Building a symmetrical psu B1 buffer

[william2001]

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.

[regiregi22]

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.

[vzs]

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

[dantwomey]

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

[regiregi22]

-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.

[Salas]

Originally Posted by vzs

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.

[dantwomey]

Originally Posted by regiregi22

-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

[Salas]

Which TO-220 diodes in use and at what CCS current is your build? Looks well put.

[vzs]

Originally Posted by Salas

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)

[AndrewT]

Originally Posted by vzs

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?