Is it OK to run each FET on its own heatsink? I'm unable to get a reasonably substantial heatsink, so have to pick up individual 10" running lengths of an extrusion for each output device. I could mount each with its own thermistor on a 1c/w heatsink, but getting everything mounted on one is going to lead me into thermal problems for sure.
Do the two halves interact with each other thermally, and is it just going to take me a lot longer to adjust the bias? Or are there other gotchas with doing this?
Do the two halves interact with each other thermally, and is it just going to take me a lot longer to adjust the bias? Or are there other gotchas with doing this?
Hi,
dual unlinked sinks could lead to thermal instability. This is way outside my area so it's just a guess.
What if one sink got a draught from facing an open window/door? Would that sink cool slightly and cause a DC offset?
Would the amp then go into a very slow hunt trying to bring the two sides back into equilibrium?
Could that slow hunt develop into an undamped oscillation?
I don't know, just throwing some thoughts into the pot.
dual unlinked sinks could lead to thermal instability. This is way outside my area so it's just a guess.
What if one sink got a draught from facing an open window/door? Would that sink cool slightly and cause a DC offset?
Would the amp then go into a very slow hunt trying to bring the two sides back into equilibrium?
Could that slow hunt develop into an undamped oscillation?
I don't know, just throwing some thoughts into the pot.
Good points Andrew. I guess I'll just hold out on the build till I hear it's fine. I think it depends on the topology, and then there's only one person who can answer this for sure.
I hope Mr. Pass gets to see the question and help me out 🙂
I hope Mr. Pass gets to see the question and help me out 🙂
As you have thermistors in this circuit, I'd be surprised if things goes bad when not thermally coupled.
Magura 🙂
Magura 🙂
I thought so too, but since the two halves interact with each other for the bias adjustment (as well as offset, a bigger issue) delinking them might create output offset if the two halves are not at exactly the same temperature, or close enough.
I think the question is: Is the heatsink temperature partly a determiner of the bias and offset, or a byproduct? If the former, it will not be possible to totally unlink the two FETs. If the latter, I assume one can do it with impunity.
I think the question is: Is the heatsink temperature partly a determiner of the bias and offset, or a byproduct? If the former, it will not be possible to totally unlink the two FETs. If the latter, I assume one can do it with impunity.
Just link the two heatsinks with metal plates and everything will be fine, I don't have any problems with my amps: http://www.diyaudio.com/forums/showthread.php?postid=1740775#post1740775
Peter
*That* implementation is almost exactly what I had in mind, obviously mine is going to look like Frankenstein compared to yours, as I will be using protoboard, EI transformers and P2P wiring. My heatsinks are not as robust as yours though, how high are your temperatures? I have a large blank in the center, and though there are fins on all sides I assume they will not be as adequate as the ones in your pictures (thermal data is not really available).
I will try and put some plates at the back and top to link up the two halves, let's see how it goes. I was initially planning black glass for the front and perspex for the rear, now maybe I'll switch to some heavy-guage aluminum instead (the heatsinks will be vertically oriented like yours).
*That* implementation is almost exactly what I had in mind, obviously mine is going to look like Frankenstein compared to yours, as I will be using protoboard, EI transformers and P2P wiring. My heatsinks are not as robust as yours though, how high are your temperatures? I have a large blank in the center, and though there are fins on all sides I assume they will not be as adequate as the ones in your pictures (thermal data is not really available).
I will try and put some plates at the back and top to link up the two halves, let's see how it goes. I was initially planning black glass for the front and perspex for the rear, now maybe I'll switch to some heavy-guage aluminum instead (the heatsinks will be vertically oriented like yours).
power thermistor circuit
Would anyone be able to post a picture of the wiring from the the AC line to the transformer? I can't find one in the thread that I can see well. I have the schematic but lack the practical experience to be certain I'm wiring this section correctly. And I'm being very cautious with AC. I'm sure I could follow a picture, being worth a thousand .....
Thanks for any assistance.
Would anyone be able to post a picture of the wiring from the the AC line to the transformer? I can't find one in the thread that I can see well. I have the schematic but lack the practical experience to be certain I'm wiring this section correctly. And I'm being very cautious with AC. I'm sure I could follow a picture, being worth a thousand .....
Thanks for any assistance.
Tie leads of black and brown together and orange/white together.
Tore black/brown to 115v in/line, and orange white to neutral.
use a small fuse 1amp or less from line to transformer line as in manual to test.
Connect volt meter + to red and - to yellow before powering up. Turn to AC mode.
Dont touch anything not covered with plastic.
I use a GFI outlet on the workbench, and it will go offline if things are corrected wrong.
Unloaded the Plitron will probably run 20-22v AC.
Tore black/brown to 115v in/line, and orange white to neutral.
use a small fuse 1amp or less from line to transformer line as in manual to test.
Connect volt meter + to red and - to yellow before powering up. Turn to AC mode.
Dont touch anything not covered with plastic.
I use a GFI outlet on the workbench, and it will go offline if things are corrected wrong.
Unloaded the Plitron will probably run 20-22v AC.
http://www.antiqueradio.org/dimbulb.htm
I think thats what he wanted to say. Otherwise may have just been an echo 🙂
Try it, it works really well and saved my amps
Uriah
I think thats what he wanted to say. Otherwise may have just been an echo 🙂
Try it, it works really well and saved my amps
Uriah
Thanks Tea-Bag and Uriah. Transformer output wired for testing a la Tea-Bag checks out fine.
Where I remain uncertain, but did not make clear in my first post, is how to wire the CL-60s. I believe one thermistor lead connects to AC, and the black transformer lead, and C9; while the other lead of that thermistor connects only to the brown transformer lead. Perhaps it just looks strange when wired because it's point to point?
Where I remain uncertain, but did not make clear in my first post, is how to wire the CL-60s. I believe one thermistor lead connects to AC, and the black transformer lead, and C9; while the other lead of that thermistor connects only to the brown transformer lead. Perhaps it just looks strange when wired because it's point to point?
AndrewT said:
Chill Out Andrew.
😎
trans said:
I wire the CL60's right to the tranny 120v wires, one to each pair.
Sorry if I raised anyone's temperature, not my intention. I've just never wired anything like the power thermistor circuit before, and I know I don't know enough to "try it and see if it works" with AC.
wiring that circuit was confusing to me to. Try numbering the wires on the diagram and the same numbers on your transformer.