I have a bit of a dilemma. I'm building a 6-channel amp with balanced XLR inputs which will be amplifying 6 outputs of a MiniDSP 4x10HD to power a pair of 3-way speakers. I only have 2 inputs into the MiniDSP -- USB (streaming Roon/Airplay via Ropieee) and an analog turntable which runs through a Schiit Mani > Sys for level control.
My main worry is that the MiniDSP only has digital volume control. The knob on the front is an encoder, so there's no zero position. Thus I never really know where the level is, so I'm always worried that the volume might mysteriously be at a dangerous level.
I'd like to run the 6 outs of the MiniDSP through a basic preamp / volume control -- nothing more than 6 balanced inputs with 6 balanced outputs and a reliable analog volume knob that I can turn to zero. Except all of my googling so far hasn't provided me with any path towards a solution.
The only thing I can think of is to use 3 of the 2-channel solutions that I can find (e.g. this Differential Volume Control from Neurochrome) and somehow calibrate them so that each knob is passing the same signal level at the same position, but even then I feel like it'd somehow always be "off" so that the treble, mid, and bass signals being sent to the speakers won't be authentic to the original mix.
How do I make this happen / what do I look for?
EDIT: Even if it was a 3-dial stepped attenuator with only 10 discreet positions, that would probably be good enough if I could match the signal level of each step exactly. I think that would allow me to dial it in perfectly every time? All I really need is some way to reassure me that the volume level is low when I start playing music and be able to turn it up gradually to a reasonable listening volume. From there I'm happy to do further adjustments with the MiniDSP's digital level encoder.
Thanks!
My main worry is that the MiniDSP only has digital volume control. The knob on the front is an encoder, so there's no zero position. Thus I never really know where the level is, so I'm always worried that the volume might mysteriously be at a dangerous level.
I'd like to run the 6 outs of the MiniDSP through a basic preamp / volume control -- nothing more than 6 balanced inputs with 6 balanced outputs and a reliable analog volume knob that I can turn to zero. Except all of my googling so far hasn't provided me with any path towards a solution.
The only thing I can think of is to use 3 of the 2-channel solutions that I can find (e.g. this Differential Volume Control from Neurochrome) and somehow calibrate them so that each knob is passing the same signal level at the same position, but even then I feel like it'd somehow always be "off" so that the treble, mid, and bass signals being sent to the speakers won't be authentic to the original mix.
How do I make this happen / what do I look for?
EDIT: Even if it was a 3-dial stepped attenuator with only 10 discreet positions, that would probably be good enough if I could match the signal level of each step exactly. I think that would allow me to dial it in perfectly every time? All I really need is some way to reassure me that the volume level is low when I start playing music and be able to turn it up gradually to a reasonable listening volume. From there I'm happy to do further adjustments with the MiniDSP's digital level encoder.
Thanks!
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I forgot that I found this attenuator design by Jos van Eijndhoven a few weeks ago, but it's no longer produced. Seems I would have to order my own PCBs and figure it out... first time for everything, etc... but he says:
Which seems to indicate that 6 boards could be used to control 6 channels of balanced audio. Is that right? Does he indicate anywhere that this many boards is possible?
Which seems to indicate that 6 boards could be used to control 6 channels of balanced audio. Is that right? Does he indicate anywhere that this many boards is possible?
Khozmo makes a relay based stepped attenuator where each board handles two channels (or one balanced channel). Multiple boards can be controlled with the same encoder. I'm using two in my fully balanced stereo preamp, but I believe you can use an arbitrary number of boards stacked together.
It may be overkill for what you are looking for, but it's very high quality. The one I'm using has an OLED display which shows the current volume. It always starts at zero on power up.
Sounds fantastic as well.
It may be overkill for what you are looking for, but it's very high quality. The one I'm using has an OLED display which shows the current volume. It always starts at zero on power up.
Sounds fantastic as well.
I don't think they have the product I bought listed. I've attached a couple of photos that they sent me, as well as photos of my preamp.
The ribbon cable from the controller is daisy-chained between boards. I'm not sure what the limit to the number of boards is, so you'd have to contact them to find out.
The ribbon cable from the controller is daisy-chained between boards. I'm not sure what the limit to the number of boards is, so you'd have to contact them to find out.
Attachments
Thanks @armandhammer. I've only had it running for a week, so still running in the caps. I have two balanced outputs - one DC coupled from the buffer, and one through Miflex copper caps. The latter is intended to roll off the low-end since I use stereo servo open-baffle subs up to about 80Hz, and this makes it a bit easier to blend the towers (also OB) with the subs.
- Jay
- Jay
PS. Good luck with your project. Arek from Khozmo was very responsive to my questions and delivered a high quality product. It took about 3 weeks to get to the US after ordering, and that included some customization (OLED display design, engraving the remote control, and selecting resistors).
Yeah I emailed back and forth with him yesterday, it seems like he has a perfect solution. The price will end up being double what I had hoped to pay by DIY'ing it myself, but it's still completely reasonable.
Now I just have to go back and figure out how to stuff it all inside the amp enclosure before I place the order at Modushop. Looks like it'll end up being a 5U Dissipante instead of 4U, just to give myself enough room to properly separate the components and make the wiring all nice and tidy. I'll try to remember to post back in a month or two when I'm done with it.
Thanks again, I never would have found this on my own.
Now I just have to go back and figure out how to stuff it all inside the amp enclosure before I place the order at Modushop. Looks like it'll end up being a 5U Dissipante instead of 4U, just to give myself enough room to properly separate the components and make the wiring all nice and tidy. I'll try to remember to post back in a month or two when I'm done with it.
Thanks again, I never would have found this on my own.
A meter would tell you where the level is. The meters in question are not VU. They are peak. Analogue or digital, single pot or individual pots the problem remains if you do not know what the set level is.
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