Switchable Hi-Z input impedance, how ? - Page 29 - diyAudio
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Old 13th September 2012, 08:57 PM   #281
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by Struth View Post
Hi Guys

Using a center-off switch to control three LEDs is easy.
hey, Kevin

trying to follow your describtion

like this
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Old 13th September 2012, 09:27 PM   #282
Struth is offline Struth  Canada
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Hi Guys

I've attached a drawing... hopefully.

Have fun
Kevin O'Connor
londonpower.com
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Old 13th September 2012, 10:05 PM   #283
tinitus is offline tinitus  Europe
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ah, I understand now, the middle LED is connected directly to power supply
but only goes on when the other LEDs are off, because of the diodes

thanks Kevin, thats great

btw, i have mounted a small 3V supply
read somewhere that its optimal voltage
ripped it out of wall plug thing
hope it will do
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Old 13th September 2012, 11:29 PM   #284
tinitus is offline tinitus  Europe
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and corrected my drawing
many thanks Kevin
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Old 14th September 2012, 12:56 PM   #285
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thought it would be nice to have a green LED close to output att/pot, together with the red one

but realized it could present a problem
output LEDs are controlled by the tube curcuit bypass/OFF/ON switch
so it will have to ON in both positions 1 and 3
but now we are on to the diodes, I found something about logic curcuits, and thought it might be useful

but will it work this way ?
any suggestion what diodes to use ?
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File Type: png bass pre layout 210 LEDs.png (18.1 KB, 23 views)
File Type: png bass pre front 210.png (34.7 KB, 22 views)
File Type: png bass pre layout 210 tube bypass switch.png (67.9 KB, 4 views)
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Old 14th September 2012, 10:37 PM   #286
Struth is offline Struth  Canada
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Hi Guys

If you want a LED that is on for both the 1,3 positions merely lift those two LEDs from ground, link them together at the cathode and insert the fourth LED.

The fourth LED will be on in both up/down positions but not in the middle.

The other LEDs will function just as before.

If you further want control over this fourth LED, you can parallel it with a switch/relay contact or BJT to shunt it off when desired but the other LEDs will still work as before.

Have fun
Kevin O'Connor
londonpower.com
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Old 14th September 2012, 11:17 PM   #287
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by Struth View Post
If you want a LED that is on for both the 1,3 positions merely lift those two LEDs from ground, link them together at the cathode and insert the fourth LED.
he, ofcourse, nice and easy
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Old 16th September 2012, 04:20 PM   #288
tinitus is offline tinitus  Europe
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ok, a few things are changed since this project started
time to see what happens if I rearrange the curcuits
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Old 16th September 2012, 04:26 PM   #289
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input att/pot/buffer and SS gain stage could be 'fixed'

and the only selectable option would be, tube output or no tube output
it does look simpler and better this way
at least on att/pot and buffer is gone this way

bummer, that was the pot to 'balance' the channels
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Old 17th September 2012, 05:00 PM   #290
Struth is offline Struth  Canada
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Hi Guys

In the tube section of the preamp, there is only one gain stage. This will provide very little tubiness.

Have you in fact tried wiring the tube as a standard fender pre? That is the basis for every tube bass preamp ever made except the Rumble which was a copy of my Spectrum preamp front end. I think you will find it is nice sounding without excess colour. With an output level you can overdrive it a bit before the power amp. You would likely find that you do not need any other switching, etc.

Have fun
Kevin O'Connor
londonpower.com
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