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Old 13th April 2010, 12:08 AM   #1311
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regiregi22:

I talked about the orange LED at post #1295. It's not a necessary component of the LDR circuit. Just a personal touch kind of thing I came up with, gives the front panel a balanced but interesting contrast I think. And a friendly reminder to run the volume at half for a long, productive life of the LDR's when in "standby" mode.

Front LED's are run by an 8V regulator, with appropriate dropping resistors of course.
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Old 13th April 2010, 07:23 AM   #1312
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Sorry Williams, my fault. I'm sorry, I was writing a post while you were posting yours There are 2 minutes of difference between them.

Enjoy your preamp, seems to be one of the best out there actually.
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Old 20th April 2010, 01:56 PM   #1313
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I want to modify the DCB1's regulator to deliver +-24V needed for a small preamp as well.

Can I use the symmetrical B1 buffer with +-24V so I can use the regulators for both?

Thanks,
Zsolt

Last edited by vzs; 20th April 2010 at 02:03 PM.
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Old 20th April 2010, 03:04 PM   #1314
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My B1 fired up for the first time perfectly with no apparent issues. Can anyone recommend a brief list of checks before I plug it into my system?

Regards,
Dan

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Old 20th April 2010, 05:57 PM   #1315
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-First, short the inputs to ground and measure the outputs. Set your DMM to mv AC, and you should see it virtually zero. Then on mv DC you should see no more than 5mv or so. Try rotating you volume control to see if it changes

-Second, connect your source to it, and check the same things. Values should stay more or less the same.

-Third, hook up some cheap speakers to the amp before hooking your expensive ones.
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Old 20th April 2010, 06:35 PM   #1316
Salas is online now Salas  Greece
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Quote:
Originally Posted by vzs View Post
I want to modify the DCB1's regulator to deliver +-24V needed for a small preamp as well.

Can I use the symmetrical B1 buffer with +-24V so I can use the regulators for both?

Thanks,
Zsolt
Not recommended. Each audio JFET will reach 250mW constant dissipation. Very precarious for 400mW max TO-92 devices. Especially here if one goes, opposite rail DC appears at the output.
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Old 20th April 2010, 08:30 PM   #1317
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Quote:
Originally Posted by regiregi22 View Post
-First, short the inputs to ground and measure the outputs. Set your DMM to mv AC, and you should see it virtually zero. Then on mv DC you should see no more than 5mv or so. Try rotating you volume control to see if it changes

-Second, connect your source to it, and check the same things. Values should stay more or less the same.

-Third, hook up some cheap speakers to the amp before hooking your expensive ones.
First very quick measurements are: PS is +10.86vdc and -10.17vdc. DC offset on the outputs appears to be .2mV and 1.0mV. I'll do the rest tomorrow.

Regards,
Dan
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Old 21st April 2010, 03:30 AM   #1318
Salas is online now Salas  Greece
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Which TO-220 diodes in use and at what CCS current is your build? Looks well put.
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Old 21st April 2010, 06:35 AM   #1319
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Not recommended. Each audio JFET will reach 250mW constant dissipation. Very precarious for 400mW max TO-92 devices. Especially here if one goes, opposite rail DC appears at the output.
What about using TO-92 clip-on heatsink? like one of these:
TO-92 Heatsink
Digi-Key - HS251-ND (Manufacturer - 575200B00000G)
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Old 21st April 2010, 09:18 AM   #1320
AndrewT is offline AndrewT  Scotland
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Originally Posted by vzs View Post
What about using TO-92 clip-on heatsink? like one of these:
TO-92 Heatsink
Digi-Key - HS251-ND (Manufacturer - 575200B00000G)
that will help power dissipation and temperatures, but you still have the risk of 48Vds on either device. How long will jFETs last with 48Vds and running hot?
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