If you haven't built the F5 (or listened to it) yet, then rather do that first. You might be surprised with what (to my ears!) sounds valve-ish, by design
I believe that non fully complementary nature of J74/K170 and IRFP devices can be "blamed" for that.
My 0.02 of local currency
add 02x0.22R at out point both IRFP
Dear Nelson Pass!
did you have idea to me ? Can I put more 2x0.22R-5w to separate circuit at OUT D gate of Q3,Q4 (keep R5,R7,R8,R6 like original circuit )and then betweent 2x0.22R will connect to speaker ???
is it will OK ????
Very likely.
Dear Nelson Pass!
did you have idea to me ? Can I put more 2x0.22R-5w to separate circuit at OUT D gate of Q3,Q4 (keep R5,R7,R8,R6 like original circuit )and then betweent 2x0.22R will connect to speaker ???
is it will OK ????
Startup procedures for F5.
I have almost finished my F5 build, and already tested the PSU. I get a nice +-24.0VDC on both rails, so that is looking good. Now I would like to fully test the F5.
I don't have a variac, or a set of spare speakers I can use for testing. I can of course use the lightbulb wire, but isn't that only used for testing the PSU? I have a bunch of DMM's and a scope at hand.
The big question is: when can I be sure that I am ready to connect them to my speakers and nothing blows up? Is 0 VDC on the outputs all I need to worry about?
EDIT: To be sure, I don't mean biasing... I have seen very good descriptions of the process on the forum. I am just looking for some checklist that I need to run before hooking it up to my main speakers...
I have almost finished my F5 build, and already tested the PSU. I get a nice +-24.0VDC on both rails, so that is looking good. Now I would like to fully test the F5.
I don't have a variac, or a set of spare speakers I can use for testing. I can of course use the lightbulb wire, but isn't that only used for testing the PSU? I have a bunch of DMM's and a scope at hand.
The big question is: when can I be sure that I am ready to connect them to my speakers and nothing blows up? Is 0 VDC on the outputs all I need to worry about?
EDIT: To be sure, I don't mean biasing... I have seen very good descriptions of the process on the forum. I am just looking for some checklist that I need to run before hooking it up to my main speakers...
Last edited:
Hi studiostevus,
I bought a 8 ohm load resistor,just for that It's rated for 100 watts ,so you can connect it instead of your speakers and watch the output on your scope,It is possible to use a small fuse inline with the speakers so it blows and not your speaker coils,I connect a freq. gen at 1000hz and run up the input voltage slowly and watch the output on the scope,you can also meter your rails DC and lower the fuse in your power supply just to test,check bias often until it gets to operating temp ,I hope this help ,a small set of test speakers can be obtained cheaply at yard sales ,radio shack or parts express,,,,,,Good luck
I bought a 8 ohm load resistor,just for that It's rated for 100 watts ,so you can connect it instead of your speakers and watch the output on your scope,It is possible to use a small fuse inline with the speakers so it blows and not your speaker coils,I connect a freq. gen at 1000hz and run up the input voltage slowly and watch the output on the scope,you can also meter your rails DC and lower the fuse in your power supply just to test,check bias often until it gets to operating temp ,I hope this help ,a small set of test speakers can be obtained cheaply at yard sales ,radio shack or parts express,,,,,,Good luck
dear ! about blows up speaker : you can check I1,I2 must be the same value at bothside of amp.
the bulb tester can and should be used to power up every change or modification to a mains powered project.
The bulb tester cannot be used to bias up the output stage. But by then all the modifications and additions will have been completed and tested and proved to be correct.
If you make a further modification after you have biased up your F5 then I strongly suggest you reduce bias back to zero and power up via the bulb tester so that you are proving to yourself that the modification has not turned a perfectly good F5 into a bomb. Then rebias.
The bulb tester cannot be used to bias up the output stage. But by then all the modifications and additions will have been completed and tested and proved to be correct.
If you make a further modification after you have biased up your F5 then I strongly suggest you reduce bias back to zero and power up via the bulb tester so that you are proving to yourself that the modification has not turned a perfectly good F5 into a bomb. Then rebias.
Ok, so the procedure would be:
1. Setting all trimmers to 0Ohms - proceed to #2
2. Power up with bulb tester - anything to measure at this stage?
3. Power up with normal wire and proceed with #4
4. Biasing procedures - No load - If everything seems ok and stable, proceed to #5.
5. Test with 8Ohm resistor or test speakers and scope - measure DC offset and bias over longer period. If everything is stable, proceed to #6
6. Declare the amp safe and move over to main speakers
Correct?
1. Setting all trimmers to 0Ohms - proceed to #2
2. Power up with bulb tester - anything to measure at this stage?
3. Power up with normal wire and proceed with #4
4. Biasing procedures - No load - If everything seems ok and stable, proceed to #5.
5. Test with 8Ohm resistor or test speakers and scope - measure DC offset and bias over longer period. If everything is stable, proceed to #6
6. Declare the amp safe and move over to main speakers
Correct?
you can always use an LM317 / LM337 set up as 400mA current limiters for the initial testing -- once you get the amp to this level it's easy to remove the current limiters and keep climbing up to the bias you want. Make sure to heat sink the regulators.
It's always helpful to make a note of which direction of the trimpot moves the bias current up or down.
And with the F5, patience in adjusting the bias is its own reward.
It's always helpful to make a note of which direction of the trimpot moves the bias current up or down.
And with the F5, patience in adjusting the bias is its own reward.
fully check
check 02 jfet Ids --will decide Vgs of IRF
check 02 IRF Ids bothside when Vgs changing also temp changing ..
and IRFP9240 seem too high Amp no need can change by other,because circuit only run whith 2,6A ..cut off by protection circuit.
check 02 jfet Ids --will decide Vgs of IRF
check 02 IRF Ids bothside when Vgs changing also temp changing ..
and IRFP9240 seem too high Amp no need can change by other,because circuit only run whith 2,6A ..cut off by protection circuit.
IRFP240 and IRFP9240 are not complementary devices.
These were likely matched at a drain current of ~250mA, at a little above 1A they'd have close to identical Vgs.
The "matched" part refers to Vgs difference between the two IRFP240, or between an IRFP9240 and the second one.
You could use 36V and 55V outputs and get 19V, providing there is sufficient current from them.
That is just these two (pairs of) wires, nothing else.