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post #1681 of 1707 Old 06-10-2019, 02:32 AM
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I had an order placed for the PL7.5....card was charged...no one could get it, at least any of the places that offered decent prices. If I ever buy another amp or upgrade I think it will be to to one of these.

Not, are you saying to add 500watts to all the burst numbers posted as they are actually the IPR7500 numbers?
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post #1682 of 1707 Old 06-10-2019, 06:02 AM
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Quote:
Originally Posted by notnyt View Post

Hate how manufacturers decide to save 10 cents per XLR connector and go for the non-locking ones. Throw that trash out in the garbage where it belongs...


Edit: just saw that the amp has a total of 4 possible TRS inputs. Are the designers just plain stupid, did somebody mod the amp or does it serve a special purpose?

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post #1683 of 1707 Old 06-10-2019, 06:13 AM
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Originally Posted by notnyt View Post
I just tested a Crest Prolite 7.5
Thank you for the hard work and posting the results!
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post #1684 of 1707 Old 06-10-2019, 09:06 AM - Thread Starter
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Quote:
Originally Posted by peniku8 View Post
Hate how manufacturers decide to save 10 cents per XLR connector and go for the non-locking ones. Throw that trash out in the garbage where it belongs...


Edit: just saw that the amp has a total of 4 possible TRS inputs. Are the designers just plain stupid, did somebody mod the amp or does it serve a special purpose?
It's so you can jumper A to B

I prefer the non locking. They hold in place just fine and make it easier to pull cables out. Just my preference, though.
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post #1685 of 1707 Old 06-10-2019, 09:07 AM - Thread Starter
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Quote:
Originally Posted by bear123 View Post

Not, are you saying to add 500watts to all the burst numbers posted as they are actually the IPR7500 numbers?

No, all the numbers are from the pl7.5 except <80hz sustained on 1ch2r which didn't save for some reason :/
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post #1686 of 1707 Old 06-10-2019, 10:07 AM
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Quote:
Originally Posted by notnyt View Post
It's so you can jumper A to B

I prefer the non locking. They hold in place just fine and make it easier to pull cables out. Just my preference, though.

Understandabe for HT. It's a PA amp thou and the system racks get moved around alot. The last tour I was on I spent half the time reassuring that all cables were plugged in. Especially power cables, as half of them fell out after a single transport. Using tape around the plugs now so they're a tight fit in the socket.

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post #1687 of 1707 Old 06-10-2019, 10:10 AM - Thread Starter
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Quote:
Originally Posted by peniku8 View Post
Understandabe for HT. It's a PA amp thou and the system racks get moved around alot. The last tour I was on I spent half the time reassuring that all cables were plugged in. Especially power cables, as half of them fell out after a single transport. Using tape around the plugs now so they're a tight fit in the socket.
The connectors still snap in, it's not like a power cable that will wiggle out. Anything that would pull it out would likely damage a connector or cable if it was in a locking connector.
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post #1688 of 1707 Old 06-10-2019, 01:46 PM
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Quote:
Originally Posted by notnyt View Post
The connectors still snap in, it's not like a power cable that will wiggle out. Anything that would pull it out would likely damage a connector or cable if it was in a locking connector.

These seem to be better quality non-locking sockets then. I have a few amps with the Neutrik NC3 FAH0 connector and these don't snap in at all. It's the worst XLR connector I've ever used (aside from some no-name on-cable solutions which fell apart after a few years of use). Gonna replace all with the Neutrik NC3 FAH1 and save me some headaches.

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post #1689 of 1707 Old 06-10-2019, 01:49 PM - Thread Starter
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Quote:
Originally Posted by peniku8 View Post
These seem to be better quality non-locking sockets then. I have a few amps with the Neutrik NC3 FAH0 connector and these don't snap in at all. It's the worst XLR connector I've ever used (aside from some no-name on-cable solutions which fell apart after a few years of use). Gonna replace all with the Neutrik NC3 FAH1 and save me some headaches.
I'm using FAH2-0 on the amps I'm putting together. Holds nicely
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post #1690 of 1707 Old 06-10-2019, 02:45 PM
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Originally Posted by notnyt View Post
I'm using FAH2-0 on the amps I'm putting together. Holds nicely

Can't seem to find that connector, but I prefer the locking one, it'll always be safe. Not taking any chances for live shows. I'll replace all non locking connections with the locking counterparts in my t.amps. Some of my DMX lights also have a non locking connector, which is extra bad for lights hanging upside down.

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post #1691 of 1707 Old 06-11-2019, 11:39 AM - Thread Starter
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Quote:
Originally Posted by peniku8 View Post
Can't seem to find that connector, but I prefer the locking one, it'll always be safe. Not taking any chances for live shows. I'll replace all non locking connections with the locking counterparts in my t.amps. Some of my DMX lights also have a non locking connector, which is extra bad for lights hanging upside down.
https://www.neutrik.com/en/product/nc3fah2-0
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post #1692 of 1707 Old 06-11-2019, 06:16 PM
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Ive had my 7.5 since its release. Great amp. I really like it. Runs my OS pros.
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post #1693 of 1707 Old 07-04-2019, 08:43 AM
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Quick question:

if, when turning an amplifier MV up, the noise floor rises, but, after a certain point, even though I raise the MV, the noise floor stays at the same level, what is happening technically?
Clipping?
Compression?

Thanks.
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post #1695 of 1707 Old 07-04-2019, 06:11 PM
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Quote:
Originally Posted by Optimus_Fine View Post
Clipping?
Compression?
No and no.

Quote:
Originally Posted by Optimus_Fine View Post
if, when turning an amplifier MV up, the noise floor rises, but, after a certain point, even though I raise the MV, the noise floor stays at the same level, what is happening technically?
There is residual background noise, and then there is amplification noise.
The two added together gives you the noisefloor.
(I could be missing a few others, but they aren't coming to mind...)

Generally we only care about the noise in the audible bandwidth, and only when it is gross-enough to hear.
With a modern day amp that is probably only likely with high efficiency tweeters in a quiet room.

Even mild clipping is still only like ~1% distortion, so we are generally talking about only 1/100th or 1/1000th of a percent of distortion in non-clipped scenarios.
Like -90db @ 1watt or -115db @ full power etc.

Speaker and subwoofer distortion is generally in the ten's of percentage of distortion, and in some cases even exceeding 100% distortion. At that point the distortion is stronger than the signal itself!

Technically: all wall reflections are nothing but distortion, hence why anechoic test chambers were born;
and yet the ear needs those in order for it to be happy and not reject it as unnatural-sounding.
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Quote:
Originally Posted by BassThatHz View Post
No and no.



There is residual background noise, and then there is amplification noise.
The two added together gives you the noisefloor.
(I could be missing a few others, but they aren't coming to mind...)

Generally we only care about the noise in the audible bandwidth, and only when it is gross-enough to hear.
With a modern day amp that is probably only likely with high efficiency tweeters in a quiet room.

Even mild clipping is still only like ~1% distortion, so we are generally talking about only 1/100th or 1/1000th of a percent of distortion in non-clipped scenarios.
Like -90db @ 1watt or -115db @ full power etc.

Speaker and subwoofer distortion is generally in the ten's of percentage of distortion, and in some cases even exceeding 100% distortion. At that point the distortion is stronger than the signal itself!

Technically: all wall reflections are nothing but distortion, hence why anechoic test chambers were born;
and yet the ear needs those in order for it to be happy and not reject it as unnatural-sounding.

That entire paragraph does not answer the question thou. It would give hints at why the noise floor stops decreasing at a certain point while lowering MV, but not why the noise stops increasing in volume while increasing MV.
A compressor would do exactly that, but the threshold would need to be set up extremely low. I can only imagine that it's some sort of 'protection' in the amp itself. My Marantz for example won't let you raise the MV over 0db, unless you unlock that function in the settings. Maybe that amp also stops increasing gain past 0MV, but still displays a change?

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I'll be more specific:

The amp in question is actually a receiver: Yamaha RX-V381.

Now, if I leave all channels active and I max out all channels trims at +10 dB and the input signal trim at +6 dB, the noise floor stops rising at +14 dB (I mean above 0.0 dB) out of a max MV of +16.5 dB.
If I disable (downmix) the center channel and/or the surrounds, the noise floor stops rising at +8 dB of the MV.
If I disable the subwoofer, the noise floor stops rising at -8.5 dB.
Also, the noise floor becomes louder when disabling the center/surrounds and/or the sub, but playback level stays the same.

Of course, I also tried with channels and input trims at the neutral 0 dB, but all it changes is an increment of the available amplification at the MV, so, theoretically, with all channels enabled, the noise floor would stop rising at +30 dB of the MV, but the function does not go beyond 16.5, so...
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post #1698 of 1707 Old 07-05-2019, 06:17 AM
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Well, until you define what you're calling the "noise floor" no one is going to be able to guess what exactly you're talking about. Further, this seems really off in the weeds.
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post #1699 of 1707 Old 07-05-2019, 08:13 AM
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Quote:
Originally Posted by Optimus_Fine View Post
I'll be more specific:

The amp in question is actually a receiver: Yamaha RX-V381.

Now, if I leave all channels active and I max out all channels trims at +10 dB and the input signal trim at +6 dB, the noise floor stops rising at +14 dB (I mean above 0.0 dB) out of a max MV of +16.5 dB.
If I disable (downmix) the center channel and/or the surrounds, the noise floor stops rising at +8 dB of the MV.
If I disable the subwoofer, the noise floor stops rising at -8.5 dB.
Also, the noise floor becomes louder when disabling the center/surrounds and/or the sub, but playback level stays the same.

Of course, I also tried with channels and input trims at the neutral 0 dB, but all it changes is an increment of the available amplification at the MV, so, theoretically, with all channels enabled, the noise floor would stop rising at +30 dB of the MV, but the function does not go beyond 16.5, so...

Maybe caused by a protection circuit in the amp.


Quote:
Originally Posted by Stereodude View Post
Well, until you define what you're calling the "noise floor" no one is going to be able to guess what exactly you're talking about. Further, this seems really off in the weeds.
Probably the hiss coming from the speakers

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post #1700 of 1707 Old 07-05-2019, 05:52 PM
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Quote:
Originally Posted by Optimus_Fine View Post
I'll be more specific:

The amp in question is actually a receiver: Yamaha RX-V381.

Now, if I leave all channels active and I max out all channels trims at +10 dB and the input signal trim at +6 dB, the noise floor stops rising at +14 dB (I mean above 0.0 dB) out of a max MV of +16.5 dB.
If I disable (downmix) the center channel and/or the surrounds, the noise floor stops rising at +8 dB of the MV.
If I disable the subwoofer, the noise floor stops rising at -8.5 dB.
Also, the noise floor becomes louder when disabling the center/surrounds and/or the sub, but playback level stays the same.

Of course, I also tried with channels and input trims at the neutral 0 dB, but all it changes is an increment of the available amplification at the MV, so, theoretically, with all channels enabled, the noise floor would stop rising at +30 dB of the MV, but the function does not go beyond 16.5, so...
My answer applies to analog amplifiers (the bulk majority of amplifiers.) A receiver is not an amplifier, it functions entirely differently in this regard.

The trims are digital, the vol knob is either digital or analog as well.
All DAC's and ADC's increase their noise when ran in multi-channel mode. So that explains why the noise profile shifts, also bass management anti-clipping maths will mess with the SNR. It has nothing to do with compressors or limiters. That would just make the SNR worse, not better.

These are all things that a traditional amplifier doesn't have (as that is a function of sound-processors for true separates.)

Generally digital adjustments have extremely low distortion, for example my DSP is Adobe Audition 2019 in my rig and that has an SNR approaching -384db in 64bit mode. It shouldn't be audible unless they are doing something wrong inside the box (like converting doubles to integers, small FFT's or re-sampling etc).

Perhaps NotNyt should start testing receivers, is that what you are alluding to here? None of them will be outputting 8kW all-channels driven.
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post #1701 of 1707 Old 07-05-2019, 06:43 PM
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Quote:
Originally Posted by BassThatHz View Post
My answer applies to analog amplifiers (the bulk majority of amplifiers.) A receiver is not an amplifier, it functions entirely differently in this regard.

The trims are digital, the vol knob is either digital or analog as well.
All DAC's and ADC's increase their noise when ran in multi-channel mode. So that explains why the noise profile shifts, also bass management anti-clipping maths will mess with the SNR. It has nothing to do with compressors or limiters. That would just make the SNR worse, not better.

These are all things that a traditional amplifier doesn't have (as that is a function of sound-processors for true separates.)

Generally digital adjustments have extremely low distortion, for example my DSP is Adobe Audition 2019 in my rig and that has an SNR approaching -384db in 64bit mode. It shouldn't be audible unless they are doing something wrong inside the box (like converting doubles to integers, small FFT's or re-sampling etc).

Perhaps NotNyt should start testing receivers, is that what you are alluding to here? None of them will be outputting 8kW all-channels driven.

Drinking a bit too much of that alien juice... just like this guy :


https://www.diyaudio.com/forums/anal...istortion.html


-384dB is mo' better than -290dB!

Ask your doctor if DIY is right for you. Side effects of DIY may include anxiety, elevated blood pressure, lightheadedness, rapid heartbeat, skeletal muscle flaccidity, euphoria, psychological dependence, insomnia, confusion, blurred vision, implusivity, uncontrolled or repeated movements.
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post #1702 of 1707 Old 07-05-2019, 08:24 PM
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Quote:
Originally Posted by michael hurd View Post
Drinking a bit too much of that alien juice... just like this guy :
https://www.diyaudio.com/forums/anal...istortion.html
-384dB is mo' better than -290dB!
REW can't even compute the distortion properly, that's how low it is!



You know it's low when REW drops into E-6 scientific-notation levels. LOL
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I repeated this SNR test after encoding the mute multichannel wave file in Dolby Digital Plus 7.1 with DialNorm -31, because the RX-V381 outputs Dolby with DialNorm -31 4 dB louder than LPCM and DTS 5.1 with DialNorm -31.

Basically, all previous levels obtained in LPCM, with Dolby, are reached 4 dB earlier, so, if, this time, I leave the input signal trim at 0.0 dB, the max SNR level, with all channels enabled, is found at +16.0 dB, just 0.5 dB below the max MV.

Could be I'm just seeing a coincidence, but it makes sense.
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post #1704 of 1707 Old 07-06-2019, 04:49 PM
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Quote:
Originally Posted by michael hurd View Post
Drinking a bit too much of that alien juice... just like this guy :


https://www.diyaudio.com/forums/anal...istortion.html


-384dB is mo' better than -290dB!

Well that is an all-digital loopback. SNR comes down to the processing precision, which is obviously very high in 64 bit mode (quantization errors generate distortion).
Here is a bit rate to SNR chart, taken directly from Wikipedia:


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post #1705 of 1707 Old 07-07-2019, 11:09 AM
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btw @notnyt , how did you safely return the measured signal to the interface? In my amp testings I used a DI box with a 'speaker' setting, but it's crap.

My Interface's input impedance is 10KOhm, so I'd need a 390KOhm resistor in series to bring a 200V signal down to 5V. Is that how you've done it?

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post #1706 of 1707 Old 07-07-2019, 05:52 PM
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I'd just like to chime in with something I learned while playing with Fusion 360 for my 30 day free trial like a year back.
This is a totally over-engineered enclosure meant to have a low pass at 1000hz:

has only 30db signal to noise ratio at 1000hz.

And this is only the resulting noise made by the panels (outside only) that will result due to the air pressure difference inside relative to the outside, which moves the panels. At 2000hz its about 24db signal to noise (so 6db/oct lowpass is out of the question obviously, even 12-18db/oct lowpass is not ideal), at 500hz its 36db, at 250hz its 42db, at 125hz its 48db.
To improve on this I could add butyl on the inside and outside (you know the stuff they add to car chassis to deaden the sound), and put rockwool on the outside, and the pillow stuffing will hopefully do the trick inside. But then it looks like a rockwool teletubby. It would certainly not have any issues in THD+N as far as the enclosure is concerned though.

Ever since I figured this out I have been rather more relaxed about the amplifier distortion. I have this order of importance now:
  1. Enclosure panel movement noise.
  2. Enclosure movement resonances (great bracing also braces the braces themselves asymmetrically, so you don't end up with massive amounts of bracing components resonating at the same frequency).
  3. Enclosure geometry resonances.
  4. Enclosure deadening (so the surfaces produce less sound when moving, because the surface is covered in butyl, rockwool and pillow stuffing, in the most extreme cases. Most importantly internally opposite the cone, and any baffle area on the front facing the listener).
  5. Sound treatment of room.
  6. Driver distortion.
  7. Amplifier distortion.
  8. Magic XLR cables I christened to bassanism with water boiled on melted JBL magnets.

The higher the frequency and the higher the decibel the more important all of these are. So there can be cases where upgrading an amp or driver is the next step without touching the above steps, but chances are there's something to be gained for half the price by taking a look at the above steps.
The top steps are the best in dollar per db in reduction in THD+N.

Sometimes a cheap floorstander set can be fixed by just running a couple braces from the left panel to the back panel and leaving the right side alone, that breaks up the resonance so you don't have both sides (and potentially also the back) resonating at the same frequency.
And often the internal closed mid woofer will have woefully inadequate stuffing, adding some butyl to the back plate (both sides since the other side of that thin MDF panel "plays" noise into the vented enclosure) and adding a thin layer of rockwool and then putting the factory stuffing back, does wonders.

Same with car stereos, when you fix your door "enclosure" it goes from a ****ty sound to a quality sound instantly. And if you spend twenty hours instead of ten you get dollar per db THE cheapest quality improvement. The amount of 1000 dollar car stereo 2-ways I've heard sound **** is too many to count, all because the owner didn't bother spending a couple hours fixing the door with some butyl and wool. Then I stick a MiniDSP in there to get rid of 3db wattage lost in heating the passive crossover, and some butyl in the door, and suddenly I'm a sound quality GOD to them.

EDIT: Point number 8 I hope you understood to be a metaphor for "audiophile stuff for sound quality" :P
michael hurd and bear123 like this.

cms, aka driver diaphragm suspension mechanical compliance: 0.000065 meter/Newton or in standard form 6.5e-05 m/N. (smaller number is better)
rms, aka driver diaphragm suspension mechanical resistance: 6.41 Newton.sec/meter. (higher number is better)

Last edited by ronny31; 07-07-2019 at 05:56 PM.
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post #1707 of 1707 Old 07-07-2019, 05:55 PM - Thread Starter
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Quote:
Originally Posted by peniku8 View Post
btw @notnyt , how did you safely return the measured signal to the interface? In my amp testings I used a DI box with a 'speaker' setting, but it's crap.

My Interface's input impedance is 10KOhm, so I'd need a 390KOhm resistor in series to bring a 200V signal down to 5V. Is that how you've done it?
I don't. I test the high voltage stuff with an oscilloscope.

Anything else can go right into my RTX6001 up to like 100Vrms

I have a pmillett sound card interface which converts high level voltage to sound card levels I'm no longer using. If you want it for this purpose to use with a normal audio interface shoot me a pm.
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