Avoiding Amp Hiss

[Sal1950]

Thanks - yes, I had just posted before your note, I was being quite stupid here.

So I did this and the hiss is unchanged.

Ah, I was just about to type this test. With the amp off I'd like to see a shorting plug in that amp rather than just letting the input float.
If the noise still exists and there is no gain setting on the amp, time for a quieter amp.
High efficiency speaker/amp interface can be tricky for a quiet noise floor.
That said, I have JBL HDI-3600 with a measured 90db and with my 25+ year old Adcoms they are dead quiet with my ear to the tweeter horn.

 

[MakeMineVinyl]

ATI amplifiers have a reputation for low noise. You could look into their 6000 series if you want class AB.

I've heard that was the case....

 

[thrangster]

Crown amps are primarily for industrial/commercial/pro sound reinforcement use and as such, noise is not an overriding concern in their specs. Ruggedness is what is important in these uses, so its no surprise that the amp is hissy. If it does have a gain adjustment, try turning it down. I have horns too, and it is extremely difficult to achieve low hiss with very efficient speakers - it comes with the territory. If turning down the gain (if you can) does not reduce the hiss, time for another amp.

The crowns were actually the recommend amps at the time I acquired the M2’s - I presume because you could load the tuning and crossover files into them

Now with the Trinnov I can set up the crossovers ther

since this hiss is there regardless of the trinnov being connected or not, I presume look more for better snr amp than a gain matched amp? Or does the gain structure in the amp itself contribute to higher noise floor on a sensitive speaker separate from snr consideration?

thanks

 

[thrangster]

ATI amplifiers have a reputation for low noise. You could look into their 6000 series if you want class AB.

Yes was looking at ATI but was unsure how much gain circuitry mattered even with no connection…even though ATI makes the Amplitude amps, they don’t have 19 db gain options so it is custom to Trinnov

 

[MakeMineVinyl]

Yes was looking at ATI but was unsure how much gain circuitry mattered even with no connection…even though ATI makes the Amplitude amps, they don’t have 19 db gain options so it is custom to Trinnov

ATI amps are extremely quiet even though they have the standard 29dB gain, so you shouldn't have any problem with hiss, even with sensitive speakers.

 

[thrangster]

ATI amps are extremely quiet even though they have the standard 29dB gain, so you shouldn't have any problem with hiss, even with sensitive speakers.

Thanks - do their class d amps have the same reputation or are you referring only to the class ab models? I think I’d prefer to go with the class d models if all else is equal

thanks

 

[MakeMineVinyl]

Thanks - do their class d amps have the same reputation or are you referring only to the class ab models? I think I’d prefer to go with the class d models if all else is equal

thanks

The class D amps are NC-500 based so the basic module is the same as in any other amp which uses this module. There is nothing unusual about the external input stage, so that should be quiet.

My only observation would be that with efficient horn speakers you might need less power than you think. I actually drive the the HF horns on my system above 500Hz with 2 1/2 watts and the 15" woofers with 40 watts (the system uses active crossovers, not passive). With this relatively small amount of power, I can plaster the listener up against the back wall with seriously high SPLs, and I doubt that I am getting anywhere near the maximum output of the amplifiers.

So you might take an inventory of what you actually need, power wise.

 

[digitalfrost]

I would look at the various implementations of Hypex or Purify amps offered. They often come with adjustable gain and are quite cheap for the performance provided. Also, a Benchmark AHB2 for the two front channels could be combined with Class D multichannel amp for the rest.

I think if you contacted manufacturers and asked for a custom gain setting most would be happy to. Just from the top of my head:

https://www.apollonaudio.com/
https://www.nordacoustics.co.uk/
https://www.marchaudio.com/
https://boxem-audio.eu/
https://www.vera-audio.com
https://www.audiosciencereview.com/...amplifier-builder-line-up-announcement.16835/

Most of them are active in this forum.

 

[thrangster]

Absolutely - based on the M2 sensitivity, distance, and listening levels, there are online calculators that about 180 watts is the most peak power I would ever need including 3 db headroom.

 

[thrangster]

I would look at the various implementations of Hypex or Purify amps offered. They often come with adjustable gain and are quite cheap for the performance provided. Also, a Benchmark AHB2 for the two front channels could be combined with Class D multichannel amp for the rest.

I think if you contacted manufacturers and asked for a custom gain setting most would be happy to. Just from the top of my head:

https://www.apollonaudio.com/
https://www.nordacoustics.co.uk/
https://www.marchaudio.com/
https://boxem-audio.eu/
https://www.vera-audio.com
https://www.audiosciencereview.com/...amplifier-builder-line-up-announcement.16835/

The Appollon purifi multichannel has adjustable gain and has caught my eye as well but I’m concerned about ordering an amp from across the pond, and support process should I have issues here in the US

 

[Dimifoot]

Why don't you discuss this with Trinnov? Let us know what they suggested

 

[thrangster]

Why don't you discuss this with Trinnov? Let us know what they suggested

They suggest their amp

but I know the current hiss is unrelated to the output of a he trinnov has I tested with it off and disconnected

my inquiry here is, in principal:

- even with the SDP disconnected, the gain stage contributes to the hiss - if I change the gain from 28 to 34 in the Crown (with nothing connected) the amp noise floor increases

- so I am assuming a higher snr trumps a gain stage mismatch, at least to the point where hiss not audible/bothersome - meaning another 28 db gain amp with a legitimate 118 or 120 db snr is the more important factor than a 19db amp with a 98-100 db snr…

Ideally I suppose is a 19 -20 db gain amp with high snr…

 

[Dimifoot]

Ideally I suppose is a 19 -20 db gain amp with high snr…

Thats why they are suggesting their amp.

Options are:

1. Their amp, or the Apollo you mentioned, or any other amp (Benchmark, Purifi or Ncore) with Gain 19-20db
2. 10db in line Attenuators

 

[thrangster]

Thats why they are suggesting their amp.

Options are:

1. Their amp, or the Apollo you mentioned, or any other amp (Benchmark, Purifi or Ncore) with Gain 19-20db
2. 10db in line Attenuators

Potentially yes… but remember, the hiss is evident without the SDP connected or on, so there is an inherent noise floor (either because of the gain circuitry at 28 db even with no signal present) and/or a poor SNR in relation to the sensitivity of speakers where attenuators would not come into play. Setting the gain structure to 34 in the Crown (with nothing connected) raises the hiss as well.

Turning the connected SDP on while connected to the amps does not seem to change this noise floor, so I am leaning toward it is less of a gain issue than a SNR quality to consider. Both are at play, but a perfectly matches 19 db gain amp at 99 SNR likely will still hiss is my assumption at the moment

Thanks

 

[Dimifoot]

the hiss is evident without the SDP connected or on

Sorry I missed that

Have you discussed this with Harman?

 

[thrangster]

Sorry I missed that

Have you discussed this with Harman?

No, as I don't think there is anything "wrong" with them, just that they are inherently noisy, at least with the M2's...

In the past I have inquired about lower gain settings, but 28 is it.

 

[Dimifoot]

No, as I don't think there is anything "wrong" with them, just that they are inherently noisy, at least with the M2's...

Isn’t this very “wrong”?

 

[thrangster]

Isn’t this very “wrong”?

They are just somewhat noisy amps, I dont think “out of spec”. The hiss is not overwhelming but in a near, multichannel environment, I can notice it during silent or very quiet passages.

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

 

[MakeMineVinyl]

They are just somewhat noisy amps, I dont think “out of spec”. The hiss is not overwhelming but in a near, multichannel environment, I can notice it during silent or very quiet passages.

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

Remember, they're amps intended for professional / industrial sound, not home audiophile use. Having low noise is far down on the importance list for these types of amplifiers for the manufacturers. They need to be reliable, especially under conditions of abuse - that's their main goal above sound quality.

 

[thrangster]

Remember, they're amps intended for professional / industrial sound, not home audiophile use. Having low noise is far down on the importance list for these types of amplifiers for the manufacturers. They need to be reliable, especially under conditions of abuse - that's their main goal above sound quality.

Yeah, it's a bit of a shame JBL recommend these (and still recommends their version of the iTech's) Back then it was either the DCIn/iTechs or a I guess some BSS Sounweb London devices to load the M2 tuning files.

With the SDP, this is no longer required as the tuning files and crossover can be installed/performed there.

The other thing is they mislead you quite a bit on amplification requirements for the M2 (1200 watts minimum!). Using Crown's own amplifier power calculator, 200 watts in my scenario is more than enough including 3 db headroom and assuming 100db SPL, which no one speaker will get close to given realistic listening levels in a multichannel environment.