[WC]

I am interested in the LDR volume control board. I was looking to build a preamp with the board, but I just wanted to clarify how the volume control would work. I share a pair of speakers and amps in a combined 2 channel/HT setup. Would I be able to run my AV receiver preouts through the preamp? Would I be able to set input 3 at a set volume level? Could inputs 1 and 2 have a different volume setting from input 3?

Thanks,

Mike

[G Georgopoulos]

I am interested in the LDR volume control board. I was looking to build a preamp with the board, but I just wanted to clarify how the volume control would work. I share a pair of speakers and amps in a combined 2 channel/HT setup. Would I be able to run my AV receiver preouts through the preamp? Would I be able to set input 3 at a set volume level? Could inputs 1 and 2 have a different volume setting from input 3?

Thanks,

Mike

av receiver preouts are controlled by receiver?,if yes,yes you can through preamp?but additional amplification by preamp will clip pwr-amp at high volumes,the point here is low-z preamp out,if av has
lowz-out preamp why use additinal preamp?? ,anyway clipping or no clipping you can use a preamp
there..

[tortugaranger]

av receiver preouts are controlled by receiver?,if yes,yes you can through preamp?but additional amplification by preamp will clip pwr-amp at high volumes,the point here is low-z preamp out,if av has
lowz-out preamp why use additinal preamp?? ,anyway clipping or no clipping you can use a preamp
there..

With LDR passive preamps there is NO amplification - hence the "passive" descriptor. Some folks argue that a preamp without an active gain stage is not a preamp at all. Not surprisingly I disagree with that view. A preamp can have the following characteristics and still be considered a preamp.

1) It comes before the amp, hence it's "pre" the amp. - MUST
2) It controls volume (attenuation) - MUST
3) It switches between multiple inputs - OPTIONAL
4) It has no buffer output stage (passive)
The following only apply to active preamps
5) It has a buffer output stage (active) - OPTIONAL
6) Has gain (voltage/volume amplification) - OPTIONAL
7) It does RIAA curve correction and amplification (active phono stage) - OPTIONAL

[tortugaranger]

I am interested in the LDR volume control board. I was looking to build a preamp with the board, but I just wanted to clarify how the volume control would work. I share a pair of speakers and amps in a combined 2 channel/HT setup. Would I be able to run my AV receiver preouts through the preamp? Would I be able to set input 3 at a set volume level? Could inputs 1 and 2 have a different volume setting from input 3?

Thanks,

Mike

Hi Mike,

You can definitely use the LDR preamp board together with a HT receiver/amp.

Each input remembers the last volume level it was at. When you switch inputs the volume setting changes to the level last associated with a given input. Assuming you want to use the HT unit to control volume when in HT mode, you would raise the volume of the LDR preamp to 100% and leave it there. When you switch the LDR preamp to some other source, the initial volume would reset to some lower value (presumably not 100%).

There's a wrinkle in this to be aware of. The LDR board has a feature whereby it limits the initial volume upon changing an input. This was done to prevent accidentally switching to an input that had a prior volume setting near or at 100%. In your case you may want to defeat this feature. The default max volume on input change is set at step 35 (out of max 70 steps). You can adjust that setting to any value you want including up to 70 (100%).

Cheers,
Morten

[WC]

Thanks Morten.

I have seen that if I would like more than 3 unbalanced inputs I would need to add another switching input card.

Other than more input connectors and another switching board in there anything else that would be needed?
For the input control, you just cycle through 6 inputs instead of 3?
Will the new LDR input switching boards allow for up to 6 inputs with 2 cards?

Thanks,

Mike

[tortugaranger]

Thanks Morten.

I have seen that if I would like more than 3 unbalanced inputs I would need to add another switching input card.

Other than more input connectors and another switching board in there anything else that would be needed?
For the input control, you just cycle through 6 inputs instead of 3?
Will the new LDR input switching boards allow for up to 6 inputs with 2 cards?

Thanks,

Mike

The new IO3LDR board (release soon) is a 3 input board. However, 2 such boards can be ganged together. There are jumpers on the board that allow one board to be addressed 1-3, and the second board 4-6.

[WC]

Is it possible to have more than 2 outputs?

[tortugaranger]

Is it possible to have more than 2 outputs?

There are practical limits connecting multiple amps to the output of a resistance based passive attenuator. Think of a passive attenuator as a resistor and your amp as a resistor. When they're connected together you have 2 resistors connected in parallel (intuitively you might think they're in series, but in actuality they are parallel).

The effective resistance of resistors in parallel is governed by the equation:  R = (R1 x R2)/(R1 + R2). So let's say your preamp has a 20k impedance and your amp has a 20k input impedance. Your source "sees" 20x20/20+20)= 10k which is a 50% reduction in effective impedance. Now connect a second amp with 20k impedance - (10*20)/(10+20) = 6.7k  Add a similar 3rd amp - (6.7x20)/(6.7+20) = 5k.

At some point the effective impedance of all those devices connected in parallel drops low enough that your source (DAC, tuner, CD player, phono stage etc) has to work too hard delivering the audio to your collection of amps. This usually means the sound quality suffers.

If your source has super low output impedance and a robust output stage capable of delivering higher current into lower impedance devices then you're good to go.

Active preamps avoid this problem because they have a buffered output stage so all your source sees is the preamp itself and not the amps.