OK so curiosity got the best of me and I fired up the amp with just the right channel and I have to say it sounded very good. Could not hear any noise at all through a Altec 19. So I have a few questions about the left channel. If I have 8.5 volts across R8 does that indicate that the jfet's are good? Can I expect a good resistance reading across the MOSFETS pins while they are attached to the board? Should I be using a grounded wrist strap when working with the MOSFETS.
How matched should irfp244's be?
I converted an aleph 30 to an aleph j. I did this by swapping out the boards.
On this particular conversion, I popped an irfp 244. (it died shorted) I had one extra irfp244 laying around and I put it in the circuit, after warm up, I measure .41 volts on the source resistor for the swapped in Mosfet and around .53 to .5 volts on the other source resistors.
Can I leave it like this?? or should I order a bunch of irfp244's to match.
I do have irfp240's lying around, can I match a pair of those and swap them in??
Thanks...
I converted an aleph 30 to an aleph j. I did this by swapping out the boards.
On this particular conversion, I popped an irfp 244. (it died shorted) I had one extra irfp244 laying around and I put it in the circuit, after warm up, I measure .41 volts on the source resistor for the swapped in Mosfet and around .53 to .5 volts on the other source resistors.
Can I leave it like this?? or should I order a bunch of irfp244's to match.
I do have irfp240's lying around, can I match a pair of those and swap them in??
Thanks...
The parallel devices will be required to meet the Idss and current requirements of the circuit.
If you have them, use them. I built an Aleph J with a sanyo P-channel jfet that measured much worse but sounded great, the J176 will be much better.
http://www.diyaudio.com/forums/atta...06-aleph-j-illustrated-build-guide-aj-sch.png
R7 4.9v
R8 8.4v
R16 355mv T5-Vgs 3.52v
R17 359mv. T6-Vgs 3.5v
R18 362mv. T7-Vgs 4.55v
R19 357mv. T8-Vgs 4.55v
Output -16.88v note the output is neg
R7 4.9v
R8 8.4v
R16 355mv T5-Vgs 3.52v
R17 359mv. T6-Vgs 3.5v
R18 362mv. T7-Vgs 4.55v
R19 357mv. T8-Vgs 4.55v
Output -16.88v note the output is neg
J176
So we want 8 ma through the input quad with each device matched 7-10 ma idss?? I have 60 of rthese and none of the 2sj74bl . i thought when i bought the boards , that i had the 74s. At least i cant find them . i nave rest of the parts including matched outputs that i bought years back from DIYTECH. thanks for your help.
So we want 8 ma through the input quad with each device matched 7-10 ma idss?? I have 60 of rthese and none of the 2sj74bl . i thought when i bought the boards , that i had the 74s. At least i cant find them . i nave rest of the parts including matched outputs that i bought years back from DIYTECH. thanks for your help.
try to slightly increase R27 (upping Iq) and slightly decrease R7 (lowering Ugs for lower mosfets , thus closing them )
two DVMs - one to monitor voltage across any of source resistors (don't go above 500mV across it) , second to monitor output DC offset (ref.gnd)
inputs grounded , no load at output
Hello I have completed my aleph J and I tried it with a backup system: because when I turn it off ul feel "bump" on the speakers?
solve the problem with a soft start?
I built the power supply with a breadboard pcb but I do not trust a lot:
where can I buy the pcb power as that used by 6L6?
thanks for the answers
solve the problem with a soft start?
I built the power supply with a breadboard pcb but I do not trust a lot:
where can I buy the pcb power as that used by 6L6?
thanks for the answers