"A 6 device Leach with such high voltage would be suicide on those loudspeakers'
My ±63V 6 device Leach has run since 1980 into 4 ohms, in 1989 the speakers were changed to 2 ohms. If driven more than 6dB into clipping it will activate the current limiter.
After 25 years of this it finally needed new outputs.
The original were MJ15011/12, the replacements were MJ21193/94.
If using plastic outputs, 10~12 plastic devices is about right to replace 6 metal devices.
My ±63V 6 device Leach has run since 1980 into 4 ohms, in 1989 the speakers were changed to 2 ohms. If driven more than 6dB into clipping it will activate the current limiter.
After 25 years of this it finally needed new outputs.
The original were MJ15011/12, the replacements were MJ21193/94.
If using plastic outputs, 10~12 plastic devices is about right to replace 6 metal devices.
djk said:
What made you arrive at a 1:2 TO-3 to TO-264 ratio?
What about the different TO-264 types, like the MJL21195/96?
\Jens
Sorry for the delay
Thanks Jens, i am not in a hurry if you may think so.
Just thinking of making a 6 or 10 transistor version.
My transformer rating is also 90v c.t. 7A
Jacco wrote:
Both parameters too high and max temperature is exceeded and the transistor dies.
And thats why this type of amps testing has more sense at about half power level then at full power output, in casu temperature.
Loek
Thanks Jens, i am not in a hurry if you may think so.
Just thinking of making a 6 or 10 transistor version.
My transformer rating is also 90v c.t. 7A
Jacco wrote:
Both parameters too high and max temperature is exceeded and the transistor dies.
And thats why this type of amps testing has more sense at about half power level then at full power output, in casu temperature.
Loek
"What made you arrive at a 1:2 TO-3 to TO-264 ratio?"
While there is not a great amount of difference in the watt rating between the plastic and the metal, there are two other factors.
Maximum junction temperature.
Thermal cycling life.
With the junction at 100*C under normal operation the plastic only has an availble Delta T of 50*C vs 100*C for metal.
The stainless steel TO3 package used by Motorola/ON has 10X the thermal cycling life the plastic or old aluminum TO3 did.
Between those two it works out to something like 2X as many plastic devices to replace 1 metal.
The future may hold different. Zetex has some lower power (less than 10W) plastic devices rated for 200*C, and IR has upgraded their plastic to 175*C.
IR was obviously doing something wrong at one point as their TO3 was only rated at 150*C (same as their plastic), and had worse thermal cycling data than the plastic.
I, for one, am glad to see ON keeping the TO3 package; Motorola was going to discontinue it.
While there is not a great amount of difference in the watt rating between the plastic and the metal, there are two other factors.
Maximum junction temperature.
Thermal cycling life.
With the junction at 100*C under normal operation the plastic only has an availble Delta T of 50*C vs 100*C for metal.
The stainless steel TO3 package used by Motorola/ON has 10X the thermal cycling life the plastic or old aluminum TO3 did.
Between those two it works out to something like 2X as many plastic devices to replace 1 metal.
The future may hold different. Zetex has some lower power (less than 10W) plastic devices rated for 200*C, and IR has upgraded their plastic to 175*C.
IR was obviously doing something wrong at one point as their TO3 was only rated at 150*C (same as their plastic), and had worse thermal cycling data than the plastic.
I, for one, am glad to see ON keeping the TO3 package; Motorola was going to discontinue it.
I wouldn't consider it as severe as that. Compare -
Pd derate at 75C at 100C
MJ15003 250W -.57%/deg 180W 143W case TO3
MJl21193 200W -.8%/deg 120W 80W case T03P
ratio 1.25 1.5 1.79
Initial expectation is lower of the plastic by 20% but, as long as it doesn't run too hot it's only derated by 33% c.f.
Pd derate at 75C at 100C
MJ15003 250W -.57%/deg 180W 143W case TO3
MJl21193 200W -.8%/deg 120W 80W case T03P
ratio 1.25 1.5 1.79
Initial expectation is lower of the plastic by 20% but, as long as it doesn't run too hot it's only derated by 33% c.f.
For TO247/264 cases i think it a good idea to go for 87.50C junction temperature instead of 100, (50% derated soa at 25C ambient).
That means going for a bigger heatsink to keep the Die junction cooler instead of opting for a higher number of devices to deliver the required current at 100C.
The latter in practice should imply cutting on heatsink cost for the 100C calculation.
Running more devices on high temperature with relatively small heatsinks, to me, sounds less logical than a small number of output devices on big heatsinks with the added advantage that lifespan is lengthened.
Under normal conditions, regular loudspeakers, the thermal load should be significantly lower than for worst case design load.
I remember the quad 303 amplifiers running on TO3 3055's on adequate heatsinks that drove the ESL's effortless, with 2.4 Ohms minimum impedance combined with maximum phaseshift in the worst frequency zone.
I would prefer TO3's too if decent ones were still made at price levels competitive with TO247 devices.
Mainly because i still have quite a bundle of TO3 Al2O3 insulators discs
(saving those for an ML2 remake, one day)
That means going for a bigger heatsink to keep the Die junction cooler instead of opting for a higher number of devices to deliver the required current at 100C.
The latter in practice should imply cutting on heatsink cost for the 100C calculation.
Running more devices on high temperature with relatively small heatsinks, to me, sounds less logical than a small number of output devices on big heatsinks with the added advantage that lifespan is lengthened.
Under normal conditions, regular loudspeakers, the thermal load should be significantly lower than for worst case design load.
I remember the quad 303 amplifiers running on TO3 3055's on adequate heatsinks that drove the ESL's effortless, with 2.4 Ohms minimum impedance combined with maximum phaseshift in the worst frequency zone.
I would prefer TO3's too if decent ones were still made at price levels competitive with TO247 devices.
Mainly because i still have quite a bundle of TO3 Al2O3 insulators discs
(saving those for an ML2 remake, one day)
Hi Jacco,
Sorry about the previous post - it was done as a table but didn't come out that way so makes poor reading.
Always when finessing a design it is TOO easy to add extra outputs but this compronises the speed so it's a balancing act, and we don't want to be prone to excess as that's a responsibility to Mother Earth to whom we are all responsible!
Every Erg needs to be justified.
Sorry about the previous post - it was done as a table but didn't come out that way so makes poor reading.
Always when finessing a design it is TOO easy to add extra outputs but this compronises the speed so it's a balancing act, and we don't want to be prone to excess as that's a responsibility to Mother Earth to whom we are all responsible!
Every Erg needs to be justified.
What about the fact that RTjc for the MJL4281 is 0.54 [C/W] while the standard TO-3 has a RTjc of 0.7 [C/W].
I think it is a 1:1.5 relationship.
\Jens
I think it is a 1:1.5 relationship.
\Jens
Mr Ball,
i never seem to get things down on a posting the way i like it, i gave up on trying to place scientific symbols on a posting after a few.
Too little can often be also too expensive, i have become to realise.
To me earth seems to become more and more a waste society, for a large portion because of reducing resources.
e.g. if you look at contemporary house construction techniques.
Nowadays in housing more attention is put in building lighter, which reduces the use of natural resources.
More attention is placed on building energy conscious by increasingly higher thermal insulation standards for newbuilds.
On the other hand average life expectancy of new houses is significantly lower.
In the long run. renovating or rebuilding may cost more than doing it right the first time with the eye pointed at longevity.
We, my doctor girlfriend and me, and some kids, live in a 1935 former orphanage.
Structural building of our home is of superior quality.
In our spare time we are renovating the house, partly with modern materials, partly with old recycled stuff of high quality.
On every spare hour i invest i admire the structural rigidity of our castle.
Renovated our home will be good for another 70 years, personally i prefer this over living in cardboard.
I agree that an amplifier design should be balanced.
Adding several pounds of transformer iron and copper without extra returns is a waste of money and resources, still something that seems very attractive in the diy scene.
The same should apply to the number of devices used and chosen heatsink factor.
Too little may proove too costly, by reducing life expectancy, the need for repairs and replacement.
For the Leach amplifier i am building i decided to construct a multi-functional chassis, one that i can use for other amplifiers i will build.
I enjoy building amplifiers, but the investment of building new chassis again and again for different amplifier projects seems a waste of my energy, and a waste of resources.
Instead of making several cheaper models for each project, constructing 2 chassis i can replace the amplifier modules of not only saves me a lot of time and energy, it saves big on materials in the long run.
Just by doing it a bit better the first time.
Perfection is balanced, not too little, not too much.
Your Eidetic amplifier is more of a beauty every time you are telling more of the design.
You know the feeling when someone else came up with the same ideas and confirms the validity of the thought ?
Regards,
J.
i never seem to get things down on a posting the way i like it, i gave up on trying to place scientific symbols on a posting after a few.
Too little can often be also too expensive, i have become to realise.
To me earth seems to become more and more a waste society, for a large portion because of reducing resources.
e.g. if you look at contemporary house construction techniques.
Nowadays in housing more attention is put in building lighter, which reduces the use of natural resources.
More attention is placed on building energy conscious by increasingly higher thermal insulation standards for newbuilds.
On the other hand average life expectancy of new houses is significantly lower.
In the long run. renovating or rebuilding may cost more than doing it right the first time with the eye pointed at longevity.
We, my doctor girlfriend and me, and some kids, live in a 1935 former orphanage.
Structural building of our home is of superior quality.
In our spare time we are renovating the house, partly with modern materials, partly with old recycled stuff of high quality.
On every spare hour i invest i admire the structural rigidity of our castle.
Renovated our home will be good for another 70 years, personally i prefer this over living in cardboard.
I agree that an amplifier design should be balanced.
Adding several pounds of transformer iron and copper without extra returns is a waste of money and resources, still something that seems very attractive in the diy scene.
The same should apply to the number of devices used and chosen heatsink factor.
Too little may proove too costly, by reducing life expectancy, the need for repairs and replacement.
For the Leach amplifier i am building i decided to construct a multi-functional chassis, one that i can use for other amplifiers i will build.
I enjoy building amplifiers, but the investment of building new chassis again and again for different amplifier projects seems a waste of my energy, and a waste of resources.
Instead of making several cheaper models for each project, constructing 2 chassis i can replace the amplifier modules of not only saves me a lot of time and energy, it saves big on materials in the long run.
Just by doing it a bit better the first time.
Perfection is balanced, not too little, not too much.
Your Eidetic amplifier is more of a beauty every time you are telling more of the design.
You know the feeling when someone else came up with the same ideas and confirms the validity of the thought ?
Regards,
J.
I have had several request during the last week for the 6 transistor version of the amp.
Does someone know how to make a wiki page where people can place an offecial order so I know how many boards to order?
\Jens
Does someone know how to make a wiki page where people can place an offecial order so I know how many boards to order?
\Jens
Leach Amp Wiki
I've created the wiki.
Its on the "everything else" wiki page. Here
Direct link is here
(http://www.diyaudio.com/wiki/index.php?page=+Leach+Amp+PCB+Group+Buy)
Now people can start modifying this to add the details.
I've created the wiki.
Its on the "everything else" wiki page. Here
Direct link is here
(http://www.diyaudio.com/wiki/index.php?page=+Leach+Amp+PCB+Group+Buy)
Now people can start modifying this to add the details.
Thank you so much.
To everybody who wants boards, please sign up.
When I have a price, I will post it here.....
An estimate can be found in post nr. 40
Thanks
\Jens
To everybody who wants boards, please sign up.
When I have a price, I will post it here.....
An estimate can be found in post nr. 40
Thanks
\Jens
Member
Joined 2002
JensRasmussen said:
Since i have done a group buy and i know what is involved i will do another : O ) I'll be ofering a group buy for parts for this leach amp. Also a group buy on the boards BUT i will only be offering this near teh middle of may 2005
Id like to get some of these board's my self.
Member
Joined 2002
JensRasmussen said:
Sorry i was giving people your email addy for this.. If you want i can control it now ?
email me and we can talk..
j'
Jason,
Do you want my temp manual also, and the assembly guide I have stated working on.... I also have simulations and mathcad worksheets of the whole thing if you like them.
Please understand that a manual is needed for the project. Potentiel leatheal voltages are involved, so extreeme care is in order.
\Jens
Do you want my temp manual also, and the assembly guide I have stated working on.... I also have simulations and mathcad worksheets of the whole thing if you like them.
Please understand that a manual is needed for the project. Potentiel leatheal voltages are involved, so extreeme care is in order.
\Jens
Member
Joined 2002
wiki update
I've added a parts col. to the wiki. you might want to edit and say offering will be in may sometime.
I've added a parts col. to the wiki. you might want to edit and say offering will be in may sometime.
Regarding parts and BOM.
I only have a partslist with numbers from my local parts shop (www.el-supply.dk) so I can only specify value and footprint used on the PCB. I don't know where you all get your parts, but I hope you understand that I do not plan to make different shopping lists with order numbers for all the different internet shops.
Sign up for boards here: http://www.diyaudio.com/wiki/index.php?page=+Leach+Amp+PCB+Group+Buy
\Jens
I only have a partslist with numbers from my local parts shop (www.el-supply.dk) so I can only specify value and footprint used on the PCB. I don't know where you all get your parts, but I hope you understand that I do not plan to make different shopping lists with order numbers for all the different internet shops.
Sign up for boards here: http://www.diyaudio.com/wiki/index.php?page=+Leach+Amp+PCB+Group+Buy
\Jens
Member
Joined 2002
- Status
- Not open for further replies.