we have actually different solutions
all of these depends on the availability of the materials.The heatsinks.
but of course one of the very best solution is one of Jens,
and I think also same as Anthony Holtons.
When you lay those outputs on a bed of roses.
and hard wiring is one of the very dangerous solutions...
ive got no enough money yet, so Jens you might want to reserve some
artwork for me in the future.
for the moment I'll just etch it my way
regards,
hienrich
JensRasmussen said:
Sounds like a great idea! I had planned on doing this for a while, after making my redesign on the original leach amp:
http://www.briangt.com/gallery/leachamppcb
It would be nice to use the flat pack devices, like in these 2 leach amps:
http://www.briangt.com/gallery/jeetamp
http://www.briangt.com/gallery/leachamp-5channel
(I helped in the design and construction of these amps for friends)
As for the component choice, I like the idea of keeping it through-hole components, so that the project is more appealing to all. I like using the compact 0.5w metal film resistors (0.2" spacing), as they allow the layout to be made a lot smaller. Almost all of the resistors in this amp will be fine with these resistors. These are also getting easy to obtain with multiple vendors making them now.
As for the features of the amp, I wouldn't deviate too far from leach's original superamp design. It would be best to minimize the size of the pcb, so that it is versatile for most chassis designs. It the boards require an 8" high chassis, then it will be harder to implement.
As for technology, 2oz copper, double-sided boards are pretty much the standard and have become affordable enough. The design can be optimized to use the 2 layers efficiency. There is no need to stick to 1 side, as if people want to etch their own boards, then they can use the original design.
As for a target price, $20-25 for a pair of boards should be feasable, and given the price to get pcbs made, this is easily done. I am willing to help out in the ordering of the pcbs if you want.
As for an alternate idea, instead of a single board for all, a main board could be done, and then 2 expansion boards, one for each side of devices. This would allow for a more 3D design to be done, possibly similar to this:
http://www.myclie.info/images/CJR0425-2.jpg
but with less output devices, (4 per side). This would also allow for the option of making different expansion boards later to allow for more parallel devices. This wouldn't add too much to the cost of the pcb, as you can still do it with 1 pcb and add scoring to allow them to easily break apart, as I have done with my gainclone boards.
If people have some ideas about modifying the design, I can talk to Dr. Leach and see if he has any input into the modifications.
Just some ideas, let me know what you think,
--
Brian
Hello jacco vermeulen,
I see maxhawks boards for a Low TIM Leach amp using plastic transistors.
I have posted pics as a tool for conversation on implementation methods. Having built several of these amps in various configurations with great success, I am a happy camper with the crude layout and standard components as recommended by Prof. Leach.
At the risk of offending folks, I already have more of these amps than I have use for and have no intention of building more at this point. My intention was and still is to be helpful. I am not going to get into any kind of p*ssing match over some minor detail with you or anyone else.
It's your amp, build it any way you wish.
Prosit
I see maxhawks boards for a Low TIM Leach amp using plastic transistors.
I have posted pics as a tool for conversation on implementation methods. Having built several of these amps in various configurations with great success, I am a happy camper with the crude layout and standard components as recommended by Prof. Leach.
At the risk of offending folks, I already have more of these amps than I have use for and have no intention of building more at this point. My intention was and still is to be helpful. I am not going to get into any kind of p*ssing match over some minor detail with you or anyone else.
It's your amp, build it any way you wish.
Prosit
Hi acenovelty,
I think Jacco was thinking about the long wires.
Hi all,
Man I think this will be a hard one to solve. That means more fun for everybody
I agree with Brian on choosing double sided boards with plated through holes, if anybody whats to make their own boards, they can use the original. Plated holes are better, and allows for a tighter layout.
I think we should keep it simple and use one whole board for everything to get rid of all the nasty wires that is needed in the original – can we agree on that?
I also think that it’s difficult to use the PCB area more efficiently than what I have done on my extended Leach amp – please comment on this
I have started the schematics drawing, and will post something during tomorrow afternoon if all goes to plan.
\Jens
I think Jacco was thinking about the long wires.
Hi all,
Man I think this will be a hard one to solve. That means more fun for everybody
I agree with Brian on choosing double sided boards with plated through holes, if anybody whats to make their own boards, they can use the original. Plated holes are better, and allows for a tighter layout.
I think we should keep it simple and use one whole board for everything to get rid of all the nasty wires that is needed in the original – can we agree on that?
I also think that it’s difficult to use the PCB area more efficiently than what I have done on my extended Leach amp – please comment on this
I have started the schematics drawing, and will post something during tomorrow afternoon if all goes to plan.
\Jens
Actually, i like a bit of spacing. Like i said, the prototype leach boards look quite nice to me.
Not that i disagree with Brian, his suggestions are fine with me.
Especially the add-on boards, that 3-D pic looked like a Classé pcb clone.
That certainly would please my smashing MT-200 Toshiba's, i've got 48 of them.
Thanks again for the quick GC delivery, Brian.
The reference to AceNovelty's picture was indeed aimed at the extensive wiring, i can imagine a number here are not fond of this. The pcb looks a bit altered, but the wiring and that the pcb was turned 90 degrees was my point.
Brian's Leach design layout clearly shows the difference and what can be gained.
Brian is a former student of Marshall Leach at Georgia Tech and made a different layout, it shows that the idea of a modern layout is not a bad one.
Not that i disagree with Brian, his suggestions are fine with me.
Especially the add-on boards, that 3-D pic looked like a Classé pcb clone.
That certainly would please my smashing MT-200 Toshiba's, i've got 48 of them.
Thanks again for the quick GC delivery, Brian.
The reference to AceNovelty's picture was indeed aimed at the extensive wiring, i can imagine a number here are not fond of this. The pcb looks a bit altered, but the wiring and that the pcb was turned 90 degrees was my point.
Brian's Leach design layout clearly shows the difference and what can be gained.
Brian is a former student of Marshall Leach at Georgia Tech and made a different layout, it shows that the idea of a modern layout is not a bad one.
PCB
I am in too.Silk screen would be nice .I would like to fit 3 channels in a 19" rack enclosure if possible.Double sided is okay with and smd stuff okay but not prefered , pc power connectors or other connectors for wires would be much better dont like the soldering wires to board.Are we going to do group buy? I found this site for enclosures , do you guys think the 160 and 161 series would be good ? http://www.bataviaenclosures.com/ . I emailed them but havent got anything back yet .The prices look great and they do small quantity. What kind of transformers will we need ? I only have one for the low tim , I dont think its large enough for the super its only 40 x 40 800 Va .
I am in too.Silk screen would be nice .I would like to fit 3 channels in a 19" rack enclosure if possible.Double sided is okay with and smd stuff okay but not prefered , pc power connectors or other connectors for wires would be much better dont like the soldering wires to board.Are we going to do group buy? I found this site for enclosures , do you guys think the 160 and 161 series would be good ? http://www.bataviaenclosures.com/ . I emailed them but havent got anything back yet .The prices look great and they do small quantity. What kind of transformers will we need ? I only have one for the low tim , I dont think its large enough for the super its only 40 x 40 800 Va .
From the Leach doc's:
T1 - The transformer should have either a center tapped secondary or two separate secondary windings which can be wired in series. With 120 V ac rms applied to the primary, the no load secondary voltage should be 120 to 130 V ac rms for a center tapped secondary or 60+60 (60x2) to 65+65 (65x2) V ac rms for two secondary windings. This should give a no load amplifier power supply voltage of plus and minus 85 to 93 V dc. Some transformers are rated at 115 V ac rms on the primary. With 120 V ac rms applied, the secondary voltage will be greater by a factor 120/115. If the transformer is rated at full load, its no load voltage will be 15% to 20% higher. I would recommend a transformer current rating of at least 6 A.
This iteration of the amp is fully documented by Prof. Leach here:
http://users.ece.gatech.edu/~mleach/superamp/
Happy reading.
Prosit
T1 - The transformer should have either a center tapped secondary or two separate secondary windings which can be wired in series. With 120 V ac rms applied to the primary, the no load secondary voltage should be 120 to 130 V ac rms for a center tapped secondary or 60+60 (60x2) to 65+65 (65x2) V ac rms for two secondary windings. This should give a no load amplifier power supply voltage of plus and minus 85 to 93 V dc. Some transformers are rated at 115 V ac rms on the primary. With 120 V ac rms applied, the secondary voltage will be greater by a factor 120/115. If the transformer is rated at full load, its no load voltage will be 15% to 20% higher. I would recommend a transformer current rating of at least 6 A.
This iteration of the amp is fully documented by Prof. Leach here:
http://users.ece.gatech.edu/~mleach/superamp/
Happy reading.
Prosit
Re: PCB
Those series 161 and 171 look very good, their prices would be a bargain on this side of the big lake.
But i wonder where you intend to place the heatsinks.
This amplifier will need sufficient cooling area, placing the heatsinks inside the enclosure will not be such a good idea.
The most logical place on the outside of the enclosure would be the back, but will the height be enough ? You would have to go for a large one, 6' minimum.
But that leaves the question how to place dual side outputs on a single heatsink.
Funny to see a company in New York with such an ancient Dutch name.
dherr555 said:
Those series 161 and 171 look very good, their prices would be a bargain on this side of the big lake.
But i wonder where you intend to place the heatsinks.
This amplifier will need sufficient cooling area, placing the heatsinks inside the enclosure will not be such a good idea.
The most logical place on the outside of the enclosure would be the back, but will the height be enough ? You would have to go for a large one, 6' minimum.
But that leaves the question how to place dual side outputs on a single heatsink.
Funny to see a company in New York with such an ancient Dutch name.
When mentioned .1" connectors, my reasoning was this:
There are a huge variety of connectors that share the layout.
You can use board-to-board direct connection, a wire-based connector for remote mounting, etc.
I was thinking last night that if the board was designed as a single board with perforations between the power/driver/output areas, and a orw of .1 spaced holes at the edge of each, then you can leave it as one bg board and jumper the holes (very small jumpers), break it into seperate boards and hard wire them or add the connector of you choice. That way we all have flexibility in mounting with a single layout design.
Sound too complicated?
There are a huge variety of connectors that share the layout.
You can use board-to-board direct connection, a wire-based connector for remote mounting, etc.
I was thinking last night that if the board was designed as a single board with perforations between the power/driver/output areas, and a orw of .1 spaced holes at the edge of each, then you can leave it as one bg board and jumper the holes (very small jumpers), break it into seperate boards and hard wire them or add the connector of you choice. That way we all have flexibility in mounting with a single layout design.
Sound too complicated?
You may want to consider four hole mounting for all the small transistors. This way central base and central collector types could be used. Same thing for the Vas, so either a TO5 or TO126 may be used.
When the Super Leach was designed the SOA on the MJ15003/04 started to fold back at 50V. With the MJ21193/94 being good to about 100V there is no real need for series connection of the output stages. Using plastic is a different story. I would use three plastic for every two metal outputs (minimum). The guy using ±60V will need three pairs per channel, those using ±85V will need six pair. If you really wanted to be flexible you could build the output board for four pair with some score marks, etc.
The AN1302 design from Motorola (ON Semiconductor) shows three pair of plastic on ±57V and does a load line on it.
This should be brought to attention:
http://www.audioxpress.com/bksprods/pcbs/solidstate.htm
ITEM # PCBP-3 Borbely 60W Mosfet Amplifier
From Audio Amateur Issue 2/82. Borbely EB-60 60W single-channel Mosfet amplifier. 3-3/8" x 6-1/8". 1 lb. $11.75
Ignore 'Mosfet', I've never used one with this board, I view it as a universal driver board. The schematic is basically the same as in AN1302.
In August they have all their boards on sale for half price, or $5.88 for this one. I buy a dozen of so every other year.
I keep some of these around too:
http://www.audioxpress.com/bksprods/pcbs/nelsonpass.htm
ITEM # PCBJ-5 Pass A40 Power Amplifier
From Audio Amateur Issue 4/78. Pass A-40 single-channel power amplifier. 3" x 3". 1 lb. $6.00
At $3 on sale how could I not?
I have built 600W amps using either of these boards as the front end.
When the Super Leach was designed the SOA on the MJ15003/04 started to fold back at 50V. With the MJ21193/94 being good to about 100V there is no real need for series connection of the output stages. Using plastic is a different story. I would use three plastic for every two metal outputs (minimum). The guy using ±60V will need three pairs per channel, those using ±85V will need six pair. If you really wanted to be flexible you could build the output board for four pair with some score marks, etc.
The AN1302 design from Motorola (ON Semiconductor) shows three pair of plastic on ±57V and does a load line on it.
This should be brought to attention:
http://www.audioxpress.com/bksprods/pcbs/solidstate.htm
ITEM # PCBP-3 Borbely 60W Mosfet Amplifier
From Audio Amateur Issue 2/82. Borbely EB-60 60W single-channel Mosfet amplifier. 3-3/8" x 6-1/8". 1 lb. $11.75
Ignore 'Mosfet', I've never used one with this board, I view it as a universal driver board. The schematic is basically the same as in AN1302.
In August they have all their boards on sale for half price, or $5.88 for this one. I buy a dozen of so every other year.
I keep some of these around too:
http://www.audioxpress.com/bksprods/pcbs/nelsonpass.htm
ITEM # PCBJ-5 Pass A40 Power Amplifier
From Audio Amateur Issue 4/78. Pass A-40 single-channel power amplifier. 3" x 3". 1 lb. $6.00
At $3 on sale how could I not?
I have built 600W amps using either of these boards as the front end.
Perhaps if one were to use high voltage transistors as the previous member suggested there would be no need for series configuration. Nowadays you can find 250v transistors from ON which are very high quality so we may go for a simple ordinary configuration, how about it?
Just a question: if we were to use say 10 or 12 transistors per channel instead of 8 would we need any adjustments in the feedback or bias? will the driver transistors be able to drive more transistors?
Just a question: if we were to use say 10 or 12 transistors per channel instead of 8 would we need any adjustments in the feedback or bias? will the driver transistors be able to drive more transistors?
"Just a question: if we were to use say 10 or 12 transistors per channel instead of 8 would we need any adjustments in the feedback or bias? will the driver transistors be able to drive more transistors?"
QSC uses 12 pair of MJ21193/94 on ±95V rails for over 1KW at 2R with only one pair of driver transistors.
The bias resistors for the zener diodes need to be changed.
QSC uses 12 pair of MJ21193/94 on ±95V rails for over 1KW at 2R with only one pair of driver transistors.
The bias resistors for the zener diodes need to be changed.
Hello folks,
As you work out the details of how to make these boards, maybe it would be a really good idea to actually READ and maybe understand all the documentation presented by Prof. Leach. It is very likely that he has seen what? hundreds, thousands of these amps built by his students. Do you suppose he may know what and how and why his design works so well?
Using plastic transistors might be considered modern and an improvement, but there must be some logical reason why a Professor of his stature would choose TO3's beyond the educational value.
For instance, this small quote:
"If you compare the Double Barreled circuit to the Low TIM circuit, you will see a lot of similarity between the two. Indeed, there is a Low TIM Amplifier embedded in the Double Barreled Amplifier. The major difference between the two is that transistors are added in series with those in the Low TIM circuit to form the Double Barreled circuit. By doing this, the voltage across the transistors is decreased so that the power supply voltage can be increased for higher output power."
RIF
Oh BTW, there might be some folks out there who would like to actually build exactly what the Prof. designed.
Prosit
As you work out the details of how to make these boards, maybe it would be a really good idea to actually READ and maybe understand all the documentation presented by Prof. Leach. It is very likely that he has seen what? hundreds, thousands of these amps built by his students. Do you suppose he may know what and how and why his design works so well?
Using plastic transistors might be considered modern and an improvement, but there must be some logical reason why a Professor of his stature would choose TO3's beyond the educational value.
For instance, this small quote:
"If you compare the Double Barreled circuit to the Low TIM circuit, you will see a lot of similarity between the two. Indeed, there is a Low TIM Amplifier embedded in the Double Barreled Amplifier. The major difference between the two is that transistors are added in series with those in the Low TIM circuit to form the Double Barreled circuit. By doing this, the voltage across the transistors is decreased so that the power supply voltage can be increased for higher output power."
RIF
Oh BTW, there might be some folks out there who would like to actually build exactly what the Prof. designed.
Prosit
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