Re: 6 transistor leach
Their values are very dependent on:
The Vdc of the supply rails
The VA of the transformer
The value of smoothing capacitance fitted
The heat dissipation capability of the heatsink
The ambient temperature
The output devices fitted, both SOA and power
The Rth c-s of the isolation film used
The value of the load impedance
The value of emitter resistor fitted
The Vbe characteristic of the protection transistor
I suspect I have omitted a few, but you must include the builder's philosophy on what current is allowed to pass at full limiting, what should pass short term without any audible effect and what transient current should pass without triggering or activating the protection transistor. All of this is referred to in various posts in the clone threads.
There is no "one fits all " solution.
these are the protection circuit resistors.lgreen said:
Their values are very dependent on:
The Vdc of the supply rails
The VA of the transformer
The value of smoothing capacitance fitted
The heat dissipation capability of the heatsink
The ambient temperature
The output devices fitted, both SOA and power
The Rth c-s of the isolation film used
The value of the load impedance
The value of emitter resistor fitted
The Vbe characteristic of the protection transistor
I suspect I have omitted a few, but you must include the builder's philosophy on what current is allowed to pass at full limiting, what should pass short term without any audible effect and what transient current should pass without triggering or activating the protection transistor. All of this is referred to in various posts in the clone threads.
There is no "one fits all " solution.
Re: 6 transistor leach
You can find info about those values on this page:
http://www.diyaudio.com/forums/showthread.php?postid=686029#post686029
and this one for another rail voltage:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=52459&perpage=25&highlight=&pagenumber=33 (bottom of the page)
If you are still unsure, I'd suggest using the original construction from Dr. Leach.
PCB can be downloaded here (Protel files): http://www.sidesign.co.nz/downloads.htm
I hope this helps
lgreen said:
You can find info about those values on this page:
http://www.diyaudio.com/forums/showthread.php?postid=686029#post686029
and this one for another rail voltage:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=52459&perpage=25&highlight=&pagenumber=33 (bottom of the page)
If you are still unsure, I'd suggest using the original construction from Dr. Leach.
PCB can be downloaded here (Protel files): http://www.sidesign.co.nz/downloads.htm
I hope this helps
you cannot use Leach's values.
They are for a different protection circuit and ONLY applicable if the whole schematic is copied exactly. 3pair can never = 2pair.
They are for a different protection circuit and ONLY applicable if the whole schematic is copied exactly. 3pair can never = 2pair.
I didn't mean using those values. I meant constructing the original Leach with the plans of Dr. Leach and to forget about this Leach clone if he has problems calculating the values for the protection circuit. That's the reason I attached a link for the original PCB plans since you can't order those anymore.
ahhh....
ahhh!!!! now i get it.
AndrewT is going to have me doing math!
Actually I'll try but maybe i'll ask for help when everything is ready? I hate to dissapoint cause he is such a nice person and has helped me a lot over the years.
ahhh!!!! now i get it.
AndrewT is going to have me doing math!
Actually I'll try but maybe i'll ask for help when everything is ready? I hate to dissapoint cause he is such a nice person and has helped me a lot over the years.
If you go to the Delta-audio.com site most of the information you need, including the protection circuit formula. Jens has a rather extensive detailed amount of helpful information. Pay attention the detailed spec dimensions for the parts. Believe me if I can build this amp from the available literature anyone can.
Remember the numbers are for the RAIL voltages not the transformer output voltage. Also pay VERY close attention to the PCM dimensions on the film capacitors or you will be placing another order. You will find that the Dale RN and RS resistors will be extremely tight in some of the pcb pads. Do not try to drill them out it is not worth it. Shoot for something more run of the mill and it will fit perfectly. Make sure the solder wicks to the front of the board.
Have fun.
Tad
Remember the numbers are for the RAIL voltages not the transformer output voltage. Also pay VERY close attention to the PCM dimensions on the film capacitors or you will be placing another order. You will find that the Dale RN and RS resistors will be extremely tight in some of the pcb pads. Do not try to drill them out it is not worth it. Shoot for something more run of the mill and it will fit perfectly. Make sure the solder wicks to the front of the board.
Have fun.
Tad
I wanted to do this project myself a few years ago, but the PCB is all about dimensions, and almost all quality components are larger.
Here is a bad example: http://img510.imageshack.us/img510/9271/random072hs8.jpg
Some of the components didn't fit at all since the constructor didn't pay attention to dimensions.
Here is a bad example: http://img510.imageshack.us/img510/9271/random072hs8.jpg
Some of the components didn't fit at all since the constructor didn't pay attention to dimensions.
duekfx,
That particular amp looks O.K. If you look through some of the threads on this forum you will see that some of the really experienced designers still stand the resistors vertical/semi-vertical out of choice not necessity.
The Leach clone is a large board as it is. To have designed it for large Rn resistors or some combination of other components would have made it so large it would have been prohibitive to have made.
I have two almost complete Leach 10 transitor boards stuffed with odd parts that I scrapped because I destroyed so many pads trying to get audiophile components on the board. I have since begun to acquire components that are just as good to my ears and much cheaper. They are also easier to work with. I learned this the hard way. If you look at some of Nelson Pass' commercial offerings you will not see any exotic components and he has one of the best reps out there.
One of the best places to spend money is on the pcb itself. If you choose a good job shop and spec heavy traces and board thickness I think the overall result is improved consisderably. I think we learn these things by trial and error. If you can not hear the difference with you own ears it does not make since to delve any deeper for components.
I have a small group of friends, none of which share my hobby interests, so I have no one to brag to about what items go in my projects. This is one reason I sold off all of my expensive gear and went DIY. If you can not boast to anyone about your expensive toys there value is lost. It is a man thing I guess. Just my rambling here.
Tad
That particular amp looks O.K. If you look through some of the threads on this forum you will see that some of the really experienced designers still stand the resistors vertical/semi-vertical out of choice not necessity.
The Leach clone is a large board as it is. To have designed it for large Rn resistors or some combination of other components would have made it so large it would have been prohibitive to have made.
I have two almost complete Leach 10 transitor boards stuffed with odd parts that I scrapped because I destroyed so many pads trying to get audiophile components on the board. I have since begun to acquire components that are just as good to my ears and much cheaper. They are also easier to work with. I learned this the hard way. If you look at some of Nelson Pass' commercial offerings you will not see any exotic components and he has one of the best reps out there.
One of the best places to spend money is on the pcb itself. If you choose a good job shop and spec heavy traces and board thickness I think the overall result is improved consisderably. I think we learn these things by trial and error. If you can not hear the difference with you own ears it does not make since to delve any deeper for components.
I have a small group of friends, none of which share my hobby interests, so I have no one to brag to about what items go in my projects. This is one reason I sold off all of my expensive gear and went DIY. If you can not boast to anyone about your expensive toys there value is lost. It is a man thing I guess. Just my rambling here.
Tad
In my point of view of "quality" is a quite complex concept, it doesn't necessarily mean boutique stuff. A cap needs to have low noise, a good type of dielectric, long life and tight tolerance. Well, these parts are quite large and don't really fit on the PCB. Those "5mm pin spacing" types give you no other choice than polyester (or even worse: ceramic). As for resistors, if you need 0.25W for example, I prefer to use 1W instead for lower noise. Look at the feedback resistors, 4 in parallel on the PCB. You need to be quite tricky to fit such in that location. The list goes on, and it's quite long. I don't mean to offend anyone, in fact I like this design. It looks really professional, otherwise I wouldn't have tried getting proper parts, but I gave up. However it doesn't suit everyone's needs. There are basic rules for PCB designs. 1 is to avoid the parasitic effects which are generated when parts are insanely close to each other, the other 1 is to keep wires as short as possible. Vertical or semi-vertical means you will have longer wire on 1 side. The best way to go is to buy parts and design the PCB after you know the dimensions of your parts. I know, not everyone can do that, and the are a lot of careless people who don't bother with "quality" components, in fact there are quite a lot. I am not the type of guy (like our beloved Carlos 
) to build 4700+ amplifiers. I prefer to build stuff that I'll use for decades, so "quality" means a lot to me.
) to build 4700+ amplifiers. I prefer to build stuff that I'll use for decades, so "quality" means a lot to me.
duekfx said:
PP or PE have both and will fit the board
duekfx said:
Why?
duekfx said:
Please explain further, I make low noise designs using 0402 SMD type parts.....
duekfx said:
I made a BOM with details for parts sizes to make sure that builders can buy part that fit the board.... If you want to use other part, please be free to do so, but don't blame me for any trouble... it is IMPOSSIBLE to make everybody happy when it comes to parts..... some like a specific brand some like an other... and the size of the PCB is a large part of the final cost!
duekfx said:
Really - tell me more
duekfx said:
Well it is 😉
duekfx said:
It was never meant to!
duekfx said:
And this was how this design was made in the first place (my private project turned into a group buy)
BTW your list of important things is missing the most important one: COMPROMIZE
\\\Jens
PE yes, PP no. C8 for example, I wasn't able to locate any PP with those specifications. PP usually starts in the nF range. And PE is a crappy type of dielectric imo.JensRasmussen said:
For better stability and aging issues, especially when it comes to symmetrical topologies.JensRasmussen said:
For the exact same reason people use 3 1Ohm resistors in parallel for a 0.33 emitter value for example, or why people oversize their trafos, or why people favor MPSAs in the VAS stage where even BC/BDs would be enough, or why you like thick copper (3oz) for your PCB etc etc etc. The keywords are "oversize" and "less stress"JensRasmussen said:
You are correct, and nobody is blaming you. There is no design that would satisfy everyone. However people like me, favor quality components and won't let a 5mm pin spacing spec. and things like this ruin the fun 😉 The best method would be to buy all parts and design a PCB for the available parts, or sell this PCB as kit inc. all components.JensRasmussen said:
The list would be really long, but 98% are size issues. Hole sizes, pin spacing, diameter of ELKOs and such. They are quite uncommon and hard to get even at international dealers (except for the quarter cent resistors which would fit perfectly but audiophiles avoid those anyway).JensRasmussen said:
In my design consulting work I have the opportunity to test lots of professional equipment before recommending them for a specific project.
More often than not, I get gear before they are commercially available.
The first thing I do is to take them apart and check for design/manufacturing flaws that would negatively impact my design (and to satisfy my curiosity). 😀
Compared to the boards I have seen from hundreds of manufacturers, the ones from Jens are second to none.
(I for one will be very happy the day I can design a board half as good as the one Jens designed for the Leach amp.)
Thanks Jens for sharing your projects with us.
More often than not, I get gear before they are commercially available.
The first thing I do is to take them apart and check for design/manufacturing flaws that would negatively impact my design (and to satisfy my curiosity). 😀
Compared to the boards I have seen from hundreds of manufacturers, the ones from Jens are second to none.
(I for one will be very happy the day I can design a board half as good as the one Jens designed for the Leach amp.)
Thanks Jens for sharing your projects with us.
Indeed. Assuming he'd have designed this for himself only, I'd rate it a 9.5/10. 9.5 because he didn't make the bottom layer corners round like the Mark Levinsons. 😀
duekfx said:
But I did design this for myself.... The GB was not my idea, I was just happy to find that someone liked the project enough to spend their time and money to build it themselves.
\\\Jens
And it is these exact comments which, I assume, have made a wealth of knowledge, aka, Jens, become so scarce these past few months.
I wish you had more time to spend here at DIY Jens, but I am aware of your other more important duties.
I for one second duda's thanks for sharing this design with us.
Good luck and thanks for dropping in.
Tad
I wish you had more time to spend here at DIY Jens, but I am aware of your other more important duties.
I for one second duda's thanks for sharing this design with us.
Good luck and thanks for dropping in.
Tad
0.6W resistors?
most of the resistors are specified for 0.6 W, is this really true? Sure cannot use .5 or .25 W for many of them as .6 will probably move you up to 1 W which is much bigger.
most of the resistors are specified for 0.6 W, is this really true? Sure cannot use .5 or .25 W for many of them as .6 will probably move you up to 1 W which is much bigger.
The original Leach used 1/4W for most positions, and the actual dissipation is significantly less than 1/4W in most. Yes, you can use mostly 1/4W. R3, R22, R26 and R34 need to be at least 1/2W depending on rail voltage.
Re: 0.6W resistors?
I use metal film types that are rated for 0.6W...
If you use older 5% types, these are often carbon types rated at 0.5W in the same size housing...
And yes, 0.25W will be fine for most parts, but as I have lots of 0.6W types in my local stock, I use these first 😉
I hope this helps 🙂
\\\Jens
lgreen said:
I use metal film types that are rated for 0.6W...
If you use older 5% types, these are often carbon types rated at 0.5W in the same size housing...
And yes, 0.25W will be fine for most parts, but as I have lots of 0.6W types in my local stock, I use these first 😉
I hope this helps 🙂
\\\Jens