Is Your CD Player/Changer Too 'Hot'?

I've recently had an experience, personally, that has affected how I set up my CD player to amp/receiver connection. The following visual explains:

 

You could always get a preamp/amp that can handle a 2V output from a (loud) CD/SACD player. I just randomly checked the specs on the McIntosh MCD-500, and the fixed unbalanced output is 2 volts; variable is 0-6.

Balanced connections also generally can take at least twice as much level.

 

That is a good but expensive alternative. My solutions, to follow, have the 99% in mind.

1. Harrison Labs RCA attenuators: http://www.parts-express.com/harrison-labs-12-db-rca-line-level-audio-attenuator-pair--266-244 (also avail in 3, 6dB variety)

2. A second-hand player like mine, the Sony CDP-C705, with variable outputs controlled by headphone vol. knob. With a test CD producing a full-scale sine and a volt meter, I was able to set output down to 1V per ch - just above 12 o'clock position.

Most typical receiver inputs are expecting only 150-200mV RMS from a CD/DVD, and cutting that output down prevents even the loudest CDs from "squaring out".

Let the objective CD comparisons begin!

 

This happened with my vintage Heathkit AR-29 receivers and AA-29 amplifiers. A CD input overloaded the preamps.

Fortunately, the Heathkits have input adjustment pots ahead of the preamps so I was able to turn it down to an acceptable level.

Doug

 

How common could this situation possibly be? The last thing we need is more gadgets (line level attenuator) in the chain or vintage CD players. Yikes.

 

I'n not sure I understand it. My CD player has a variable output. In the manual, they say I should set it at the max. Does this mean it can be too "hot"?

 

Yeah, I imagine this is primarily an issue with vintage gear. I'd be surprised if modern gear couldn't handle the output of any CD player (but I've been surprised before).

 

That's just the ol' 'louder is better' mentality. They conveniently forget that you own a volume control. lol!

Another word starting in'vol..' guided my quest for getting the best sound out of existing equipment. It ends in 'tage'.

My CD player puts out 2.5V max(via fixed, and via variable outs set to max). That's over five times what my receiver line inputs expect to see(147-200 mV).

With the aforementioned test CD full scale tone and a voltmeter, I was able to get a peak reading of 1.0V per channel from the player.

Certainly, I now have to raise my receiver volume a little higher than before, but I'm hearing more detail from my CDs, especially the deep bottom and the highs. Plus, I can really crank my volume - when I need to - and not hear any distortion or lose any detail.

If we start gain staging sound systems in terms of voltages instead of how loud it sounds, we won't believe what we've been missing sonically. It starts with matching the output of one component with what the next is expecting to "see" coming in. This applies to home stereo components as much as to a live P.A. in Madison Square Garden.

 

The CDP-C705 (circa 1990) could be characterized as operating in the +4 dBu range (as opposed to -10 dBV). +4 dBu is generally characterized as "professional line level" and is common with studio gear. Consumer gear that correctly operates in the -10 dBV range would not need an attenuator to interconnect with other gear that operates in the -10 dBV range.

While you no doubt did the right thing attenuating the signal coming out of that 24 year old CD player, most people will not find themselves in your situation. I can't even speculate why the CDP-C705 was designed to generate that hot a line level signal.

EDIT: More info on line levels here.

EDIT2: It appears the CDP-C705 has a "Level File" feature that will normalize the output level of all tracks played from all disks in the changer. This might explain why the fixed level is so hot. There's lots of gain there for "soft" CDs. Oh man, this was pre-Loudness-Wars player for sure.

 

That's what I'm thinking, too. All these people about here who worry about something as trivial as an AC outlet and AC cable, and that's not even in the analogue signal pass. An attenuator really is in the signal path and will have an effect.

 

Honestly I use the Harrison Attenuators of -12 dB on my Rega Planet 2000. I don't really notice too much of a difference, other than the volume of course. I've got my speakers in close proximity out of need for space, coupled with a really loud CD, (ie Songs for the Deaf by Queens of the Stone Age), and the fact that a common problem with the Fisher 500c is the volume pot at very low levels aren't entirely perfectly equal on the left and right channels, it just bugged me to death.

I haven't actually noticed it overloading my receiver, it was just I couldn't get the volume loud enough to get past the point of unequal volume without blowing my ears out on specific CDs. That was worth 30 bucks for me, at least.

 

My problem is that my aforementioned Sony CD changer has some serious logic control problems - especially when shuffling a carousel full of CDs!

IE: After shuffling ok for a few songs, it will suddenly stop playing in the middle of a track. Or, it will get stuck in shuffle mode, cycling through the five disc icons rapidly ad infinitum, until I either press stop or turn the deck completely off and back on.

Hey, I 'Macklemored' this thing from a THRIFT SHOP for only 8 bucks, so what could I expect? LOLOL!

 

Absolutely.

-=-
Something like a CD player should NOT produce a signal that is too hot, that is bad manufacturer.
OTOH however a receiver SHOULD be able to handle a signal that is too hot. As long as it isn't ridiculously hot.

In my opinion.

 

Review my illustration and keep in mind: Most receivers have a range of input sensitivity and do not automatically adjust for very high or very low input signals.

 

Correctly designed professional audio equipment will provide +4 dBm into a 600 0hm load.

Since the IHF has left and gone away, like Joe DiMaggio, there is no official correct for consumer gear. It is a rough consensus. Generally 775mV into no lower than 50 k ohms is to be expected, but higher is common.

 

So I read that wiki on pro and consumer line levels and I think I have my player in the ballpark.

I arbitrarily set the peak output voltage to 0.5V/channel using the full scale 1k Sine wave(track #8 on the Autosound 2000 CD) and a multimeter.

According to the diagram under Nominal levels:
UseNominal levelNominal level, VRMSPeak Amplitude, VPKPeak-to-Peak Amplitude, VPP
Professional audio+4 dBu1.2281.7363.472
Consumer audio−10 dBV0.3160.4470.894

I'm about .053V over where I should be: 0.5V - Peak amplitude(Vpk) for consumer(0.447V) = .053V. Not bad!
.5V puts the headphone/variable output knob at around 11 o'clock on my particular Sony changer, for anyone else with one who wants to set theirs.

Receiver volume knob movement is proportionate to the amount of change I hear when adjusting it - not too twitchy, not too wide.

I suspect that Level File feature is peak-based, and is of little use in matching actual loudnesses.

 

You can get very transparent ones that may have less effect than your interconnect cables. You could also use high quality autoformers.

 

I don't have manuals for these, so I don't know; but do you think my Rega DAC is the right voltage for my '90s-era Linn Majik amp?

I mean, it sounds alright to me; but I wouldn't know, possibly.

 

Did some actual research:

Here are specs of some 5-disc “carousel”-style changers either still in production or discontinued(my apologies if some links do not work for you):


http://resources.jvc.com/Resources/00/00/90/LVT0234-001B.pdf


http://audio.manualsonline.com/manuals/mfg/technics/slpd887.html?p=18


http://usa.yamaha.com/products/audio-visual/hifi-components/cd-players/cd-c600_black__u/?mode=model


They all seem to indicate 2Vrms output in the spec sections of these manuals for these players, and I have been told and assume that is per-channel.


Contrastingly, most consumer-grade receivers are expecting between 150-200mV – that’s 0.15 to 0.2V!!! - , at impedances of 47kilo-ohms.


I have been told that cables do matter and yes, while some cables are genuinely snake oil, there are RCA cables out there with attenuation built in, 6dB, 12B, etc. In addition to the Harrison Labs attenuators, those cables are an option, although very expensive from what I saw.


If there are high-impedance boutique cables out there I’m not aware of them, but the point is there are options for the 99% of consumers I’m trying to help to get better sound out of their CD or DVD players. I also don't expect most consumers to be able to open up their gear and know which pots to turn, where to connect a multi-meter, to dial in the right amount of attenuation at the receiver/amp end.


For folks with separate pre-amp > amp setups, the output of the CD player doesn't matter that much - they can compensate for it on the front of the pre-amp.

 

Just received my 12dBs today:

http://www.parts-express.com/harris...source=google&utm_medium=cpc&utm_campaign=pla


Solid pieces, well built. At present am testing them out on my DVD/VHS combo unit. Definitely do the job, a little too well I think! They do not affect tonal balance to any degree I can hear, except now I can hear deeper low end than before(entire audio spectrum is well below clipping point now).

But...
I have to jack my receiver volume up to 12-1 o'clock to hear dialogue, but the loud scenes and music blow out the room! So I'm experiencing dynamic range I never know this player had, but I can't follow the interaction very well.

Think I will exchange them for the 6dB pads, and get a second pair of 6's for future use.


I highly recommend them, and I'm hearing details in my DVDs and even VHS that I didn't hear 10-20 years ago when I saw these films in the theatre(!) but I'm at fault for selecting overly aggressive attenuation for my setup.

 

A Harrison labs attenuator, the volume knob on my Sony changer, and a knob on a sep. pre-amp are all attenuators, so you can't escape putting *something* in the signal path to cool it down.


And I consider the clipped, too-hot input in my slide above to be more disruptive to my listening than any pad or attenuator.


But as some are trying desperately to prove(on this and many other topics), I could be wrong.

 

Gain structure is all over the place these days, and you are likely to have issues pairing a modern source with a vintage reciever/pre as No-Remasters points out. I think it is very useful for folks to be aware of these kind of issues. Usually we have a lot more gain than needed, and if so I think the attenuators are a better solution that having a volume pot turned down to a low level as this will probably sound worse than attenuator + volume knob closer to the middle or top of it's range. And as was mentioned volume pots don't always track evenly at low levels.

If setting up a system or buying new gear you should be aware of the gain structure of the components you are matching up and try to avoid having excess gain. Since I built my own preamp/amp I can choose how to build them and I ended up with a system that has only 15 dB of gain, much lower than normal. I have my preamp (20 dB gain) driving an EL34 SET amp with no driver section, so the amp actually has negative gain due to the OPTs. It also means my amp has an input sensitivity of nearly 20V RMS, which is no problem at all for my preamp. So using a high gain preamp with a modern source is likely to give you much, much more gain than needed, so one should consider using a zero-gain tube buffer or passive preamp depending on the source (does it have a low enough output impedance to drive the signal through a passive pre + cabling?) and the amplifiers input impedance (is it low enough to make a buffer worthwhile?). With a strong source and high input impedance amplifier a passive pre/volume control might be the answer.

 

I have had "discussions" with members of other forums in the past concerning this issue and some of them insisted it is a non-issue because most amplifiers have the volume control as the first component in the chain and all you have to do is turn it down if overloading occurs.

Even if that were true, they are completely ignoring the tape output stage which is before any volume control and can easily be overloaded by the vastly increased output from a typical CD player. An increase from 150mV to 2 volts? Forget about it.

I also agree that a volume control is NOT meant to compensate for gross differences in inputs. It is meant to maintain fairy equal levels between input levels of reasonable difference.

I consider the lack of backward compatibility at the outset of the digital source era a gross negligence. At least those players with a variable output allowed correction on the part of the user even if that wasn't the intent of providing that feature.

As I stated earlier, I am fortunate that my Heathkit pieces have built-in variable attenuators which were actually provided to precisely balance different inputs from different sources even in the all analog era. But what about those who have typical equipment from other manufacturers with preamps before the volume control or, of course, the preamp for tape output? This is an unnecessary problem created by an industry recklessly trying to impress the public with the superior signal-to-noise of CDs.

Doug

 

Not saying this is right or wrong, just some info .......

http://www.russandrews.com/viewinde...&customer_id=PAA1088079214210WCUWKJRFPEJLNYLR

 

Alan Shaw of Harbeth has plenty to say about output/input mismatch in modern-day audio equipment. He's another pro-attenuator person. As moops said, just one more data point.