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post #1 of 39 Old 11-03-2013, 01:44 AM - Thread Starter
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I've been away for a week or so. Went on vacation. Just before I left, during, and on since I've been home I've read a lot about the mini-dsp. It seems the mini has some shortfalls that have been noted and that I've confirmed.

Stereodude, and several others, have been great contributors to this. I will try to list some references but the main point of this thread is to point out my findings.

Tonight I triple checked settings and measurements. I'm driving DIY subs via a Peavy pro audio amp that requires 2.25 input volts to put out full power. My quest began to make sure i was getting full power out of my amp. I am.......... no problem there.

My Equipment -
Pioneer SC1522-k
Peavy IPR2 7500
6 Stereo Integrity D-4 subs
BALANCED Mini-DSP

The problem is within the mini-dsp and its input side. Here's my procedure, triple checked. I know it's been posted a lot but bear with me.

I used the Home Theater Shacks guides to
1) determine clean output of my AVR and ( http://www.hometheatershack.com/forums/home-theater-receivers-processors-amps/35677-gain-structure-home-theater-getting-most-pro-audio-equipment-your-system.html#post317692 )

2) Set amp gain ( http://www.hometheatershack.com/forums/home-theater-receivers-processors-amps/35677-gain-structure-home-theater-getting-most-pro-audio-equipment-your-system.html#post317697 )

1) Determining clean output of my AVR
- Pure direct mode, all processing off (double checked, kept checking t-out the testing)
- MV of AVR set to max
- Sub trim set to max
- x-over set to highest
Result is 10.6 volts using DMM.

30% of 10.6 volts is 7.42. 7.42 volts out of the LFE RCA jack is ~ +1.5 on the M. Volume of the AVR. So next>>

2) Set Peavy amp gain

-Master Volume on AVR is +1.5
-Sub Trim - max (0)
-Again - pure direct, all processing OFF

-Turn amp gain to zero
-Play REW pink noise at -3.0 DB FS on the sub cal setting
-turn up the amp gain until clip lights come on steady--
DONE

Mini-dsp input is at 2.0 volt setting and is saturated during pink noise test used to set PA amp gain. Saturated at +0.7-0.1. <<--- this leaves NO ROOM for ANY BOOST on the filter portion of the mini dsp

3)
Set subs to 75 DB using the AVR noise, UMIK-1, (calibrated by Herb at Cross Spectrum Labs), and REW SPL meter. The ONLY method of calibration to 75 DB is the reduction in sub trim on the AVR.
Sub trim is now at -7, AVR is of course -0.

4)
Test for minidsp saturation (+0 or above) using
- The REW tone AND a bass demo track w/ different songs, rap, jazz, techno, and some chest pounding bass.
- Using the REW test tone as noted above with the above settings calibrated to the noted 75 DB and a 2.0 input voltage setting on the minidsp the mini read ~-15db.
-add 10 db to the sub trim on the AVR (10 db hot, right? everyone likes some hot bass now and then) and the mini reads ~ 4.5. THAT'S HARDLY ANY ROOM FOR ANY BOOST before the mini dsp is going to clip its inputs.

During the sub demo track (AVR MV @ 1.5, subs +3, or 10db hot, mini dsp input reached single digit negative numbers frequently. This is AT THE 2.0 volt setting.

While not clipping at those levels, REMEBER, there is NO boost applied. No LT, no nothing.

All the while I have plenty of volts from my AVR into the minidsp, and, GET THIS, more than 2.0 volts out of the minidsp. The minidsp is speced as having only 2.0 volts out regardless of input!


My main complaint is ..... at the least minidsp should document some of these things. I'm going to have to play some of the movie demo discs at the same realistic demo volumes I did these tests at before Ill know if I can keep the mini-dsp with my AVR

As I mentioned I've been reading. Very few times have I seen mini-dsp give a sort of attitude to say...... towards their customers with questions RE: these issues. It seems you must 'beat them' at their game before you get any respectful answers.

I've seen read many times people suggest these exact findings need to be documented in the manuals. Yet it has not happened.

Links
This is a good read-

http://www.diyaudio.com/forums/minidsp/230470-signal-level-minidsp-x-over.html

http://www.avsforum.com/t/1442255/alpine-swr-1223d-diy-sub-build-for-ht/0_100#post_22663392

http://www.avsforum.com/t/1281290/minidsp/1100_100#post_22711797

http://www.avsforum.com/t/1443652/minidsp-require-signal-boost-with-pro-amps/0_100

Here's some sources, or if you're going to pick my words a part, some good reading to support my findings and complaints.

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post #2 of 39 Old 11-03-2013, 05:13 AM
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How did you get that initial 10.6 volt reading in the beginning of step 1? Did you measure the output voltage of the actual output connector using a multi meter? Not sure what a DMM is?

What is the reason that you took 30% off of the AVR's output voltage, going from 10.6% to 7.42%?

With regards to setting the amps gain and playing a -3.0 dbfs test tone, how do you adjust the volume of the test tone to know that it is -3.0 dbfs? I mean, the volume on the AVR is the only way to adjust it up or down, so how did you know that the volume on your AVR was at -3.0dbfs?
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post #3 of 39 Old 11-03-2013, 12:09 PM - Thread Starter
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Quote:
Originally Posted by Martycool007 View Post

How did you get that initial 10.6 volt reading in the beginning of step 1? Did you measure the output voltage of the actual output connector using a multi meter? Not sure what a DMM is?

DMM = digital multi meter. So thats a big 10-4. smile.gif

What is the reason that you took 30% off of the AVR's output voltage, going from 10.6% to 7.42%?

Thats in the home theater shack guide I linked to above. It is just one more way to estimate when your AVR is clipping. Ricci suggests taking off 20% of max AVR volume. Obviously the best would be a loopback and RTA or better yet a scope but I don't have either.


With regards to setting the amps gain and playing a -3.0 dbfs test tone, how do you adjust the volume of the test tone to know that it is -3.0 dbfs? I mean, the volume on the AVR is the only way to adjust it up or down, so how did you know that the volume on your AVR was at -3.0dbfs?

The REW test tone window has a DB FS volume box. If that doesn't work for you, the Home Theater Shack articles have the test tones in them.

Hi Marty, answers in bold.

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post #4 of 39 Old 11-03-2013, 02:57 PM
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Quote:
Originally Posted by pdxrealtor View Post

Tonight I triple checked settings and measurements. I'm driving DIY subs via a Peavy pro audio amp that requires 2.25 input volts to put out full power. My quest began to make sure i was getting full power out of my amp. I am.......... no problem there.

Please be aware that this 2.25 Volt input figure only applies when the gain of the power amp is set to maximum. If you reduce the gain by, say, 6 dB (a factor of 2), then you will now need 4.5 Volts to drive it to full power. The miniDSP is spec'ed to put out 4 Volts RMS, though Stereodude has measured it to be somewhat higher than that.

Bottom line: Ignore the HTS article. Set the gain of the power amp to maximum, then use only the sub trim of the AVR to get the correct relative level of subs and mains using the measured frequency response with REW.
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post #5 of 39 Old 11-03-2013, 03:11 PM - Thread Starter
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Originally Posted by andyc56 View Post

Please be aware that this 2.25 Volt input figure only applies when the gain of the power amp is set to maximum. If you reduce the gain by, say, 6 dB (a factor of 2), then you will now need 4.5 Volts to drive it to full power. The miniDSP is spec'ed to put out 4 Volts RMS, though Stereodude has measured it to be somewhat higher than that.

Bottom line: Ignore the HTS article. Set the gain of the power amp to maximum, then use only the sub trim of the AVR to get the correct relative level of subs and mains using the measured frequency response with REW.

Can you please point to the spec of balanced minidsp output of 4.0 volts?

All I ever found was 2.0 volts out. It goes up to 4.0 volts IN if using unbalanced, but nowhere have I read 4.0 out as an official spec.

And, I too have measure almost 5.0 volts out of the mini.

I see no reason to set the power amp to max gain, at all. If I am driving it to clip at 3/4 max that means the amp is getting enough volts to put out max power, at the approximate time (only approximate because of the method used to guess when avr out is clipping) that the AVR is clipping.

Unless Im completely off the charts not understanding gain structure settings I think what you just said makes very little sense. Correct me if Im wrong. I am still learning but what you just said contradicts a lot of what Ive been reading.

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Originally Posted by pdxrealtor View Post


Can you please point to the spec of minidsp output of 4.0 volts?

It is here.

It is given as 2 Volts RMS from + to ground. But the output is not taken from plus to ground in balanced mode. It is taken differentially, and this results in a difference-mode voltage of 4 Volts RMS (V - (-V) = 2*V = 4 Volts RMS). Confusingly, they specify this as "14 dBu in balanced mode" instead of specifying this as RMS Volts. To conveert dBu to Volts RMS, use:

VRMS = sqrt(0.6) * 10^(dBu/20)

Plugging in the numbers, you get: 3.88 Volts RMS.
Quote:
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I see no reason to set the power amp to max gain, at all. If I am driving it to clip at 3/4 max that means the amp is getting enough volts to put out max power, at the approximate time (only approximate because of the method used to guess when avr out is clipping) that the AVR is clipping.

Unless Im completely off the charts not understanding gain structure settings I think what you just said makes very little sense. Correct me if Im wrong. I am still learning but what you just said contradicts a lot of what Ive been reading.

Okay, do whatever you want to do.
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post #7 of 39 Old 11-03-2013, 04:30 PM - Thread Starter
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Quote:
Originally Posted by andyc56 View Post

It is here.

It is given as 2 Volts RMS from + to ground. But the output is not taken from plus to ground in balanced mode. It is taken differentially, and this results in a difference-mode voltage of 4 Volts RMS (V - (-V) = 2*V = 4 Volts RMS). Confusingly, they specify this as "14 dBu in balanced mode" instead of specifying this as RMS Volts. To conveert dBu to Volts RMS, use:

VRMS = sqrt(0.6) * 10^(dBu/20)

Plugging in the numbers, you get: 3.88 Volts RMS.

Awesome! Even more retarded BS from minidsp.

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Originally Posted by pdxrealtor View Post

Awesome! Even more retarded BS from minidsp.

Yup! biggrin.gif
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post #9 of 39 Old 11-03-2013, 07:51 PM
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Originally Posted by pdxrealtor View Post

Awesome! Even more retarded BS from minidsp.

Take it easy there. These threads pop up from time to time, and no the mini isn't perfect, BUT, all the tests have shown it to well exceed the published voltage input/output specs. For whatever reason people rip on these things, but I'd rather have a manufacturer be conservative on their there spec sheet than deceptive/puffed up.

BTW, in most pro amp manuals, they actually recommend you keep the gains at max to ensure you have all the amps power on tap when called upon.
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post #10 of 39 Old 11-03-2013, 08:03 PM
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Originally Posted by pdxrealtor View Post

Can you please point to the spec of balanced minidsp output of 4.0 volts?

All I ever found was 2.0 volts out. It goes up to 4.0 volts IN if using unbalanced, but nowhere have I read 4.0 out as an official spec.

And, I too have measure almost 5.0 volts out of the mini.

I see no reason to set the power amp to max gain, at all. If I am driving it to clip at 3/4 max that means the amp is getting enough volts to put out max power, at the approximate time (only approximate because of the method used to guess when avr out is clipping) that the AVR is clipping.

Unless Im completely off the charts not understanding gain structure settings I think what you just said makes very little sense. Correct me if Im wrong. I am still learning but what you just said contradicts a lot of what Ive been reading.

He's right, if you can set them to max on the amp and trim the LFE output it's best. Right here in the ipr2-7500 manual:



Having the amp gains at max means you're at less risk of:

1. clipping the lfe output on your receiver
2. clipping the input in the minidsp
3. clipping the input on your amp

Scenario 3 is the least likely, but this did happen to me with a Yamaha amp when the gains were only at half. The balanced 2x4 had enough voltage to clip in the inputs on the amp!
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post #11 of 39 Old 11-03-2013, 08:15 PM - Thread Starter
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Originally Posted by lukeamdman View Post

Take it easy there. These threads pop up from time to time, and no the mini isn't perfect, BUT, all the tests have shown it to well exceed the published voltage input/output specs. For whatever reason people rip on these things, but I'd rather have a manufacturer be conservative on their there spec sheet than deceptive/puffed up.

BTW, in most pro amp manuals, they actually recommend you keep the gains at max to ensure you have all the amps power on tap when called upon.

Its as simple as documenting some simple information regarding input voltage and headroom data along with how the input and output attenuators work.

Clearing up BS like explained by andy above couldn't hurt either.

Neither could including a power supply. rolleyes.gif

And..... How about a max input / clip indicator? Even though they corrected the meter its still difficult to see when its maxing out. And why is it so close to maxing out with my AVR s conservative settings?

Im calm..... Calmly going to hopefully be moving onto a different device.

The minidsp is being used by thousands like me who don't really have a lot of experience with this stuff. A simple thing called proper and consistent documentation (known as a manual) is as common as a power supply with most electronics. Minidsp cant seem to do either.

RE: the amp gain. Yes, you are correct. Even my Peavy manual states just that. Then in their advice section they explain the gain structure process and its importance.

Its no secret theres two camps..., at least in home theater, max the gains or set them to work with the first device in the chain which in most cases seems to be the AVR.

I just think the latter makes more sense for me.

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Originally Posted by lukeamdman View Post

He's right, if you can set them to max on the amp and trim the LFE output it's best. Right here in the ipr2-7500 manual:



Having the amp gains at max means you're at less risk of:

1. clipping the lfe output on your receiver
2. clipping the input in the minidsp
3. clipping the input on your amp

Scenario 3 is the least likely, but this did happen to me with a Yamaha amp when the gains were only at half. The balanced 2x4 had enough voltage to clip in the inputs on the amp!

If you set the PA amp to clip at the point your AVR clips how in the heck is raising the amps gain going to stop the AVR from clipping??

Please explain....

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post #13 of 39 Old 11-03-2013, 08:20 PM
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Quote:
Originally Posted by pdxrealtor View Post

Its as simple as documenting some simple information regarding input voltage and headroom data along with how the input and output attenuators work.

Clearing up BS like explained by andy above couldn't hurt either.

Neither could including a power supply. rolleyes.gif

And..... How about a max input / clip indicator? Even though they corrected the meter its still difficult to see when its maxing out. And why is it so close to maxing out with my AVR s conservative settings?

Im calm..... Calmly going to hopefully be moving onto a different device.

The minidsp is being used by thousands like me who don't really have a lot of experience with this stuff. A simple thing called proper and consistent documentation (known as a manual) is as common as a power supply with most electronics. Minidsp cant seem to do either.

RE: the amp gain. Yes, you are correct. Even my Peavy manual states just that. Then in their advice section they explain the gain structure process and its importance.

Its no secret theres two camps..., at least in home theater, max the gains or set them to work with the first device in the chain which in most cases seems to be the AVR.

I just think the latter makes more sense for me.

The company has only been around for a few years, and when they've received input from the DIY community, they have responded with better specs and software updates to improve their products. Regardless, harping on a company for their products exceeding published specs is definitely a first world problem...good gravy people...
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Originally Posted by pdxrealtor View Post

If you set the PA amp to clip at the point your AVR clips how in the heck is raising the amps gain going to stop the AVR from clipping??

Please explain....

You want your amp's output to clip before anything else. If something in your signal chain clips before the amp does, your amp will be sending square waves to your drivers...which is bad.
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post #15 of 39 Old 11-03-2013, 08:32 PM - Thread Starter
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Originally Posted by lukeamdman View Post

The company has only been around for a few years, and when they've received input from the DIY community, they have responded with better specs and software updates to improve their products. Regardless, harping on a company for their products exceeding published specs is definitely a first world problem...good gravy people...

Im not complaining about exceeding specs. Not at all.

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If you set the PA amp to clip at the point your AVR clips how in the heck is raising the amps gain going to stop the AVR from clipping??

Please explain....

This needs to be understood in the context of a fixed SPL at the subwoofer output at the listening position. This in turn corresponds to a fixed RMS acoustic pressure. Let's call this RMS acoustic pressure pRMS (which has units of Pascals). The SPL in dB is:

SPLdB = 20 * log10(pRMS/2e-5)

The RMS acoustic pressure is proportional to the RMS voltage at the power amp output. So holding the acoustic pressure fixed is the same as holding the RMS voltage at the power amp output fixed. Adjusting the power amp gain means that for a fixed RMS output voltage, the amp's required input voltage varies. Maximizing the power amp gain means that for a fixed subwoofer SPL output, the required input voltage to the power amp is minimized. That means the output voltage of the miniDSP is minimized, thus giving the maximum headroom.

Note that this is not the same thing as simply changing the power amp gain without changing anything else. It means that if you increase the power amp gain by, say, 10 dB, you must decrease the AVR's subwoofer trim by this same amount to keep the SPL of the subwoofer constant. But the end result is that the output voltage of the AVR sub out and miniDSP out are reduced by 10 dB (a factor of roughly 3 in voltage) to keep the subwoofer SPL constant.
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post #17 of 39 Old 11-03-2013, 08:38 PM - Thread Starter
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Originally Posted by lukeamdman View Post

You want your amp's output to clip before anything else. If something in your signal chain clips before the amp does, your amp will be sending square waves to your drivers...which is bad.

Right. And if you set the AVR to clip at max settings, whatever they may be, and then you turn up the gain on the PA amp until it clips, you will never send the PA amp a clipped signal as your AVR is never run maxed out.

And.... This is part of my complaint with the mindsp. It runs very close to clipping AFTER the AVR settings are dialed back to normal listening levels, not maxed trims and MV levels.

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post #18 of 39 Old 11-03-2013, 08:41 PM
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Originally Posted by pdxrealtor View Post

Right. And if you set the AVR to clip at max settings, whatever they may be, and then you turn up the gain on the PA amp until it clips, you will never send the PA amp a clipped signal as your AVR is never run maxed out.

And.... This is part of my complaint with the mindsp. It runs very close to clipping AFTER the AVR settings are dialed back to normal listening levels, not maxed trims and MV levels.

Read andy's post above.

It's as simple and not attenuating the signal within the amp when you don't have to. You can achieve the exact same SPL all while making your AVR and Mini work less and be really far from clipping.

I keep my AVR sub trim at -10db...
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post #19 of 39 Old 11-03-2013, 08:50 PM - Thread Starter
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Originally Posted by lukeamdman View Post

Read andy's post above.

It's as simple and not attenuating the signal within the amp when you don't have to. You can achieve the exact same SPL all while making your AVR and Mini work less and be really far from clipping.

I keep my AVR sub trim at -10db...

My AVR sub trim is at -7, with a 75db reading at 0 on the AVR. Thats +3 for a LFE signal thats 10 db hot. That leave +9 more to go on the sub trim AND 1.5 on the master volume before I will clip the Power amp.

Hows that so hard on the AVR?

The mini, or any eq, attenuator sliders should be unity, which mine are, at max. The input levles on the mini, if attenuated, will not solve the problem of the adc being driven to clipping (think i said that right). So there is no reason to lower the input and therefor the output, of the mini dsp.

Edit**still want to research the effect of lowering the output of the mini to tweak sub levels but only for the purpose of FR smoothing. I imagine at that point the entire gain structure would have to be reset, but what it does to the input side being that lowering the input side wont reduce clipping I have no clue. Haven't had time to ask the DIY guys or re read the thread over there.

Hoping I wont need that feature and can say goodbye to the mini. Might have to say goodbye simply because the inputs cant not be overdriven. mad.gif

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post #20 of 39 Old 11-03-2013, 08:58 PM
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Quote:
Originally Posted by pdxrealtor View Post

My AVR sub trim is at -7, with a 75db reading at 0 on the AVR. Thats +3 for a LFE signal thats 10 db hot. That leave +9 more to go on the sub trim AND 1.5 on the master volume before I will clip the Power amp.

Hows that so hard on the AVR?

The mini, or any eq, attenuator sliders should be unity, which mine are, at max. The input levles on the mini, if attenuated, will not solve the problem of the adc being driven to clipping (think i said that right). So there is no reason to lower the input and therefor the output, of the mini dsp.

I'll take one more stab at this and then someone else will have to try and explain this to you. Sorry buddy.

Facts:

1. The balanced miniDSP has enough voltage to drive the the IPR2-7500 to maximum output.
2. If your gains on the amp aren't at max, your attenuating (not using) some of the signal the Mini is sending to the IPR.
3. If you're clipping the MiniDSP, your gain structure is wrong because fact #1 still remains, and it probably has something to do with fact #2.

It seems you're trying to make 0 on the receiver either reference or max output? If that's the case, more power to you, but you can't fault the Mini because you haven't figured out your gain structure yet.
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post #21 of 39 Old 11-03-2013, 09:02 PM - Thread Starter
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Originally Posted by andyc56 View Post

This needs to be understood in the context of a fixed SPL at the subwoofer output at the listening position. This in turn corresponds to a fixed RMS acoustic pressure. Let's call this RMS acoustic pressure pRMS (which has units of Pascals). The SPL in dB is:

SPLdB = 20 * log10(pRMS/2e-5)

The RMS acoustic pressure is proportional to the RMS voltage at the power amp output. So holding the acoustic pressure fixed is the same as holding the RMS voltage at the power amp output fixed. Adjusting the power amp gain means that for a fixed RMS output voltage, the amp's required input voltage varies. Maximizing the power amp gain means that for a fixed subwoofer SPL output, the required input voltage to the power amp is minimized. That means the output voltage of the miniDSP is minimized, thus giving the maximum headroom.

Note that this is not the same thing as simply changing the power amp gain without changing anything else. It means that if you increase the power amp gain by, say, 10 dB, you must decrease the AVR's subwoofer trim by this same amount to keep the SPL of the subwoofer constant. But the end result is that the output voltage of the AVR sub out and miniDSP out are reduced by 10 dB (a factor of roughly 3 in voltage) to keep the subwoofer SPL constant.

You lossed me on the math, not your fault its just over my head..

But again, if my AVR sub trim is -7 , and max is -12, it would seem I have a strong signal going to the amp.... With a lot of headroom.

That same signal is causing me problems on the input side of the minidsp.

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Originally Posted by lukeamdman View Post

I'll take one more stab at this and then someone else will have to try and explain this to you. Sorry buddy.

Facts:

1. The balanced miniDSP has enough voltage to drive the the IPR2-7500 to maximum output.
2. If your gains on the amp aren't at max, your attenuating (not using) some of the signal the Mini is sending to the IPR.
3. If you're clipping the MiniDSP, your gain structure is wrong because fact #1 still remains, and it probably has something to do with fact #2.

It seems you're trying to make 0 on the receiver either reference or max output? If that's the case, more power to you, but you can't fault the Mini because you haven't figured out your gain structure yet.

1) yes, it does. I measured it
2) the amp does not need all of the signal from the mini, or my AVR ALONE, or both together, to clip the inputs before gain wide open.
3) the clipping on the mini dsp is happening on the input side. Its clipping the adc because the signal from the avr is too high. Ive toned this down to only 5db from max volt out on the sub preamp. I want that 5db to turn the subs down a bit at will, it has NOTHING to do with trying to make zero reference or anything else.


If hour telling me the mini dsp is not supposed to work with the sub trim almost all the way down on a pioneer receiver, and that setting 0 to be 10 on the avr to chop the voltage so the minis inputs wont clip great, that will work. But thats a bs bandaid to fix my exact reason for starting this thread.

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post #23 of 39 Old 11-03-2013, 09:18 PM
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Quote:
Originally Posted by pdxrealtor View Post

1) yes, it does. I measured it
2) the amp does not need all of the signal from the mini, or my AVR ALONE, or both together, to clip the inputs before gain wide open.
3) the clipping on the mini dsp is happening on the input side. Its clipping the adc because the signal from the avr is too high. Ive toned this down to only 5db from max volt out on the sub preamp. I want that 5db to turn the subs down a bit at will, it has NOTHING to do with trying to make zero reference or anything else.

You're answering your own question smile.gif

With the mini's input set to the 2v option, it will output exactly what is input until clipping, so there's no "combination' of the mini or AVR happening here.

Tell you what, let's hypothetically say you move your IPR gains to max and that increases the output from 100db to 105db when you're playing a test tone on the subs. Now, you compensate by adjusting your AVR sub trim from -7 to -12, and the tone returns to 100db.

Do you know what just happened? Your AVR is outputting less signal, and your Mini's input is therefore receiving less signal (the issue you're having is too much to the input, right? =) ), and wait a second, the output from the amp is EXACTLY the same! eek.gifsmile.gif

Input clipping problem on the Mini solved!
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post #24 of 39 Old 11-03-2013, 09:36 PM
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Quote:
Originally Posted by pdxrealtor View Post

Right. And if you set the AVR to clip at max settings, whatever they may be, and then you turn up the gain on the PA amp until it clips, you will never send the PA amp a clipped signal as your AVR is never run maxed out.

And.... This is part of my complaint with the mindsp. It runs very close to clipping AFTER the AVR settings are dialed back to normal listening levels, not maxed trims and MV levels.
all i could understand from reading the first post till the end is that you're very rigid in following the HTS advice in setting the gain structure.
why don't you stop following the article and adjust the gain according to your own setup and requirement?

0. reset all the gain knobs to the poweramp, minidsp and avr to 0.
1. set the avr trim for the sub output to +0.
2. set the poweramp gain to something like half.
3. set the minidsp gain to -6db (both input gain and output).
4. output a test tone at the avr for the sub channel.
5. increase (or decrease) the poweramp gain until you have +75db from the sub.

there, you have -12db to +12db trim at the avr.
from -30db (if i remember correctly ) to +6db at the minidsp
and whatever gain left on the poweramp.

if you feel the need to provide more gain headroom at the minidsp, increase the gain on the poweramp.
i guess you already know that there's input gain and output gain on the minidsp so also take those into account. don't wanna set the output gain to -30db and complain there's no output.

the hts article is good, but it's a suggestion, recommendation, advice and not a rigid structure that must be followed.

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post #25 of 39 Old 11-03-2013, 09:37 PM
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Quote:
Originally Posted by lukeamdman View Post

You're answering your own question smile.gif

With the mini's input set to the 2v option, it will output exactly what is input until clipping, so there's no "combination' of the mini or AVR happening here.

Tell you what, let's hypothetically say you move your IPR gains to max and that increases the output from 100db to 105db when you're playing a test tone on the subs. Now, you compensate by adjusting your AVR sub trim from -7 to -12, and the tone returns to 100db.

Do you know what just happened? Your AVR is outputting less signal, and your Mini's input is therefore receiving less signal (the issue you're having is too much to the input, right? =) ), and wait a second, the output from the amp is EXACTLY the same! eek.gifsmile.gif

Input clipping problem on the Mini solved!

Additionally, if after doing all this hypothetical stuff you wanted the ability to trim the sub more but now can't because you're maxed at -12, simply return the sub trim to -7 and add 5db to your LCR and surrounds. You'd be level matched where you were before but could still trim your sub more if you wanted.
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post #26 of 39 Old 11-03-2013, 09:39 PM
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additional information:
if you're still clipping the minidsp input when the avr trim is 0, might wanna change the input sensitivity. minidsp have 0.9v and 2.0v if i remember correctly. try and change it and see if you still clip the input. i can't remember what mine is set at but i did experimented with it.

+0 trim at the avr shouldn't drive the minidsp input to clipping. if you still have it the something is wrong. check it first then we'll continue from there.

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Quote:
Originally Posted by lukeamdman View Post

You're answering your own question smile.gif

With the mini's input set to the 2v option, it will output exactly what is input until clipping, so there's no "combination' of the mini or AVR happening here.

Tell you what, let's hypothetically say you move your IPR gains to max and that increases the output from 100db to 105db when you're playing a test tone on the subs. Now, you compensate by adjusting your AVR sub trim from -7 to -12, and the tone returns to 100db.

Do you know what just happened? Your AVR is outputting less signal, and your Mini's input is therefore receiving less signal (the issue you're having is too much to the input, right? =) ), and wait a second, the output from the amp is EXACTLY the same! eek.gifsmile.gif

Input clipping problem on the Mini solved!

And I lose any option of dialing back the subs via avr remote. All to fix an input level on the mini dsp that would seem to many off kilter, a little skewed, clipping too early..... Whatever you want to call it.

I get what you're saying, bit I don't think setting any one thing to an extreme is the way to go when setting gain structure.

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post #28 of 39 Old 11-03-2013, 09:42 PM
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Quote:
Originally Posted by pdxrealtor View Post

And I lose any option of dialing back the subs via avr remote. All to fix an input level on the mini dsp that would seem to many off kilter, a little skewed, clipping too early..... Whatever you want to call it.

I get what you're saying, bit I don't think setting any one thing to an extreme is the way to go when setting gain structure.

We kinda posted at the same time, but I wrote a solution to this problem above.
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post #29 of 39 Old 11-03-2013, 10:09 PM
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Now, I'm not excusing the miniDSP's lousy dynamic range and p-poor documentation.

However, there is a situation here in which the maximum output of the AVR is boatloads higher than the maximum input of the miniDSP that follows it. Pflughaupt's article assumes a wet dream scenario in which all circuits hit clipping at once as the input signal is increased. This scenario is physically impossible in this particular case. Short of putting an attenuator at the AVR output, the miniDSP will always clip before the AVR out does. Any procedure, such as the one in his article, whose purpose is to steer the result to try to achieve this physically impossible scenario of simultaneous clipping of all outputs is bound to result in a sub-optimal configuration when the target scenario is unrealizable.
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post #30 of 39 Old 11-03-2013, 10:13 PM - Thread Starter
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Quote:
Originally Posted by paskal9 View Post

all i could understand from reading the first post till the end is that you're very rigid in following the HTS advice in setting the gain structure.
why don't you stop following the article and adjust the gain according to your own setup and requirement?

0. reset all the gain knobs to the poweramp, minidsp and avr to 0.
1. set the avr trim for the sub output to +0.
2. set the poweramp gain to something like half.
3. set the minidsp gain to -6db (both input gain and output).
4. output a test tone at the avr for the sub channel.
5. increase (or decrease) the poweramp gain until you have +75db from the sub.

there, you have -12db to +12db trim at the avr.
from -30db (if i remember correctly ) to +6db at the minidsp
and whatever gain left on the poweramp.

if you feel the need to provide more gain headroom at the minidsp, increase the gain on the poweramp.
i guess you already know that there's input gain and output gain on the minidsp so also take those into account. don't wanna set the output gain to -30db and complain there's no output.

the hts article is good, but it's a suggestion, recommendation, advice and not a rigid structure that must be followed.

I'm tired. I've seen his discussion beat to death more than once so there's no need to do it again. That said, several people, web sites, and companies have wright ups on how to set the gain structures in many different situations. The ONLY option I don't have and I have used two different methods, one from RICCI, and one from the HTS, is the part about determining for certain when the AVR sub out is clipping.

The mini dsp has the 2.0 volt setting and .09 setting. The .09 setting adds approximately 6db, so the input is more saturated. I've already tested it, and wrote my findings in my sonotube build thread.

The problem with turning down the input on the minidsp is it does not prevent the minidsp from clipping the INPUT to the ADC. It attenuates after the ADC, too late. This is documented on the DIY forums and is linked above in my first post of this thread.

To answer your question a bit more.... I have a 2 ohm four woofer load on output one and a 4 ohm two woofer output load on the output 2. If I set each to level at a 0 test tone one channel clips before the other. When I asked about this it was suggested that I gain match the amp and use the lower output of the 2 woofer four ohm load as is, since those are my 'floater' subs anyways.

It still remains the bottom line that my AVR, and others, are overdriving the input of the minidsp and doing so without abnormal settings. It is also happening with little awareness due to the poor documentation from mini-dsp.

If you read my first post you'll see my notes, and numbers. This was the second day I've spent just 'with the equipment' not including reading, which if I didn't read and read and read some more would be happily clipping away the inputs of the minidsp.

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