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Budget input switcher + tone control: advice needed

andreasmaaan

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#1
Hey all,

A friend of mine has asked me for a recommendation for a cheap-ish (<$200) device that would allow him to switch between inputs and do some basic tone control.

The requirements are:
  • 2 x switchable single-ended inputs
  • 1 x single-ended or balanced output
  • Bass & treble tone controls, or basic parametric EQ
The inputs are from a phono preamp (RCA) and a laptop onboard soundcard (RCA or 3.5mm jack).

The outputs are to a pair of Eve Audio subs (XLR or RCA).

The best I've come up with so far is this. Specs look ok but not great. Inputs appear to be balanced TRS, which is not ideal but workable. EQ filters are in about the right places though.

There are various other similar units from other pro audio manufacturers. I looked at Soundcraft initially, but their budget mixers don't allow the line inputs to pass through the tone controls. Perhaps others know of something else good out there that I've overlooked?

I also thought of the Schiit Loki, but it's expensive where he is in Australia and has only one pair of inputs.

DIY boards would also be fine I think.

The main requirement is that the device interferes with the signal as little as possible.

Any suggestions welcome :)

Andreas
 

Xulonn

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#4
Schiit Sys + Loki?
 

sergeauckland

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#6
I had the same issue myself. I built a tone control, mono switching and headphone driver into a 1U (44mm) rack mount box I had available.
For the tone control, I used a Velleman kit, http://www.velleman.co.uk/contents/en-uk/p326.html as this is based on a 5532 opamp, and as such is pretty much transparent. I bypassed the volume control.

For headphones, I use a pair of LM 1875 chip amps which I bought as a kit here https://www.ebay.co.uk/p/24008796221?iid=202749347368

Buying ready made kits is just very good value, as the thing I find most difficult is designing and etching a PCB, or converting a circuit to veroboard. In these cases, the kit price was worth it just for the PCB.

Both kits worked exactly as expected. You would need a +-15v power supply, but again, there are kits available for this, or it's pretty easy to make one from separate components. The greatest difficulty I've had is to find a decent box to put projects in, which is why I've kept the cases for any products I've scrapped as beyond repair.

S.
 
OP
andreasmaaan

andreasmaaan

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Thread Starter #7
I had the same issue myself. I built a tone control, mono switching and headphone driver into a 1U (44mm) rack mount box I had available.
For the tone control, I used a Velleman kit, http://www.velleman.co.uk/contents/en-uk/p326.html as this is based on a 5532 opamp, and as such is pretty much transparent. I bypassed the volume control.

For headphones, I use a pair of LM 1875 chip amps which I bought as a kit here https://www.ebay.co.uk/p/24008796221?iid=202749347368

Buying ready made kits is just very good value, as the thing I find most difficult is designing and etching a PCB, or converting a circuit to veroboard. In these cases, the kit price was worth it just for the PCB.

Both kits worked exactly as expected. You would need a +-15v power supply, but again, there are kits available for this, or it's pretty easy to make one from separate components. The greatest difficulty I've had is to find a decent box to put projects in, which is why I've kept the cases for any products I've scrapped as beyond repair.

S.
Thanks Serge. I'll see if he's up for some soldering ;) Good to know you've used these kits and can vouch for their quality.
 

TimW

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#8
What about a used stereo preamp? They of course switch inputs but also often include basic tone controls. I'm always coming across units like this from Adcom, Rotel, NAD, and occasionally the Japanese brands.

If those are the only two sources though, why not use a miniDSP 2x4HD? The analog input can be used with the phono preamp and the laptop can connect via usb. Much better tone control and EQ options with that.
 
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andreasmaaan

andreasmaaan

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Thread Starter #9
What about a used stereo preamp? They of course switch inputs but also often include basic tone controls. I'm always coming across units like this from Adcom, Rotel, NAD, and occasionally the Japanese brands.

If those are the only two sources though, why not use a miniDSP 2x4HD? The analog input can be used with the phono preamp and the laptop can connect via usb. Much better tone control and EQ options with that.
Thanks @TimW, I originally suggested doing the EQ digitally for better precision/sound quality, but this friend says he'd prefer something simple and tactile in this case.
 
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