RMI-FC100, a single stage audio power amplifier - Page 102 - diyAudio
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Old 29th September 2010, 03:19 PM   #1011
housing is offline housing  Hong Kong
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I think they're real, and are the same as those used by Roender. Nichicon KG Type I is not that expensive. In fact they're selling at about USD$6.- in PRC, excluding shipping and remittance fee.
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Old 29th September 2010, 03:39 PM   #1012
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I would very like to build this beautiful amplifier, but I need some advice.

Can I use for RMI-FC 100 amp as J1 and J2 2SK170V or they have to have idss not more than 12mA?

What are pros and cons of using 0.18 ohm emitter resistors for not perfectly matched output devices instead of 0.1 Ohm for matched ones? AS I remember, Mihai told before that another RMI-FC100 amp he made for his friend with not perfectly matched devices sounds the same as with matched ones.

If 1W glass case 1N4148 is not available, can I use 500mW one as D1. Likewise green rectangular LEDs - with 2.2Vf, 20ma (according to datasheet)?

What is the power dissipation of the amp at it's full output power?

To operate the amp at 38VDC for output and 43VDC for front end I need to change only Zener diodes to 41V?

Can I use fast recovery rectifiers for amp PSU?

What value of input capacitor can I put if I need it?

Any support will be appreciated.
Regards.

ZDR,
regarding Nichikon Gold you can ask manufacturer if this shop is their authorized distributor. If not you may get to know where to buy it.
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Last edited by AndriyOL; 29th September 2010 at 03:43 PM.
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Old 29th September 2010, 04:21 PM   #1013
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Already found the answer regarding D1.
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Old 5th October 2010, 11:03 AM   #1014
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Does anybody be so kind to help me out?

Do you ever consider to use more superior BF862 or BF861B instead of 2SK170?

Regards.
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Old 5th October 2010, 11:39 AM   #1015
roender is offline roender  Romania
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Quote:
Originally Posted by AndriyOL View Post
Does anybody be so kind to help me out?

... more superior BF862 or BF861B instead of 2SK170?

Regards.
Would you please explain why specified devices are "more superior" than k170?
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Old 5th October 2010, 03:26 PM   #1016
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Quote:
Originally Posted by roender View Post
Would you please explain why specified devices are "more superior" than k170?
Nice to see you back Mihai.
Just found today on forum looking for LSK170 as replacement for jfets which also seems to have better specs than 2sk.
For BF862:
V(BR)GSS-20V
Pd-0.3W
IDSS-10~25mA
Ft-715MHz
En-0.8nV/Hz
Ciss-10pF
Crss-1.9pF
Yfs-45mS

For BF861B:
V(BR)GSS-25V
Pd-0.25W
IDSS-6~15mA
Ft-unknown
En-1.5nV/Hz
Ciss-10pF
Crss-2.1pF
Yfs-16-25mS

For 2SK170:
V(BR)GDS-40V
Pd-0.4W
Ft-unknown
En-1nV/Hz
Ciss-30pF
Crss-6pF
Yfs-22uS
People who use BF862 claim it sounds better than 2SK170 and costs today a half of 2SK170.
There is comparison table made by Scott Wurcer, in "B1 JFET alternatives list" thread, post 15.
Regards.
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File Type: jpg table.jpg (96.3 KB, 748 views)
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Last edited by AndriyOL; 5th October 2010 at 03:28 PM. Reason: More polite, grammar
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Old 5th October 2010, 08:11 PM   #1017
roender is offline roender  Romania
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Well, BF862 seems to be a very good candidate to replace k170.
Whit that small SMD (sot23 ?) case it won't be easy to sort them for the same Idss.
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Old 5th October 2010, 08:38 PM   #1018
Sheldon is offline Sheldon  United States
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Quote:
Originally Posted by roender View Post
Well, BF862 seems to be a very good candidate to replace k170.
Whit that small SMD (sot23 ?) case it won't be easy to sort them for the same Idss.
True, but cheap and in stock at Digikey and Mouser (and probably Euro distributors). Guess one could make a little jig to clamp them to for testing. Note that drain and source are interchangeable too. Only caveat is that it's a 20V part, so not interchangeable for all apps.

Sheldon
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Old 6th October 2010, 06:31 AM   #1019
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Mihai.
What you think about Toshiba 2SK30ATM jfet? It' seems to par with BF862 in NF and Ciss, but has lower Idss and Pd.

Perhaps this can be of help about installing technique of SOT23 package: B1-Turbo on a Chip

There is about experience of matching SOT23:
Pass Discrete Opamp in DIP-8 Package

And: 2SK170 matching
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Last edited by AndriyOL; 6th October 2010 at 06:42 AM. Reason: Just remember
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Old 6th October 2010, 07:16 AM   #1020
wahab is offline wahab  Algeria
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Quote:
Originally Posted by AndriyOL View Post
Mihai.
What you think about Toshiba 2SK30ATM jfet? It' seems to par with BF862 in NF and Ciss, but has lower Idss and Pd.

]
Most important, it has a too low transconductance (gm).
About 1.2mS while the used devices are on the order of 10mS.
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