Thanks. My background over the past few years has been learning how to build speakers. While I am still learning, I understand crossover components. What is new to me is amp building. Before posting my question I reviewed all 63 pages of posts and did find Tungsten’s original email and other premium parts lists, but this one resistor did not have have the same specifics as the other parts or I missed it. I will go back and check again.
Post #15 is an excellent start for TA's excellent suggestions. If you've already reviewed the thread, there's probably no reason to go back through.
If you have a specific part question, there are generally good substitutes. Which resistor?
If you have a specific part question, there are generally good substitutes. Which resistor?
I guess my question is surrounding resisters in general. TA’s parts list is very specific in listing a brand and specs for many if the parts but for the metal resistors there is no reference to a brand. In reviewing other posts, like 598, it is very specific to Vishay/Dale which I am gathering now is the go to metal resister? And then within a specification, using mouser’s filter function, there are often a few that meet the primary parameters but are different in size (I think?) and product line (CMF, RL,ETC). Is there a preferred product line.
Changing gears, is there a good reference book for someone like me with no background to better understand amp building?
Changing gears, is there a good reference book for someone like me with no background to better understand amp building?
Hi every one, I just tried to power my ACA amp with premium parts with a linear power supply of 48V DC; trying to get some more juice out of it, and it turns on but no audio comes out of it, like some protection system reacts to the higher voltage.
Any clue what is going on?, Am I doing something wrong?
Thank you.
Any clue what is going on?, Am I doing something wrong?
Thank you.
Do you have any clue as to what is going on? 🙂
Did you just switched power supplies and powered up?
There are a number of possible issues:
-did you make any adjustments to the circuit to handle the 48V?
-the jfet at the input stage may be at risk of burning up
-the electrolytic capacitors may not be able to withstand 48V
-the circuit may not have been adjusted for the 48V
-did you measure any voltages/currents?
Did you just switched power supplies and powered up?
There are a number of possible issues:
-did you make any adjustments to the circuit to handle the 48V?
-the jfet at the input stage may be at risk of burning up
-the electrolytic capacitors may not be able to withstand 48V
-the circuit may not have been adjusted for the 48V
-did you measure any voltages/currents?
A wish for infinity sound ended with zero sound?
A shame if the input Toshiba JFET could not take it......the other components are easier to replace.
As far as I know those input JFETs were matched parts (L and R) if ordered from Store as a kit.
Were kit from Store not considered "Premium parts"?
A shame if the input Toshiba JFET could not take it......the other components are easier to replace.
As far as I know those input JFETs were matched parts (L and R) if ordered from Store as a kit.
Were kit from Store not considered "Premium parts"?
Hi Ben Mah,
I switched back to the original 24 V brick and everything works fine still.
The only adjustment, sort of, i did, was to change the capacitors to 50V, 85°C.
No I haven't measured the voltages or currents, any advice of what to look after?
Thank you.
I switched back to the original 24 V brick and everything works fine still.
The only adjustment, sort of, i did, was to change the capacitors to 50V, 85°C.
No I haven't measured the voltages or currents, any advice of what to look after?
Thank you.
If you want to use the 48V supply, you will need to address the jfet voltage. I think there might have been one or two people that have done that. So if you ask for help, perhaps someone who has done it successfully will give you some advice. With the higher voltage you will need to make sure you heat sinks have enough capacity.
As for measurements you should probably monitor the current through the output mosfets, and also adjust the voltage at the drain of Q1 to about half of the power supply voltage.
As for measurements you should probably monitor the current through the output mosfets, and also adjust the voltage at the drain of Q1 to about half of the power supply voltage.
One possible solution to the jfet voltage if you use the 48V supply is to add a voltage dropping resistor in series with the jfet drain. A 5k Ohm resistor would do. You would need to cut the trace to the jfet drain and insert the resistor, plus add a decoupling capacitor with the positive between the resistor and jfet drain and the negative to ground. That would drop the voltage to the jfet to about 24V.
A 6k resistor might even be better as it would drop the voltage to the jfet to about 20V.
A 6k resistor might even be better as it would drop the voltage to the jfet to about 20V.
Ben, check out the Mountain View circuit, it uses one component rather than two.
I think that I drew rework-quickie for 48V rail, in original thread
somewhere in the start of thread, I believe
somewhere in the start of thread, I believe
Thank you guys, the original idea was to use 24V per channel to get more power out of the amplifier. Does it make any sense?
Do the 48V rail rework could help?
Do the 48V rail rework could help?
You are right, ended up with zero sound.
I believe I fried the input JFETs, the ACA amp sounds but very, very low and the heat sinks are cold as ice.
What else do you think I burned when I connected the 48V power supply?
Thank you.
I have received the FQH44N10 from Arrow. Does it matter if they are not matched? Thia is to build 4 boards for bridged amp. I know Papa is a firm believer in matching / testing output Mosfets. The stock 240’s are from the store.
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The ACA isn’t picky about matching of the output devices.
If spending extra time on the build is your thing, you could do a rough match between the devices that you plan to run in parallel amps. That’s not my thing, so I‘m not going to go into the details.
If spending extra time on the build is your thing, you could do a rough match between the devices that you plan to run in parallel amps. That’s not my thing, so I‘m not going to go into the details.