You are correct , sir. Or just:
(41Vrms^2)/8R=210W
No actual need to calculate the current.
thanks guys
yes always 8ohm and i do understand losses. i always like the idea of cost no object power supplies. not sure if mentioned this but two chassis and 2 seperate power supplies.
so maybe i will only need 600va 65-0-65 as long as i'm not hurting any thing with 91v rails.
i have only built esp p101's and hoping slew will be easy as that was.
but see esp has a bill of components list that tells you exactly what to get.
i have never ordered parts from a schematic which has me worried.
building the board does not and i have both chassis started in aluminum.
like jwilhelm , i like the idea and sound when high power amps are used.
yes always 8ohm and i do understand losses. i always like the idea of cost no object power supplies. not sure if mentioned this but two chassis and 2 seperate power supplies.
so maybe i will only need 600va 65-0-65 as long as i'm not hurting any thing with 91v rails.
i have only built esp p101's and hoping slew will be easy as that was.
but see esp has a bill of components list that tells you exactly what to get.
i have never ordered parts from a schematic which has me worried.
building the board does not and i have both chassis started in aluminum.
like jwilhelm , i like the idea and sound when high power amps are used.
Full Vrms (with my 72V rails) with the 5 pair ops (njw0281/0302) is not
sustainable.
My 3 pair MT-200 version CAN sustain this abuse .
I was running a 7R industrial resistor array for load -
@>50Vrms (>300W)
5-pair became too hot - not using that for 4R use anyways.
3 Pair MT-200 , put a fan on that (boiled some water with the resistors
).Output device choice determines how big of a "monster" the slewmonster is.
either a 225W or a 400w watt amp is what you would have with a "stiff"
65-73V rail.
Either choice is way beyond what my mid-level speakers can handle.
OS
I'd suggest going about twice the VA rating as you expect in delivered power to the load, so a 500W into 8 ohm capable amplifier should be sporting a 1000VA transformer. I know many OEMs go the other way and use transformers rated at about 70% of the amplifier output to save some expense on copper and iron (and shipping I suppose too), but there's something about a build you could full power soak-test for days without issue.
This will be overkill for general domestic use, but if it is worth doing, it's worth over-doing!
This will be overkill for general domestic use, but if it is worth doing, it's worth over-doing!
I'd go a bit lower with the rails ... Even semelab outputs or the sanken's take quite
the SOA "hit" over 80V. For absolute max power slightly over>75V rails and
the better output devices will give close to 400W.
Consider , these amps play music , not resistive loads. Transients of well over
500w are easily done with any output configuration.
OS
Slewmaster comparison.
Very similar amps -
Pass Labs X250 (6K$).
-1Kva toroid /125Kuf / 75-0-75V supplies
- 6 pair outputs
-Rated 250w/8r 500W/4R
Parasound HCA-2200
- 800VA shielded trafo /150Kuf / 72V supplies
- also 6 pair outputs
-200W / 385W (4 R)
HK 990
- 2 X400VA / 2 X32K uf / 75V rails
- Just 5 pairs OP
-150W / 275W
-smaller PS's degrade rating
- all 3 use a "spooky" type complimentary input stage.
So , we have 2K - 6K$ amplifiers that are almost the exact same
as a slewmonster/spooky combo. But we can choose any level
right up to the PASS ! (the best one).
OS
Very similar amps -
Pass Labs X250 (6K$).
-1Kva toroid /125Kuf / 75-0-75V supplies
- 6 pair outputs
-Rated 250w/8r 500W/4R
Parasound HCA-2200
- 800VA shielded trafo /150Kuf / 72V supplies
- also 6 pair outputs
-200W / 385W (4 R)
HK 990
- 2 X400VA / 2 X32K uf / 75V rails
- Just 5 pairs OP
-150W / 275W
-smaller PS's degrade rating
- all 3 use a "spooky" type complimentary input stage.
So , we have 2K - 6K$ amplifiers that are almost the exact same
as a slewmonster/spooky combo. But we can choose any level
right up to the PASS ! (the best one).
OS
To me, +-90v rails is too high. It just puts a strain on everything. I have two amp that run that high of rails, Leach Super amp and a Perreaux 9000B. The Leach uses a cascoded output section so the output don't see the full brunt of it. The 9000B uses 6 pair Exicon Latfets per channel and it needs a fan running in AB mode. I think Prreaux had pro sound in mind when they built this amp. My JBLs don't like it. Just too much power. IMO, a 55-0-55vac transformer is about perfect for the Slewmaster. It will literally shake the windows without breaking a sweat. Waaaay louder that I would ever choose to listen unless I'm showing off.
Blessings, Terry
Blessings, Terry
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yes sir i am in the same mind frame as you. there is just something about hand made items that makes me love them. chassis are one that you see and love for hours after hours and years.
last week i was never looking for another amp build till i looked at the post solid state pictures.
your chassis lead me down this path . the p101 are in clean plain chassis i built this time the slews are going to be pieces of all out art. that is if i can make what is in my mind. you know if i can make my ideas look right. need to get what ever heatsink first to get a overall size scale right.
thanks i always want the best i can do or get, don't care what it cost. just takes me longer to build but in the end it will be over built. i only say 1000va for this reason, to insure over built. my 2 p101 have a 300va that looks to small . works perfect to make around 150 w peak and i alway use about 50 watts output.
awesome terry brother thats is exact for builders need. 50-0 -50 it is.To me, +-90v rails is too high. It just puts a strain on everything. I have two amp that run that high of rails, Leach Super amp and a Perreaux 9000B. The Leach uses a cascoded output section so the output don't see the full brunt of it. The 9000B uses 6 pair Exicon Latfets per channel and it needs a fan running in AB mode. I think Prreaux had pro sound in mind when they built this amp. My JBLs don't like it. Just too much power. IMO, a 55-0-55vac transformer is about perfect for the Slewmaster. It will literally shake the windows without breaking a sweat. Waaaay louder that I would ever choose to listen unless I'm showing off.
Blessings, Terry
still4given
jkuetemann
jwilhelm
ostripper
and guys the four of you are mentors in my mind
i have such great respect for you all
please don't think you can't call me wrong or sent me in different direction
i value your ideas
so today i called plitron about 2 toroidal they tell me they can do 625vac 50-0-50 or 1000va 50-0-50
they asked what i was building and told me 625vac was all i needed said the 1000vac was really ok but just a waist.
so ordered 2 625vac right now yeah
another question comes up
how wide is the board with the outputs mounted to mount on a heatsink? i want to get these ordered from heatsink usa
ostripper
i got you brother with the amp examples perfectly clear
thanks guys
gordie
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You should likely go at least 6" tall with the heat sink if you are using their 1.3" extrusion. That will give you some room inside the chassis for parts. It would be wise to draw up your amp internals and figure out how much space you need. These things fill up fast with those big transformers and supply caps. That's the safest way to figure out heat sink size. Mine are 16" long and I still ended up mounting the inputs sideways.
Ha, if you are anything like the rest of us, this is only one of many. Don't pay too musch attention to the wattage claims of OEM amps. They claim crazy stuff like 200W per channel in their 6.1 system. You open it up and it has one 40-0-40 300va transformer. With 50-0-50vac 625va per channel, that Slewmaster is going to be VERY impressive. Keep in mind that an amp has to produce 10X the power to sound twice as loud. Most of the time, you will likely be listening at less that 10w output power and very likely less than 5w. Then when you want to show your friends why you went to all this work you can crank it up and watch them grin. Looking forward to sharing in your build here on the forum.
Blessings, Terry
Blessings, Terry
thanks terry
audio has been a real trip over the years. and this is no different . funny how audio takes over your mind . the chassis for these mono block will be my #1 concern .
see this is what gets my ideas swirling i hate the look of this p101 with that whimpy looking 300va. if you see what i do you will understand were the slews are going, they will be monster manly amps.
http://[URL=http://s400.photobucket.com/user/91owner/media/speaker%20building/esp%20p101.jpg.html]
audio has been a real trip over the years. and this is no different . funny how audio takes over your mind . the chassis for these mono block will be my #1 concern .
see this is what gets my ideas swirling i hate the look of this p101 with that whimpy looking 300va. if you see what i do you will understand were the slews are going, they will be monster manly amps.
http://[URL=http://s400.photobucket.com/user/91owner/media/speaker%20building/esp%20p101.jpg.html]
An externally hosted image should be here but it was not working when we last tested it.
[/URL]
FISCHER ELEKTRONIK does big heat sinks. f.cool - Heatsinks directly from the manufacturer . Newark is a dealer for them but I'm not sure what all sizes they carry.
DIY Heatsink These can look neat too if you can get someone to fly cut the surface for you.