pre out voltage

[JohnnieB]

Ok my pre/pro has 1.0v/1kohms pre amp output. If I understand this correctly, this is the rated voltage before clipping. I mated it with an Emo XPA2 with an amplifier gain of 29db. I was doing some reading in the AV research tab and was wondering if I'm not getting as much headroom or dynamic range as I could, if I had a pre with a higher pre out voltage, or an amp with a larger gain rating. Conversely, is it possible to go too big with either of these numbers? Trying to wrap my little pea brain around this

 

[TLS Guy]

Ok my pre/pro has 1.0v/1kohms pre amp output. If I understand this correctly, this is the rated voltage before clipping. I mated it with an Emo XPA2 with an amplifier gain of 29db. I was doing some reading in the AV research tab and was wondering if I'm not getting as much headroom or dynamic range as I could, if I had a pre with a higher pre out voltage, or an amp with a larger gain rating. Conversely, is it possible to go too big with either of these numbers? Trying to wrap my little pea brain around this

It had better not be! If it clips at 1 volt, that will give you no headroom. I have been on about this many times. Headroom is one of many specs that is very seldom specked and should be. Peter Walker of Quad taught me years ago, that this is one of the most important design features of the voltage amp stage of any piece of audio gear. Units with low head room sound bad period. He always designed in enormous head room, which is one of many reasons his gear sounds so good.

I'm glad to say my Marantz pre pro has fairly good head room, clipping stats at 14 volts, which gives it just under 10 db of headroom.

I have never had a chance to measure any receiver preouts, but it is something I always wonder about. That would be the single most important spec. that would tell you if receiver pre outs are as good as the output form a pre pro. I have a hunch I know the answer to that.

 

[Alex2507]

I'm glad to say my Marantz pre pro has fairly good head room, clipping stats at 14 volts,

My RX-V2600 rec'r has pre-outs that hit I think 4 volts and that's considered good! 14 volts sounds insane.

 

[Irvrobinson]

Output voltage capability is my biggest issue with the Outlaw 975 pre-pro, now that we've learned to operate the poorly designed remote. The 975's output voltage is completely inadequate, though Outlaw rates it at 2V. No way it's 2V into the input impedance of the ATI amp I'm using. We're probably going to re-do that video system soon, and when I do the 975 is history, and so is Outlaw in general with me. I tried to save money and regretted it, though its SQ is a big step up over the Sony AVR I was using before. (Why that's true is a mystery too.)

No one thinks about line-stage capability, but it actually makes a difference. Some amplifiers have nice high input impedances that keep line stage power requirements low; 100K ohms used to be typical. Now I think 10K-20K ohms is more prevalent. My ATI is rated at only 26K ohms, and I suspect that combined with the low for these days 28db of gain it's stressing out that cheap-ass 975 output stage.

 

[TLS Guy]

My RX-V2600 rec'r has pre-outs that hit I think 4 volts and that's considered good! 14 volts sounds insane.

If you have four volts, that is only just over 3 db and a spit in the ocean. I can tell you form my live reel to reel recoding, that is nothing.

You had to use all available modulation on tape, or you paid a huge signal to noise penalty. On the best tapes you only had 3 db headroom. I can tell you that was a really difficult management problem. You had your eye on the ballistic and peak meters, and tried to follow the score at the same time. You had to be ready to artfully gain ride at any moment , and have keep a hand on the faders. I can tell you 3 db headroom is a tight rope and nowhere near adequate.

I'm just grateful I had such good mentors as a youngster, who taught me how to engineer for the real world.

First item of business with any pre/amp or voltage amplifying device, like a mixer say, is to measure the headroom. 10db is the absolute minimal in my book, more is better.

I have a hunch that if I actually got to measure the most important parameters of a lot of the gear you use, you would be horrified when you got the report.

 

[Alex2507]

If you have four volts, that is only just over 3 db and a spit in the ocean. I can tell you form my live reel to reel recoding, that is nothing.

You had to use all available modulation on tape, or you paid a huge signal to noise penalty. On the best tapes you only had 3 db headroom. I can tell you that was a really difficult management problem. You had your eye on the ballistic and peak meters, and tried to follow the score at the same time. You had to be ready to artfully gain ride at any moment , and have keep a hand on the faders. I can tell you 3 db headroom is a tight rope and nowhere near adequate.

I'm just grateful I had such good mentors as a youngster, who taught me how to engineer for the real world.

First item of business with any pre/amp or voltage amplifying device, like a mixer say, is to measure the headroom. 10db is the absolute minimal in my book, more is better.

I have a hunch that if I actually got to measure the most important parameters of a lot of the gear you use, you would be horrified when you got the report.

I don't know ... my set up is pretty sweet.

I thought most home audio pre-outs were just 1 volt and some pro amps required 1.4 volts to achieve maximum gain hence the Samson S-converts. Am I completely off my feed here? I mean the voltage difference is so vast that I'm wondering if we're talking about the same thing even though I'm not exactly well versed in what I'm talking about.

This is where I'm getting my ideas from:

"We tested the preamp section of the Yamaha RX-V2600 and were able to drive over 4V RMS. This is a welcome change for Yamaha as prior models such as the RX-V2400 and RX-V2500 weren't even able to achieve 2V RMS unclipped. Max input voltage before clipping was a whopping 4.550Vrms. This means you can pretty much drive any power amp on the market to full power, without the Yamaha preamp section adding any unwanted harmonic distortion."

 

[TLS Guy]

I don't know ... my set up is pretty sweet.

I thought most home audio pre-outs were just 1 volt and some pro amps required 1.4 volts to achieve maximum gain hence the Samson S-converts. Am I completely off my feed here? I mean the voltage difference is so vast that I'm wondering if we're talking about the same thing even though I'm not exactly well versed in what I'm talking about.

This is where I'm getting my ideas from:

"We tested the preamp section of the Yamaha RX-V2600 and were able to drive over 4V RMS. This is a welcome change for Yamaha as prior models such as the RX-V2400 and RX-V2500 weren't even able to achieve 2V RMS unclipped. Max input voltage before clipping was a whopping 4.550Vrms. This means you can pretty much drive any power amp on the market to full power, without the Yamaha preamp section adding any unwanted harmonic distortion."

Your ideas are in line with what usually tales place, and as is so often it is not good enough.

Music has a huge dynamic range. So if you want to keep the preout voltage at 1 volt or even four, the average signal is going to be very low.

Why does this matter? It matters because of signal to noise. In order to keep the signal out of clipping range the average signal is very low. Remember music has a dynamic range of 100 db commonly and 130 db or so for some. So I think you can see the problem.

In order to keep the average signal where signal to noise is excellent, then you need huge head room to prevent clipping.

This is what really sorts the mediocre, from the excellent. But of course it adds expense the design.

 

[Irvrobinson]

Music has a huge dynamic range. So if you want to keep the preout voltage at 1 volt or even four, the average signal is going to be very low.

Why does this matter? It matters because of signal to noise. In order to keep the signal out of clipping range the average signal is very low. Remember music has a dynamic range of 100 db commonly and 130 db or so for some. So I think you can see the problem.

Since most amps take less than 3 volts to be driven to clipping, I'm not seeing the problem as you are. However, as I said earlier, I seriously question the ability of some pre-amp output stages to drive three or four volts into lower impedance inputs, say 10K ohms. I like John Atkinson's testing because he tests pre-amps into a 600 ohm load, which tends to weed out the posers.

 

[PENG]

Your ideas are in line with what usually tales place, and as is so often it is not good enough.

Music has a huge dynamic range. So if you want to keep the preout voltage at 1 volt or even four, the average signal is going to be very low.

Why does this matter? It matters because of signal to noise. In order to keep the signal out of clipping range the average signal is very low. Remember music has a dynamic range of 100 db commonly and 130 db or so for some. So I think you can see the problem.

In order to keep the average signal where signal to noise is excellent, then you need huge head room to prevent clipping.

This is what really sorts the mediocre, from the excellent. But of course it adds expense the design.

Your argument seems to be based on people using their amps at full rated output all the time. My amps typically output on average under 1W so the preout will be at very low mV values and so I have tons of headroom. If you regularly runs your pre-outs at 1V or higher, then yes I see your point.

As to 14V at clipping, one British lab tested the Denon AVR-3808A (A=silver) at over 18V rms at clipping. while some high end preamps, tested at less than 2V. I won't pay too much attention to those figures unless we are comparing the results done in the same lab using the same instrument, methodologies; and by the same person who knows what he/she is doing.

 

[Alex2507]

The S/N ratio number that I associate with decent quality is around a hundred which I'm pretty sure this particular rec'r is close to but what number are you thinking about? I'm curious is all, as I'm sure you understand. I'm also curious what PENG has to say about that pre-out voltage. I wonder what it is on a Denon 4311.

 

[PENG]

I don't know ... my set up is pretty sweet.

I thought most home audio pre-outs were just 1 volt and some pro amps required 1.4 volts to achieve maximum gain hence the Samson S-converts. Am I completely off my feed here? I mean the voltage difference is so vast that I'm wondering if we're talking about the same thing even though I'm not exactly well versed in what I'm talking about.

This is where I'm getting my ideas from:

"We tested the preamp section of the Yamaha RX-V2600 and were able to drive over 4V RMS. This is a welcome change for Yamaha as prior models such as the RX-V2400 and RX-V2500 weren't even able to achieve 2V RMS unclipped. Max input voltage before clipping was a whopping 4.550Vrms. This means you can pretty much drive any power amp on the market to full power, without the Yamaha preamp section adding any unwanted harmonic distortion."

Pre-outs, like power consumption, rated power output, phase angles etc., are one of those specs that are hard to compare even if published. You have nothing to worry about the RX-V2600 and I know you are not worrying at all because you likely have more headroom than you need already. For those who worry, read the following:

http://www.audioholics.com/audio-amplifier/amplifier-voltage-gain

http://www.sengpielaudio.com/calculator-amplification.htm

The calculator shows if you feed 14V (TLS seems to think he has use for that..) to an amp with 29 dB voltage gain, you get almost 395V so even well below the preamp starts clipping the power amp will have clipped much sooner. I don't see much need for more than 2.5 to 3 good quality V.

 

[PENG]

I have not seen lab measurements for the 4311 but the following should give you some idea.

Denon 3805 3.12
Denon 3808 8.55/8.54
Denon 3808A 18.16/18.34
Denon 4308 3.43/3.44
Denon A1HD 16.4/16.23
Krell Evolution 222 0.782/0.781
Marantz SC-7S2 1.607/1.616
Marantz PM7003 12.06/12.05
Marantz PM6003 4.04/3.98
Marantz PM8003 11.75/11.92
McIntosh C22 2.75/2.75
McIntosh C2300 2.426/2.432
McIntosh C22 2.75/2.75
NAD C315BEE 1.81/1.82
NAD M15 5.97/5.98
NAD T765 5.99/6.03
NAD C316BEE 4.503/4.508
Onkyo 605 3.35/3.33
Onkyo 507 8.918/8.949
Pass Lab X2.5 1.089/1.098
Quad Elite 1/1.01
Sony DA5400ES 5.96/6.08
Yamaha Z11 14.81/14.69
Yamaha Z7 7.65/7.55

All those are from the same source, presumably by the same lab, but who knows if they were all done the same way. I think in most cases there is no need to worry about this, as long as your system sounds sweet, just enjoy the music!

 

[Alex2507]

Thanks, PENG. I wanted to establish a difference of informed opinions and yes, my modest power needs are easily met.

 

[JohnnieB]

I'm running a Sherborn PT7030 pre. At work on my phone so link posts are a pain. I will link the spec sheet for it in A.M. I may be wrong on the preout voltage, but pretty sure 1v was the spec. The sound is quite good and I can run 95 db, but would like to know where I'm really at with this. I have been considering selling the Sherbourn for an AVR or different pre/pro.

 

[PENG]

I'm running a Sherborn PT7030 pre. At work on my phone so link posts are a pain. I will link the spec sheet for it in A.M. I may be wrong on the preout voltage, but pretty sure 1v was the spec. The sound is quite good and I can run 95 db, but would like to know where I'm really at with this. I have been considering selling the Sherbourn for an AVR or different pre/pro.

This review http://www.soundandvision.com/content/sherbourn-pt-7030-surround-processor-pa-7-350-amplifier-ht-labs-measures indicated the PT7030 had no problem pairing with the PT-7350 to produce more than the 350W rated output. Again, it does not mean a whole lot to say a preamp's output is 1V or whatever, without more details. It could mean 1V continuous into a certain load impedance but then the output could be much higher under another set of conditions (e.g. peak).

There is no compelling reason for a mid range preamp to be limited in output in a detrimental way. it is not rocket science and there are low cost AVRs that have been tested to output peak V rms of respectable values.

 

[gene]

Preamp out voltage specs are typically NOT unclipped max ratings unless otherwise specified. Many products I've seen speced 1V/1kohm typically measured at least 2Vrms at 600 ohms unclipped. Only way to know for sure is to measure it.

 

[JohnnieB]

I guess the next question would be, how do you measure it? Voltmeter on the RCA terminal?

 

[slipperybidness]

I guess the next question would be, how do you measure it? Voltmeter on the RCA terminal?

O-scope

 

[PENG]

O-scope

Of course, but I trust my $500 Fluke multimeter is good enough.

 

[slipperybidness]

Of course, but I trust my $500 Fluke multimeter is good enough.

Good enough for government work? Good enough for community college work?