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GB For Salas I-Select Mesmerize Type input selector and volume control

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#107
When you want to use it as selector only, link the middle pot pads to their respective ones on the right.
 

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#113
A quick question here that Tea suggested i pose to the forum. I am planning to use the i-select as input selector for a BA-3 front end-based preamp. The BA-3 boards run off 24V, which comes from a 22V dual secondary 80VA transformer through a Rod Elliot LM3x7-based power supply. The power supply has an additional unregulated DC aux tap running approx 31V after rectification.

Since the i-select runs off either AC up to 22V or DC up to 30V, what would be the better option for power here:
a) AC 22V - i wonder, and Tea seemed to agree, that this is too high for comfort since it wouldnt take much fluctuation to bring it up too high. or
b) DC but put a dropping resistor before the i-select to drop something like 5-6V. I guess something like a 600 ohm, 2W (or 5 to be safe) would do?

Or another option? I suppose i could also tap one side of the 24V regulated DC output from the psu, but i am worried that might impact things downstream on the BA3 side?

Opinions appreciated!
 
#114
Your I-select will draw little current, so an easy option is to use a couple of cheap diodes in series to bring down the voltage by a few V. The 22V AC could be used this way. You should be able to feed the output of the diodes into the AC input of the I-select.

I would not use a resistor to bring the DC down because it can result in a variable voltage to the I-select (depending on it's variable load). You could use diodes in series to bring the unregulated 31V DC down, just like for the AC input.
 
Last edited:
#115
silasmellor said:
A quick question here that Tea suggested i pose to the forum. I am planning to use the i-select as input selector for a BA-3 front end-based preamp. The BA-3 boards run off 24V, which comes from a 22V dual secondary 80VA transformer through a Rod Elliot LM3x7-based power supply. The power supply has an additional unregulated DC aux tap running approx 31V after rectification.

Since the i-select runs off either AC up to 22V or DC up to 30V, what would be the better option for power here:
a) AC 22V - i wonder, and Tea seemed to agree, that this is too high for comfort since it wouldnt take much fluctuation to bring it up too high. or
b) DC but put a dropping resistor before the i-select to drop something like 5-6V. I guess something like a 600 ohm, 2W (or 5 to be safe) would do?

Or another option? I suppose i could also tap one side of the 24V regulated DC output from the psu, but i am worried that might impact things downstream on the BA3 side?

Opinions appreciated!
Click to expand...

I am using the same setup with the Salas BiB psu boards of +/-24V DC output. I tapped couple of wires from 0,+24V DC of the psu and powering the I-Select board and no issues at all. Go ahead and use the psu output as I can see that the Salas psu never had a drop of even 1mV when used both for powering the BA3 preamp as well as I-Select boards.
 
#116
albertNL said:
Your I-select will draw little current, so an easy option is to use a couple of cheap diodes in series to bring down the voltage by a few V. The 22V AC could be used this way. You should be able to feed the output of the diodes into the AC input of the I-select.

I would not use a resistor to bring the DC down because it can result in a variable voltage to the I-select (depending on it's variable load). You could use diodes in series to bring the unregulated 31V DC down, just like for the AC input.
Click to expand...

Thanks AlbertNL, i would like to use the AC since its there, so this seems like a viable option. Let me just ask a potentially dumb question here (i am just a hobbyist, and learning at that): If i drop 6V DC with a resistor and wire that into the DC in on the board, won't that still give plenty of room for regulation by the i-select regulator, even if some voltage fluctuations occur?

But maybe regulated DC from the PSU as manniraj suggests is the way to go, my feeling is also that the power draw from the i-select is too small to matter much, but i wasnt sure...

Thanks for the input to both of you!
 
#117
silasmellor said:
Thanks AlbertNL, i would like to use the AC since its there, so this seems like a viable option. Let me just ask a potentially dumb question here (i am just a hobbyist, and learning at that): If i drop 6V DC with a resistor and wire that into the DC in on the board, won't that still give plenty of room for regulation by the i-select regulator, even if some voltage fluctuations occur?
Click to expand...



To be honest, I do not know. I am also just a hobbyist 🙂


The reason I would use a string of diodes is because I know it will do exactly what I want, namely a reduction by a voltage I can determine beforehand.

The voltage drop due to a resistor in series with the circuit will depend on the varying "resistance" of that circuit. It is quite possible that it will work fine in this or other cases. Not having analysed the circuit I opted for the easier/lazier fool-proof option: diodes.
 
#119
Yes, pretty much any diode but do not use low voltage drop diodes as that defeats the purpose 🙂

The I-Select doc specifies 1N4003 for use on the board so there probably is a reason not to use 1N4001 or 1N4002.
I would use any of the 1N4003 through 1N4007 (you can mix if you do not have enough of the same type).
 
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