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but 20 leds in series = 400ma?
better in parrell?
If the LEDs are 3.5V white ones then 20 in series need a voltage of 70V plus more voltage for a current-limiter.

They each have a slightly different voltage so if 20 are connected in parallel then the one with the lowest voltage will hog most of the current and quickly burn out. Then the next one with the lowest voltage will burn out. Then the next one ...

Connect two 3.5V LEDs in series then they use about 7V. Then with the barely used -9V regulated supply there will be 2V across a current-limiting resistor. A 100 ohm resistor will limit the current to about 20mA. Use 10 of these series strings of LEDs.
 
Gots to go simple

I like your idea go simple
Using blue smd leds
using two in series, 9v+ 125ohm resistor we get 16.78 ma.
sounds good to me.
just hoping the 1amp 24vct transformer has enough poop
 

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  • 9vpower supply.GIF
    9vpower supply.GIF
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D1 and D2??

thats what the schematic I found had on it.
Could be for regulation of voltage or current?
YES the Osram LB A676 J2-1 are 3.5 volts see attached.
need to recheck schematic etc before designing pc boards
 

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  • LB_A676_Pb_free.pdf
    380.8 KB · Views: 259
You do not need diodes at the output of the voltage regulators.

The LEDs are typically 3.5V but could be anywhere from about 3.2V to 4.1V at 10mA.
Some are very bright and others are not. I hope yours are the same.
 
The Kits R Us design is for the LM317 and the diode is not across GND and VOut. On the trainer it's most likely to act as a crowbar to blow the fuse when a student hooks one power source to another power source.
 
The diode across the output stops the regulator from blowing up if a kid connects a higher voltage negative supply to the lower voltage positive supply and vice versa.
 
Eliminating an op amp?

Started laying out the pc board and noticed that I might be able to eliminate U1A3 and U1B3 as the output from the mixer has basically samp setup. Only difference is the capacitor/resistor arrangement.
Thinking of eliminating the U1A3 and U1B3, Dropping R182 and R183Mixer outputs and just go with U1a and (not pictured U4A) with the 220nf/ 100k in series to the filter op amp
YES, NO, MAYBE
this would eliminate the extra op amp (only using 1/2 of U1A3 and U1B3 op amp.
 

Attachments

  • R channel mix.GIF
    R channel mix.GIF
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  • R channel.GIF
    R channel.GIF
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sweep of one op amp gone,

resistor to ground and cap in series.sharp sweep
db gain is 90+
YES eliminate op amp duplication and run resistor to ground? or??
 

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  • op amp gone.GIF
    op amp gone.GIF
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You have huge 10uF input capacitors feeding opamps with an input impedance of only 1k ohms and a voltage gain of 100. For low impedance microphones?
The input opamps will be overloaded with line-level signals.
The input capacitors should be 220nF poly type and the opamp's input resistor should be 100k for a voltage gain of 1.

If you remove U1A3 and U1B3 then the output level of the circuit depends on the resistance of the load.
Remove C5, R183, C12, U1A, r1 and R11 and the same parts on the other channel.
U1A3 and U1B3 can drive the filters and the CD4066 directly.

The CD4066 is not biased and not powered correctly.
With inputs from -8V to +8V then it should have a dual-polarity supply of -8v and +8V.

Your simulation shows an opamp with a gain of about 200,000 because it doesn't have the series input resistor that normally feeds an inverting opamp.
The 220nF input capacitor blocks frequencies below about 300Hz (or less) and the very high gain cuts high frequencies.

+90dB is a voltage gain of 32,000.
A resistor to ground at the input of an inverting opamp does not do anything because the feddback resistor makes the input at the same voltage as the non-inverting input which is ground in your circuit.
 
I want to experiment to LEARN

I already removed op amps and resistors.
will try the examples audioguru mentioned.
 
?? 4066

The 4066 is powered by 9v+
If you connect the control pin to Vdd (9V+) then the contacts close.
Grounding the control pin opens the contacts
Am I missing something??
The inputs/outputs are not dependent on Vdd?
I thought I changed the input caps?
The inputs are line level (tv set, radio, stereo, Ipod or Mp3)
the outputs feed a 25w amp
 
Your OPAMPs are on +9 & -9, your CD4066 is a quad analog switch but it won't pass signals lower than it's lowest (VSS) voltage properly unlike a relay. BUT it's only rated for 15V max so a split +/- 7V supply might be a better fit. There are better analog switches available.
 
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I hope this is correct?

I made changes you suggested.
I hope I got them right?
 

Attachments

  • revamped circuit.GIF
    revamped circuit.GIF
    62.9 KB · Views: 136
The revamped circuit looks good but C32 can be replaced by a piece of wire.
 
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