I am (finally) busy building this amp using boards I generously got from @002 all the way from the Outback. @LKA, just a stupid question about this section of the schematic - it looks like a typical Baffle Step Compensation circuit between the amp and speakers. What is the purpose of this circuit, and can I safely omit this section without ill effect if I’m already running my speakers using a BSC (4R7 + 1mH inductor)?
Inductance there is usually to prevent capacitive loads from destroying the amplifier through RF oscillation.
BTW, I recently experimented with quasi output, tried slow transistors like KD503 (2MHz) and MJL21194 (4MHz). The result is quite satisfactory.
KD503
MJL21194
KD503
MJL21194
Thanks Mark. I have destroyed amplifiers before, but because of my own stupidity. 😊
Trying to avoid this now as best I can.
This seems like a very nice project - I have so far only built amps with a LTP input. How do I obtain the latest Gerbers? Thanks
I don't know - you would have to ask @LKA
Given the retro inspirations behind the project, it could be that he chose older devices for the fun of it, but I can't answer on a technical level which one is "better".
I seem to have a problem with my 60V build and need some assistance please. Boards are populated and mounted on heatsinks. I am following the startup procedures, but I am not getting the correct voltage in step 5.
The toroid transformer I ordered was for a 150VA 2 x 44V secondaries. The toroid I received says 150VA 2 x 47.5V secondaries but actually measures 2 x 49.7V ! I took the chance and hooked it up.
Step 1 says measure the voltage of the power supply with no fuse installed. I measure a whopping 70.3V. But the problem starts at step 5 - with a 1K/5W resistor in the fuse holder (which actually measures 1.04K), I only get a voltage of 6V (instead of 30V or what should be around 35V with my transformer) behind the fuse. The same problem with the other board.
Any suggestions on where to look for the fault?
The toroid transformer I ordered was for a 150VA 2 x 44V secondaries. The toroid I received says 150VA 2 x 47.5V secondaries but actually measures 2 x 49.7V ! I took the chance and hooked it up.
Step 1 says measure the voltage of the power supply with no fuse installed. I measure a whopping 70.3V. But the problem starts at step 5 - with a 1K/5W resistor in the fuse holder (which actually measures 1.04K), I only get a voltage of 6V (instead of 30V or what should be around 35V with my transformer) behind the fuse. The same problem with the other board.
Any suggestions on where to look for the fault?
I turned P2 fully anti-clockwise before applying power. Is that the same as counterclockwise?
I realise that 70V is looking for trouble with 63V caps. I will have to drop the input voltage - get another toroid.
Thanks.
I realise that 70V is looking for trouble with 63V caps. I will have to drop the input voltage - get another toroid.
Thanks.
I have
T4, T5 - BD139
T6 - 2SC4793
T7 - 2SA1837
T8 - NJW0281G
T9 - NJW0302G
Question - can I run this amp on lower input voltage (say 50VAC or 40VAC) without ill effect?
T4, T5 - BD139
T6 - 2SC4793
T7 - 2SA1837
T8 - NJW0281G
T9 - NJW0302G
Question - can I run this amp on lower input voltage (say 50VAC or 40VAC) without ill effect?
hi twocents
you mean rail voltage!
with 40VAC on the secondaries you get about 56V on the rail
with 50VAC you get 70V too much for your caps(63V)
kr
chris
you mean rail voltage!
with 40VAC on the secondaries you get about 56V on the rail
with 50VAC you get 70V too much for your caps(63V)
kr
chris
Yes, you' are correct - should be 40V to 50V rail voltage, not VAC secondaries.
Thanks for pointing this out.
Hi LKA
as read your target is to use as less bias to have minimum heat but did you have tried more current to get more Class A out?
or is this a fail interpretation by my side?
kr
chris
as read your target is to use as less bias to have minimum heat but did you have tried more current to get more Class A out?
or is this a fail interpretation by my side?
kr
chris