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Old 17th May 2011, 07:51 AM   #191
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Patrick

It Is a better way to collect parts for this project In many steps and not at one time because of the high price
still there are no official schematics
so can you please confirm that your F5X will use Toshiba 1530/201 as output devices and not some other pairs and 2SK3497/2SJ618 as regulator devices so I can purchase
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Old 17th May 2011, 08:26 AM   #192
qusp is offline qusp  Australia
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the 2SK3497/2SJ618 are for the regulator board. not outputs, which are the k1530/j201
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Old 17th May 2011, 07:35 PM   #193
EUVL is offline EUVL  Europe
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> so can you please confirm that your F5X will use Toshiba 1530/201 as output devices and not some other pairs

Yes. And frontend JFETs will be 2SK170BL (Idss about 7mA) and 2SJ74BL (about Idss 7.8mA).

> and 2SK3497/2SJ618 as regulator devices

Correct, if you choose to use a regulator of my design.


Patrick
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Old 17th May 2011, 09:56 PM   #194
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Quote:
Originally Posted by EUVL View Post
>

Yes. And frontend JFETs will be 2SK170BL (Idss about 7mA) and 2SJ74BL (about Idss 7.8mA).

Patrick
wow with Idss specs like that , many are going to be very disappointed . while i'm sure that the 25 or so initial will be able to come up with them ......

i'm trying to find some time tonite to sort , but out of 30 j74's only 2 are in that range . most are coming up in the 9's with some 8's and 10's .

i haven't even started with my k170's 'cept for a few which are in the 8's

cheers Woody
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Old 17th May 2011, 10:23 PM   #195
NYCOne is offline NYCOne  United States
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Quote:
Originally Posted by Woody1911a1 View Post
>

Yes. And frontend JFETs will be 2SK170BL (Idss about 7mA) and 2SJ74BL (about Idss 7.8mA).

Patrick
wow with Idss specs like that , many are going to be very disappointed . while i'm sure that the 25 or so initial will be able to come up with them ......

i'm trying to find some time tonite to sort , but out of 30 j74's only 2 are in that range . most are coming up in the 9's with some 8's and 10's .

i haven't even started with my k170's 'cept for a few which are in the 8's

cheers Woody
Is the difference in Idss for the "degeneration trick". If so, are you going to make the changes to resistors too?

I know I had a heck of a time finding an Octet with the "degeneration trick" match. Two Quads are more attainable.
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Old 17th May 2011, 10:37 PM   #196
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Originally Posted by NYCOne View Post
Is the difference in Idss for the "degeneration trick". If so, are you going to make the changes to resistors too?

I know I had a heck of a time finding an Octet with the "degeneration trick" match. Two Quads are more attainable.
are you asking me or patrick ?
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Old 17th May 2011, 11:53 PM   #197
NYCOne is offline NYCOne  United States
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Quote:
Originally Posted by Woody1911a1 View Post
are you asking me or patrick ?
Patrick, the double quote was for context.
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Old 18th May 2011, 01:49 AM   #198
flg is offline flg  United States
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I think somewhere back in the thread Patrick mentions the Idss should be about 10% higher for th P JFET. It is not that they need exactly 7mA and 7.8mA Idss, but that with typical devices the 10% ratio difference would be the typical "Trick" values.
Some experimenting could prove this to be slightly different with the devices you have, or end up with. But, you are no doubt closer to the designed targets using these values.
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Last edited by flg; 18th May 2011 at 01:52 AM.
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Old 18th May 2011, 04:48 AM   #199
EUVL is offline EUVL  Europe
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You can use any values of Idss for the JFETs as long as P-P and N-N are matched, and the P-JFET has the same bias current after the 5R degeneration.
It works out to be about 0.8mA more than the N-JFET. I have to publish a default value, so I choose the same as NP, at around 7mA.

So if you have 2SJ74s at say 9mA, you want to find a pair of 2SK170s with about 8.2mA.

The exact formula for calculating this has been published before.
I am in a rush to leave home now, so if someone could kindly dig it up for me please.


Patrick
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Old 18th May 2011, 09:44 AM   #200
GuidoR is offline GuidoR  Italy
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Quoting from EUVL:
"If you use the 5R degeneration on the 2SJ74, as I recommended, then you can calculate the Idss of the 2SJ74's using the following equation :

Idss (2SJ74) = Id * (1 + Rs.Yfs)

where Id = Idss of the 2SK170 in this case; Rs =5.1R; Yfs = 0.033 S for 2SJ74 at that bias range.

It works out to roughly 1mA higher than the Idss of the 2SK170s.

Get matched quads for both K170s and J74s if you can, so that both left and right channels are the identical.

Guido
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