Double shot schematics!!

[dschwartz]

the power supply:



the preamp:


imho the switching is pretty clever.....
any comments are VERY appreciated!!

[dschwartz]

  c´mon i worked hard for this!! 

[bancika]

It's little hard to follow the schematic 

[dschwartz]

Just follow the signal path and dont get confused with the relays..
It´s a 5 stage preamp, similar (or cuasi- identical) to a dual rectifier red channel..
The relays switch channels..
when clean channel is on, i cut the ground line for bypass cap of 4th, 1st, 2nd stages..expecting to lower the gain and get good headroom..

[StephenGiles]

c´mon i worked hard for this!! 

No me digas!

[dschwartz]

SI te digo...hasta en el trabajo metido en el layout..

[pjwhite]

Your 6 volt source (100K voltage divider) won't provide enough current to run any relays or LEDs, I'm thinking.

[dschwartz]

yes?? should i lower the resistors?

[stephanovitch]

I think that you can use a zener diode for your tension regulation.

[dschwartz]

but if i use a zener diode, i will loose the 12v output..all the line will have a lower voltaje (the zener voltage)..i need those 12V for the heaters..

[stephanovitch]

You must replace the first serial resistance with 100 ohm and put a capacitor(try150 to 220µf)  in parallele with your zener diode instead of the second resistance

[stephanovitch]

Another tips:
you can add a 1N4007 diode between the ref pin of your 7812 and the ground to have 12,6 (Vf of this diode is 0.6 to 0.7V).

[dschwartz]

i already have 12.6 volts after regulation..lm7812 are not that precise (luckly!)

hmm.. i tested the zener idea with livewire.. seems to work! but i think that the 220uF is not necesarry since the source of voltage is already regulated..

[stephanovitch]

this capacitor is necessary for reduce zener noise but for relays and led sit's not critical

[pjwhite]

The easiest solution would be to use another regulator IC.  Zener regulators can be tricky -- you have to choose the series resistor and zener wattage carefully or you risk burning it out with too much current. 

I don't know what kind of relays you are planning to use, but putting an LED in series with the coils is a little odd.  If the relays are low resistance, the LED may burn too brightly, if they are high resistance, the LED may not turn on at all and if the relays require low current to turn on they may stay on all the time (due to the current through the LED), regardless of your switch position.

You could eliminate one of the protection diodes on the relay coils, since they are wired in parallel.

[dschwartz]

i am using 1/2 watt resistor for the divider..and the relays are 5vdc DS2Y.. the have low coil resistance (125 Ohms) and low power consumption (200mW nominal, 98mW min) operation current is 40mA..

Are you sure that the voltage divider wont work?is just for relays and leds...

if not...i have a 78L05 regulator..will it stand 12VDC and the power needed? i plan to put it at the same pins of the divider resistors...

anyway the leds are not going to be withgout their respective current limiting resistors....

[Aharon]

Huevoncito !!  you are on a roll man,keep up the good work!!!
Thanks for sharing
Aharon

[dschwartz]

after doing some math...the voltage divider will droptoo much voltage with the expected load... (around 150ma)..maybe the voltage regulation will work better...

i hope a 78L05 , with a series diode to ground to get 5.6V, will stand the current (they are rated for 500mA i guess)

pd: i guessed wrong.. they stand 100mA..i think i´ll go for the zener...

[stephanovitch]

i think that your 6V relay can operate with 5V only.
Are you sure that the relay current is 40mV?

[dschwartz]

nominal operation current 40mA.. that´s what the datasheet says....
they´re standard DS2Y - 5VDC relays
http://pewa.panasonic.com/pcsd/product/sign/pdf_cat/ds2y.pdf