I am starting this thread to gauge interest in a group buy for the Leach clone 12 output amplifier.
I have recently received many requests for pcb's which are not available.
If you are interested in purchasing these fine pcb's which are FR4 fiberglass, 2 oz. copper, green soldermask and white lettering respond to this thread and I will determine whether it is cost effective enough for me to proceed.
I can say for sure that with 80 to 100 boards manufactured we should be able to get them for less than 20.00 U.S. each. Advanced Circuits has the gerber files and can proceed anytime. I would like to have at least 150 made to bring down the price if at all possible. This Leach design has all of the components that Dr. Leach originally included in the amp with the additional devices totalling 12 outputs. The feedback trace is incorporated on this amp exactly like the original. Jens Rasmussen has done a superb job of designing this board and I think this is the best Leach amp layout to date.
You can leave your responses here in this thread or send me an email with the number of boards you will need, your full name AND diy audio name, plus legal address and email address. It is sometimes very hard to determine who one is with the diy name different from the legal name.
Remember we are gauging interest there are currently no boards ordered. Please remember this. If you have been wanting to build a very nice BJT amplifier with all of the good stuff in it, plus mucho available horsepower, this is the amp to build. It is not cheap.
Tad
I have recently received many requests for pcb's which are not available.
If you are interested in purchasing these fine pcb's which are FR4 fiberglass, 2 oz. copper, green soldermask and white lettering respond to this thread and I will determine whether it is cost effective enough for me to proceed.
I can say for sure that with 80 to 100 boards manufactured we should be able to get them for less than 20.00 U.S. each. Advanced Circuits has the gerber files and can proceed anytime. I would like to have at least 150 made to bring down the price if at all possible. This Leach design has all of the components that Dr. Leach originally included in the amp with the additional devices totalling 12 outputs. The feedback trace is incorporated on this amp exactly like the original. Jens Rasmussen has done a superb job of designing this board and I think this is the best Leach amp layout to date.
You can leave your responses here in this thread or send me an email with the number of boards you will need, your full name AND diy audio name, plus legal address and email address. It is sometimes very hard to determine who one is with the diy name different from the legal name.
Remember we are gauging interest there are currently no boards ordered. Please remember this. If you have been wanting to build a very nice BJT amplifier with all of the good stuff in it, plus mucho available horsepower, this is the amp to build. It is not cheap.
Tad
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I'd be in for a minimum of 3 boards but more then likely I'd like to get probably 6 depending on what we can get the cost down too.
I don't know if there is a way for me to be a first time customer to get the 500 dollars without having to put up the money, aka me be the customer, someone else pays and has them shipped to the payer. This way we can get the discount and drop the price a bit more. If there is a way to work it out I'd have no problems with it. Otherwise I'd have to do pre-orders to get the discount because I just don't have that kind of cash to put up.
I don't know if there is a way for me to be a first time customer to get the 500 dollars without having to put up the money, aka me be the customer, someone else pays and has them shipped to the payer. This way we can get the discount and drop the price a bit more. If there is a way to work it out I'd have no problems with it. Otherwise I'd have to do pre-orders to get the discount because I just don't have that kind of cash to put up.
Doug,
I have been looking for ways to get the five hundred dollar discount everytime we order but doing the right thing has it rewards. The board houses have to make a living too. Heck there is no telling how many free samples the diy audio crowd receives from the chip companies -- me included.
Once we get this thing rolling I will ask my rep at Advanced Circuits if there are any rewards for loyal repeat customers. If the company can come off of a few hundred that would help tremendously. The economy as a whole has made hobby projects for most people an item of last resort.
So far we have 10 boards spoken for. We still have a way to go.
Here is a picture of the pcb's next to the 10 output board. Tad
I have been looking for ways to get the five hundred dollar discount everytime we order but doing the right thing has it rewards. The board houses have to make a living too. Heck there is no telling how many free samples the diy audio crowd receives from the chip companies -- me included.
Once we get this thing rolling I will ask my rep at Advanced Circuits if there are any rewards for loyal repeat customers. If the company can come off of a few hundred that would help tremendously. The economy as a whole has made hobby projects for most people an item of last resort.
So far we have 10 boards spoken for. We still have a way to go.
Here is a picture of the pcb's next to the 10 output board. Tad
A friend of mine is hooking me up with some encapsulated custom transformers. I'm going to be building 2 mono block amps. I'm going to use an 800VA transformer for these but I'm curious about the voltage? This one will be using all 12 output devices and it would be nice to have 600 watts or so into 4ohms. My speakers are closer to 8ohms nom though so ~400 watts into 8 ohms would be my goal for the mono blocks? Although if I can do better by all means 
The chassis's I plan on getting have large heatsinks. They are from Hifi2000 and 3U high cases 300mm deep with the heatsinks on the sides.
The second amp will be in the same size enclosure, but it's going to be 3 channels. I'll be only using 6 devices per board on this one. I plan on using a 1KVA transformer.
So basically I need to know what specs I need for the transformers. I'm thinking for the 3 channel it'll be 40-0-40 or maybe 45-0-45. The mono blocks I've no idea... Was thinking 85V rails? So a 60VAC transformer or so? Or would 100V rails be possible? Looking for your guys suggestion before I tell him what I need. I can pretty much have anything I want so let me know what you'd do.
The chassis's I plan on getting have large heatsinks. They are from Hifi2000 and 3U high cases 300mm deep with the heatsinks on the sides. The second amp will be in the same size enclosure, but it's going to be 3 channels. I'll be only using 6 devices per board on this one. I plan on using a 1KVA transformer.
So basically I need to know what specs I need for the transformers. I'm thinking for the 3 channel it'll be 40-0-40 or maybe 45-0-45. The mono blocks I've no idea... Was thinking 85V rails? So a 60VAC transformer or so? Or would 100V rails be possible? Looking for your guys suggestion before I tell him what I need. I can pretty much have anything I want so let me know what you'd do.
Hi,
an amplifier that can push 400W into 8r0 but be capable of also driving a 4ohm speaker should easily get 700W into 4r0.
Running this from an 800VA transformer is not going to release the power it should be capable of.
400W into 8r0 needs 80Vpk at the speaker terminals. A 50Vac transformer will give about 72V to 75V supply rails, 55Vac ~ 78V to 82V supply rails.
So 60Vac giving 85 to 90V on the supplies looks about right.
That is about the maximum you can use 100Vdc smoothing capacitors with.
If you need 700W into 4ohm speakers then I'd suggest a 1200VA 60+60Vac transformer.
If 500W into 6r0 is adequate for your needs then 800VA 60+60Vac will be about right.
1kVA 45+45Vac should take your 3channel 3pair into 8ohm output stages to their limits if you can cool them enough.
40+40Vac can use 63Vdc capacitors.
an amplifier that can push 400W into 8r0 but be capable of also driving a 4ohm speaker should easily get 700W into 4r0.
Running this from an 800VA transformer is not going to release the power it should be capable of.
400W into 8r0 needs 80Vpk at the speaker terminals. A 50Vac transformer will give about 72V to 75V supply rails, 55Vac ~ 78V to 82V supply rails.
So 60Vac giving 85 to 90V on the supplies looks about right.
That is about the maximum you can use 100Vdc smoothing capacitors with.
If you need 700W into 4ohm speakers then I'd suggest a 1200VA 60+60Vac transformer.
If 500W into 6r0 is adequate for your needs then 800VA 60+60Vac will be about right.
1kVA 45+45Vac should take your 3channel 3pair into 8ohm output stages to their limits if you can cool them enough.
40+40Vac can use 63Vdc capacitors.
Sakis,
If you are sincere and want to learn AndrewT can be a very helpful person to have around. He most definately is a storehouse of information.
To the best of my knowledge Antek transformers has the best all around prices on toroid transformers. To go from 700 va to 1kva transformer is not too much more money and you get what you need and some.
I am using a 1kva transformer for each channel with 70+ volt rails on the older Leach 10 and I have a lot of unused watts on hand.
I will be doing the same for the Leach 12 with a regulated frontend. I can not think of too many speakers this setup will not melt together. We are talking about DIY Audio power not commercial peak power. Most of the amp builds on this forum are true powerhouses and deliver good strong RMS output. The expensive kind of power.
Tad
If you are sincere and want to learn AndrewT can be a very helpful person to have around. He most definately is a storehouse of information.
To the best of my knowledge Antek transformers has the best all around prices on toroid transformers. To go from 700 va to 1kva transformer is not too much more money and you get what you need and some.
I am using a 1kva transformer for each channel with 70+ volt rails on the older Leach 10 and I have a lot of unused watts on hand.
I will be doing the same for the Leach 12 with a regulated frontend. I can not think of too many speakers this setup will not melt together. We are talking about DIY Audio power not commercial peak power. Most of the amp builds on this forum are true powerhouses and deliver good strong RMS output. The expensive kind of power.
Tad
Well 700 may of be a stretch. I don't need that much power but I like overbuilding.
I do plan on using one of the boards for a sub amp, I want to build an active crossover and build the amp capable of 700 or so watts for sure then. Should be pretty neat.
The transformers I'm getting made should be free if not very cheap at the most. I can probably do 1200VA 60VAC no problem. Although I think an 800VA would be plenty for my needs. I do neeed it to drive 4ohm speakers though. Does 6r0 mean 6 ohm? I think what I should do is shoot for 400@8ohm and make it capable of running 4ohm, but I don't want it to run out of steam either. So do you think in this case I should use the 1200VA 60VAC?
The 6 pair output leach amp should be able to do just about any amount of power I want I just have to scale parts of it up, like the capacitors and what not correct?
I'm strongly considering doing a regulated PSU for mine as well. If I do this I believe I should get a bit higher then the 60VAC, maybe 65VAC as I would regulat the rails down to the voltage I want correct?
I do plan on using one of the boards for a sub amp, I want to build an active crossover and build the amp capable of 700 or so watts for sure then. Should be pretty neat.
The transformers I'm getting made should be free if not very cheap at the most. I can probably do 1200VA 60VAC no problem. Although I think an 800VA would be plenty for my needs. I do neeed it to drive 4ohm speakers though. Does 6r0 mean 6 ohm? I think what I should do is shoot for 400@8ohm and make it capable of running 4ohm, but I don't want it to run out of steam either. So do you think in this case I should use the 1200VA 60VAC?
The 6 pair output leach amp should be able to do just about any amount of power I want I just have to scale parts of it up, like the capacitors and what not correct?
I'm strongly considering doing a regulated PSU for mine as well. If I do this I believe I should get a bit higher then the 60VAC, maybe 65VAC as I would regulat the rails down to the voltage I want correct?
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