Amp Sensitivity Question

mark090852

I've been doing a little reading and research on amps and was wondering about something. I see that the Yamaha Aventage receiver that I just purchased has pre-out output levels of 1 volt. When looking at the specs of different amps, the input sensitivity varies quite a bit. I have seen some that are as low as a few hundred millivolts at rated load at 8 ohms, up to about 2 volts at rated load at 8 ohms. Does that mean that if I had an amp with a listed input sensitivity higher than the pre-out level of my receiver, I would not be able to be fully utilized the rated power of the amp?

[Deleted User]

In order to maximize the signal-to-noise ratio it is probably a good idea to select a power amplifier that has an input sensitivity fairly close to 1.0 volt. However, output and input impedances are also important for linear frequency response. There should be a ratio of at least 1:10 with 1:20 even better.

smglbrth

I also find this an interesting topic. I've noticed that same thing with input sensitivity with amps. My Reference 200.2 is 1.4 volts, my PT3 Series II preamp doesn't list an average output but has a max output of 8 V rms.

Wouldn't this has something to do with trying to find just that right "match"? I know manufacturers make their components "mate" together, most of the time. I would think mixing/matching different components from different companies makes it harder to find just that right sound verses buying all the same brand. However, it makes the audio world go 'round and 'round...

tonyb

smglbrth wrote: »

I also find this an interesting topic. I've noticed that same thing with input sensitivity with amps. My Reference 200.2 is 1.4 volts, my PT3 Series II preamp doesn't list an average output but has a max output of 8 V rms.

Wouldn't this has something to do with trying to find just that right "match"? I know manufacturers make their components "mate" together, most of the time. I would think mixing/matching different components from different companies makes it harder to find just that right sound verses buying all the same brand. However, it makes the audio world go 'round and 'round...

Yes....

What that 1.4 volts means to your 200.2 is that it takes 1.4 volts to drive the amp to full power. Mismatches in impedance between pieces, and even cables, can make one piece sound dull or flat and another too lively and distorted. Why you need to turn the volume way up over a previous piece to get the same levels. This is also why one piece can sound like dog poo in one system and like a God send in another. Same applies to cables and why one set of speaker cables can sound so different in different systems.....aside from the other aspects.

That's also why you have to take reviews with a grain of salt, pay attention to the associated gear used, and the reviewers preferences.

In audio, hype sells....too many times a piece comes out and it's reviewed as the second coming of Jesus. You order it, put it into your system and are less than impressed. You immediately lay blame on the piece without investigating such things as impedance mismatches. When we talk system "synergy", this has a lot to do with it.

Reviews then read as...this piece sucks....that piece is great, leaving you even more confused. Nothing in audio is absolute, too many variables with gear and preferences to say what is the cream of the crop and what is horse ****. You have to do your research, try a few things if you want to move forward.

I can offer 2 examples of this in the past year and one recent. Dougs cables....everyone raved about them so I thought I'd give them a whirl. First the Furez standard cable Doug sells. Eh....not very good in my system. It even sounded like I had a huge impedance mismatch with the amp. Borrowed some Alpha's from Brian, Dougs higher end cables which some here raved about. Same thing was happening but to a slight lessor degree. Got in the AZ Satori's and bam, instant synergy. Now...is that because Dougs cables sounded like poo or just a bad match for my system ? See how reviews can be one side or another....without knowing the specifics ?

Second is with the newly acquired Joule la-100. I was told it may need a fresh re-tube because it just didn't sound up to snuff, good....just not where it should be. Got it, slid it in place, and again, bam....instant synergy with it's playmates. My amp even sounds better now. I was scratching my head wondering wtf could be happening given I was expecting a not so stellar sound. Consider too, that impedance mismatches within your system can also make your speakers sound less than appealing, and you'll blame the speakers. Right ?

Like I said, pay attention to reviews, take them with a grain of salt, take note of associated gear and cables used, and the reviewers preferences. Hang around here long enough to get to know the members who's ears you trust and may have the same preferences as you. That way when they try a new piece, their review to you is going to carry much more weight.

tonyb

I might add, it takes some experience to be able to distinguish between what could possibly be an impedance mismatch and what is just a characteristic of the piece of gear. Once your ear is trained to listen for it, it becomes easier to pick out.

mhardy6647

impedance mismatch = tone control

smglbrth

mhardy6647 wrote: »

impedance mismatch = tone control

Dang, now that's funny right there...

Carl249a

Hi Mark, I also have a Yamaha reciever ( RX-A3040 ). Had started looking at amps only to find out my pre outs are 1 volt. Can't imagine why Yamaha did this on an expensive reciever. All amps I've looked at need more than that. Let me know if you find a solution.

mark090852

Hi Carl. Here is my take on it. My receiver's preouts have a maximum output of 1 volt. I believe that maximum would only be reached with the volume control at maximum volume, or high enough that there are spikes approaching maximum output. Realistically, we never run our gear at full volume. We modulate the volume resulting in a lower than 1 volt output (except for the spikes) from the preouts. When the specs of an amp list the input sensitivity at 1.5 volts, they are listing the input voltage requirement to result in the full rated power of the amp at an 8 ohm load. So a 1.5 volt signal from the preouts into the amp would result in the full power signal to the speakers through the speaker wires. However, since we don't run our gear anywhere near full volume, we are always using less than the full power of the amp.

In my case, I have preouts putting out less than 1 volt because I don't have the receiver volume control turned up to full volume. That signal is sent to a two channel amp (with an input sensitivity of 1.5 volts) rated at 300 watts per channel at an 8 ohm load. The amp will perform quite well even though it will never use its full 300 watts per channel since the input voltage will never exceed 1 volt. I could be completely wrong on all of this, and hopefully others that are more knowledgeable will enlighten us.

tonyb

Mark pretty much has it right. That scenario is also why your speakers may not sound as good at lower volumes as it does when you start turning it up.
Separate decent quality dacs usually have more line voltage as do many pre amps.
Normally for HT this doesn't matter much since volumes are typically higher.

gmcman

Very interesting topic indeed, I also have a B&K 200.2 and may have a slight mismatch with my VTL 2.5 preamp. Mind you it sounds very good, but despite the tube rush, I think something else is going on.

My Ref 50 pre is practically dead quiet when paired to the amp, but with the VTL it has a slight buzz...nothing terrible, but I can just barely hear it from 10' away.

I don't know what the output voltage is of the VTL, I do know that some tubes are worse than others but could be the nature of the preamp.

I've been over this situation already in regards to tubes, I have a few pairs that work well from other members...it's MUCH quieter than when I first got it so I'm leaning on a impedeance mismatch or something else.

Not trying to hijack the OP's thread, but trying to learn about this as well.

tonyb

A slight buzz can be a tube issue or a grounding issue as in a ground loop. Also when we talk about mismatches in impedance, cables can also have an affect in these matters. That's why some cables sound great in one system and lacking in others.

If you don't mind me askin', what cables are you using with the VTL and speakers ? Is the VTL plugged into the wall or a power conditioner ? All the tubes solid, nothing ending it's lifespan ?

You have to match volume levels between the ref 50 and VTL to determine if your having a loss of drive. Personally I think that VTL has plenty of voltage to drive your amp, your issues may be elsewhere.

mhardy6647

I dunno, for me the root cause of a slight buzz is usually drinkin' a beer on an empty stomach.

rimshot!

gmcman

tonyb wrote: »

If you don't mind me askin', what cables are you using with the VTL and speakers ? Is the VTL plugged into the wall or a power conditioner ? All the tubes solid, nothing ending it's lifespan ?

IC's are Shotgun S1, both from CD to pre, and pre to amp, S1 to speakers. VTL is plugged into wall, all tubes are good, some are noisier than others but the quietest ones I have are the 4003 and 4024 Mullards, both together have the least amount of noise which is still audible from the seating position.

I believe when I plugged it into the power conditioner the noise was just slightly higher...I've moved so many cords around it's hard to keep track.

I'm not well versed in a scope but I have an older Tek 465B I could fire up as well as a signal generator if someone wanted to PM me and walk me through a troubleshooting test.

tonyb

You try different positions on the impedance boxes with those S1's ? Try a cheater plug on the amp, not the pre. Have you tried a different power cord with the VTL ? Some tubes are inheritably more noisy than others , not much you can do about that. A buzz sound though says ground loop to me.

gmcman

Cd player is on one outlet, amp and preamp on another outlet but same circuit, they were the only 3 components turned on and I had a faint buzz in the speakers, even with the preamp off.

So I unplugged the Panamax from the wall and the buzz stopped. I have the TV, AVR, cable box, Turntable, X-Box and phono stage plugged into the Panamax. I was thinking it might be the cable box, but this one is the newer quantum box with a DC power supply but I will look into this later today.

gmcman

I don't want to derail this thread too far away from being an amp sensitivity issue so I will start another concerning my possible ground issue.