no need to change anything, if you add trimpot to series resistor, except from cosmetic reasons
all numerous happy Campers, having original FW J2, for instance, are listening happy notes, pushed across trimpot , connected in drain of input JFet
trimpot in CCS, much less critical position
go figure
reminder - how to do
instead of 51, use whatever you have, just recalc voltage sag for 10mA
all numerous happy Campers, having original FW J2, for instance, are listening happy notes, pushed across trimpot , connected in drain of input JFet
trimpot in CCS, much less critical position
go figure
reminder - how to do
instead of 51, use whatever you have, just recalc voltage sag for 10mA
Attachments
I perhaps expressed myself wrong. Sorry for the confusion.
- I understand I would need to solder the pot or the pot + resistor
- I understand I measure the voltage drop not only in-circuit, but operating
- I move the trim pot to required value
At this point I:
A. NEED to desolder both and measure their resistance off-circuit to determine the correct resistance to purchase, or...
B. COULD measure the resistance of the pot or pot+res in circuit (not turned on) in order to purchase the correct resistance, but keeping the working pot+res in place until they arrive (which will be a month or so)
So, the question is, could I measure the end resistance of the correct values without desoldering to avoid having to resolder those until I get the correct valued resistors?
Thanks agian.
Thanks! Makes perfect sense. So, still I would need to put in R4 something lower than the recommended value, or else I would not be able to overcome the offset, right?
it really depends
if you have JFet with higher Idss, you need more than original value of R4
and the other way
no use of babbling, go figure it in vivo
I too need to find out the right values for R4.
You can do that on the PCB, but soldering and desoldering parts can leave a mess on the board. If you have a 12V power supply you can determine R4 with a breadboard. Breadboard - Wikipedia. No soldering required. Another advantage of this method is that you do not accidentally fry other components while experimenting.
I just stuck the resistor in the board, bent the legs just a bit to make sure they made contact, and measured the voltage drop. No soldering necessary until you have found the right resistor value.
I might be mistaken. I think the guy was on Audiogon, been fixing amps for ages, if I temember correctly, and also making custom silver cables on order. Last I saw his site he had stopped. But now I can’t find it. Maybe his name was not Audiobear after all. But I think he was from Alaska, and the nick played on that, bears and all
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That’s it! Turns out his nick was Bear here on diyaudio.com. Well well, close enough. Thanks, Amanda!
And sorry Audiobear for the mixup
Though it looks like the hand made silver IC business in his area is up for grabs since 2012.Cheers,
Andy