Avoiding Amp Hiss

[MakeMineVinyl]

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The other thing is they mislead you quite a bit on amplification requirements for the M2 (1200 watts minimum!).

Yeah, well, that sounds a bit like JBL taunting potential customers "are you man enough (or woman enough or whatever) to be able to handle this monster of a speaker"?!?! With my 2 1/2 watts, I feel positively feeble and unworthy, but I sure as hell don't hear hiss! But then again, this amplifier has zero (unity) voltage gain.....

 

[thrangster]

So I will try the ATI 8x200 as a start, especially to see if I think they drive the M2's adequately (200 watts each per D2 and LF drivers, so should be way more than sufficient...)

I was REALLY interested in the Appollon Purifi multichannel, but am concerned about overseas support should things go awry, am I'm thinking the linear power supply might be the better choice for high-transient home theater application...

Plus its easier way to sell if I need to change to the 500w model!

 

[theyellowspecial]

FYI the Crown XLS amps have adjustable input gains suitable for consumer gear. No multi-channel options, unfortunately.

Aiyima now has multi-channel boards using the newest op-amps.

 

[thrangster]

FYI the Crown XLS amps have adjustable input gains suitable for consumer gear. No multi-channel options, unfortunately.

Aiyima now has multi-channel boards using the newest op-amps.

Thanks, but I think the noise floor of the Crowns supersedes all issues - as noted, the hiss is there with no connection to the SDP...

 

[theyellowspecial]

Thanks, but I think the noise floor of the Crowns supersedes all issues - as noted, the hiss is there with no connection to the SDP...

Missed that part!

 

[bobopich]

I think if you use the crowns in bridge mode the hiss ( SNR) will be way higher, I had similar problem with PA amp and switched to just one channel of the amp avoiding the bridge mode and the hiss was acceptable not loosing much in power output vs SPL gain.

 

[thrangster]

I think if you use the crowns in bridge mode the hiss ( SNR) will be way higher, I had similar problem with PA amp and switched to just one channel of the amp avoiding the bridge mode and the hiss was acceptable not loosing much in power output vs SPL gain.

Thanks - I'm not in bridge mode however...

I've hemmed and hawed this summer so haven't done anything yet, plus waiting on a possible projector upgrade, so perhaps this fall I will make a change...

 

[Jonas_h]

Did you solve your problem? FYI, most amps without DSP will improve your situation. The DCIs are not noisy _amplifiers_ but they have a noisy DSP built in.

 

[thrangster]

Did you solve your problem? FYI, most amps without DSP will improve your situation. The DCIs are not noisy _amplifiers_ but they have a noisy DSP built in.

No never did anything (multiple diversions among many reasons)

Still on my radar likely the ATI’s or the Appollon (though I hesitate to buy such a thing from an overseas source)

 

[babadono]

It’s just that JBL recommended these amps more for the tuning file-loading capabilities I think than for optimal audio quality.

And cuz there both made by the same company?

 

[thrangster]

And cuz there both made by the same company?

Didn't hurt I'm sure.... but unless one didn't care about the tuning files, which included the crossover information, there was no way to leverage them other than (I found out later) a BSS solution, which makes using the amp interface seems easy.

Now with the Trinnov-based SDP, one can set up the tuning files and cross overs there and any amps...

 

[73hadd]

I don't recall where I saw the anecdote that "less power is less hiss" in some of these amps. Is this true at all in anyone's experience? Specifically with a Crown DCI going from a 2400W down to 1250W or even 600W etc.

 

[morpheusX]

Could this be an interesting option for powering the CD?
- https://www.audiosciencereview.com/forum/index.php?threads/topping-pa5-measurements.28058/

50W@8ohms, gain 19db, SINAD 124dB, 349€ ?

 

[MakeMineVinyl]

I don't recall where I saw the anecdote that "less power is less hiss" in some of these amps. Is this true at all in anyone's experience? Specifically with a Crown DCI going from a 2400W down to 1250W or even 600W etc.

This shouldn't happen since most all amplifiers have the same gain (29dB).

 

[Slayer]

I can understand the hiss being annoying and i think some folks are just more susceptible to this than others. Plus choice of speakers play a big part of that also. Like MakeMineVinyl, i can put my ear right in the horn and it's dead silent. Which Is a big factor as t why I am loyal to Anthem amps. Over the past 40 yrs or so, i've tried many and Anthem has been the quietest. Plenty of power, RCA and XLR inputs and 120db snr, not much to complain about Even after 20 yrs of hard service i did not think twice about replacing it. Instead i sent it in to get recapped and a full service for anything that might need replaced. I think they also replaced the output relays and a few other things, don't recall all at the moment.
But for about $250, I basically have a new amp again. They may be a little on the expensive side, but for performance and reliability, I think it's worth it. Plus you can usually find a dealer that will give you a pretty good deal.

 

[mdsimon2]

I don't recall where I saw the anecdote that "less power is less hiss" in some of these amps. Is this true at all in anyone's experience? Specifically with a Crown DCI going from a 2400W down to 1250W or even 600W etc.

Lower gain is helpful in achieving low hiss as any noise from the DAC will be multiplied by the amplifier. Even SOTA DACs can have rather substantial noise contributions with 29 dB of gain from an amplifier.

Michael

 

[73hadd]

Has any M2 owner complained of hiss, when using the Crown I-Tech 5000, 9000, 12000, or even the 3500 (4ch which has different specs than the 2ch versions)?

 

[Absolute]

The Crown stuff is useless for SNR. They will hiss, even with downpadding. I used this to pad the tweeters down; https://www.soundimports.eu/en/l-pad-100w-mono.html

I had Crown 4/1200 cdi with the option to lower the gain to 24 dB, but without downpadding it was crazy loud. With the downpadding it was still very noticeable at 3,5 meter/11 feet away.
SNR is best-case scenario, usually around full output. With powerful amps like the Crowns, that might be in the kilowatt area meaning that at low output it's not anywhere near what the specs say. What we're looking for is the residual noise aka inherent constant noise.

I went for some custom built neurochrome-stuff for the tweeters and have actually just received it today. With 14 dB gain and around 20w max output it should be dead quiet even without any downpadding. If it sounds good I'll let you know later.

The Topping amp seems like a perfect fit for compression drivers, if it had been available a month ago I would try it out.

Here's a picture of hiss vs room noise with the Crown, absolute levels not calibrated. Of course you'll hear this.

 

[AnalogSteph]

SNR is best-case scenario, usually around full output. With powerful amps like the Crowns, that might be in the kilowatt area meaning that at low output it's not anywhere near what the specs say.

104 dB worth of SNR still is a crapton of output noise in a 1200 wpc amplifier... about 620 µV, or -73.2 dBW. When combined with a compression driver + horn setup north of 100 dB SPL / W / m, required attenuation may exceed 30 dB for home listening levels. Yep, negative overall voltage gain.

I went for some custom built neurochrome-stuff for the tweeters and have actually just received it today. With 14 dB gain and around 20w max output it should be dead quiet even without any downpadding.

And I'm assuming nominal SNR at full output would be a good bit higher, too. Not sure about the no padding thing, you may still have too much gain, but chances would no doubt be substantially better. You'd need something like 116 dB of full power SNR, preceding DAC output noise included.

 

[babadono]

Man I'm late to this but ...building a line level balanced attenuator is simple. 3 resistors soldered into connector at input end. You must know the input impedance you are trying to match and of course the amount of attenuation desired. The output Z can be assumed to be close enough to zero that it doesn't figure into calc. A pad for microphone will not be optimal. Also you will not be connecting anything to ground and will not effect or loose CMR.