I bought one of these to use in my HT and allow me to bi-amp my speakers. Once I installed it, I realized it was too noisy for my efficient speakers and now it is sitting in a box unused. I tried selling it locally with no interest and on another site (fellow 100+dbers), but I was honest in my responses and as such I still own it.
This leads to my question, I am into this thing 600 bones and it makes me sick to think it is going unused. Any advice or suggestions on a project or something that I could use it for? I don't believe I even own a speaker that's less than 100db at 1 Watt, that might be my problem as it's a SQ thing. Anyone care to post what they have done with a similar unit that maybe I could check out? It's the fully loaded flagship version. I think it might be OK as a sub woofer DSP, but I can manage all of that with the Xillica I replace it with. Which I must say is a very fine DSP, I highly recommend it if SQ is your top concern.
Thanks.
This leads to my question, I am into this thing 600 bones and it makes me sick to think it is going unused. Any advice or suggestions on a project or something that I could use it for? I don't believe I even own a speaker that's less than 100db at 1 Watt, that might be my problem as it's a SQ thing. Anyone care to post what they have done with a similar unit that maybe I could check out? It's the fully loaded flagship version. I think it might be OK as a sub woofer DSP, but I can manage all of that with the Xillica I replace it with. Which I must say is a very fine DSP, I highly recommend it if SQ is your top concern.
Thanks.
Just put attenuators on your amp inputs to fix the gain structure. It's a dollar's worth of resistors.
John, can you elaborate on what is needed and what this does? Doesn't that reduce the gain provided by the amp? If you provide a link, I'll give it read through. I must admit though, I did research and look at this as a solution and I could not find anyone that actually solved it by this method. I run 105db speakers and my amp provides 14db of gain if that helps any.
Another note, I also started this whole project with an McIntosh MC2205 that has a gain knob, I tried turning that down but never got it good enough. I can give it another go with that amp, but need some advice on what I am doing wrong.
Another note, I also started this whole project with an McIntosh MC2205 that has a gain knob, I tried turning that down but never got it good enough. I can give it another go with that amp, but need some advice on what I am doing wrong.
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Sorry, I don't have time to explain what an attenuator is here. The essential point is that you need to adjust the overall gain from DSP output to speaker so that you get the right tradeoff between noise floor and maximum output.
Most of the issues reported by people with miniDSP and high sensitivity speakers seem to be when using analog in and connecting the analog out straight to the power amplifiers. In this case you can end up having to put huge levels of attentuation in the digital domain in order to be able keep volumes at a sane level. with 105dB speakers the average level is likely to be in the order of -30dbW (or 1000th of a Watt).
What is likely to work is attenuation between MiniDSP and power amplifier so you are using a minimum of gain control in the miniDSP itself.
Big sensitive horns are always a challenge. Sadly miniDSP due to not having an analog volume control has a bad name in those circles, which is not entirely fair. Hopefully one day someone will do a miniDSP version of Jan Diddens Behringer upgrades.
What is likely to work is attenuation between MiniDSP and power amplifier so you are using a minimum of gain control in the miniDSP itself.
Big sensitive horns are always a challenge. Sadly miniDSP due to not having an analog volume control has a bad name in those circles, which is not entirely fair. Hopefully one day someone will do a miniDSP version of Jan Diddens Behringer upgrades.
14db gain is very low for a power amplifier. Seemingly low enough to effectively offset the high efficiency of your speakers. Are you sure it's actually 14db?
I think there might be more to this story than a simple case of excess gain causing noise in the speakers. Some other variable at work here most likely.
Dave.
I think there might be more to this story than a simple case of excess gain causing noise in the speakers. Some other variable at work here most likely.
Dave.
I do not believe I have "too much" gain. It is a First Watt M2. 14db per Nelson Pass's manual.
No, I don't believe you have too much gain. I think John and Bill's quasi-recommendations are incorrect.....in this case.
I think your low power amplifier voltage gain is probably well-suited to the high-efficiency speakers you're using.
I think the noise problem is caused by another issue and not excess voltage gain.
Some users with wide-bandwidth amplifiers have noticed possible issues with out-of-band noise above the audio range being "modulated" by the power amplifier into audible noise within the audio range. That may be your issue here.
I think rather than attenuators between the miniDSP and your power amplifier you might try some low-pass filtering. A simple shunt capacitor working in conjunction with the output resistance of the miniDSP unit might solve this issue. I've made a few posts on this previously on this and other forums and users have had success doing it.
Cheers,
Dave.
I think your low power amplifier voltage gain is probably well-suited to the high-efficiency speakers you're using.
I think the noise problem is caused by another issue and not excess voltage gain.
Some users with wide-bandwidth amplifiers have noticed possible issues with out-of-band noise above the audio range being "modulated" by the power amplifier into audible noise within the audio range. That may be your issue here.
I think rather than attenuators between the miniDSP and your power amplifier you might try some low-pass filtering. A simple shunt capacitor working in conjunction with the output resistance of the miniDSP unit might solve this issue. I've made a few posts on this previously on this and other forums and users have had success doing it.
Cheers,
Dave.
14dB is right according to the specs, which is 500mV in for 1W out. If you are able to do some testing it would be great to get to the bottom of if there is a real problem with miniDSP and high efficiency speakers. A couple of people on here are very vocal about them being not fit for use with >99dB/W drivers but would be great to try and investigate more.
Well, that's already been proven by numerous users.
I've hinted at a possible solution above. Much depends upon the high frequency response of your amplifier and if band-limiting its input will reduce the audible noise you experienced.
I haven't found output noise to be dependent upon the internal DIP switch position which controls analog gain output, but other users have noted this. I would start with that and then add a shunt capacitor across the miniDSP outputs to limit the above-band noise (that I showed above) and see if that results in improvement.
Dave.
I have an order for another project in my cart from mouser. I am not that part savvy, care to give me a part number? I can capitalize on shipping? I'll give it a go. If the DIP is just gain, I doubt that will do it. I just as well prepare for that.
Thanks for your help.
This is just proof-of-concept for your application, so just about anything would be fine. I would select a polyester leaded capacitor of 10nF and try that.
This would be fine:
MMK5103K50J01L4BULK Kemet | Mouser
Dave.
This would be fine:
MMK5103K50J01L4BULK Kemet | Mouser
Dave.
You might also try a transformer coupling and see if that helps. Something like a Jensen ISO-MAX.
This provides an effective low-pass filter above the audio band.
Dave.
This provides an effective low-pass filter above the audio band.
Dave.
I order the part you recommended. Should be here in a a few days. I'll need some help in its placement.
I google that Jensen and that seems to be an expensive solution, one not required on the exact same system running through my Xillica 4080. What does this item do exactly.
I apologize for my lack of knowledge on this subject.
I google that Jensen and that seems to be an expensive solution, one not required on the exact same system running through my Xillica 4080. What does this item do exactly.
I apologize for my lack of knowledge on this subject.
To try the capacitor shunt I would get a short "Y" adaptor (RCA male ---> two RCA females) and a spare RCA plug with removable shell. Attach the capacitor to the RCA plug and then attach that plug to one of the females. You can then insert the "Y" adaptor at either your power amp input or the miniDSP output.
No guarantee this will solve your issue, but it won't cost you much to find out. 🙂
Cheers,
Dave.
No guarantee this will solve your issue, but it won't cost you much to find out. 🙂
Cheers,
Dave.
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