Dac with low noise floor for 104db sensitivity speakers

[AnalogSteph]

i expext to use my Yamaha p2500s , while not high end sound it Sounds more than okay, but i havent heard it with a 104db speakers so not aware of how noisy it will be.

Probably not all that great. Spec for residual noise is <= -70 dBu (20-20k), that's 245 µV or -81 dB ref. 2.83 V (or by the metric Amir uses, -85 dB ref. 5 W / 4 ohm). So with 104 dB speakers you can expect about ~23 dB SPL @ 1 m anechoic. That's about 19 dB more than you'd ideally want. Just from the power amp at minimum gain.

Not to mention that a 250 wpc amplifier is vastly oversized in general, but you know that. For 110 dB SPL peak, you'd only need about 4 W.

If you can dial in the levels (or use a line-level attunator) you don't actually need a super duper high-strung DAC, although the ones that comes with a volume control knob will generally be plenty good enough.

So these are the speakers?

You know, instead of (or before) buying another amp you could also make a passive attenuator (L-pad). About 7.5 ohms at ~250 W total and 1 ohms at ~25 W total, so for the former you would no doubt have to combine a number of fat power resistors while providing good cooling.... not exactly pure canned efficiency I'll admit.

I had a look at the schematic for the P2500S, and the limiting factor in terms of noise - aside from relatively high gain - seems to be the inverting opamp circuit used as a level pot buffer and as an inverting summing stage for the limiter circuit. That circuit alone would seem to be costing them about 10 dB or so. (it generates about 4 µV, times 40 = 160 µV. The power amp alone would be at little over 20 µV. So room for improvement = up to 17 dB or so.)
Not exactly an easy mod though, unless you can live without the limiter and with inverted absolute phase (in which case you could remove R431/432 and R507/508 on the "DC" board and run a jumper wire from the input end of R431/432 (facing the PCB connector to input board) to the output end of R507/508 (facing the coupling caps)).
Not sure how much gain reduction one could risk in addition to that. If really needed, I might change R304/308 in the input stage instead. While you're on the input board, it looks like XLR jack wiring is not yet AES48-2005 compliant, though it seems there might be a star ground point to chassis right next to them, which would make this a minor concern at best.

 

[Panduro]

Hey steph, thx for the answer, although Way above my lvl off knowlegde and skillset…

yes that is my new speakers.

does that mean i have to attenuate 19 dB before i Can expect Them to be hiss Free?

yes im aware i dont really need need that kind of power, it’s Old amps i have owned which are doing nothing currently, so in the intérêst of getting the best gear i Can afford i have to live with other parts being less than ideal.

both the nad and the yamaha i plan on using to drive 4 subs/Helper woofers.

No i dont need limiter, i dont know what absolute inverted phase means or erhmm does… i dont really feel comfertable modding my amplifiers, i like them in WorKing condition .
Well maybe if it’s simple and it Will make them quiet enoughf, if not i would rather live with hiss until i Can afford getting a amplifier with the right specs.

best Regards

ben

 

[AnalogSteph]

does that mean i have to attenuate 19 dB before i Can expect Them to be hiss Free?

Pretty much. Or at least 16ish.

i dont know what absolute inverted phase means or erhmm does…

It flips the polarity of the signal. Not generally something our hearing is very concerned with, except possibly in the bass.

 

[Roland68]

Dac with low noise floor for 104db sensitivity speakers

Hello Ben, the noise floor of the DAC is irrelevant for the sensitivity of the loudspeakers, regardless of whether it is 104 or 89db, as it is reproduced in the same ratio.
There are now many DACs with low background noise that have been well tested on ASR, e.g. Topping D30pro, Gustard X16, Sabaj D5 or SMSL SU-9.

But the noise floor of the amplifier has a direct effect on the increasing sensitivity of the speakers.

 

[Panduro]

Thx steph, my Brain like to have Numbers to work with…

roland, having never owned a stand alone dac, ill Take your Word for that. To me it’s pretty simple though, the lower noise floor in every part of my system the better.

i Will look into power amps, at some point, but not atm.. also need to figure out how Little wattage my speakers Will do Well with, but ill prob look into purify at lowest gain, or something like it when time is right.

i Think im leaning towards gustard x16.
best regards
ben

 

[voodooless]

Also note that above 1kHz efficiency is “only” 98 dB:

That will help a lot in terms of amp hiss.

 

[Panduro]

Yeah true. Also shows why designer often says his designs are made to use with multible subs, although it should Pick up Some boundary gains.

ben

 

[AnalogSteph]

A somewhat peculiar response; looks like this one could use a low shelf of -6..-8 dB with a cutoff somewhere around 700 Hz. That in turn may then afford enough headroom to flatten out the bass response to 55ish Hz with a peak EQ... mind you, you better check in-room bass response via measurements and adjust accordingly.

 

[MakeMineVinyl]

Just about any current DAC will have a low enough noise floor even for sensitive horn speakers. I have an SMSL M-400 and do not have noise problems at all. I think most of the noise is going to come from power amplifiers as these are typically quite a bit noisier than any good DAC. I wouldn't get too hung up on balanced connections because these are no real use unless you have a problem with common mode noise for instance with very long cable runs.

 

[Panduro]

Thx for all the advice guys, it’s appriciated!

ben

 

[Robin L]

hola guys, am i asking the wrong question since the answers came to a halt?

best regards

ben

Check the DAC reviews here, read the fine print. According to Arim, anything more than 115db combined s/n and distortion is effectively inaudible.

If you want AES balanced digital in, that's your business.