[cloudbaseracer]

I am looking a the NAD M51 currently and it has a digital volume which many say is excellent and does not sound like any other volume controls.  What I do not understand is what does a volume control sound like and how would anyone know what they are hearing.  It just sounds (no pun intended) strange to me.  Please enlighten me if you can. 

I did read this on another forum where a guy was talking about the NAD M51 but it really does not help:


"And the volume control is excellent. I would describe it as the equivalent of zooming in with a telephoto lens when using a 'regular' preamp as opposed to being physically transported closer to your subject when using the m51 as preamp. No other analog or digital volume control/preamp I have used has given me such a sensation."

What does analog volume sound like?  Is this stuff real? HA!

Cheers,

James

[Rclark]

Very, very real.

[galyons]

"What does analog volume sound like?  Is this stuff real? HA!"   The perfect analog volume control has no sound.  It would attenuate the signal with no sonic signature of its own.  But, alas, no attenuator is perfect. The best do the least harm.  You will know it when you don't hear it!!  Cheers, Geary

[DaveC113]

Well, you need to attenuate the signal somehow, or adjust gain and listen near full volume all the time.

You can attenuate a signal with a volume potentiometer, which is made of carbon or plastic. You can use a stepped or ladder style attenuator, which passes the signal through resistors. There's also a TVC or transformer based volume control... and the digital control on your computer, which degrades the resolution.

All of these solutions are audible in the sense a plastic pot will sound different than a stepped attenuator in the same system.

How people can judge a volume control that's part of a complete amplification device is beyond me. I'd think you'd need to use different volume controls in the same device.

[geezer]

In my own simple minded way, I think of it this way: Any element in the signal path can affect the signal to more or less degree. If any element is switched out for another, there may be a noticeable change in what you hear, for better or worse, or the change might be so small as to be undetectable. Since the volume control is in the signal path, the same applies for it.

[*Scotty*]

DaveC113,

I'd think you'd need to use different volume controls in the same device.

You got it in one,been there done that. I've tried a number stepped attenuators as well as simple $3 carbon film pots in a number of projects over the years. Interestingly the cheap carbon film pot is still one of the better sounding alternatives out there, Alpha makes one for $2.73 that is readily available.
OEMs have a broader range of attenuators available to them than DIYer, including in house designed circuit board based relay switched resistor arrays.

 As to the sound of the pots I've tried that are readily available to the DIYer, most hurt the size of the space and sound-stage, many also tend to noticeably restrict the dynamic life of the music. Some also add a fine amount of grain and whitish quality to the music, not quite bleached. Plastic pots have no grain at all but they sound a little dark.
 
 So far the best of the physical attenuators that I have tried has been the DACT brand when compared to all of the other types of pots, conductive plastic and carbon film. The DACT has the biggest space, best dynamics and the most holographic presentation of the music. The closest to the DACT has been the lowly ALPHA brand carbon pot which adds low level grain and a slight whitish quality to the music. The plastic pots sound quite two dimensional compared to the DACT and ALPHA pots.
 
There are clones of the DACT attenuator, which, if the SMD resistors used are as good as the DACT may be as good or better sounding for less money. Attenuators with through hole resistors are also available. They may also be competitive but you are putting the signal through more material and you have leads on the resistors as well which adds inductance compared to a surface mount resistor. The best bang for the buck may be the DACT clones like the Goldpoint, but I haven't tried one yet.
 Unfortunately the analogue attenuator is still a necessary evil in many cases. You have to attenuate most sources to below unity gain on many pre-amplifiers to a have a suitable playback level.
Scotty

[InfernoSTi]

There is also the optocoupler volume control that doesn't degrade the signal...I use a Warpspeed but other brands/types exist. 

http://www.6moons.com/audioreviews/warpspeed/1.html

I feel this type of attenuation is the best solution currently available...and I've bypassed all my volume pots (in my preamp DAC and amp) so the only attenuation is from the Warpspeed Optocoupler.  It makes such a difference if your system is sufficiently resolving. 

Best,
John

[*Scotty*]

John what type of gear are you using and what type of pots came standard with it that you wound up bypassing? It sounds like you killed many birds with but one stone so to speak.
Scotty

[InfernoSTi]

I use the Warpspeed optocoupler between the preamp/DAC and the main amplifier, so it has a set of RCA ICs rather than a volume pot in each. 

The preamp/DAC is a Boulder Cable Co. modified Eastern Electric tube DAC with a Bybee Music Rail power supply.  Wayne bypassed the volume pot when he did the modifications. I don't know what type of volume pot the EE DAC uses.

The amp is a "self" modified Bottlehead Stereomour 2A3 SET amp and I bypassed both the multiple input selector switch and the volume pot so it is essentially a power amp.  I am currently building a set of Bottlehead Paramount direct coupled 2A3 mono block amps that don't have any switches in the original design.  The original volume pot and switch are decent quality "standard" switches/pots.

I use high (about 98 db) OB speakers (Hawthorne Audio References) that have the bass augmented with two 370 watt SS plate amps.

I found the clarity and dynamics were an immediate improvement over volume pots. I wouldn't go back at this point...although I think if I had to, I would go the stepped attenuator route with high quality resistors.

Hope that explains things a bit more....

Best,
John

[Quiet Earth]

Cloudbaseracer,

I don't think you can fairly compare the sound of digital volume adjustment with the sound of analog volume controls. The entire digital signal must be altered, changed, or manipulated in the digital realm to have a digital volume control,  whereas it can be left intact and simply converted to analog otherwise. So, you are not really comparing the sound of the attenuation, you are comparing the manipulation schemes (or lack of manipulation) in the digital domain. Clear as mud?

InfernoSTi,

Did you ever compare your opto with a tvc or autoformer? If so, can you describe what you like better about the opto?

[roymail]

From my experience, the DACT and Goldpoint stepped attenuator are virtually the same, but I prefer the Goldpoint due to the design.  It's easier to solder the connections with the Goldpoint, otherwise all is the same.  They sound more open than cheap plastic pots, in my opinion.

Whatever you try, keep the value of the attenuator lower than the input impedance of the amplifier.  10K will usually work well for most amplifiers.  An input impedance of 47K or higher will work well.

I've auditioned one octocoupler volume control in the past, and it sounded very good in my system but not "HOLY COW" better than my Goldpoint.

Keep in mind that is is based on my personal experience with my system.  Your mileage may vary.  All the best 

[Mark Korda]

Cloudbaseracer,I don't think anyone touched this.Most volume controls in audio are logarithmic(Log Taper),some times called (Audio Taper).Some use a (Linear Taper).If you have a sceintific curiosity and want to find out what happens when a linear pot is used instead of a log tapered pot,try using a linear pot as a volume knob.Your ear will(think) that you have reached maximum volume at (2 o'clock)and probably won't hear much additional volume past that point.I don't know if this answers your question,but I read this out of (How to service your own tube amp)by Tom Mitchell.....maybe some one else could explain it better...take care...Mark Korda

[DaveC113]

I've auditioned one octocoupler volume control in the past, and it sounded very good in my system but not "HOLY COW" better than my Goldpoint.

I'm not sure if everyone understands the signal in the light based volume controls goes through a LDR (light dependent resistor), which DOES degrade the signal to a certain extent. Also, the LDR is not optimized for audio as are many conventional resistors. I can't see it being much different or better than a stepped attenuator, in fact I could see a stepped attenuator being better if it uses good resistors. Also, there are issues with heat if it's used with active devices, so as far as I can tell, it's best used in it's own chassis. And it requires a power supply... So after looking into it I decided it's not worth considering.

[*Scotty*]

The problem I see with LDR based attenuators is that the device is active and has a transfer function.
It also adds more distortion than a simple resistor attenuator. How audible this is will depend on the variables present in the end users system including their ears.
 As it stands I wouldn't use them in a critical application in my system,obviously YMMV.
Scotty

[Davey]

I wouldn't either. 

As you can see on the many DIYaudio threads, much extra work is required to "optimize" LDR operation for reduced distortion and increased longevity.  Constant current drive, series/shunt configuration, etc, etc.  And they really should be buffered....as the Warpspeed is.  But by the time you get done you have another full-blown active preamp....which seems not in the spirit of the original intent of such an application.

I know there are many opinions on how superior they "sound," but that's just a result of the increased distortion.

There is no more superior attenuator (for this application) than a stepped-attenuator that uses matched, discrete resistors of the proper value in the proper configuration.  Not the most convenient, but all others are competing for second place both objectively and subjectively.

Cheers,

Dave.

[DaveC113]

I settled on this volume control for my preamp, it may not be the best but it should be a good value. I got the switches and PCBs for $29 and spent $18 on PRP resistors (1% metal film, non-magnetic).

http://glass-ware.stores.yahoo.net/m1mostat.html

[galyons]

There is no more superior attenuator (for this application) than a stepped-attenuator that uses matched, discrete resistors of the proper value in the proper configuration.  Not the most convenient, but all others are competing for second place both objectively and subjectively.

As is usually the case in audio...simpler is better.  The closer the signal path is to a straight wire the truer the fidelity.

The volume pot in my older, second string, preamp was replaced with a DACT, the improvement was not subtle. My first string preamp came with a nice remotely controlled higher end pot.  Put in a DACT and the increase in clarity and detail was obvious. Convenience is almost always at the cost of fidelity.

I am building a Hageman Clarinet.   DIY case, choke PS, no electrolytics in PS or B+ coupling, board populated with PRP & Kiwame resistors.  I have a stepped ladder, Goldpoint and DACT to try for the cleanest attenuation. 

The entire signal must go through the volume control.  Do the least harm here and everything downstream sounds better!!

Cheers,
Geary

[DaveC113]

I am building a Hageman Clarinet.   DIY case, choke PS, no electrolytics in PS or B+ coupling, board populated with PRP & Kiwame resistors.  I have a stepped ladder, Goldpoint and DACT to try for the cleanest attenuation. 

Cheers,
Geary

Sounds like a great project, but IMO don't use too many Kiwame resistors, they are warm and soft sounding... I replaced Kiwame with Mills non-inductive wirewound in the cathodes of my power amp and the result was a cleaner sound. My Aikido is using AB carbon as gridstoppers, but there are Mills and PRP everywhere else.

I also replaced an electrolytic in the last part of my amp's PS filter with a Mundorf M-cap and the improvement was huge. I am using the JJ electrolytics in my Aikido bypassed w/ FT3 teflons, those M-caps aren't cheap and the pre needs 2 of them! One day I will upgrade them...

I think the ladder attenuator must be the best of the bunch, but needs A LOT of resistors!

[Early B.]

I know there are many opinions on how superior they "sound," but that's just a result of the increased distortion.

Let me get this straight -- you're saying that LDR-based volume controls appear to sound better due to increased distortion????   Wow -- I didn't know more distortion sounds better than less distortion. I had it backwards.

[*Scotty*]

Everything is relative. If you have replaced a piece of crap with a LDR based attenuator you may hear an improvement. Likewise if you replace an inferior preamp with an optocoupler with a buffered output you may hear an improvement.
 However if you have a minimalist buffer/preamp as I do these things are counter-indicated.
In my case my preamp has 5 parts in the signal path, one of them is a 15 amp pass transistor.The rest of the parts are passive and include a DACT attenuator at the front of the circuit. The preamp/buffer will pass a 1MHz square-wave perfectly from input to output and even cleans up the leading edge of the square-wave because it will drive the input of the oscilloscope better than the output of signal generator. This indicates that the device has at least a 10MHz bandwidth as it will pass the 1MHz square-wave in an unaltered form. The THD+noise  is 0.002% for 2 volts output.
 It would be the height of folly to put something with more circuit complexity and an inferior power supply in place of the DACT attenuator and expect a superior outcome.
No thank-you.
Scotty