input sensitivity question

[woody77]

I have a Marantz NR 1403 reciver. I was thinking of using my old B&K EX 442 amplifier on the marantz pre amp outs for the front speakers. I noticed that the 1403 has an input sensitivity of 1.3 volts while the ex442 has a 1.65 volt rating. Problems concerns, anyone?

 

[jagdish_p]

I have a Marantz NR 1403 reciver. I was thinking of using my old B&K EX 442 amplifier on the marantz pre amp outs for the front speakers. I noticed that the 1403 has an input sensitivity of 1.3 volts while the ex442 has a 1.65 volt rating. Problems concerns, anyone?

No problems or concerns. Go ahead and connect. The usual line voltage is above 2 volts and amps can handle higher input voltages. The input sensitivity refers to the minimum voltage requirement and not the maximum.

 

[hydrovac]

I have a Marantz NR 1403 reciver. I was thinking of using my old B&K EX 442 amplifier on the marantz pre amp outs for the front speakers. I noticed that the 1403 has an input sensitivity of 1.3 volts while the ex442 has a 1.65 volt rating. Problems concerns, anyone?

Input sensitity is the max input signal voltage that drives the amp at max output. You will want to match it with the output level of whatever is before the amp in the audio chain. What is the signal out put level from your AVR?

Often overlooked by those unaware of its importance, this one parameter can have significant implications on actual performance when an amplifier is introduced into an AV system. Understanding the impact that different levels of voltage gain can have in your system can very well be the difference between poor sound and getting the most out of an external amplifier.

Reading the above, it may seem that those who seek the additional output of an external amplifier are caught in a vicious catch 22. Certainly if you happen to have a combination of an AVR with a poor preamplifier output section combined with ultra-high sensitivity loudspeakers, you may want to reconsider some of your hardware choices; beyond that, careful selection can help ensure that you get the most out of your equipment. Further, it should be noted that while some low end receivers may not be the ideal starting point for adding separate amplifiers.

Long story short: if you want to add power to a lower end receiver with pre-outs, you probably want something with a better than average amount and a low input sensitivity.
The preamp section of this receiver should have no problems cleanly driving any external power amplification to its full output capability.

hope this helps

happy days mate

 

[sanj]

Hi Hydrovac

Sorry for jumping in the thread but i too need some understanding about the matching input senstivity (volt/impedence) of preamp and power amp for optimal performance.
My Rotel power amp has input senstivity of 1volt/ 33 k ohms,
what does it mean ..can I use only preamp which have these matching sensitivity for good sound or can use different senstivity preamp?.
Please let me explain I will be really greatful to you as I am planning to buy a new preamp for it.

Rgds.
Sanjay.

Input sensitity is the max input signal voltage that drives the amp at max output. You will want to match it with the output level of whatever is before the amp in the audio chain. What is the signal out put level from your AVR?

Often overlooked by those unaware of its importance, this one parameter can have significant implications on actual performance when an amplifier is introduced into an AV system. Understanding the impact that different levels of voltage gain can have in your system can very well be the difference between poor sound and getting the most out of an external amplifier.

Reading the above, it may seem that those who seek the additional output of an external amplifier are caught in a vicious catch 22. Certainly if you happen to have a combination of an AVR with a poor preamplifier output section combined with ultra-high sensitivity loudspeakers, you may want to reconsider some of your hardware choices; beyond that, careful selection can help ensure that you get the most out of your equipment. Further, it should be noted that while some low end receivers may not be the ideal starting point for adding separate amplifiers.

Long story short: if you want to add power to a lower end receiver with pre-outs, you probably want something with a better than average amount and a low input sensitivity.
The preamp section of this receiver should have no problems cleanly driving any external power amplification to its full output capability.

hope this helps

happy days mate

 

[hydrovac]

Hi sanj,

Any device which generates a voltage has what is called an output impedance. The output voltage from the source is developed across the input impedance of the destination (often called the load impedance, or simply the load). However, the input and output impedances will also affect the current that flows around the circuit too.

Naturally too much or too little of anything can present a problem. Utilizing a poorly implemented preamplifier outputs can be a problem when coupled to a high powered amplifier with relatively low voltage gain and consequently a high input sensitivity, which is the amount of voltage needed from the preamp to drive the amplifier to full unclipped power. Suppose you have a preamp that can deliver 1 volt RMS from its outputs before clipping; if you pair this with a high powered amplifier wit a low gain expecting a huge boost in headroom, all youre going to do when you push harder is get garbage as it clips the signal to the amplifier or potentially trip its protection circuits.

Are you interested in purchasing a separate pre amplifier? then youre probably also interested in the specs of the amp as well. This little detail often overlooked, can be the difference between a truckload of distortion or noise and nice clean sound. Take care in your selection, and youll avoid the problems outlined above.

Happy listening!

 

[koushik]

No problems or concerns. Go ahead and connect. The usual line voltage is above 2 volts and amps can handle higher input voltages. The input sensitivity refers to the minimum voltage requirement and not the maximum.

Just the opposite that you know. i/p sensitivity is the input signal voltage at which Amp runs at it rated power unclipped.

 

[sanj]

Hi sanj,

Any device which generates a voltage has what is called an output impedance. The output voltage from the source is developed across the input impedance of the destination (often called the load impedance, or simply the load). However, the input and output impedances will also affect the current that flows around the circuit too.

Naturally too much or too little of anything can present a problem. Utilizing a poorly implemented preamplifier outputs can be a problem when coupled to a high powered amplifier with relatively low voltage gain and consequently a high input sensitivity, which is the amount of voltage needed from the preamp to drive the amplifier to full unclipped power. Suppose you have a preamp that can deliver 1 volt RMS from its outputs before clipping; if you pair this with a high powered amplifier wit a low gain expecting a huge boost in headroom, all youre going to do when you push harder is get garbage as it clips the signal to the amplifier or potentially trip its protection circuits.

Are you interested in purchasing a separate pre amplifier? then youre probably also interested in the specs of the amp as well. This little detail often overlooked, can be the difference between a truckload of distortion or noise and nice clean sound. Take care in your selection, and youll avoid the problems outlined above.

Happy listening!

Hi Hydrovac,

Thanks for explaining in detail,in nut shell considering my Rotel's input sensitivity which is 1volt/33K ohms so i have to look for pre-amp which has out put sensitivity of 1volt/33kohm will only match, and in my parasound FET900 preamp the specs says :
Max.Output :10volt before clipping, Minimum Output is not mentioned.

so what does it mean and is it good mach with my power amp technically?.

Rgds.
sanjay

 

[hydrovac]

Hi Hydrovac,

Thanks for explaining in detail,in nut shell considering my Rotel's input sensitivity which is 1volt/33K ohms so i have to look for pre-amp which has out put sensitivity of 1volt/33kohm will only match, and in my parasound FET900 preamp the specs says :
Max.Output :10volt before clipping, Minimum Output is not mentioned.

so what does it mean and is it good mach with my power amp technically?.

Rgds.
sanjay

The Pre-Amp is designed to be a very clean signal voltage and take care of any signal modifications you might want to make to the signal (music) BEFORE the signal goes to the amplifier.

Pre-amp signal is usually LOW, it was designed to be low so there is less distortion at this stage. Home pre-amps usually operate with about 1 to 1.5 volts of output, the idea was to keep the voltage down as low as possible to keep the distortion down as low as possible in the pre-amp stage and then after the signal leaves the pre-amp we let the amplifier do what it does best.

Clipping is when the any of many variables are exceeded, under powering, distortion, "dirty" power. all an amplifier does, is amplify whatever signal is put into it..

Too much signal voltage into the amp the system will get loud too soon on the volume swing. Some people find the added voltage an advantage cause now they think their amp will play louder! NOT TRUE! The amp will still have its maximum output power and it will not change in most cases of the amps max drive can be achieved, and they only notice that with the higher voltage the system gets loud at 10 (on the volume scale) and you used to have to turn it up to 20..!!

 

[sunder]

Input sensitity is the max input signal voltage that drives the amp at max output. You will want to match it with the output level of whatever is before the amp in the audio chain. What is the signal out put level from your AVR?

Often overlooked by those unaware of its importance, this one parameter can have significant implications on actual performance when an amplifier is introduced into an AV system. Understanding the impact that different levels of voltage gain can have in your system can very well be the difference between poor sound and getting the most out of an external amplifier.

Reading the above, it may seem that those who seek the additional output of an external amplifier are caught in a vicious catch 22. Certainly if you happen to have a combination of an AVR with a poor preamplifier output section combined with ultra-high sensitivity loudspeakers, you may want to reconsider some of your hardware choices; beyond that, careful selection can help ensure that you get the most out of your equipment. Further, it should be noted that while some low end receivers may not be the ideal starting point for adding separate amplifiers.

Long story short: if you want to add power to a lower end receiver with pre-outs, you probably want something with a better than average amount and a low input sensitivity.
The preamp section of this receiver should have no problems cleanly driving any external power amplification to its full output capability.

hope this helps

happy days mate

Hi hydrovac, generally we can measure the output signal voltage by the meter, but can we measure for what could be the input sensitivity of an amp? we can only rely on the specification available with the electronics, isnt it? In some vintage model amps, we could not get the tech. specification and we will not be sure about that. When we match and try to get the best sound, Should the output sensitivity of the source be higher than the input sensitivity of an amp? Please clarify.
Thank you,
Regards.
sunder.

 

[hydrovac]

Hi hydrovac, generally we can measure the output signal voltage by the meter, but can we measure for what could be the input sensitivity of an amp? we can only rely on the specification available with the electronics, isnt it? In some vintage model amps, we could not get the tech. specification and we will not be sure about that. When we match and try to get the best sound, Should the output sensitivity of the source be higher than the input sensitivity of an amp? Please clarify.
Thank you,
Regards.
sunder.

You "could" use just a AC volt meter...but the reason you need a scope is to make sure your signal is not being distorted...A distorted signal will show erroneous Gain..since the harmonics will be averaged in to the RMS sum..thus showing a larger Gain than what is really there...

Try putting a 100mV to 200mV input signal into the amp...you can use a CD player as a signal generator..since you can buy CD's with test audio signal on them...then put the track on repeat..

You can download a cheesy free shareware oscilloscope for your PC that works for the audio band..you simply use your line-input on your sound card...just make sure to use a good blocking cap...

The input sensitivity doesn't in any way mean that's the maximum or limit you can put in. What it really means is that's the minimum level necessary to get full power out of the unit at a certain point of the volume control. You can even put in less, but you might not get full rated power out, or might have to turn the volume knob beyond the reference point (whatever that is).

Amplifier manufacturers usually back engineer the amplifier voltage gain such that it will achieve full output when driven by a standard level input signal of between 1 and 2Vrms. This is referred to on specification sheets as the SENSITIVITY of the amplifier. This does not mean that one has any more or less output power capacity than the other. It simply means they need to be driven with different input signal levels to achieve full output.

Hope this clarifies.....

 

[sanj]

The Pre-Amp is designed to be a very clean signal voltage and take care of any signal modifications you might want to make to the signal (music) BEFORE the signal goes to the amplifier.

Pre-amp signal is usually LOW, it was designed to be low so there is less distortion at this stage. Home pre-amps usually operate with about 1 to 1.5 volts of output, the idea was to keep the voltage down as low as possible to keep the distortion down as low as possible in the pre-amp stage and then after the signal leaves the pre-amp we let the amplifier do what it does best.

Clipping is when the any of many variables are exceeded, under powering, distortion, "dirty" power. all an amplifier does, is amplify whatever signal is put into it..

Too much signal voltage into the amp the system will get loud too soon on the volume swing. Some people find the added voltage an advantage cause now they think their amp will play louder! NOT TRUE! The amp will still have its maximum output power and it will not change in most cases of the amps max drive can be achieved, and they only notice that with the higher voltage the system gets loud at 10 (on the volume scale) and you used to have to turn it up to 20..!!

Hi Hydrovac,

Thanks for your explanation so please suggest if my preamp and power amp is good match or not considering its specs.

rgds.
sanjay

 

[hydrovac]

Hi Hydrovac,

Thanks for your explanation so please suggest if my preamp and power amp is good match or not considering its specs.

rgds.
sanjay

It appears as though you are not following the posts keenly. Please go through the previous posts for further clarifications, if any.

Rgrds
Krishna Reddy

 

[sunder]

You "could" use just a AC volt meter...but the reason you need a scope is to make sure your signal is not being distorted...A distorted signal will show erroneous Gain..since the harmonics will be averaged in to the RMS sum..thus showing a larger Gain than what is really there...

Try putting a 100mV to 200mV input signal into the amp...you can use a CD player as a signal generator..since you can buy CD's with test audio signal on them...then put the track on repeat..

You can download a cheesy free shareware oscilloscope for your PC that works for the audio band..you simply use your line-input on your sound card...just make sure to use a good blocking cap...

The input sensitivity doesn't in any way mean that's the maximum or limit you can put in. What it really means is that's the minimum level necessary to get full power out of the unit at a certain point of the volume control. You can even put in less, but you might not get full rated power out, or might have to turn the volume knob beyond the reference point (whatever that is).

Amplifier manufacturers usually back engineer the amplifier voltage gain such that it will achieve full output when driven by a standard level input signal of between 1 and 2Vrms. This is referred to on specification sheets as the SENSITIVITY of the amplifier. This does not mean that one has any more or less output power capacity than the other. It simply means they need to be driven with different input signal levels to achieve full output.

Hope this clarifies.....

hydrovac, thank you for the detailed explanation. But the testing which will be easy for a technician and little difficult to a consumer.
Regards.

 

[Kumar442244]

Reviving this old thread again.

This is one such topic which i fail to understand no matter how much effort i put into it. And I am sure that there are lot of folks in this forum who would have encountered this issues around pre- to power amp matching, what I am not sure is that how many of us got it right in first few steps.

I have an integrated amp which has a pure class A pre amp section with sensitivity on 920mV which I am planning to use as a pre-amplifier to drive my speakers.
Below is the specs for the preamp out:-


Need some suggestions as to what numbers in Power amp should I be looking at to match the above mentioned preamp configurations?
alongside, would be great if some suggestions can follow in too.

Happy diwali in advance.. Cheers

 

[IndianEars]

Hi Kumar,

Your preamp will drive most Power Amplifiers, even though the Output Voltage is a bit on the lower side.

Just make sure that your Power Amp has an input sensitivity of 0.92 Volts ( ie 920 milli Volts) or less... eg 0.77 Volts input sensitivity will be even better.

 

[IndianEars]

SENSITIVITY & IMPEDANCE

PART-1 Understanding Input Sensitivity

Questions posed by Woody & Sanj, (revived by Kumar442244) are common & should not perplex anyone. I will attempt to answer them as well as clarify - in very simple language - the concepts involved.

I will split my Response in 2 separate posts ... Part-1 for Input Sensitivity & if there is an interest, Part-2 for Input & Output Impedance.


1. Input Sensitivity of a Amplifier is The voltage required to drive the amplifier to its maximum output power.

INPUT SENSITIVITY:

(Input Signal) ---------> AMPLIFIER ----> SPEAKER
1.65 Volts (Full Amplifier Power)
Hence if:

a. Woody's B&K EX442 amp has an Input sensitivity of 1.65 Volts, it means the B&K needs 1.65 Volts input signal to deliver its full / rated output power.

Woody's Marantz must feed the B&K (ie Marantz Output to B&K input) an ouptut of 1.65 Volts, to enable the B&K to deliver its Full Power to the Speakers.

MARANTZ ----> (1.65 V) B&K -----> To Speakers

Woody, you have to look at the OUTPUT specification of the Marantz Pre amp output. You have stated the Marantz's INPUT sensitivity, which is not the required info.
Hence, your query cannot be answered.


b. sanj's Rotel power amp has an input senstivity of 1 Volt/ 33 k ohms.
This means it requires an input signal of 1 Volt to be able to deliver its full output power into the speakers connected to it.

What ever Preamp you buy, you will need to ensure that your new pre-amp can deliver an output of atleast 1 Volt. (Most pre amps will do this).

If the Pre amp delivers even more than what is required, its welcome... No Harm.
It means that your Volume Control knob will not need to be turned to full Volume (eg. 2 o-clock position may be enough), for the power amplifier to deliver its full power.


PRACTICAL EXAMPLE
As a Practical example, my Audio Research Ref 6 Pre Amp has the following Key specifications.

My Gamut Monoblock Power Amps (200 Watts RMS into 8 Ohms) have in input sensitivity of 0.7 Volts. This means they need 0.7 Volts input signal to deliver their full output power of 200 Watts.

Lets interpret these SPECS from the Input Sensitivity point of view:

RATED OUTPUT
2V into 200K ohm load
Maximum output capability is 70V RMS at less than 0.5% THD at 1kHz.

DISTORTION
Less than .01% at 2V RMS BAL output.

OUTPUT IMPEDANCE
600 ohms Balanced, 300 ohms Single Ended.
20K ohms minimum load.


So the Pre-amp can deliver upto 70 Volts , but with Higher Distortion.
Its Very happy delivering 2 Volts, with very low distortion.

The Power Amp requires only 0.7 Volts, so the Pre amp is a good match for the Power Amps (in terms of input sensitivity).

 

[Kumar442244]

Thanks @IndianEars for a detailed yet easy-to-understand explanation.

My takeaway from this is that I need to look for the a PA which is <1V input volt.
Any suggestions on the PA with this specs?

 

[ssf]

@IndianEars

Also, if you don't mind my asking, what does the volume control on the pre-amp do ? Increase the voltage ? If so, is the 2 volts at a lower volume position and the 70 volts at it's highest point ? Which is better, keeping the preamp volume higher or amplifier gain higher ? Thanks.

 

[Hiten]

Volume control can not increase voltages. It just attenuates the voltage required for next stage. 70V denotes how much the preamplifier is capable of amplification.

 

[IndianEars]

Thanks @IndianEars for a detailed yet easy-to-understand explanation.

My takeaway from this is that I need to look for the a PA which is <1V input volt.
Any suggestions on the PA with this specs?

Yes, you are correct that you need to buy a Power Amplifier with an input sensitivity of <1 Volt. More than 80% of power amplifiers will meet this specification.

However, there are other Far more important criteria to select your Power Amplifier. These Include:

• Maximum Power Out ( Ideally linked to the Speakers you will use and the Room Size)
  
  
• Solid State Or Valve (Each have their strengths and sonic signatures)
  
  
• The Sound Of Your Power Amp. (Every Power Amp Sounds Different and you want to pick a Power Amp that in conjunction with your Speakers, delivers the "sound" ie Tone, Dynamics, Resolution, etc that you like. )

If I may ask, which Pre-amp are you referring to ? Have you already bought it ? Maybe you can consider an integrated amplifier ?