Pre Outs on Marantz NR1506 suspect?

M

Mathias

Enthusiast
Hello all.

I own a Marantz 1506 receiver that functions as both a preamp in a 2.1 channel system and as the nerve center of a (still incomplete) 5.1 home theater system. I have a pair of JBL590 Tower speakers for the fronts and an ATI 1202 power amp. The speakers are are rated at 6 Ohms (minimum of 4.8 Ohms at 100 hz if memory serves) and 92 db sensitivity. The amp is a very conservatively rated 120 watts into 8 ohms. My room is an 11.5' by 19' by 8.5' (ceiling joists exposed) garage.

Here's the rub: when I connect the ATI amp to my Dark Voice 336se vacuum tube headphone/preamp it gets INCREDIBLY LOUD. I NEVER go past 10:30 on the dial and I like to listen loud. There is more tonal saturation too but its very noisy and the treble is absolutely etched in acid so listener fatigue sets in quick with any brightly recorded material.

With the ATI hooked up to the Marantz using the front L/R preouts I have to crank up the receiver to past 80 on the volume on some recordings! Can that be normal? Also I have to set the gain on my ATI amp (one for each channel) to the max which also, apparently, puts extra strain on the power amp?

Could this be a voltage mismatch between power amp and receiver? Marantz tells me the 1506 puts out between 1.5 and 2 V out of the preamps...reading the latest Audioholics review of a Yamaha receiver the author mentions the "magic" number of 2V as being important. Maybe I'm not getting enough voltage output from the Marantz preout?

I know there is an article on Audioholics about this topic written a few years back but the math is too advanced for a liberal arts dummy like myself so I was hoping someone could offer some insight, albeit slightly modified for the layman/dilettante.

Appreciate any comments/suggestions.
 
lovinthehd

lovinthehd

Audioholic Jedi
Does sound like your headphone pre has a higher output but that doesn't mean the Marantz output level is too low; your amp has a sensitivity rating of 1.3V so the Marantz should be fine. It could even be the headphone pre is too high a level (didn't see any specs with a quick search). The gain adjustment on your amp is just for situations like this, matching up to your pre's output level. I doubt ATI designed the amp where it can't be run without issue with the gain knob within its adjustment range....
 
slipperybidness

slipperybidness

Audioholic Warlord
Hello all.

I own a Marantz 1506 receiver that functions as both a preamp in a 2.1 channel system and as the nerve center of a (still incomplete) 5.1 home theater system. I have a pair of JBL590 Tower speakers for the fronts and an ATI 1202 power amp. The speakers are are rated at 6 Ohms (minimum of 4.8 Ohms at 100 hz if memory serves) and 92 db sensitivity. The amp is a very conservatively rated 120 watts into 8 ohms. My room is an 11.5' by 19' by 8.5' (ceiling joists exposed) garage.

Here's the rub: when I connect the ATI amp to my Dark Voice 336se vacuum tube headphone/preamp it gets INCREDIBLY LOUD. I NEVER go past 10:30 on the dial and I like to listen loud. There is more tonal saturation too but its very noisy and the treble is absolutely etched in acid so listener fatigue sets in quick with any brightly recorded material.

With the ATI hooked up to the Marantz using the front L/R preouts I have to crank up the receiver to past 80 on the volume on some recordings! Can that be normal? Also I have to set the gain on my ATI amp (one for each channel) to the max which also, apparently, puts extra strain on the power amp?

Could this be a voltage mismatch between power amp and receiver? Marantz tells me the 1506 puts out between 1.5 and 2 V out of the preamps...reading the latest Audioholics review of a Yamaha receiver the author mentions the "magic" number of 2V as being important. Maybe I'm not getting enough voltage output from the Marantz preout?

I know there is an article on Audioholics about this topic written a few years back but the math is too advanced for a liberal arts dummy like myself so I was hoping someone could offer some insight, albeit slightly modified for the layman/dilettante.

Appreciate any comments/suggestions.
Yeah, that gain knob is actually better described as an "input attenuation knob". Running it at 100% is removing the attenuation from the circuit, removing the knob from the circuit for all practical purposes.

The simple answer--Don't make this difficult! Can you get the audio to the desired volume with the Marantz? If yes, then you don't have a problem.

These "10 O'clock and 80%" on the volume knob numbers that you are throwing out--these positions are all arbitrary, without getting too technica--all you are doing is adjusting the gain structure--it's all relative to the input voltage.

If the headphone amp is really noisy, then it suggests to me that you have a problem with your gain structure--you are amplifying a lot of noise and killing your S/N.
 
M

Mathias

Enthusiast
Does sound like your headphone pre has a higher output but that doesn't mean the Marantz output level is too low; your amp has a sensitivity rating of 1.3V so the Marantz should be fine. It could even be the headphone pre is too high a level (didn't see any specs with a quick search). The gain adjustment on your amp is just for situations like this, matching up to your pre's output level. I doubt ATI designed the amp where it can't be run without issue with the gain knob within its adjustment range....
Ok. So I gather it's "safe" to run the ATI at full gain. That's reassuring. Thanks for the reply.
 
M

Mathias

Enthusiast
Yeah, that gain knob is actually better described as an "input attenuation knob". Running it at 100% is removing the attenuation from the circuit, removing the knob from the circuit for all practical purposes.

The simple answer--Don't make this difficult! Can you get the audio to the desired volume with the Marantz? If yes, then you don't have a problem.

These "10 O'clock and 80%" on the volume knob numbers that you are throwing out--these positions are all arbitrary, without getting too technica--all you are doing is adjusting the gain structure--it's all relative to the input voltage.

If the headphone amp is really noisy, then it suggests to me that you have a problem with your gain structure--you are amplifying a lot of noise and killing your S/N.
You ask whether I can achieve the desired volume with the Marantz -- yes but only just. It seems odd that I have to turn up the volume to 80 (in some cases) to get a decent spl when the max is 98 -- if the dial is linear than I"m at over 80% of output. I do wonder if the output voltage of the Marantz preouts is insufficient. Thank you for your reply.
 
lovinthehd

lovinthehd

Audioholic Jedi
You ask whether I can achieve the desired volume with the Marantz -- yes but only just. It seems odd that I have to turn up the volume to 80 (in some cases) to get a decent spl when the max is 98 -- if the dial is linear than I"m at over 80% of output. I do wonder if the output voltage of the Marantz preouts is insufficient. Thank you for your reply.
Your volume dial is in dB, it's logarithmic, not linear (for every 3dB you're doubling the wattage output). 80 on the absolute scale (which you appear to be using rather than the relative scale) would be close to movie reference level, which is quite loud (assuming you calibrated your unit using the Audyssey feature or manually calibrated it). You don't necessarily want to use every notch on the volume dial, either.
 
slipperybidness

slipperybidness

Audioholic Warlord
You ask whether I can achieve the desired volume with the Marantz -- yes but only just. It seems odd that I have to turn up the volume to 80 (in some cases) to get a decent spl when the max is 98 -- if the dial is linear than I"m at over 80% of output. I do wonder if the output voltage of the Marantz preouts is insufficient. Thank you for your reply.
Like I said, it's all relative! Typically, volume controls are logarithmic, they must be on the log scale to make a volume change "seem" linear to the human ear.

You need some final voltage to drive the speakers to a satisfying spl (and current, but let's make it simple and focus on voltage gain only here). So, how much gain (i.e. gain = signal amplification) will you need to get to that final voltage that you need?

Well, that depends on--What is the amplitude of the source signal voltage, and how much gain does the pre-amp stage provide to the amp? That will tell you how much gain the amp must provide to hit the desired spl.

So, some sources have smaller signals. Turntables are a perfect example of a low signal. When I use my AVR phono input, I must turn the volume knob up ~30% higher than when I use my CD input, because the CD input has a "hotter signal", i.e. the amplitude of the CD source signal is larger than the phono signal. If you had a function generator, an O-Scope, and a general knowledge of amplifier gain, it would be trivial to show a real world example on an O-Scope--We did this for my solid state class at the community college.

There is nothing wrong with the Marantz pre-outs! If anything, there may be something wrong or more likely mis-matched in the gain structure when you try to use your headphone amp as a pre-amp.

Do you understand, saying "It seems odd to turn the Marantz to 80% to get to the desired spl" would be the same thing as saying "It seems odd to press the gas peddle in my car to 80% to achieve my desired speed"!


So, you have 3 options here. And option #1 is my rec:

1) Turn the knob to get the desired level, trust our judgment, and don't worry about it and continue to enjoy your system.
2) Go educate yourself on gain structure focusing on the items that I mentioned above. After you educate yourself, you will understand why option #1 is the BEST answer that you will get on this topic.
3) Continue to blindly question the good advice that you have gotten, and start chasing ghosts and problems that don't exist on your system. Good luck with that.
 
Last edited:
P

PENG

Audioholic Slumlord
Ok. So I gather it's "safe" to run the ATI at full gain. That's reassuring. Thanks for the reply.
Not only it is safe to do so, it is normal as well. Many power amps don't come with volume knob so consider an amp with volume knob set to maximum = power amp that comes without volume knob.
 
slipperybidness

slipperybidness

Audioholic Warlord
Not only it is safe to do so, it is normal as well. Many power amps don't come with volume knob so consider an amp with volume knob set to maximum = power amp that comes without volume knob.
Agreed, I prefer to use the more accurate term of "input attenuator" or perhaps "gain adjustment knob" rather than "volume knob", but in practice these are typically interchangeable terms.

But, whatever you call it, the bottom line is that if your POWER AMP has a gain adjuster/input attenuator/volume knob, then that is a LUXURY for a power amp (by no means a necessity). When you do have that luxury, it gives you more flexibility to try to get your gain structure configured correctly.
 
P

PENG

Audioholic Slumlord
Agreed, I prefer to use the more accurate term of "input attenuator" or perhaps "gain adjustment knob" rather than "volume knob", but in practice these are typically interchangeable terms.

But, whatever you call it, the bottom line is that if your POWER AMP has a gain adjuster/input attenuator/volume knob, then that is a LUXURY for a power amp (by no means a necessity). When you do have that luxury, it gives you more flexibility to try to get your gain structure configured correctly.
My bad, gain adjuster sounds good.
 
P

PENG

Audioholic Slumlord
According to the ATI 1202 manaul

Input Sensitivity for Full Rated Power: 1.3 Volts

So OP can definitely relax and enjoy the music.
 
slipperybidness

slipperybidness

Audioholic Warlord
According to the ATI 1202 manaul

Input Sensitivity for Full Rated Power: 1.3 Volts

So OP can definitely relax and enjoy the music.
You know, I just reviewed a couple posts and the OP seems to say "I need to push the knob past 80 on some recordings".

That suggests that "some recordings I don't have to push past 80". So, that suggests that his source material may also be at different peak levels.

So, he may have other issues going on here, but not the Marantz as root of the problem.
 
M

Mathias

Enthusiast
Like I said, it's all relative! Typically, volume controls are logarithmic, they must be on the log scale to make a volume change "seem" linear to the human ear.

You need some final voltage to drive the speakers to a satisfying spl (and current, but let's make it simple and focus on voltage gain only here). So, how much gain (i.e. gain = signal amplification) will you need to get to that final voltage that you need?

Well, that depends on--What is the amplitude of the source signal voltage, and how much gain does the pre-amp stage provide to the amp? That will tell you how much gain the amp must provide to hit the desired spl.

So, some sources have smaller signals. Turntables are a perfect example of a low signal. When I use my AVR phono input, I must turn the volume knob up ~30% higher than when I use my CD input, because the CD input has a "hotter signal", i.e. the amplitude of the CD source signal is larger than the phono signal. If you had a function generator, an O-Scope, and a general knowledge of amplifier gain, it would be trivial to show a real world example on an O-Scope--We did this for my solid state class at the community college.

There is nothing wrong with the Marantz pre-outs! If anything, there may be something wrong or more likely mis-matched in the gain structure when you try to use your headphone amp as a pre-amp.

Do you understand, saying "It seems odd to turn the Marantz to 80% to get to the desired spl" would be the same thing as saying "It seems odd to press the gas peddle in my car to 80% to achieve my desired speed"!


So, you have 3 options here. And option #1 is my rec:

1) Turn the knob to get the desired level, trust our judgment, and don't worry about it and continue to enjoy your system.
2) Go educate yourself on gain structure focusing on the items that I mentioned above. After you educate yourself, you will understand why option #1 is the BEST answer that you will get on this topic.
3) Continue to blindly question the good advice that you have gotten, and start chasing ghosts and problems that don't exist on your system. Good luck with that.
Again, thank you for your input -- I very much appreciate it. I think you misunderstand the intent of my response -- I am in no way "questioning" your good advice. I am simply asking more questions in order to gain (pun intended) more understanding NOT disagreeing with your insights. To learn we ask questions; when our questions are answered, rather than being satisfied, we are driven to ask more questions. Does that make sense? I respect your willingness to help and the evident wealth of knowledge you have on the subject and am essentially convinced by what you say.

I simply thought it was odd that the Marantz would have to be pushed near its limit to achieve the SPL I desire -- my sources are a CD player and or Spotify streaming through Chromecast Audio btw. To extend the car analogy you introduced, if I had a new Mustang GT I wouldn't want to have to push it to within 20% of its upward limit in order to feel that I was finally going fast. But as you say if the reading is logarithmic not linear than I'm not near the ceiling anyway. Perhaps also this perception is due to my Preamp's comparatively high gain structure (probably suspect, as you suggested). Or maybe I'm half deaf! Anyway, looks as if I have little to worry about -- I will crank it up to 80 on the dial, enjoy the music and read up on circuits. Appreciate your time and input.
 
M

Mathias

Enthusiast
According to the ATI 1202 manaul

Input Sensitivity for Full Rated Power: 1.3 Volts

So OP can definitely relax and enjoy the music.
Thank you Peng. Looks like a consensus opinion. I'll stop fretting.
 
slipperybidness

slipperybidness

Audioholic Warlord
Again, thank you for your input -- I very much appreciate it. I think you misunderstand the intent of my response -- I am in no way "questioning" your good advice. I am simply asking more questions in order to gain (pun intended) more understanding NOT disagreeing with your insights. To learn we ask questions; when our questions are answered, rather than being satisfied, we are driven to ask more questions. Does that make sense? I respect your willingness to help and the evident wealth of knowledge you have on the subject and am essentially convinced by what you say.

I simply thought it was odd that the Marantz would have to be pushed near its limit to achieve the SPL I desire -- my sources are a CD player and or Spotify streaming through Chromecast Audio btw. To extend the car analogy you introduced, if I had a new Mustang GT I wouldn't want to have to push it to within 20% of its upward limit in order to feel that I was finally going fast. But as you say if the reading is logarithmic not linear than I'm not near the ceiling anyway. Perhaps also this perception is due to my Preamp's comparatively high gain structure (probably suspect, as you suggested). Or maybe I'm half deaf! Anyway, looks as if I have little to worry about -- I will crank it up to 80 on the dial, enjoy the music and read up on circuits. Appreciate your time and input.
No problem. Asking questions, chewing on the response, and asking more questions is always a good thing!

It just kind of seemed like you were re-asking the same questions and perhaps expecting a different answer--that isn't a good thing.
 
P

PENG

Audioholic Slumlord
You know, I just reviewed a couple posts and the OP seems to say "I need to push the knob past 80 on some recordings".

That suggests that "some recordings I don't have to push past 80". So, that suggests that his source material may also be at different peak levels.

So, he may have other issues going on here, but not the Marantz as root of the problem.
I noticed that too, but I assume he knew the effects due to different recordings, most people do.
 

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