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Old 14th August 2014, 11:48 AM   #1311
DQ828 is offline DQ828  Australia
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Quote:
Originally Posted by BobEllis View Post
Close, leave R3 connected as in the original circuit - to the "virtual" ground created by R8 and R10. Notice that they create a voltage midpoint between the + supply and ground.

If you reference to ground as shown you create a large voltage difference between the inputs and the output will lock up.
Like this?

Obviously with this setup there is no connection to ground for the inverting input of TP-IC1 which I assume is ok?
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File Type: jpg Signal Switch MOD V2.JPG (84.8 KB, 209 views)
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Old 14th August 2014, 12:45 PM   #1312
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That's it. Yes, no resistor directly to ground from the negative input. That's standard inverting opamp configuration. Ground return to the negative input is through the feedback connection and the source.
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Old 18th August 2014, 01:04 PM   #1313
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Quote:
Originally Posted by BobEllis View Post
That's it. Yes, no resistor directly to ground from the negative input. That's standard inverting opamp configuration. Ground return to the negative input is through the feedback connection and the source.
It was fairly easy to modify the PCB's I had made and I'm glad to say the changes work . I haven't tried it with the linear supply yet but will do.

It will be a few weeks before I get to test the sound, can't what it's been a long haul this project.

With the R5 resistor that was increased to 510K which way do I go resistance wise to increase sensitivity?

Many thanks
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Old 18th August 2014, 01:18 PM   #1314
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Increasing R5 will increase sensitivity.
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Old 19th August 2014, 12:29 PM   #1315
DQ828 is offline DQ828  Australia
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Bob

I know I'm way OT but I thought you'd probably like to know the result of your advice. As mentioned earlier the revised signal switch worked with the SMPS so tonight I installed the linear supply as before & got exactly the same result that the signal switch wouldn't turn off. I reconfigured the grounding for the linear PSU and the things its powering at the moment by running the ground from the linear PSU output directly to the Ground/Earth point and then ran the crossover and speaker protection board power grounds directly to the Ground/Earth point (Star ground I guess) and low and behold it worked well at least for today

I should get to test the new speakers with the crossover in the coming weeks and then I'll have to adjust the crossover filters as required to get the sound right, which means you'll probably hear from me again

Many thanks,
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Last edited by DQ828; 19th August 2014 at 12:40 PM.
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Old 19th August 2014, 01:22 PM   #1316
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Hooray for star grounds!

A friend demonstrated ground loops in a high power RF amp by soldering a 22 gauge wire to the chassis, running it up an inch, horizontal for 8" and then soldering it to another point on the chassis. Using a screwdriver he was able to pull an arc from the middle 2/3 of the wire to the chassis.
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Old 21st August 2014, 09:23 AM   #1317
icsaki is offline icsaki  United States
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I'll bump up my order to 24 if we reach $5.5 per board (125 boards). Add 4 more PSU boards in that case.
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Old 21st August 2014, 12:32 PM   #1318
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So far

Boring 4AF4, 2 PSU
icsaki 8 AF4 conditional (24/4)
Kindhornman 4 AF4
Curryking 4 AF4
gwrskein 6 AF4 and 4 PSU (possibly 16 and 8 if $5)

Total 26(50) AF4, 6(10) PSU
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Old 21st August 2014, 12:34 PM   #1319
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So far - Closing September 1

Boring 4AF4, 2 PSU
icsaki 8 AF4 conditional (24/4)
Kindhornman 4 AF4
Curryking 4 AF4
gwrskein 6 AF4 and 4 PSU (possibly 16 and 8 if $5)

Total 26(50) AF4, 6(10) PSU
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Old 26th September 2014, 07:20 AM   #1320
icsaki is offline icsaki  United States
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Anyone else for the AF and PSU boards? How are we doing with this?
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