do if you design the output stage to handle the dissipation caused by full current into a dead short.
Have fun
Kevin O'Connor
I tried to build the Double Barrel in 2004. I was really excited to get it all hooked up but got no sound out of it. I triedlike crazy to find the problem but never did. I still have all of it and hope some day to know enough to find the issue. However I think I used the trafo for something so I will have to get another If I ever get it going. Looking forward to following this thread.
Get yourself a transformer, start a new thread and post a lot of pictures. We can make it work.
Gajanan Phadte
Gajanan Phadte
were you able to power it up without smoke coming out?
if no smoke, then you have to check he output offset voltage, it should be more than +-100mV .....
then set the output trannie bias...
It just dawned on me that i have an old Soundcraftsman amp that is shot. I belive that has a transformer that would be sufficient for this amp. I will check it out today. I will take your advice and start a new thread so as not to derail this one.
Blessings, Terry
Blessings, Terry
I just pulled the Soundcraftsmen apart and the Tx is outputting 66-0-66 VAC so it should work. Now I can do some investigation while I watch what you guys are doing here. Man I love this stuff!
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