[doughnutguy]

I seem to recall reading about others using the 410 straight into a power amplifier, but cannot find the thread(s). I just bought a Parasound 5-channel amplifier and would like to do this. Would anyone who has actually tried such a configuratoin please respond.


On an unrelated but still 410 side-note: since this card does the bass cross-over for all channels and time delays based on distance per channel I was wondering if some other crossover feats might be possible. (BTW, thanks again Cliff for all the amazing work on this card!) What about using four channels for stereo output with the card acting as crossover for a 2-way speaker design? (You would still send low frequencies to the designated bass channel at a frequency of your chosing as now.)


The main reason I am interested in this is because there are a number of DIY speaker plans and kits out there. With this capability you could build something without an internal crossover network. Just 3/4" MDF, drivers, wiring, cabinet insulation, and 2 pairs of hi-quality binding posts. Now, just imagine if each of the 4 channels on the card had it's own 2-channel parametric EQ? With good amplification and a decent sub we're talking potential "giant-killer" hi-end sound.

 

[helzerr]

I was using a 410 wired directly to an amplifier for stereo music. The results were O.K., especially Cliff's bass management.


However, I went back to using a pre-amp so I could improve the signal to noise ratio of the Delta 410 by turning it up all the way and attenuating the output with the pre-amp. The pre-amp's tone controls also allow a fuller sound for my configuration.


I'm also using home-brew DIY Voight pipes ( http://melhuish.org/audio/diy17.htm ) using a single Radio Shack 40-1354a full-range driver. These speakers have GREAT bass and midrange, but need a little treble boost. When set up right they sound almost as good as my friend's $1400 pair of B&W's and cost me about $40 to build ; )


Maybe Cliff can get tone control added to the drivers (please?) and I'll go back to direct once I get a cleaner power supply for my PC.


My next project is looking into building some 47 Labs Gaincard Gainclones to bring my amplification up to the 410's standards.

 

[K-Wood]

I'm routing the analog outputs of my Delta 410 through a preamp (Sony TA-P90000ES), mostly because I need the additional 5.1 inputs for an external surround decoder (handles DSS and AccessDTV) and for an eventual SACD player. I haven't tried to running it directly into my amps, so I can't tell whether I would have the S/N issues that Ron has experienced.


I see no reason why the crossover feature would not work as an active crossover for full-range speakers. You would be limited in your selection of crossover points and slopes, so there wouldn't be much room for fine-tuning. But you would have the ability to switch it on the fly and hear the results (I've done this with the crossover to my sub -- and concluded that setting the crossover to 40Hz and letting the speakers roll off naturally (60Hz -3dB point) was the best choice).


You should also consider the possibility of using either a Delta 1010 with more channels or TWO Delta 410's to give you the ability to experiment with stereo crossovers AND run a full 5.1 surround setup. I'm currently using channels 7/8 to power second zone and have thought about adding a second 410 card to power additional zones.


- Ken

 

[helzerr]

I am beginning to think a preamp is a necessity for the 410, let me explain.


The Delta 410 D/A has 101.5 dB S/N ratio under ideal circumstances. Certainly not a bad number! However, I believe this number only holds true if the output is being driven full volume, I.E. not using the monitor mixer, variable output signal levels, or bass management to reduce the volume. The reason I think this is true is because the noise floor is at a fixed, constant level regardless of volume or output voltage settings used.


Therefore, if I set the master volume in monitor mixer or bass management to -25 dB (comfortable listening level for my setup), I'm only getting 76.5 dB (101.5 -25) S/N ratio... Not too good at all.


The only way to maintain the 101.5 dB S/N ratio is to run the Delta card full volume and attenuate the signal to the amplifier or reduce the amplifier gain. This kind of bursts the bubble of those hoping to skip the preamp and maintain excelent sound, especially if you have a high gain amplifier or high efficiency speakers...


Please note: I am still VERY pleased with the sound quality of my 410... I'm currently playing with speaker placement for stereo audio and the quality of the output from the 410 is superb, maybe the best digital audio I've ever heard! It's just better with a preamp instead of the mixer (but I still use and love the bass management, thanks again, Cliff!).


Cliff: Is the 101.5 dB S/N rating spec'ed for the consumer or -10 dBV setting?

 

[Pootle]

Helzerr, I don't understand your point about noise level.


I have my 410 straight into power amps (a combination of naim and quad). The noise level of the combined set up is such that I can only hear the noise floor if I stick my ear right against the tweeter.


This noise floor is always the same irrespective of the volume levels set anywhere in the 410.


So it doesn't matter what level I am playing things at, the noise floor is inaudible in even the quietest passages.


Any amp is much the same, a power amp will have a noise level of (say) 110db relative to peak input, so if you feed it a quiet signal (say 60db down from peak), then the signal to noise ratio is only going to be 50db. As long as the noise floor is below the threshold of hearing there isn't a problem.

 

[Cliff Watson]

I think Ron is getting S/N mixed up with dynamic range.

 

[helzerr]

Pootle... I agree with you, but my speakers are efficient and my amplifier has a high fixed gain and that makes the noise floor more audible.


Using a preamp allows me to attenuate the noise when reducing the volume, preserving the high S/N ratio of the 410. I can barely tell the difference, but I can tell! I also spend more time listening at lower volume as I am an apartment dweller, so I may be more likely to hear the difference than those listening at reference levels.


I just wanted to point this behavior out to others that may be planning to use the 410 to skip the preamp, your results may not be as good as with a preamp.

 

[helzerr]

Cliff... Please excuse me, I'm not trying to be a smart a$$, if I am incorrect about any of this I'd like to learn. According to my understanding of the terms, I think dynamic range and signal to noise ratio are interchangeable in this discussion... If my use of S/N ratio is incorrect and we substitute dynamic range, 76.5 dB dynamic range with the volume slider at -25 isn't very good either.


All of this may be moot to most 410 users as I think I have too much gain/efficiency for my listening situation and preferences. However, I can turn down the volume on my preamp and preserve a clean sound, I can't do that with the 410.


S/N ratio definition:

----------

In analog and digital communications, signal-to-noise ratio, often written S/N or SNR, is a measure of signal strength relative to background noise. The ratio is usually measured in decibels (dB).

----------


Since the noise floor of the 410 is constant, and reducing the volume reduces the signal strength, the S/N ratio is altered when reducing the volume.


Dynamic Range definition:

----------

Dynamic range describes the ratio of the softest sound to the loudest sound in a musical instrument or piece of electronic equipment. This ratio is measured in decibels (abbreviated as dB) units.

Dynamic range measurements are used in audio equipment to indicate a component's maximum output signal and to rate a system's noise floor.

----------


Once again, if the noise floor is fixed at a certain value, and the maximun output is altered (via volume slider) then the dynamic range has been altered.


The research I've done indicates that at maximum output, dynamic range and S/N ratio are the same... http://www.sfu.ca/sonic-studio/handb...mic_Range.html


This speaks to the heart of what I'm trying to say... The maximum dynamic range and S/N ratio are only obtainable from the 410 at maximum output since the volume slider doesn't lower the noise while lowering the volume.

 

[Cliff Watson]

â€All of this may be moot to most 410 users as I think I have too much gain/efficiency for my listening situation and preferences. However, I can turn down the volume on my preamp and preserve a clean sound, I can't do that with the 410.â€


Ron,


While S/N and DR are often use interchangeable they are not the same.


Now to you problem. Without having you system in my lab I really can’t analyze why you’re having the noise problem with the 410 connected directly to your amp. It could be the rated output is overdriving your amp and when connected to a pre/amp the output voltage could be lower than the 410 or any other number of reasons.


Not trying to be a smart-ass either, but could you please explain how a pre/amp with a rating of 102dB (dynamic range 96dB) be any different than the 410 when the volume control is reduced?

 

[Cliff Watson]

Ron,


I conducted some tests to see if I could reproduce the problem you have and found some interesting things.


Like Pootle I get a small amount of hiss from the tweeters at full volume into an amp. I turned the 410-volume control down to –100dB and the hiss is still there. Next I muted the output from the 410 and the hiss remained. Here is the kicker, I disconnected the analog cables between the 410 and the amp and still have the hiss.


My guess would be it is caused by thermal noise in the amp or induced by other equipment in my rack.

 

[Pootle]

Of course! there will always be some noise in the power amps as well.


I tried just disconnecting the power amp inputs, but that gave me a very low level hum, so I shorted the power amp inputs, and this did reduce the noise level from only audible 6" from the tweeter to only audible 1/2" from the tweeter, so the noise floor of my back end appears to be noticeably lower than the noise floor from the 410, which is about right as pre-amps are always noisier than power amps (or were in the days when I last studied such numbers!)


This suggests that the best answer might be a simple fixed reduction between the 410 and your power amps, as this will enable you to run the 410 at much higher volume settings for the same sound output level.


If you decide on the maximum volume setting you would ever want to use with your power amps connected directly (say -25db on the 410 control panel scale) take a few off just for the odd very quiet source you may come across (leaving 20db), then make a simple divider to reduce all your outputs by 20db.


I think you should be able to do this with a simple passive circuit, Cliff can probably advise on this, I would be tempted to try a simple resistor divider with something like a 10K and 100K resistor- use tight tolerance low noise parts - it'll probably cost all of 10$ by the time you've put it on a small board, in a box with sockets.


Of course you loose your tone controls doing it this way, but its a helluva lot simpler than keeping your pre-amp. If you made the adapter box active though, you could incorporate a fixed setting treble boost.

 

[DRS]

Quote:

Originally posted by Pootle -snip- the noise floor of my back end -snip-

Sorry, couldn't resist


I'm receiving a 410 today and will be hooking it up to a McCormack .5 DNA deluxe. I'll try and post my impressions later...

 

[helzerr]

I like Pootle's idea of a passive divider, I may try building one. Since I've relocated my speakers, I no longer require the trebble boost. If I short the input to my amplifier, I get absolute silence at the speakers (woohoo I happen to have a VERY quiet amplifier), if I do the same with the pre-amplifier, I get just a slight bit of hiss with my ear @ the speaker regardless of the volume control position of the preamp. If I have the 410 at any volume position hooked up to the preamp, I get a slight bit of hiss that increases with volume setting on the preamp. If I hook the 410 directly to my amplifier I get a slightly higher amount of hiss that is constant regardless of volume setting on the 410.


I'm not complaining about the 410, it is certainly quiet enough! I think the 410 has opened my ears to a new level of audio quality, and I'm on a quest to eek out every last ounce of performance, if using a preamp or passive divider can improve the performance slightly, why not?

 

[helzerr]

Cliff, since there is already filter code in the 410 driver for bass management, can tone control be added in the next driver revision?

 

[DRS]

Wow! Holy crap! My CD's haven't sounded this good since I parted with my McCormack Microline drive preamp and audio alchemy transport/outboard dac. Very cool.


About the hiss, my findings are similar to the above. With the 410 plugged into the amp I can discern a faint hiss from about 6 inches away. With nothing plugged into the amp I have to put my ear essentially on the speaker to hear any hiss.


I'm thinking one possible solution to the hiss might be more precise volume control. At half volume through PDVD and WinMP I'm blown out of the room. The first quarter of the volume control is about all I really need. Like helzerr said I'm not complaining--Now where did I put that Cassandra Wilson CD?

 

[helzerr]

If you think it sounds good now, try setting the sampling rate to 88.2 KHz and turning rate lock on in the hardware settings tab of the mixer, you might be able to notice a slight improvement. While you are there, set the variable output signal level to it's lowest level, you'll be able to use more of the volume control that way.


Be sure to turn the rate lock back off or set the rate to 48 KHz when you want to play a DVD.

 

[DRS]

helzerr I just did something similar only a step 'better'. During the first year that DVDs were coming out Chesky Records came out with a "DVD audio" sampler disc. They claim it is 24/96 although by default when playing through PowerDVD the M-Audio mixer panel sees it as 48. Anyway, I set it to 96khz and check the lock rate option.


I have forgoten how scarry good musical reproduction can be. When I have played this disc through the DVD player then through the receiver it sounds good but the soundstage through the 410 is incredible--the speakers dissapear. The reason I describe it as scarry is your brain (at least mine) thinks there are other people in your listening room but when you open your eyes they aren't there ala Sixth Sense only opposite, and they aren't dead, errr, nevermind...


BTW does PDVD "decode" HDCDs also? Any special settings?

 

[Cliff Watson]

Hi Guys,


I attenuated the analog output by –18dB and the hiss is gone. The output voltage may be a little hot. I’ll discuss it with the engineers.

 

[K-Wood]

FWIW -- I believe that Windows Media Player decodes HDCDs. Haven't tried it though.

 

[helzerr]

DRS:

I wish I had one of those Chesky discs... I've got a couple of Telarc DTS CD's 24/44.1 5.1 I downmix to stereo but the content is mostly cheesy 5.1 FX stuff.


I've been playing with speaker placement yesterday and today to get that same "in the room with you" feeling ; )


Cliff:

I kinda like the output of the 410 on the "hot" side, I think most of my problem is having too much gain in the amplifier I am using. I am planning to building a pair of " GainClones " and will be able to use lower gain in the amplifier. That in conjunction with the 410's hot output should yeild a very clean, quiet system.