I guess I'm in need of a monitor controller - Help

[jarbar]

I just had the same experience here with MC3 - the sound passing through it really lost something so I returned it. Too bad, it's got great features.

Anyone have any experience with the Coleman LS3? I was thinking of getting that and eventually pairing it something like a Main Gain. For now I'm adjusting volume with software but would love to access to more than one pair of monitors.

[Brad McGowan]

Originally Posted by travisbrown

I think Greg Scott said that the MainGain operates at unity wide open, so the active buffer must be making up that difference.

If you turn the Main Gain's volume all the way up it will output unity gain. The amps in the circuit are gain staged to that effect. Any setting turned down from that will be attenuating the signal as it passes through circuit. With the knob at about 2 o'clock the user should calibrate their monitor trims so that they are getting about 86 dB SPL at the listening position (refer to Bob Katz' K-System for monitor calibration). That gives you some range of travel to go louder on your monitors and ensures that you won't be clipping the input stage of your monitors.

Brad

[travisbrown]

Originally Posted by warhead

No, it's not typical. I don't appreciate the implication that I'm misleading people either. People need to know what they are buying, I don't know why you're researching this with phone calls and follow ups and finger pointing, but it feels odd to me.

Because I wrote a review on the product and had earlier recommended it in this thread to the OP. It was not my experience with the pre-release unit that there was debilitating attenuation or, as others have claimed, utter destruction of signal (obviously hyperbole). Even today I experienced the dB loss you wrote about, but it wasn't discernably colouring the signal. Once level matched, it was fine.

I was relaying Radial's response: the 6dB loss is a result of the passive chain (variable i/o impedance mismatch?) They don't claim it was by design, but incidental to the design. That's what I mean when I wrote that it was misleading to say they designed it that way. Implies intentionality. Since there is really only a pot and a trim in the path, they pretty much couldn't do any less design. Design was essentially picking the model of potentiometer then going for lunch.

Maybe the unit I tested had a different pot than what was ultimately in the production run, but A/Bing that unit definitely did not present the issues you experienced.

I'm not finger pointing or discounting your experience. I'm trying to clarify conflicting information about and experiences with a monitor controller in a thread about monitor controllers.

[travisbrown]

Originally Posted by Brad McGowan

If you turn the Main Gain's volume all the way up it will output unity gain. The amps in the circuit are gain staged to that effect. Any setting turned down from that will be attenuating the signal as it passes through circuit. With the knob at about 2 o'clock the user should calibrate their monitor trims so that they are getting about 86 dB SPL at the listening position (refer to Bob Katz' K-System for monitor calibration). That gives you some range of travel to go louder on your monitors and ensures that you won't be clipping the input stage of your monitors.

Brad

Thanks Brad. Out of curiosity, if you know, can a passive attenuation circuit achieve unity or will differing i/o impedances incurred by way of a pot always attenuate the signal. Main Gain obviously amplifies the signal up to unity, but was that because it was otherwise problematic?

[warhead]

OK, I was told -9dB minimal loss in this design which is more like what we saw.

It's their design, they could have made it unity and passive, they did not. It's inherent to their design and choice of components.

Radial are good guys, this was the only "WTF?" moment I ever had with that company's products.

War

[travisbrown]

Originally Posted by warhead

OK, I was told -9dB minimal loss in this design which is more like what we saw.

It's their design, they could have made it unity and passive, they did not. It's inherent to their design and choice of components.

Radial are good guys, this was the only "WTF?" moment I ever had with that company's products.

War

Maybe they've since updated the pot again that brought it up to 6dB. Next time I'm over there I'll ask why not unity. When I enquired yesterday, the answer from one of the engineers was a matter-of-fact "because it's a passive design. That's what happens."

I'm kind of interested in finding the answer because I was going to build a passive controller of similar design but with more monitor (and pre-emptive) selection and a stepped attenuator.

[jarbar]

Bumping as I'm curious if anyone has paired a Coleman LS3 with a good volume control and if it affects the sound at all.

[Peakly]

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[Peakly]

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[Peakly]

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[Brad McGowan]

Originally Posted by travisbrown

Thanks Brad. Out of curiosity, if you know, can a passive attenuation circuit achieve unity or will differing i/o impedances incurred by way of a pot always attenuate the signal. Main Gain obviously amplifies the signal up to unity, but was that because it was otherwise problematic?

Sure. you can have unity gain with a passive topology. There can be impedances issues that affect things, but assuming the design is good, unity gain can be achieved.

The Main Gain doesn't amplify the signal upto unity. It goes in at unity, and then comes out at unity (if you have the knob fully clockwise...all the way up). When we talk unity gain, we mean that the input equals the output regardless of what that level is. Passive or active electronics can attenuate level. Only active electronics (excluding transformers) can increase level. In the case of the Main Gain we chose not to offer any level boosting because we wanted to maximize headroom for lowest distortion going into a set of monitors.

When you design a piece of gear with active electronics you ensure that proper gain staging exists in your circuit, sources can drive loads, and that absolute polarity is maintained. There was nothing problematic in the Main Gain along these lines. It's a very simple design with four op amp stages...a differential input, a fader buffer, a summing amp (for the mono), and an output amp. Hence its ultra pristine and accurate presentation of sound.

Brad