Hi

From the manual, it shows 950's maxium output is 6.3Vrms. Is that 6.3V per channel? or all channels combined 6.3V?

At the analog section, it shows Rated output is 1V at 0dB gain in Bypass Mode. How many volts it can output if in process mode at 0db?

How many gain do I need to raise in order to hit at least 4V?

Will it clip at 5V or 6V range? Is there any way to tell if it is clipping?

I am sorry if this seems confusing. Hope you understand.

Thanks

These questions are probably best answered by Outlaw, and while they do read every post here they don't often reply. You might want to repeat this question in their support center .

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gonk -- 950 Review | LFM-1 Review | Pre/Pro Comparison Chart | Saloon Links

I don't know what power amplifier(s) you may be using, but Outlaw amps will give you basically 100 watts into 8 ohms with a 1-volt input. The Outlaw amps that have a 200-watt output into 8 ohm rating give their full output at less than 2 volts input. I believe the 6 volts or so available on the output of the 950 is for headroom to make sure that an amplifier does not receive a clipped input signal.

I know that in some cases people try to provide a signal to a device that has a balanced input with an industry standard reference level of +4dB from a device with an unbalanced output at a consumer standard level of -10dB. In order to do so there is going to have to be some gain somewhere. Usually the output of the consumer device is not going to be able to be set to a +4dB reference and have the headroom it was designed to have.

Voltage output is usually specified on a per-channel basis. So that would be 6.3vrms per channel, which would correspond to about 9 volts peak amplitude.

I would expect that these voltages are close to the clipping levels of the active output stage (close in this case being within a factor of two).

To go from 1 volt to 4 volts requires a voltage gain of 4 ( 4 divided by 1) which corresponds to a voltage gain of 12dB. Each doubling of voltage (or current) requires 6dB of gain.

I do not expect an output of 4v (whether it is peak or rms) will clip the output stage, but if the input signal is too large, and with the volume control turned down so that sections of the circuit after the volume control (potentiomenter, digital attenuator, or whatever) are not clipped, there may still be clipping of circuitry prior to the volume control) IF THE INPUT SIGNAL IS TOO LARGE.

Without special ciruits designed to indicate clipping (or an o'scope to look at waveforms), short term clipping is not likely to be heard. Severe clipping can be heard.

Paul

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the 1derful1

Hi

Thanks for your reply. They are very informative and helpful.

Hi bestbang4thebuck

I am currently using QSC amp. The model is RMX 850 and they require input level of 1.5V to reach their full power. Because there's a 6db level difference between consumer's low unbalanced and pro's high balanced line. I sometimes have to deal with this level problems especially for those equipments that aren't capable of putting out even 1V. I ever tried to use the receiver as a pre-amp,but the signal they are outputting is so weak even when I turn the gain to the max. Right now, I am using a Behringer 1/3 octave 31 band equalizer with +-15db gain control as a preamp just for 2 channel stereo listening and watching TV with SRS processing. I think they work ok; the sound is pretty full and surrounding with only 2 speakers and am considering to purchase 950 for Dolby digital decoding. But, I really don't know if they can pre-amplify the low level signal strong enough; hence the question.

The device you are talking about I believe is called Active DI-Box. It purpose is just like you said, converting -10dbv level to +4dbu level and with pre amplification of low-level signal. I considered such device before, but XLR cable is not cheap and not compatibale with most consumer devices therefore I am still feeding the amp with unbalanced RCA line. Because as long as the RCA cable length is short; there shouldn't be any problems. The only problem would be signal level issues.

Hello Paul

If it is 6.3V per channel, Does that mean I will get 44.1 V total from 950 if all channels are used. Is that correct? I don't understand this very well and hope you can guide me.

"IF THE INPUT SIGNAL IS TOO LARGE"

I agree with you paul. I also found that CD's signal is very strong compared to DVD at the same volume. I use a cheap SONY DVD player that has 2V output from analog jack to play the CD with SRS processing. I sometimes have the signal at the pre-amp stage clipped before the amp when playing
the CD. I observed this by looking at the Pre-amp's signal level indicator. When I set the pre-amp's gain at 0db position and playing certain high dynamic range disks; the signal would always hits the +16db sometimes even goes to +18db position ( not very constant) which is pretty loud and if I add 3 more db it reaches the clipping light. I am unable to turn more gain on the amp above 6.5 db position before they reach the full power; although I have more gain available on the amp,but it's already starting to show bit of harshness in my small room.

Was that signal peak or RMS? Let me know what you think, Paul.

Thanks again

"I am currently using QSC amp. The model is RMX 850 and they require input level of 1.5V to reach their full power."

This is a typical value for an input signal to drive a power amp to full power. The 950 will work fine with this.

This means that a voltage sine wave with an RMS value of 1.5V will drive the amplifier to full rated output power into the specified impedance. A signal source to this amp that can supply 6.3Vrms will have no problem driving the QSC amp to full power. This does NOT mean that the source will overdrive the amp UNLESS you turn up the volume way too high. The 6.3V is a maximum rating.

An analogy, my Ferrari (which exists in my dreams) has an engine rated at 500 horsepower. When I move it from one end of my garage (which also exists in my dreams) to the other, a distance of 100 yards, the engine only uses, maybe 50 horsepower max. This is controlled by the Ferrari's volume control ... oops ... gas pedal.

"If it is 6.3V per channel, Does that mean I will get 44.1 V total from 950 if all channels are used. Is that correct? I don't understand this very well and hope you can guide me."

Yes, it is 6.3v (rms) per channel. Combinging, as you did, to get 44.1 V total is meaningless. Deal with each channel one att a time. You have 6.3 v at each of the 6 outputs. This is a rated maximum voltage. If you are putting in a very small signal, even with the volume control all the way up, you will get out much less than 6.3 volts at each channel.

"Was that signal peak or RMS? Let me know what you think, Paul."

Which signal are you refering to?

Paul

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the 1derful1

[This message has been edited by Paul J. Stiles (edited April 12, 2004).]

My venture into the +4dB vs. –10dB arena was just a comment because I could think of no other reason someone might want more than 6 volts on each output of a pre/pro like the 950. My comment was not necessarily a suggestion that you use a gain/impedance/unbalanced-to-balanced matching device.

Out of curiosity, why would you need more than 6 volts per pre/pro output channel if your amp will go to full output with a 1.5-volt input? And what purpose did you have in mind when thinking about trying to combine outputs for even higher voltages? Is it just that you need more gain on signals that are too low from some devices? The maximum output voltage of a pre/pro is not a direct indicator of how much gain it can provide for incoming weak signals. Because your amp can give a full output with a 1.5-volt input, a pre/pro that can boost a signal by a factor of 10,000 up to 6 volts is more useful than a pre/pro that boosts a signal by a factor of just 1,000 but up to 60 volts.

I guess I’m rambling a bit because I’m not sure of the goal. Is it to make sure the 950 will offer you enough gain for your source to properly feed the amp?

If there are questions that can’t adequately be answered here or by email, there is always the Outlaw 30-day, money-back-if-you-don’t-like-it offer. The 950 is hard to beat without spending a lot more.

bestbang4thebuck

My goal here is trying to have as much gain as possible at the early signal stage to maintain the best signal to noise ratio without raising too much gain at the amplifier stage.

A strong signal level will be prominently above the noise floor. A weak signal level may be partly buried in the noise floor. You can try this by lowering the gain at pre-amp and raise the gain on the amplifier and you'll notice how weak the sound is and how much noise you'll get. I don't know about outlaw's amp because they didn't seem to have gain control on them, but I can basically tell you that's the way it works.

A strong signal sent into the power amp won't require as much gain in the amp, meaning I can turn the gain controls down on the amplifier and still be able to reach full power with more headroom. A weak signal will require a lot of gain in the amp, so in addition to boosting the signal a lot at the amplifier stage rather than pre stage, I will be boosting the noise just as much, and I will be more likely to hear hum, buzz, and hiss or perhaps weak sound. I hope you understand what I am trying to say.

Paul

I was refering to either one of them, but I wasn't really sure.

For example, listening to some CD. Although I set the gain on the equalizer at 0db position, but when there is a large scale of orchestra or big drum bass or when rock' n 'roll band starting to get crazy that kind of heavy signal. The signal would always suddenly jump from 0db position to +9db or +10db position; sometimes even hit +16db on the signal indicator and getting louder and louder. Why is that? This happens on some disks. Especially for movie sountracks, rock music, and some big chorus music. But, is not the case for some older recording.

Is there any formula to convert between db to volt and dbv to dbu?

For example, ? db = ? volt like that.

Thanks




[This message has been edited by theendofday (edited April 13, 2004).]

I use an elevated level (+15dbu for digital full scale) on the output of my preamp into my electronic crossover to hit the crossover harder. This is because the crossover uses video buffer ICs with relatively high noise, but they sound wonderful. The inputs to the power amplifiers are attenuated to make up for the increased signal level at the crossover stage.

I don't know if this is what you are doing, but like my setup, if you are presenting a component with a higher than normal input level, that must be reduced later either by attenuation or by the following component having abnormally low gain in order for this procedure to work at all.

Hi

I don't know what you may be refering to, but I think this has something to do with equipment's maxium input/output level. If your crossover's input level is capable of receiving +15dbu signal from the pre-amp without clipping then you probably will be able to boost few more gain at crossover stage to hit even harder to the amp stage if it is capable of that high headroom. As long as the amp or crossover don't overload and the gain is set reasonable then I think attenuation won't be necessary.

I used to have a dynamic compressor to limit those signal peak, but found it actually screw the sound alot and eventually end with just lowering the gain instead. It actually sounds better. Just from my experience

Analog Devices, at

http://64.233.167.104/search?q=cache:_2Fi1tqs_cUJ:www.analog.com/Analog_Root/static/techSupport/designTools/interactiveTools/dbconvert/dbconvert.html+dBu+dBv&hl=en&ie=UTF-8

has a converter calculator for various dB standards, as well as definitions of them.

For best signal to noise ratio, you would want as large an input signal (say, from your CD or DVD player) as possible and use the least amount of gain of the preamp (or 950) in order to drive the power amps to desired output.

What soundhound is doing in regards to using his active crossover, with nice sounding, but noisy video buffers is maximizing the signal to noise ratio of the active crossover by giving it a really big input signal. When he attenuates the large output of the active crossover, he is also attenuating the noise inherent in the output of the active crossover. Similarly, in your case, you give the preamp (or 950) a big signal and use the preamp (or 950) to attenuate the signal (and the noise in it) to a reasonable level for your power amp.

If you set things up to use your preamp (or 950) at maximum gain, then any noise coming into the preamp, or generated at the preamp's input stages, will be made much worse. Beings you are using your preamp at maximum gain, the input signal from the source (CD or DVD player) will have to be small so as to not overload the preamp or power amp.

Paul

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the 1derful1

Thanks for the link, Paul. This program is really convenient. It does all the conversion in one single package. Nice.

Now I understand soundhound. I usually use the gain control on the amp to attenuate the signal to my desired volume. Because I think running unnecessarily low signal levels through cables and equipment is bad for optimizing signal-to-noise ratio; it's much better to have strong signal levels that are well above the noise floor, but not clipping at early signal stage. Then the final stage, the power amplifier, doesn't need as much gain. Consequently, the residual hum and noise doesn't get amplified as much, either. I think setting up the gain structure this way results in much less audible hiss and hum in the system.

You are right - the higher the signal level is while it traverses through each component and along interconnects, the higher it will be above any potential noise picked up along the way. This is a simple (and free) tweak that I'm surprised more people haven't picked up on as a very effective way to reduce noise.

Of course one thing to watch out for is that the component stage that does the initial signal boosting must be quiet in itself so that it doesn't contribute it's own noise.