bias issues
Hi
I have F5 (V3) powered up, 24,4V on the rails, started with a variotrafo and no smoke...
But i cant bias R7 / R8 above 200mV.
Now I have meassured idss on my sk170 /sj74 (9v battery, no resistors) to 4,1mA. I have searched threads and found that I have to increase R5/R6. How much?
Or is there a way to calculate "right" value for drain resistors, now knowing idss????
(I actually started out with all resistor wrongly placed regarding V2/V3 labeling - sigghh, all replaced and pretty sure nothing is roasted.)
baek47
Hi
I have F5 (V3) powered up, 24,4V on the rails, started with a variotrafo and no smoke...
But i cant bias R7 / R8 above 200mV.
Now I have meassured idss on my sk170 /sj74 (9v battery, no resistors) to 4,1mA. I have searched threads and found that I have to increase R5/R6. How much?
Or is there a way to calculate "right" value for drain resistors, now knowing idss????
(I actually started out with all resistor wrongly placed regarding V2/V3 labeling - sigghh, all replaced and pretty sure nothing is roasted.)
baek47
Isolation Transformer
I've been trying to solve a problem with my F5 (no inputs connected) having a slight hum with my ear a few inches away from the speaker. Also a louder hum with the BA-3FE and Pearl II connected (ground loop), which can be heard from the listening position. I've tried different ways of grounding with no success.
I installed two Jensen JT-11P-1 isolation transformers (Thanks vdi_nenna) on the inputs of the F5 and the system is quite as a church mouse. The F5 still has a slight hum with no input connected but when the inputs are connected it's silent.
No downside so far, I've only listened to a few songs but I can't tell any difference from before other than the dead quite background.
As you can see one transformer is higher than the other. I let my 7 year old son drill the holes in the chassis. It got away from him a little. Hey anything to get the kids involved, right?
I've been trying to solve a problem with my F5 (no inputs connected) having a slight hum with my ear a few inches away from the speaker. Also a louder hum with the BA-3FE and Pearl II connected (ground loop), which can be heard from the listening position. I've tried different ways of grounding with no success.
I installed two Jensen JT-11P-1 isolation transformers (Thanks vdi_nenna) on the inputs of the F5 and the system is quite as a church mouse. The F5 still has a slight hum with no input connected but when the inputs are connected it's silent.
No downside so far, I've only listened to a few songs but I can't tell any difference from before other than the dead quite background.
As you can see one transformer is higher than the other. I let my 7 year old son drill the holes in the chassis. It got away from him a little. Hey anything to get the kids involved, right?
Do you mean infinite continuity (no resistance)
I just checked my F5 at the + speaker terminals and there is continuity but ~60Ω resistance.
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Maybe. I used both.
Generic ps schema say cl-60
See upper right corner of ps schmatic for small bold print.
http://www.diyaudio.com/forums/pass-labs/241729-aleph-j-illustrated-build-guide.html
Generic ps schema say cl-60
See upper right corner of ps schmatic for small bold print.
http://www.diyaudio.com/forums/pass-labs/241729-aleph-j-illustrated-build-guide.html
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CL60 suits big transformers rated for 110/120Vac mains power.
A CL60 does NOT suit 240Vac mains power.
Your transformer soft start needs a much higher resistance, than the 10 to 15ohms of a CL60.
Even two CL60 in series (for 240Vac) does not reduce the starting current enough to enable close fuse rating.
