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Can anyone on here tell me if it is possible to mod the miniDSP to ouput 4V for car?
Can anyone on here tell me if it is possible to mod the miniDSP to ouput 4V for car?
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Old 14th October 2010, 03:33 PM   #1
JZatopa is offline JZatopa  United States
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Join Date: May 2003
Location: Chicago
Default Can anyone on here tell me if it is possible to mod the miniDSP to ouput 4V for car?

The MiniDSP looks like a great product for car. The only problem is that it's V out is about 2-3 volts to low. Can anyone on here tell me how I could boost the V out without adding another piece? I know that a line driver would make this possible but I want to make this system as simple as possible.
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Old 14th October 2010, 03:44 PM   #2
Perry Babin is offline Perry Babin  United States
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If the DSP IC drives the output directly and the IC operates from 5v, the maximum possible output could only be about 1.5v. According to the datasheet, the output is only 0.9v but the specs are confusing and the output may actually be closer to 0.7v. I think there are threads on other diyaudio forums.
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Old 15th October 2010, 06:23 PM   #3
JZatopa is offline JZatopa  United States
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So in other words an output circuit would have to be built and put in line or added to the board, right?
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Old 15th October 2010, 06:33 PM   #4
Perry Babin is offline Perry Babin  United States
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If you have an amplifier that can be driven to full power with only 0.2v (fairly common), you don't need anything between the DSP module and the amp.
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Old 17th October 2010, 07:52 PM   #5
JZatopa is offline JZatopa  United States
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Perry that was possibly common in car audio in the late 80's early 90's but not now. Most car amps need 2V-4V input to be properly driven.
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Old 17th October 2010, 08:07 PM   #6
Bertje is offline Bertje  Netherlands
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It is possible to drive amps with the standard output of the minidsp. You only have to adjust the gain (sensitivity) of the amplifier to 0,9V. And that is also the disadvantage because it reduces the system/noise ratio.
Adding a linedriver (4ch per minidsp) could be a solution, but active linedrivers add also noise. But modifing the minidsp isn't possible, it's output is direct from the dsp-chip.
Rob.

Last edited by Bertje; 17th October 2010 at 08:12 PM.
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Old 17th October 2010, 09:23 PM   #7
Perry Babin is offline Perry Babin  United States
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DJNUBZ, one example:

Sony amplifier XM-1652Z with the gain set to 0.3v, the amplifier was driven into clipping with only 0.256v RMS input. This amp and many others can easily be driven to clipping with 1/2v.
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Old 20th October 2010, 01:49 PM   #8
jol50 is offline jol50  United States
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I had a dual xia2460 and had a hard time driving it to clipping with a old HU that I think is 2v, iirc I could not. Very few other amps have I run into this. Back then I was just testing on subs and not measuring, but there was a significant difference; full gain didn't give me much output. Some models of the brands from power acoustic would gain so high I got feedback with them, not sure why other than maybe 20% on the HU would clip them and that was very unusual. The RCA on the HU are actually grounded through a fuse to the PS so I know it was shielded properly. (from the point internally that they ground as I blew that up, so I ran wire to an external fuse)

Another issue I see with cheaper to mid amps is when they have an adjustable bass boost they often have less gain, but not true of all of them. Note some even have the remote run the boost and not the gain. I have a mrd-m500 alpine which I would consider middle of the road and not a junk amp, I have the gain set to max in my car. I don't use the boost as I have a 16 band EQ and sub level in the HU with 5v preout, but sometimes on CDs and certain radio I have to run the sub level to near max on the HU to get good output....which seems odd. It is running at 2 ohms also though I doubt I am using even half its output in normal use it typically shows under 10A draw. The subs are IB 15s, they don't need much power to make thump and are only in there to get under 30Hz with no box. On a boosted bass CD they go really loud/low so it is certainly capable of sufficient output. While another amp will gain higher, I'm considering a bass processor if it can help control the various level issues I am getting or at least a remote level. I can turn the other amps down, but am close to max volume on the HU now for some sources. ATM the highs are only 50rms/ch so I would consider it an issue, but I do have other amps to try. This has nice readouts for temp/voltage/amperage/etc is why I wanted to run it for a while.

All that said I ran 2v HU until a few years ago in many systems and never had an issue with noise or enough output or ability to clip the amps. Had I ran into just the right amps I may have, but line drivers are not needed in typical systems IMHO.
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