Do you have any reliable source for 2sk170 (ebay or somwhere else) preferably in matched quads?
The ONLY genuine source of Toshiba Jfet is Spencer at Fetaudio.com .
You could also buy a number of the excellent LSK170 from the diyAudio store and match them yourself.
You could also buy a number of the excellent LSK170 from the diyAudio store and match them yourself.
Thanks 6L6.
Diyaudio store allows only 16 items purchase so it would be dificult to match set for Pearl.
Definitly I'll try fetaudio.
I'll have two 2sk389 laying around so I could use them for output transistors but I guess it would be beter to have mached pair beetween chanels.
Diyaudio store allows only 16 items purchase so it would be dificult to match set for Pearl.
Definitly I'll try fetaudio.
I'll have two 2sk389 laying around so I could use them for output transistors but I guess it would be beter to have mached pair beetween chanels.
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
Does input tranis realy need to be matched in quads per chanel or better would to have slight diferences in one chanel but summ of Idss keeped similar beetween chanels?
My idea was to buy two quads for input and use half of each quad per chanel
My idea was to buy two quads for input and use half of each quad per chanel
It will work if they are different Idss, but the strong one will hog the current, as in any parallel application.
If there was ever a circuit that deserves fantastically tight quads, it's this one.
If there was ever a circuit that deserves fantastically tight quads, it's this one.
BF862 from NXP are low noise, high gm -- while they are surface mount, it's very easy to find adapters on EBay. They are $0.343 each in quantities of 10 at Mouser. If you purchase 40 among friends you'll get many sets of matched quads.
No, it means (2) quads. This is about current sharing for noise performance, not gain matching.
😀
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So there is no disadventages for diffrent current beetween R and L chanels ex. L - Idss=6mA; R - Idss=10mA?
You can always match the gain by varying R14 slightly between the channels. That is what I did.
...interesting - I didn't know that it's actually not matching 2 x 6 JFETs for the channels but only 2 x 4 instead and adjusting the gain between the channels by the resistor...
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?
Change the resistor to adjust gain if your cartridge needs more. Don't adjust the gain down from stock.
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.