And if they differ in Idss like my 2SK170's did, you will have to buy a lot more than 2 sets of 8, which will be very expensive.
I bought some of mine over here:
2SK170-BL n-jfet
I bought some of mine over here:
2SK170-BL n-jfet
So if we reached R14.
Which resistor is better to update in case I want to have variable attenuation?
Wayne was referring to R14 for +10dba attenuation but in further discussion others discussed R16 update but also with some problems that forced capacitors update.
My idea was to be able to change R14 from 300 to 3300 for +/- 10db attenuation. Mostly I'm interested in -10 but in future +10 maybe needed too.
Is it a good approach?
Which resistor is better to update in case I want to have variable attenuation?
Wayne was referring to R14 for +10dba attenuation but in further discussion others discussed R16 update but also with some problems that forced capacitors update.
My idea was to be able to change R14 from 300 to 3300 for +/- 10db attenuation. Mostly I'm interested in -10 but in future +10 maybe needed too.
Is it a good approach?
Hello,
I've changed the gain values back to stock. And here's the voltages I get at the offset measuring point before the caps and right at the output.
Left channel:
a max wander of 30 mV DC on the offset node and a change of 6mV DC after the caps
Right channel (more wild):
a max wander of 35mV DC and a change of 16mV DC after the caps.
All the mV change observed for one minute at all points with the lid off and the DUT of 10 minutes warm.
Are they in the "safe" range?
I've changed the gain values back to stock. And here's the voltages I get at the offset measuring point before the caps and right at the output.
Left channel:
a max wander of 30 mV DC on the offset node and a change of 6mV DC after the caps
Right channel (more wild):
a max wander of 35mV DC and a change of 16mV DC after the caps.
All the mV change observed for one minute at all points with the lid off and the DUT of 10 minutes warm.
Are they in the "safe" range?
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Errrr 0.0001 mV ? 
More seriously, if all your installation is amplifying DC, you should minimize DC at the source.
If you have a capacitor in the signal path, it's less important, but the less the better.
Talking about the Pearl2, the DC Offset measuring pad is before C13, the output cap, so there is no specific acceptable DC value, IMHO.
You should have no offset at the output pad.
C13 is a 22uF electrolytic cap, try to adjust offset at the offset pad on the other polarity (ou resolder your polarized cap reversed)
More seriously, if all your installation is amplifying DC, you should minimize DC at the source.
If you have a capacitor in the signal path, it's less important, but the less the better.
Talking about the Pearl2, the DC Offset measuring pad is before C13, the output cap, so there is no specific acceptable DC value, IMHO.
You should have no offset at the output pad.
C13 is a 22uF electrolytic cap, try to adjust offset at the offset pad on the other polarity (ou resolder your polarized cap reversed)
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Maousse, nice to hear some ideas and thoughts about my "problem".
Yesterday I plugged PEARL 2 in to my system and spent some hours listening.
Sounds like it does the job OK.
But I'm here for a bit of knowledge and understanding.
So, I try to adjust offset before the cap as close to 0 as I can, but it drifts as indicated in my previous posts.
Sorry, I can't grasp is this part of your comment:
"try to adjust offset at the offset pad on the other polarity"
Yesterday I plugged PEARL 2 in to my system and spent some hours listening.
Sounds like it does the job OK.
But I'm here for a bit of knowledge and understanding.
So, I try to adjust offset before the cap as close to 0 as I can, but it drifts as indicated in my previous posts.
Sorry, I can't grasp is this part of your comment:
"try to adjust offset at the offset pad on the other polarity"
Hi,
An electrolytic cap is polarized and acts as a short when used reversed (minus a certain variable DC value).
As is it supposed to block the DC component, if you still have DC at the ouput, then may be it can be the DC you have is of reversed polarity of the cap.
If you can setup a negative DC measured at the offset pad using P1, then try, you won't have to resolder your caps for this.
If not, then plug your soldering iron and try resolder C13 reversed or change C13.
I don't use polarized caps for C13 but paper in oïl, big russian ones, lol, so I don't have your problem.
An electrolytic cap is polarized and acts as a short when used reversed (minus a certain variable DC value).
As is it supposed to block the DC component, if you still have DC at the ouput, then may be it can be the DC you have is of reversed polarity of the cap.
If you can setup a negative DC measured at the offset pad using P1, then try, you won't have to resolder your caps for this.
If not, then plug your soldering iron and try resolder C13 reversed or change C13.
I don't use polarized caps for C13 but paper in oïl, big russian ones, lol, so I don't have your problem.