OK, that explains they looked rather redundant to me also. Upping the gain leaves less for feedback and it seems rounder in LTSPICE already anyway. Will start my 28dB attempt without comp caps, but with layout uncertainties they may come up handy in the end, will see. Thanks for addressing that one.
Amusing: Same story on my Crescendo modified SSA.
While i was the first to worry about caps compensation in a current feed back configuration, i had put 2.35pf (ridiculous) to linearize the square waves at 100kHz in simulation for they look fashionable. And no need in real life. I suppose the parasitic caps of the board helps for once.
Lazy Cat deserve with no doubt some kind of honor medal.
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Hi guys
Is there a thread dealing with higher power SSA's say 100 W?
I'm about to tear up a new Teac amp (100W) to use its PSU, heatsink and box.
Apparently Nico Ras had the intentions to do so, but apparently didn't work out as expected, a pity.
Tony
Is there a thread dealing with higher power SSA's say 100 W?
I'm about to tear up a new Teac amp (100W) to use its PSU, heatsink and box.
Apparently Nico Ras had the intentions to do so, but apparently didn't work out as expected, a pity.
Tony
sorry i am building ssa bigbt . i just tried to post the photo of pcb. have to look some where how to post it
i have the photo in d drive . but in insert image it asks for url
i am attaching it again .. here ...
i am attaching it again .. here ...
not insert.
attach
edit.
I see it now.
nice in focus pic. Slightly out of focus towards the far side.
Could this have been cropped to make the file size smaller or much smaller?
attach
edit.
I see it now.
nice in focus pic. Slightly out of focus towards the far side.
Could this have been cropped to make the file size smaller or much smaller?
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Go advanced -> scroll down, click on Manage Attachments -> then in new window you'll see Upload File from your Computer, click Browse and select which picture you want to upload and then click Upload.
placed orders in mouser for transistors . hope to build it soon . as and when i will post photos and my listening observation about the sound quality .
instead of bf471/472 can i use 2sc2705/2sa1145 since power dissipation is less. my transformer is 24-0-24.
instead of bf471/472 can i use 2sc2705/2sa1145 since power dissipation is less. my transformer is 24-0-24.
For anyone interested in the simple thermaltrak version, I did a little experimentation.
I wired up an NJL3281 and 1302 per Lazycats schematic. Between the bases of the thermaltrak(TK) is a string consisting of 2.4k, TK diode, pot, TK diode, 2.4k.
The TK parts had 0.2R emitter resistors and are mounted to an aluminum rectangle (7x25x4mm) The supply is +/-35V, so the bias string sees about 15mA.
With this set of conditions, the output buffer is slightly undercompensated. With a starting temperature of 21C, and initial bias current of 100mA, the system stabilizes at 45C and 114mA. If the bias resistors are doubled, the system stabilized at 44C and about 112 mA. So increased bias current seems to slightly reduce the compensation. If I reduce the bias resistors by half, the bias current is about 150mA with the pot set to zero, and the temperature keeps rising with this minimal sink/radiator.
I think it should be OK somewhat undercompensated like this, but it will require generous heat sinking to prevent thermal run away if you want to bias it hot or run it hard. Or, in that case, a safety shut down with a thermal sensor.
Sheldon
I wired up an NJL3281 and 1302 per Lazycats schematic. Between the bases of the thermaltrak(TK) is a string consisting of 2.4k, TK diode, pot, TK diode, 2.4k.
The TK parts had 0.2R emitter resistors and are mounted to an aluminum rectangle (7x25x4mm) The supply is +/-35V, so the bias string sees about 15mA.
With this set of conditions, the output buffer is slightly undercompensated. With a starting temperature of 21C, and initial bias current of 100mA, the system stabilizes at 45C and 114mA. If the bias resistors are doubled, the system stabilized at 44C and about 112 mA. So increased bias current seems to slightly reduce the compensation. If I reduce the bias resistors by half, the bias current is about 150mA with the pot set to zero, and the temperature keeps rising with this minimal sink/radiator.
I think it should be OK somewhat undercompensated like this, but it will require generous heat sinking to prevent thermal run away if you want to bias it hot or run it hard. Or, in that case, a safety shut down with a thermal sensor.
Sheldon
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Yes, just now received the 5th check-up corrected and it looks very fine. Just have to adjust SCH with some added parts to be identical to the PCB. Coming soon ... 😉
So have anyone tried to build the amp in the first post yet ?
It wouldent be too hard to try it now that i have some laterals to play with, but if im not mistaken the ecp ones stated in the schematic are depletion fets while the 2sk135 and 2sj50 are enhancement type.
Correct me if im wrong.
It wouldent be too hard to try it now that i have some laterals to play with, but if im not mistaken the ecp ones stated in the schematic are depletion fets while the 2sk135 and 2sj50 are enhancement type.
Correct me if im wrong.
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