I'm hoping it will be ok for two channels, but I can always run the bias a little lower for the time being until i get something bigger. I am in negotiation with a UK supplier that makes lots of heatsinks for the audio industry, so if successful, I might be offering a group buy to the forums... 
too high...
...not necessarily...
How big are you planning to make your heatsinks? Just how fast can those fans spin...do you have air conditioning?
Hey, wait, aren't you the one that wanted 45v rails at the beginning...
You can always use a CRC or CLC power supply, you know the sort of stuff...email me if you need details...
tell me again, what is the AC rating of the toroids you purchased?
Stuart
...not necessarily...
How big are you planning to make your heatsinks? Just how fast can those fans spin...do you have air conditioning?
Hey, wait, aren't you the one that wanted 45v rails at the beginning...
You can always use a CRC or CLC power supply, you know the sort of stuff...email me if you need details...
tell me again, what is the AC rating of the toroids you purchased?
Stuart
fans
pinkmouse,
if your fans can double the passive efficiency then the sink is big enough, everything after that is gravy. It is basically big enough for one channel with no fan...
Heck if you get enough air moving you could make an AV amp, 5 channels, 140watts idle power each, at least the snow won't bother you next year...
Stuart
pinkmouse,
if your fans can double the passive efficiency then the sink is big enough, everything after that is gravy. It is basically big enough for one channel with no fan...
Heck if you get enough air moving you could make an AV amp, 5 channels, 140watts idle power each, at least the snow won't bother you next year...
Stuart
fans
Nice explanation about cooling:
http://homepages.which.net/~paul.hills/Heatsinks/HeatsinksBody.html
I hope this will be helpfull.
Loek
Nice explanation about cooling:
http://homepages.which.net/~paul.hills/Heatsinks/HeatsinksBody.html
I hope this will be helpfull.
Loek
NUTTTR said:
See Mark if your results are like mine... obviously different due to the rails, but overall current....I tried calculating my current flow, maybe i'm stupid, or it's too late, but i couldn't get any figures that made any sense at all......They all seemed silly amounts of low....
However the amp passed the listening test.... Today a mate listened, other than my speaker sounding rather flat and there being no headroom the amp is very clear and quite nice sounding, at least we think so, he agreed that even if we spend more than planned on it, it's still well worthwhile building... so i guess that says it!
Aaron
Wim, it was for aaron...
...he was asking if his rails were too high...
Aaron, your Vbe multiplier current is ~10ma, currently lower than it will be once you set the idle current to the 2 or 3 amps you expect to use. My ballpark figure is 25ma, perhaps Marks current settings will be closer to that. As far as I can tell the other numbers you have are not massively influenced by rail voltage. The rest of the currents are within a 2:1 range of what I had figured, so I don't think there is anything wrong with your setup...
Stuart
...he was asking if his rails were too high...
Aaron, your Vbe multiplier current is ~10ma, currently lower than it will be once you set the idle current to the 2 or 3 amps you expect to use. My ballpark figure is 25ma, perhaps Marks current settings will be closer to that. As far as I can tell the other numbers you have are not massively influenced by rail voltage. The rest of the currents are within a 2:1 range of what I had figured, so I don't think there is anything wrong with your setup...
Stuart
Re: Wim, it was for aaron...
They aren't... after running my amp for hours and hours and hours...(about 10 hours running time so far) it doesn't get as hot as i thought it would... obviously in my test setup... It's running a cheapo small heatsink and is still managing to dissapate a fair bit of heat...
I've got a peavey PV8.5 or something i think it is and i have now got one channel running the krell, other running the peavey...
I've noticed the bass in the krell stands out a little more, treble seems a little brighter... not sure if it's too bright, i don't think it is...
The peavey sounds flat and lifeless on normal music and dvd's, etc however once the krell is on the left channel actually has "life" and sounds good... I'm impressed so far... not sure if anyone else would agree with me! Sometimes i notice the low midbass seems a little hollow, but it could be my speakers or my room, etc....
Aaron
Stuart Easson said:
They aren't... after running my amp for hours and hours and hours...(about 10 hours running time so far) it doesn't get as hot as i thought it would... obviously in my test setup... It's running a cheapo small heatsink and is still managing to dissapate a fair bit of heat...
I've got a peavey PV8.5 or something i think it is and i have now got one channel running the krell, other running the peavey...
I've noticed the bass in the krell stands out a little more, treble seems a little brighter... not sure if it's too bright, i don't think it is...
The peavey sounds flat and lifeless on normal music and dvd's, etc however once the krell is on the left channel actually has "life" and sounds good... I'm impressed so far... not sure if anyone else would agree with me! Sometimes i notice the low midbass seems a little hollow, but it could be my speakers or my room, etc....
Aaron
pcb mounting
To Mark:
In post 1027 (with the pictures) I saw your design.
Your wiring to the powertransistorboards is running under the pcb and can stray into the input part of the amp.
If you turn the main pcb 180 dgrs this is cleared and you can easier connect the inputwire. But maybe you have a special reason to mount it this way.
Loek
To Mark:
In post 1027 (with the pictures) I saw your design.
Your wiring to the powertransistorboards is running under the pcb and can stray into the input part of the amp.
If you turn the main pcb 180 dgrs this is cleared and you can easier connect the inputwire. But maybe you have a special reason to mount it this way.
Loek
Actually I mounted it that way so the drivers and heat sink are at the top. They disipate heat better this way. Thanks for pointing out your concerns and I had breifly thought about this too. I was in more of a hurry to get the thing up and running to see how well it worked and sounded and if the continued effort to finish it would be worth it.... Yes it is!
I will eventually re-route the driver and feedback leads as per your suggestion around the sides of the board. The DC leads can stay put though.
I should get to measuring those DC voltages tommrrow... been busy tonight getting the second channel up and running running.
Now I can finally hear these in stereo tommrrow night after work.
Mark
I will eventually re-route the driver and feedback leads as per your suggestion around the sides of the board. The DC leads can stay put though.
I should get to measuring those DC voltages tommrrow... been busy tonight getting the second channel up and running running.
Now I can finally hear these in stereo tommrrow night after work.
Mark
Hi guys,
Anyone going to use cans (i.e. MJ21193/4) instead of flatpacks? I managed to lay my hands on original Krell heatsink cubes, so natrually cans are preferred.
What would be the best: Keeping the output boards on the main PCB and take the transistor wires straight from there, or leave the boards altogether and hardwire the resistors, diodes etc at the cans themselves?
Thanks for all the pioneering work
Pierre
Anyone going to use cans (i.e. MJ21193/4) instead of flatpacks? I managed to lay my hands on original Krell heatsink cubes, so natrually cans are preferred.
What would be the best: Keeping the output boards on the main PCB and take the transistor wires straight from there, or leave the boards altogether and hardwire the resistors, diodes etc at the cans themselves?
Thanks for all the pioneering work
Pierre
Mark,
nice photo of your setup. Well done.
The fans appear to be blowing (definately better than sucking).
Can you invert the sink so that natural convection augments the fan pressure?
The heatsink will have slightly higher efficiency if you can mount the output transistors about 40% of length up from the bottom. Some sources say middle of length but I disagree. Any comments?
nice photo of your setup. Well done.
The fans appear to be blowing (definately better than sucking).
Can you invert the sink so that natural convection augments the fan pressure?
The heatsink will have slightly higher efficiency if you can mount the output transistors about 40% of length up from the bottom. Some sources say middle of length but I disagree. Any comments?
my 2c
Playing with the plate heatsinks I've got I've shows that the devices being spread in an even line at right angles to the direction of airflow is optimum. I.E. if the air flow is from bottom to top, the devices need to be spread evenly from side to side. I haven't quantified it by taking the time to measure the result, but all else being equal comparing it to devices spread top to bottom, even my fingers can tell the difference, so it's quite big...
Flying back to play with mine today...assuming the snow allows me to reach the airport...England has a tendency to close down in the presence of small amounts of snow...
Stuart
Playing with the plate heatsinks I've got I've shows that the devices being spread in an even line at right angles to the direction of airflow is optimum. I.E. if the air flow is from bottom to top, the devices need to be spread evenly from side to side. I haven't quantified it by taking the time to measure the result, but all else being equal comparing it to devices spread top to bottom, even my fingers can tell the difference, so it's quite big...
Flying back to play with mine today...assuming the snow allows me to reach the airport...England has a tendency to close down in the presence of small amounts of snow...
Stuart
